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Full text of "Silos; construction and service"

SILOS 

COHSTRUCTIOS AH? SERVICE 



M.L.KiNG 



SILOS 

CONSTRUCTION AND SERVICE 



By 

M. L. KING 

// 

Formerly Silo Investigation Expert, 
Iowa State College 




COPYRIGHT, 1913 

BY 
WEBB PUBLISHING COMPANY 



PREFACE 

During the past few years, I have had occasion to examine 
and to study the construction of a large number of silos in a 
dozen states, both in the East and in the Middle West. As 
the result of this study I have become thoroughly impressed 
with the belief that many of the mistakes and difficulties in 
the building of silos might be avoided if the builders had a 
more thorough knowledge of the fundamental principles of 
silo construction and the preservation of silage. There is 
no recent American book on silo building and none of any 
date which covers the many types of silos now in use and 
gives details of their construction. There are a number of 
experiment station publications on the subject, but these are 
necessarily either brief in their treatment or limited to special 
types. It is with the object of presenting to the intending 
builder the principles of silo construction and the advantages 
and disadvantages of the different types, and more parti- 
cularly of giving the actual methods of construction, that 
this book is written. 

The first part of the volume takes up the fundamentals 
of silage preservation, descriptions of the different types of 
silos follow, and an explanation of the details and the con- 
struction of all the important types. These details and the 
p ans and specifications are in nearly all cases from first- 
hand knowledge. 

Where the information has occasionally been gleaned from 
others, full credit is given. The author wishes to acknowl- 
edge his indebtedness to all engineers and mechanics with 
whom he has associated in his silo work, as they have all 
contributed ideas very helpful in developing silos. Promi- 



300292 



PREFACE 



nent among these should be mentioned C. H. VanZee, E. Y. 
Cable, and A. O. Alexander. For careful editing and helpful 
suggestions as to methods of presenting the facts contained 
in this volume, the author is very grateful to Professor Fred 
W. Beckman. 

M. L. KING 



CONTENTS 



CHAPTER PAGE 

I. EARLY DEVELOPMENT . . . 7 

II. FUNDAMENTALS OF SILAGE PRESERVATION 11 

III. WOOD SILOS 

IV. MASONRY SILOS 

V. PLANNING THE SILO 

VI. ERECTION OF STAVE SILOS . . 52 

VII. MONOLITHIC CONCRETE SILOS 60 

VIII. THE IOWA SYSTEM OF BUILDING BLOCK SILOS . 65 

IX. SAFE STRENGTH OF MATERIALS . . &4 

X. BUYING AND CONTRACTING SILOS . . 96 



Silos: Construction and Service 



CHAPTER I 
EARLY DEVELOPMENT 

Origin. The silo probably originated in the southern 
part of Europe somewhat previous to 1845. 

Subsequent Development. The first silos used were 
simply pits in which green fodders were packed and covered 
with earth. Later these pits were made more permanent 
by lining with masonry. To keep the upper layer of this 
fodder moist and the whole more compact, the top was gen- 
erally covered with earth or other heavy material. When 
the fodder was used it was found that the silage at the bottom 
was better preserved than that at the top, and that the 
amount of inferior silage at the top was practically the same, 
regardless of the depth of the silo. Thus the deeper pits had 
a smaller percentage of inferior silage than the shallow ones. 
The logical development, therefore, was to increase the depth 
of the silo pit. However, soil waters often limited the depth, 
so that it became necessary in many cases to build a super- 
structure, or what we now consider a silo. 

Under modern conditions we find that in most cases it is 
cheaper to build above ground than below, so that today the 
silo generally goes into the ground only deep enough to secure 
a firm foundation; or in the case of a bank barn, it extends 
down to a level with the barn floor. For Northern or North 
Central states, the pit extends in the ground 3 or 4 feet, while 
the superstructure, or silo proper, in case of wood, is gener- 
ally built 30 feet high. Wood sflos should not be built much 



.7 



8 



' SILOS: 'CONSTRUCTION AND SERVICE 



higher than this, unless extra precautions are taken in guying. 
With the masonry silo, the practical height is not less than 
40 feet. 

Development of the Round Silo. The original silos were 
built square or rectangular, but upon developing the high 
silos it was found that a large amount of silage spoiled in the 
corners. This lead to the boarding up of the corners with 
straight boards, making an octagonal silo; or bent lumber 
was used, making it round. This was a great improvement, 
but was only an intermediate step in the development of the 

round silo, which, during 
the later part of the '80 's, 
became quite common. 

Improvement of Door 
and Door-Frames. At first 
the round silo had only 
one door at the bottom, or 
none at all, all silage being 
lifted over the top It was 
gradually learned that 
doors could be maae as 
tight and smooth as the rest of the wall, and then silos be- 
came common with doors placed at more or less conven- 
ient intervals. In the square silos the doors were made 
continuous, just as in a grain bin. Likewise, in the early 
'90's, continuous doors became common in what is known 
as the Wisconsin or sheeted silo. It was only necessary to 
place rods across the doors to prevent the jambs from 
spreading. It was not quite such a simple matter to build 
continuous doors in the stave silos; therefore they were 
seldom used prior to 1896. Later a patent was issued cover- 
ing this feature, and the use of continuous doors in stave silos 
has been more or less involved in litigation. 




Fig. 1. Construction 
square silo. 



dutails oi 



EARLY DEVELOPMENT 




10 SILOS: CONSTRUCTION AND SERVICE 

Development of the Masonry Silo. The use of wood and 
masonry in silo construction commenced at about the same 
time in the United States, namely, in the '70's. However, 
steel is necessary in the construction of masonry silos, and 
the lack of this general knowledge, together with the cost of 
steel, caused many serious failures. For this reason rapid 
advancement in the development of masonry silos has 
occurred only since the beginning of the present century. 
Masonry silos were originally built with very thick walls, 
2 feet or even more being a common thickness. By the use 
of a combination of steel and masonry, 3 to 6 inches is suffici- 
ent. The establishment of this fact has, of course, been a 
great factor in the development of an economical masonry 
silo. 

The general features of the modern silo are greater height, 
smaller diameter, and convenience in construction and use. 



CHAPTER II 
FUNDAMENTALS OF SILAGE PRESERVATION 

Nature of the Process. In the silo the corn or other fod- 
der undergoes a slight chemical change quite similar to that 
which occurs in making sauerkraut. The latter is such a 
well known process and is so similar to the preservation of 
silage that the comparison is oftentimes used. In the forma- 
tion of silage, the action of two principal kinds of bacteria 
determines its quality. These are the bacteria that form 
lactic acid and those that form acetic acid. 

In the early development of the silo, it was common to 
cut the corn quite green, which condition favors the formation 
of acetic acid. Acetic acid is very much stronger than lactic 
acid, and silage containing much of it is what is ordinarily 
considered sour silage. 

Time for Cutting. The present practice is to permit the 
corn to become as ripe as possible without losing much mois- 
ture. That is, the corn should become well dented and glazed, 
but should not be given opportunity to harden or dry out. 
When a few leaves near the bottom of the stalk have dried 
and the same with the husks, that indicates about the proper 
time for filling the silo. The silage made from such corn 
will be what is known as sweet silage. The acid formed will 
be principally lactic. Within a very few hours after the 
corn is placed in the silo it begins to heat. Only a certain 
percentage of acid can form, as it kills the bacteria and thus 
automatically controls acidity. The rise of temperature 
also aids in the destruction of the bacteria. 

Quality of the Silage at the Wall. At the wall of any 
silo the rise in temperature due to fermentation is interfered 



12 SILOS: CONSTRUCTION AND SERVICE 

with on account of heat passing out through the wall; and 
since heat is one of the factors in checking fermentation, 
there are different conditions and results at the wall than 
in the center. This is noticeable in any kind of silo. In 
silage taken from against the wall, a slight difference in odor 
can always be detected, no matter how good and tight the 
walls are. This does not mean that the silage at the wall 
is materially inferior to that elsewhere, nor does it mean that 
just because there is a little difference in the odor the silage 
is all bad. The writer has never found a silo in which this 
difference could not be detected. 

With a rise in temperature, any material is certain to 
expand. The silage settles very rapidly the first few days, 
and this, together with the rise of temperature, is the main 
source of the outward pressure; during the first few days 
after the silo is filled it is greater than at any other time. 

The growth of mold or the decay of the silage can only 
occur when air is admitted. If the silage is at all dry and 
air is admitted mold results. If, however, the moisture 
content runs as high as 65 to 70 per cent, and air enters, the 
result is usually rotten silage. It is important to mention 
this, as the rotten silage prevents air from reaching the rest 
of the silage, so the loss in this case is usually not very great. 
In the case of dry silage, however, the admission of air causes 
a growth of mold which does not prevent to so great an extent 
the entrance of air. 

The growth of mold does not effectively prevent air from 
reaching adjoining silage. Therefore the loss is often much 
more serious than would have been the case with more mois- 
ture in the silage. In some cases concrete silos could more 
appropriately be called gravel silos, as they allow the air to 
filter through and at the same time absorb moisture from the 
silage, making the conditions right for the development of 



SILAGE PRESERVATION 13 

heavy mold near the wall. This is not true of a good con- 
crete silo, but has usually been the case where sufficient 
cement was not used. 

Forage or Mold Poisoning. Some of these silage molds 
are poisonous, especially to horses. The following is a state- 
ment taken from Press Bulletin No. 30 (Iowa), by C. H. 
Stange, head of the Veterinary Department of the Iowa State 
College, with reference to this problem: 

"Iowa farmers have suffered heavy losses in the past few 
months by the death of horses from a disease that affects 
these animals almost exclusively. It is usually fatal; it is 
not contagious, and it is quite certain that it comes from the 
eating of moldy fodder or grain. There is only one safe- 
guard against it and that is the rejection of any feed that 
shows signs of mold. Ensilage and corn fodder of any kind 
and hay from swampy lands need to be inspected with special 
care, for they are the most likely to be moldy. Cattle often 
seem to eat spoiled plant food without harm, but to horses 
it is poisonous. 

"This disease has been called by various names: Forage 
poisoning, cryptogamic poisoning, enzootic cerebritis, epi- 
zootic cerebro-spinal meningitis, leuco-encephalitis, etc. 

"It usually appears in isolated outbreaks and generally 
the horses on a single farm in a community are affected. In 
some cases where horses are not fed alike, only those given 
a certain kind of feed are taken sick. In these facts there is 
quite conclusive evidence that the disease is associated with 
the food eaten and that it is not transmitted from one animal 
to another. The outbreaks appear more frequently in low, 
swampy districts because conditions there are more favorable 
for the development of the molds and the undesirable changes 
in plant foods believed to be responsible for the disease. It 
is not by any means confined to these districts, however, 



14 SILOS: CONSTRUCTION AND SERVICE 

nor is it limited to any certain food stuff. It merely occurs 
more frequently in some foods than others, due to their 
nature and method of storing. 

"Causes. Forage poisoning is likely to appear whenever 
moldy grain or fodder is fed to horses or mules, but it does 
not follow in every case where such food is given. More- 
over, it very seldom affects cattle. Horses and mules may 
sometimes be fed for a considerable time on fodder contain- 
ing more or less mold without sickness while in other cases 
a comparatively small amount of such feed will cause death 
in a short time. Danger lies in the use of fermented foods, 
also, on account of poisons developed in fermentation. 
Some plants are likewise poisonous at a certain stage of their 
growth or when partially wilted. This is true of sorghum, 
particularly the second growth, which in some cases causes 
almost instantaneous death. 

"There are several molds which grow on food materials 
under certain conditions which are more or less injurious. 
The most common are the black mold, the blue mold and 
the green mold. They are found most frequently in ensilage, 
corn, hay, oats and ground feeds. Moisture favors their 
development on all food stuffs. 

"Ensilage. Ensilage is one of the most important and 
valuable foods available to the Iowa farmer, but it is often 
responsible for forage poisoning. Sweet ensilage is of proved 
worth as a feed for horses as well as for cattle, but speaking 
generally ensilage feeding is attended by some dangers that 
the owners of silos should know. Ensilage contains the 
necessary moisture and, in most cases, the required heat, to 
favor the development of molds. On this account it is more 
often a cause of forage poisoning than other food stuffs. Per- 
haps 80 to 90 per cent of the outbreaks reported to this station 
come from feeding moldy ensilage. The quantity of mold 



SILAGE PRESERVATION 15 

may be so small as to be overlooked and yet be dangerous. 
Especially is that true of hay coming from low, marshy 
ground ; though the mold in it may not be seen at first glance, 
there may be enough of it to produce poisoning and death. 

"Moldy corn has been responsible for several outbreaks 
of forage poisoning. Ears that have been attacked by the 
corn ear worm are particularly liable to be moldy. 

"Symptoms. Two forms of the disease are most common, 
the acute and sub-acute. 

' 'In acute forage poisoning loss of appetite and lack of 
thirst, associated with depression and lack of spirit are usu- 
ally the first symptoms. Following this usually come un- 
steadiness of gait and inability to control the hind quarters, 
which become worse until the animal either lies down or 
falls and is unable to rise. At the same time there is in prac- 
tically all cases a paralysis of the muscles of the throat and 
cheeks as a result of which there is slobbering, due to inability 
to swallow, and a flabby condition of the cheeks, which appear 
swollen and pouched. After the animal is unable to rise it 
will sometimes lie quietly for hours, and sometimes it will 
struggle or show spasms at frequent intervals. In acute 
cases there is usually profuse sweating and many times a 
peculiar staring appearance of the eyes. The temperature 
is normal or frequently below normal, which is contrary to 
the fact in contagious diseases. The breathing is usually 
irregular and jerky. The acute cases invariably die after 
a course of 12 to 72 hours and are usually the first animals 
to be affected after moldy food is eaten. 

"In sub-acute cases the symptoms are similar to those in 
acute cases but they do not come on so suddenly and are less 
violent. The sub-acute cases occur among animals that 
have eaten less of the poisonous food and they are the last 
to show symptoms. Dullness and difficulty in swallowing, 



16 SILOS: CONSTRUCTION AND SERVICE 

associated with slobbering and dropping partially chewed 
cuds of food into the manger and feed box, are early signs of 
the disease. These are followed by increasing paralysis, 
especially of the limbs, weakness, and often indications of 
delirium. In fatal cases death follows in from several days 
to a couple of weeks. A few of the less severe cases may 
recover. 

"The length of time between the feeding and the appear- 
ance of the symptoms, the suddenness of the attack and its 
duration, depend upon the amount of poisonous food taken. 
The course is shorter, from 2 to 4 days, the attack is more 
sudden and death soon follows in from 12 to 36 hours 
when large quantities are consumed. 

"Prevention. Since horses and mules are very liable to 
poisoning with moldy foods where cattle may eat the same 
foods with little or no danger, the method of preventing the 
disease is clear. Under no circumstances feed horses or mules 
ensilage that is in the least molded or decayed. In feeding 
ensilage to cattle do not put it or scatter it where horses or 
mules can get to it, for they will sometimes eat the leavings 
in the feed trough after the cattle have picked out the best 
food. Do not throw waste ensilage where horses or mules 
can reach it. Sweet ensilage is a wholesome food for horses 
and of known nutritive value, but unless it is certain that it 
is perfectly fresh and free from mold it should not be fed to 
horses at all. Moldy silage has already caused such heavy 
losses on some farms that it will take all the profits a silo can 
bring to make good the cost. 

"The hay, corn, oats and other grains fed to horses should 
always be of the best quality and the water troughs should 
be kept clean and the water pure and fresh. With all these 
precautions, forage poisoning can be eliminated." 



SILAGE PRESERVATION 17 

Settling. As has already been mentioned, the heavy 
fodder packed into the silo to a depth of from 30 to 50 feet 
settles rapidly for the first few days. In case the silo wall 
is smooth and vertical, the silage in settling does not draw 
away from the wall perceptibly, and there is no occasion for 
spoiled silage against the wall. If, however, the wall is not 
smooth, the silage will not come in contract with the surface 
of the wall in the recesses. These spaces will, of course, con- 
tain air, and the result will be moldy or decayed silage. In 
case a silo leans, the silage will settle a little heavier against 
one side and draw away from the other, thus allowing the 
entrance of air and consequent spoiling of silage. 

It is sometimes reasoned that a silo should be built a 
little larger at the top than at the bottom in order that the 
silage will in all cases crowd the wall. On the other hand, 
it is sometimes reasoned that the silo should be smaller at 
the top than at the bottom, thus reducing the pressure of the 
silage against the wall when settling. Either of these two 
practices is poor, as the good of the one increases the danger 
that the other is designed to correct. In all cases the prop- 
erly built silo is round, smooth, and plumb. 

Material of the Walls. The material of the walls must 
be such that it will absorb as little moisture as possible. The 
wall absorbing no moisture would of course not admit air. 
The admission of air or the absorbtion of moisture will cause 
poor silage. 

Strength and Rigidity. It is almost needless to say that 
the silo must have walls sufficiently strong to withstand the 
pressure of the silage, and should, of course, likewise be rigid 
enough to stand the action of wind. 

Fire Exposure. Placing a wood silo among the other 
farm buildings reduces the distance a fire would need to jump 
in order to connect with other buildings. It is not only 



18 SILOS: CONSTRUCTION AND SERVICE 

exposed to destruction itself, but it also increases the danger 
of fire spreading from one building to another. Ordinarily, 
silage is not materially damaged by fire, but it is exposed to 
decay after the silo is burned. 

On the contrary, a masonry silo built of concrete or clay 
blocks is not subject to serious danger of damage by a fire. 
Moreover, it does to a certain extent serve as a fire wall be- 
tween other buildings, actually interfering with the spread 
of fire from one building to another. 

FROZEN SILAGE 

Extent of Loss. The problem of reducing the quantity 
of frozen silage is very important with every silo user. Froz- 
en silage is not necessarily a loss, but it is of ten a serious incon- 
venience. When thawed and fed soon after, it is practically 
as good a feed as before it was frozen. The loss comes from 
allowing it to stand exposed to the air too long after it is 
thawed, causing it to rot. Thus the danger of loss depends 
upon the amount of frozen silage that is allowed to accumu- 
late. In most cases if frozen silage is taken from the wall 
each morning and piled in the center of the silo it will be 
thawed out by night. This of course depends largely upon the 
severity of the weather and whether or not the roof is tight 
and the door is kept closed. There is always sufficient heat 
in the main mass of silage to thaw the usual amount of silage 
frozen over night, provided this heat is not allowed to escape 
through a poor roof or open door. 

How Heat is Lost. Heat may be lost from a silo in two 
ways. One is by conduction away from the silage through 
the wall. Plainly the amount of this loss will depend largely 
and directly upon the kind of material of which the silo is 
built. 



SILAGE PRESERVATION 19 

Heat is also lost by convection, which is the carrying 
away of heat by the circulation of air from the surface. 

The best kind of house would be uncomfortably cold 
in the winter if it had no roof or if the doors were left open; 
it is just as true of the silo. If the doors are open or the chute 
poorly constructed, much cold air comes in and warm air 
escapes. This is particularly true of a poor roof or no roof 
at all. These two losses of heat combine at the surface near 
the wall to make the freezing most serious at this point. 
Also, it happens that this point is farthest away from the 
main body of the silage. Therefore heat reaches it more 
slowly, and the result is more serious freezing at that point 
than elsewhere. 

Prevention. Generally, a few inches below the surface 
there is little, if any, frozen silage near the wall. In view 
of these facts, two-thirds of the freezing of silage can be pre- 
vented by simply keeping the outer eighteen inches of the 
surface of the silage beveled down toward the wall. Thus 
the silage most likely to freeze is removed before it has time 
to freeze. During warm or moderate weather the silage 
surface should always be kept level, but when the silage 
begins to freeze, the surface should always be beveled near 
the wall. Absolutely no silage should be allowed to cling to 
the wall of any silo. 

The roof should always be made tight, and the following 
pages will show how every roof can be made so. Also, the 
doors should be kept closed when practicable. If that is 
impossible, it is doubly important that the chute be well built 
and kept closed. 

The loss of heat from the surface, due to allowing the 
silage to stick to the walls, is much greater than the loss of 
heat out through the walls themselves. So the difference 
in materials of which the wall is made is of very much less 



20 SILOS: CONSTRUCTION AND SERVICE 

importance than has usually been supposed. As will be seen 
in the following paragraphs, air does not conduct heat away 
from silage as rapidly as building materials; therefore, as 
little material as possible should extend continuously from 
the inner to the outer parts of the wall. Air spaces are of 
considerable advantage, and the larger the percentage of air 
space the better. However, it is very questionable if a man 
who must be careful of his dollars can afford to let this ques- 
tion of warmth influence his choice of materials to any great 
extent. 

So many conditions enter into the question of freezing 
silage, that it is very difficult to form any conclusion without 
examining carefully a large number of silos which have been 
cared for in a similar way, having similar good roofs, doors, 
and chutes, and which are similar in exposure to cold winds, 
and are fed down to about the same place, at about the same 
rate. It is very doubtful in the mind of the writer whether 
or not there is much difference to be found between the loss 
of heat through a 2-inch stave wall and through a 6-inch 
concrete wall. The hollow wall, such as cement block, clay 
block, and monolithic concrete, has some advantage, but it 
is questionable if an 8-inch clay block wall is any better in 
this respect than a 4-inch. That is, the air spaces are not 
separate, and there is more material extending across the 
wall in the case of an 8-inch wall than in a 4-inch. 

Air Spaces in Walls. It is always a good thing, so far as 
warmth is concerned, to prevent the circulation of air in the 
wall spaces. To illustrate, suppose the air space is vertical 
and the air free to circulate. When the silo is half emptied 
and the weather cold, the air is slightly warmed in the lower 
part of the wall by contact with the inner side of the wall 
next to the silage. This causes it to rise, carrying heat from 
the silage up to the colder parts of the walls at the top of the 



SILAGE PRESERVATION 21 

silo. The cold air falls, thus the circulation continues to 
carry away heat from the silage. If the circulation of air 
is restricted by horizontal partitions, this circulation and 
consequent loss of heat does not occur. 

In double-wall wood silos, it is often well to provide for 
circulation at times. After the silo is emptied, air can be 
allowed to circulate in the walls, thus drying them and pre- 
venting rapid decay, which would otherwise occur. This, 
however, is not the case with masonry silos. There seems to 
be no advantage of air circulation in the walls of masonry 
silos, and there certainly are very marked disadvantages. 

Influence of Materials. Materials differ in the ease 
with which heat passes through them; or, as it is generally 
stated, there is a difference in their conductivity. Aside 
from this, about the only general law of heat transfer which 
need be considered is that, other things being equal, the rate 
of heat flow through the wall will vary inversely as the 
thickness of the wall or the distance which the heat must 
travel. Heat will pass through a 1-inch wall twice as rap- 
idly as through a 2-inch wall of the same kind. Also, the 
content of moisture increases the conductivity of most 
materials, because the pores of the material contain moisture 
instead of air, and air is a poor or slow conductor of heat. 
Thus it will be seen that while dry wood is a very poor 
conductor, wet wood conducts heat very much more rapidly. 

Although there are several other features in silo building 
more important, it seemed advisable to explain this 
matter of freezing in order to correct the misunderstanding 
that a 2-inch stave silo is so much warmer, or is so much less 
subject to freezing, than a thicker masonry wall. The actual 
facts do not bear out any such impression as this. In fact, 
about the only way to secure marked improvement in this 
respect is to build two walls entirely separate and if possible 



22 SILOS: CONSTRUCTION AND SERVICE 

restrict circulation. It is, however, very doubtful if the 
average man can afford to spend very much money for the 
slight advantage to be realized in this way. 

In the handling of frozen silage it is always best to 
remember that a preventative is better than a cure. Frozen 
silage is not a good feed any more than snow is a good drink, 
and will cause trouble; therefore silage should not be put in 
the troughs during cold weather any length of time before 
the stock is turned in to eat, and never should the silage be 
put into troughs which are already half filled with snow. The 
frozen silage which does occur should always be spread out 
in the center of the silo and covered lightly with other silage. 
This will usually remove the frost before evening feeding. 



CHAPTER III 
WOOD SILOS 

The wide distribution and cheapness of lumber during 
the early stages of silo development were conducive to its 
extensive use. A very large proportion, 80 to 90 per cent, 
of all the silos in use are wood. Lumber and its uses have 
been more widely known to average mechanics, which also 
contributes to making the wood silo the most common type. 
It can be secured in convenient forms of good grade, and is 
quite durable if used properly. Wood swells quickly when 
in contact with the moist silage, which makes it an important 
and very useful silo-building material. 

Kinds of Wood. Practically all authorities are today 
agreed that the various woods related to cedar, such as 
cypress, California redwood, and Oregon (Douglass) fir, are 
the most desirable kinds for silo purposes. There is room 
for choice among these woods, as cypress, while extremely 
durable, cannot be secured in as clear and long length 
stock as the redwood and fir. The redwood is more expen- 
sive than the fir, but it also is considered superior to it. It 
can be secured in a very clear quality and in any length 
required. The fir can also be secured in good quality and 
long lengths. 

A good quality of white pine is very difficult to get today. 
Hemlock is not used a great deal, but for cheap silos a 
yellow pine or tamarack serves very well. The heartwood 
of the yellow pine or tamarack is very durable, and whenever 
possible clear heartwood should be secured. 

Painting Wood Silos. With any kind of wood it is 
mportant, at least for the sake of appearances, to paint 



24 



SILOS: CONSTRUCTION AND SERVICE 



the outside. There is some question whether or not paint 
on the outside increases the life of the silo, as the moisture 
and heat on the inside cause the inner surface to decay 
rapidly. 

Some paints, such as creosote, not only protect the wood 
from moisture, but also are poisonous to the microscopic 
plants which cause decay, thus preventing decay, if 
the wood is thoroughly saturated. This is accom- 
plished by means of heat and pressure. It will undoubtedly 
increase the lasting qualities of the silo if the staves are 
merely painted. This should be done, however, after it has 
been delivered on the farm, as the farmer can then determine 

the quality of the wood 
before painting. It is 
better to paint the 
staves before erecting 
the silo, as the joints 
can then be thoroughly 
covered. 

Frame Silos. The 
first wood silos were 
square frame structures 
studded vertically and 
sheathed horizontally. 
In the development of 
the round silo it was 
only natural to follow 
the same plan, using 

Fig. 3. The construction of the Wisconsin silo. lumber thm OUgh to 

bend conveniently. Per- 
haps the best known of this type of silo was originated 
by F. H. King, of the Wisconsin experiment station, in 
the '80's. The lumber extending around the siln has suf- 




WOOD SILOS 25 

ficient strength to prevent the silage from bursting it. Gen- 
erally one thickness of siding was placed outside, and two 
or three thicknesses with tar paper between were placed inside. 
This construction is plainly shown by Fig. 3, taken from an 
early Wisconsin bulletin. H. B. Gurler, of DeKalb, Illinois, 
substituted lath and plaster for the inner sheathing of the 
Wisconsin silo. It was originally designed for use inside of 
the barn and Has been more successful there than outside. 
This silo has been quite popular, especially in Illinois. In 
recent years the quality of lumber found on the market has 
decreased considerable, so that it is now difficult in many 
localities to secure at a reasonable cost such quality of lum- 
ber as can be bent for circular sheathing. 

The Wood Hoop Silo originated in the western part of 
New York, and is shown in Fig. 4. The first silo of this 
type that the author has been able to learn of was built in 
1894, by J. T. Wells, a builder and contractor of Scottsville, 
New York, and had a continuous door. This silo has several 
advantages over the Wisconsin silo in that the sheathing is 
not circular and only enough lumber is bent around to pre- 
vent the silo from bursting open. Common flooring is used 
for sheathing and is nailed vertically on the inside. Where 
better work is desired, it is also sheathed on the outside ; this 
gives a hollow wall. The silo is nailed together so that, as 
in the case of the Wisconsin and Gurler silos, there is nothing 
to tighten or loosen at any time. It is made entirely of 
standard lumber. If necessary the hoops can be made of 
weather boarding. Braces are placed between the hoops for 
jambs, and at the door 2-inch material is placed vertically 
between the hoops. The hoops are generally placed 3 feet 
apart, and all are of such size that the pressure will be taken 
care of. Fir, white pine, or cedar siding may be depended 
upon to withstand a pull of from 1400 to 1800 pounds per 



26 



5/7,05: CONSTRUCTION A ^D SERVICE 









WOOD SILOS. 



27 



square inch, so that 
for a 16x30 silo the 
hoops should be ap- 
proximately 3 inch- 
es square. This size 
is necessary at the 
bottom in order to 
stand the pull, and 
the same size should 
be used at the top, 
so that the hoops 
will be large enough 
to brace the silo wall. 
This silo is not very 
widely used, but 
seems practicable in 
a very wide range of 
conditions, and in the 
opinion of the writer 
is destined to become 
one of the very popu- 
lar wood silos. 

Stave Silos. The 
stave silo is common- 
ly called the tub silo, 
and is ordinarily 
made of 2x6 tongued 
and grooved staves 
held together by 
hoops made of steel 
rods, joined at the 
ends by means of mal- 
leable iron lugs and 




Fig. 5. The independent door. 



28 



SILOS: CONSTRUCTION AND SERVICE 



nuts. Originally this form of silo was used only with indi- 
vidual doors, that is, doors placed between every other pair 
of hoops. At present a great many companies are mak- 
ing the continuous-door 
stave silo, differing only 
in minor features of the 
door frame. Several of 
these are shown in order 
to illustrate the different 
kinds. A great advan- 
tage of the stave silo is 
the rapidity with which it 
can be built. It requires 
only one or two days for 
erection. That it is a 
moderate priced silo, port- 
able, and has a capacity 
to resist wind as success- 
fully as some of the other 
types, are also advant- 
ages. 

If the silo is secured to 
the foundation and the 
top guyed by means of 
three or four wires, nine- 
tenths of the difficulty of 
blowing down can be 
done away with. It 
should be secured at the 
bottom to the foundation 

s^t four to six places, and the guy wires should extend out 
quite a distance or across to the framework of the barn. 
They should never be placed close to the foot of the silo and 




Fig. G. The Unadilla door. 



WOOD SILOS 



29 



never steeper than 45 
degrees. For silos 
twelve feet or over in 
diameter, the stave 
should be 2 inches 
thick and 4 to 8 
inches wide, the most 
common width being 
6 inches. In the case 
of silos 12 feet in di- 
ameter or less, they 
have, in some locali- 
ties, been built from 
1-inch flooring and 
the ends of the floor- 
ing joined together by 
steel splines. The 
1-inch stave is quite 
economical, and for 
small silos has been 
found very successful. 
In the care of the 
stave silo it is neces- 
sary, of course, as it 
becomes empty and 
dried out, to tighten 
up the guys and the 
hoops. S u ffi ci e n t 
threads are provided 
for this so that it can 
be accomplished very 
easily. One of the 
most common mis- 




Fig. 7. The Indiana door. 



30 



SILOS: CONSTRUCTION AND SERVICE 



takes made in caring for the silo is to neglect to loosen 
the hoops when the staves swell after the silo has been filled. 
This should be attended to; as soon as the silo tightens up the 

hoops should be let out 
to the same point where 
they were when they were 
originally erected. The 
paint on the ends of the 
rods will indicate this 
point, or it may be 
marked by means of a 
punch. If this is not 
done the door-jambs will 
be crushed together, the 
edges of the staves 
crushed, and the lugs 
broken or at least bent 
seriously. It requires only 

a few years of neglect in this way to use all the threads on the 
hoops. Then the silo can not be further tightened without 
washers or short pieces of gas pipe under the nuts. 




CHAPTER IV 
MASONRY SILOS 

Advantages and Disadvantages. Masonry and steel 
makes a successful and permanent silo when properly used. 
The chief advantages are permanence and the slight amount 
of care necessary. The disadvantages are the length of 
time required to build and the difficulty of getting men prop- 
erly skilled in this kind of work. It is necessary, as with any 
other silo, to use sufficient material to prevent the pressure of 
the silage from bursting the sides. Masonry alone cannot 
be depended upon to withstand this pressure, and steel must 
be applied in the form of wires and rods to withstand this 
tension or outward pressure. In order that the steel may be 
as permanent as the masonry, it must be protected from the 
air by at least an inch of mortar or concrete. 

Quality of Materials. It is necessary, in the use of 
masonry, to use only such material as will be practically 
air tight; that is, it must not be capable of absorbing water 
to the extent of more than one-tenth to one-twentieth of 
its own weight. In case the masonry silo is found to be 
faulty in this respect, it can be improved by plastering the 
inside with good rich plaster, or covering with coal tar, 
creosote, or similar substance. 

It is a poor plan to make one link of a chain weaker than 
the others; it is likewise foolish to build one part of a silo less 
permanent than another. Wood door frames are less per- 
manent and more expensive than masonry, and often cause 
leakage of air between the door frames and the wall. To do 
away with this difficulty, it is simply necessary to mold con- 
crete door frames to receive the doors. The only logical 



32 SILOS: CONSTRUCTION AND SERVICE 

roof for the masonry silo is masonry. It is easy to build it 
either of concrete or clay products, and then it becomes fully 
as permanent as any other part of the silo. 

Stone Silos. The use of stone silos is naturally confined 
to localities where stone is plentiful; and probably the great- 
est number of these stone silos are to be found in Wisconsin. 
The cost of material under favorable circumstances is very 
slight, in fact almost nothing when it must be gathered from 
the field to permit cultivation. The labor feature is an 
important factor, and as the cost of labor increases, the 
building of stone silos decreases. 

It was common to depend upon very thick walls to with- 
stand the outward pressure, but, as already stated, it is never 
safe to depend upon masonry to withstand any force which 
tends to pull it apart. Where liberal amounts of steel have 
been placed in the wall they have not cracked, and where 
they have been plastered inside with a good cement plaster 
they have made very satisfactory silos. 

Concrete Silos. With the advent of concrete, and 
especially reinforced concrete, it was only natural that it 
should be tried for silos. It has been used in many different 
ways in monolithic construction (molded in place in forms) 
with both single and double wall, and is also made into silo 
blocks of different kinds. It is difficult to say just who was 
the first to use concrete for silos, or even in which section of 
the country this use of concrete originated. But today it is 
successfully and very widely used. 

Like the stone silo, the advisability of using it depends 
very largely upon the supply of material; that is, gravel or 
crushed stone. It has been found durable for all climates, 
is storm proof and fire proof, in fact it is difficult to see how 
anything could be built more permanently. Double walls 
are advantageous in resisting frost. This form of construe- 



MASONRY SILOS 



33 



tion can be made to embody all of the essentials of silo con- 
struction. The precautions to be taken are to secure 
competent workmen, thorough reinforcement, and properly 
mixed concrete. 







Fig 9. The stone silo. 



34 



SILOS: CONSTRUCTION AND SERVICE 




Fig. 10. 



A concrete silo, constructed under the supervision of the Nebraska 
experiment station. 



Plastered Silos. A modification of the concrete silo that 
has come into more or less prominence in some localities in 
the last few years is the plastered silo. Its essential feature 
is simply a skeleton of expanded steel used as reinforcing. 
This steel is covered with two or three coats of plaster on each 
side, so that when complete it is 2 or 3 inches thick. It is 
necessary to use as much steel, or more, in this construction 
than is indicated in the reinforcing plate shown on page 78, 



MASONRY SILOS 



35 



and in addition a scaffold for temporarily holding the steel 
in position is required. 

Clay-Product Silos. The economical masonry building 
materials of the present time may be divided into two general 
classes, concrete or stone, and clay products. 

Either of these classes furnish excellent building materials 
for silos. Therefore it is only natural that in many places 
brick was used in the early development of the silo. As in 




Fig. 11. The cement block silo. 



36 SILOS: CONSTRUCTION AND SERVICE 

any other masonry material, the outward pressure must be 
taken care of or resisted by steel placed in or around the wall, 
preferably in the wall, as it is then protected from rust. In 
the earlier forms of this silo, as in the concrete and stone 
silos, wooden door frames were used. 

As already suggested, the choice between clay products 
and concrete will usually depend upon the local conditions 
and the supply of these materials. Therefore, it was only 
natural, while collecting material for the publication of 
Bulletin 100 of the Iowa Agricultural experiment station, 
that the author put forth an effort to design a successful, 
economical, and durable silo for localities in which materials 
for concrete construction were scarce and expensive. From 
this effort has resulted the Iowa silo, described in Bulletin 
117, the distinguishing features of which are a reinforcing 
system and a door-frame design for bricks or blocks, either 
clay or cement. The fact that it was developed in portions 
of the state where concrete material was scarce, resulted 
in almost exclusive use of hollow clay blocks or building 
tile. 

The door frame was built of reinforced concrete, molded in 
the form of either individual or continuous doors. A 
special and simple reinforcing system was designed. The 
door jambs are reinforced vertically and are tied together 
across the door opening by a half more steel than is used in 
the same height of the wall. Heavy wire is used in the mor- 
tar joints extending around the silo and secured to the ver- 
tical steel in the door jambs. Considerable time and effort 
were spent upon the development of a convenient scaffold, 
modifications of which are used by most of the Iowa silo 
builders. At present this silo has established itself as one of 
the economical and practical types of silo in use. Like any 
other silo the general precautions to be taken are to 



MASONRY SILOS 



37 





Fig. 12. The old brick silo. 



38 SILOS: CONSTRUCTION AND SERVICE 

secure good material and have it put together in a work- 
manlike manner, as in any other masonry silo the work- 
manship is very important, even more so than in a wooden 
silo. 

Interlocking Block Silos. There are on the market 
several kinds of interlocking devices for silo building blocks. 
In general this depends, in one way or another, upon the 
tensile strength of the blocks taking care of the outward 
pressure of the silage. If the proper amount of steel is used, 
these silos become safe; otherwise, too large a percentage of 
them burst, as masonry can not be depended upon to with- 
stand a pull. If a sufficient amount of steel is used the inter- 
locking devices become an unnecessary expense. 



CHAPTER V 
PLANNING THE SILO 

Selecting the Location. One of the first questions con- 
cerning location is, Shall the silo be placed inside the barn, 
or not? It is very seldom that there is an occasion for placing 
the silo inside the barn. There are good reasons for this : 

First, the silo, with the exception of a few types, is of such 
construction that it does not need the protection of a covered 
building. 

Second, it is not economical to place a silo in a building 
where it will occupy space which may be put to other use. 

Third, a silo located inside of a building is often unhandy 
to fill. The forage cannot be delivered to the cutter con- 
veniently. 

Fourth, by locating a silo outside of the building and 
connecting it thereto with a passage provided with doors, 
-the objectionable odor of the silage may be kept out of the 
building. 

In general, it seems that there are few advantages in 
building a silo inside of a barn, and many in building it out- 
side. There are types of barns, however, the large round 
barn for instance, which make it possible for a silo to be con- 
veniently located at the center. 

There are other considerations concerning the location of 
the silo which should be taken into account. The conven- 
ience in feeding is one of the most important. It is ordinarily 
most convenient to place the silo just outside the barn and 
directly connected to one end of the feed-way or feed room. 
Thus a cart or litter carrier may be loaded with silage and 



40 SILOS: CONSTRUCTION AND SERVICE 

pushed along the aisle, making a convenient method of dis- 
tribution. If yard feeding is practiced, the carrier can be 
arranged to run over a line of bunks. In this case the silo 
would probably not be placed facing the barn. If silage is 
fed both inside and outside, the carrier can be arranged to run 
both ways. Sometimes part of the silage will be fed in the 
barn and the rest carried in a wagon to the feed boxes. This 
is the case on many general stock farms. Then the silo 
should be placed far enough from the barn to allow a wagon 
to be driven under the chute, thus loading it conveniently. 
Large doors can be provided on each side of the passage, so 
that while feeding in the barn one does not need to go out 
doors to get the silage. 

Often, after giving these matters thorough consideration, 
there is still an opportunity for choice with reference to expos- 
ure to weather or the location of the silo in relation to the 
general group of buildings. Other things being equal, it is 
well to place the silo where it will be protected as much as 
possible from the north and northwest winds and from expos- 
ure to the sun. In the case of light wood or stave silos, it is 
often of the utmost importance to place the structure so that 
it will be protected from the stronger summer winds. This 
can often be done by locating it back of groves or in the L of 
the barn. 

The question of general appearance of the farm buildings 
is too often neglected. This should be only of second con- 
sideration, as there is beauty in utility. Often the upper 
portion of a well-built silo showing above the sloping roof of 
some of the other buildings adds very materially to the 
general appearance of the group of buildings. Also the 
side near the top often affords the best place for the farm 
name. 



PLANNING THE SILO 41 

Cost Considerations. The question of cost must be 
viewed from every possible angle. First, perhaps, is a con- 
sideration of the financial affairs of the prospective builder 
or purchaser. Lack of money should never be a reason for 
going without a silo. Properly used, it will put a farmer in 
far better condition to meet his financial obligations than 
before. It does, however, often happen that a man is 
loaded so heavily with financial obligations that it does not 
seem advisable to assume more debts. Yet under these 
circumstances it might also happen that labor and help 
could be secured from the neighbors, with the understanding 
to repay it in labor in the future. In such circumstances it 
is clear that the cash outlay for material becomes of the first 
importance, and cost of labor becomes second. To illus- 
trate, a man in such circumstances might have gravel on 
his farm. Also, he might have lumber which he could use tem- 
porarily for the scaffold. The cost of cement block molds is 
slight, and if this man were somewhat of a mechanic he would 
find it advantageous to secure a mold or molds and make his 
own cement blocks at odd times. In this way a cement 
block silo could be built with less cash outlay than any other 
form of silo. In most cases, however, it would be necessary, 
in considering cost, to figure the cost of the labor of making 
the blocks, etc., so that for the man who must consider time 
as money, or who would realize immediate cash returns for 
his time, some other type would be a better investment for 
him. In such a case the cash outlay might not exceed $150 
for a 16x40 silo, while the cost of all material and labor might 
exceed $400. 

In considering the cost of material it is evidently impor- 
tant to take into account the amount of material that must 
be purchased, also the amount of material that may be fur- 
nished from the farm itself. In furnishing such material, 



42 SILOS: CONSTRUCTION AND SERVICE 

however, it should not be figured as costing nothing simply 
because there is no cash outlay, but it should be considered 
at its market value. The same is true of labor, which many 
times is not figured in because money has not been paid. 
This is not only a poor way of figuring, but it is extremely 
misleading when costs figured in this way are reported to the 
press or in any other way to the public. 

Two classes of material are required in building a silo; 
namely, that which becomes permanently a part of the silo, 
and .he falsework and other equipment, scaffold, forms, 
hoisting apparatus, etc. If these are furnished by the con- 
tractor or can be sold or rented subsequently, this cost should 
not, of course, be charged to the silo. 

In regard to the quantity and cost of labor, it is important 
to remember that labor can not be figured on definitely for 
several reasons, unless it is contracted. Then the con- 
tractor assumes the responsibility, and the farmer pays for 
being relieved of the same. 

The question of the efficiency or perfection of the silo is 
of course primarily important. However, each type shown 
in this book, is, when properly built, very efficient. Any of 
them properly built and filled will preserve silage with prac- 
tically no unnecessary loss, so that it becomes a question of 
first cost, durability, and probably cost of repair and care. 
The silos requiring paint or other attention should be charged 
up with that item. In any building the cost of repair 
becomes important, and one should consider the cost of 
repairing different parts, and the probable length of time 
before such repair will be necessary. Finally, the rate of 
depreciation must always be considered. 

The amount of investment may be considered as the sum 
necessary not only to cover the first cost, but also to provide 
a sinking fund of enough money put at interest to furnish 



PLANNING THE SILO 



43 



cost of care and repair permanently, and to have accumu- 
lated enough by the time the original building ceases to be 
useful, to replace it. In order that such an investment shall 
be good, it must produce not only interest but profit upon 
this original cost and so-called sinking fund. 

Planning the Size of the Silo. The best general advice 
as to the dimensions of silos is to build them small in diameter 
and great in height. The diameter must be such that at 
least 2 inches can be fed from the silo each day. The follow- 
ing tables will serve as the basis from which the amount of 

Table 7. Capacity of round silos. 



Inside 
diameter 


Height 


Capac- 
ity, 
Tons 


Amt. to be 
fed daily. 
Lbs. 


Inside 
diameter 


Height 


Capac- 
ity, 
Tons 


Amt. to be 
fed daily. 
Lbs. 


10 
10 
10 
10 
10 
10 


28 

30 
32 
34 

38 
40 


42 
47 
51 
56 
65 
70 


* 525 
525 
525 
525 
525 
525 


16 
16 
16 
16 
16 
16 
16 


28 
30 
32 
34 
36 
38 
40 


108 
119 
131 
143 
155 
167 
180 


1340 
1340 
1340 
1340 
1340 
1340 
1340 


12 
12 
12 
12 
12 
12 
12 


28 
30 
32 
34 
36 
38 
40 


61 
67 
74 
80 
87 
94 
101 


755 
755 
755 
755 
755 
755 
755 


18 
18 
18 
18 
18 
18 
18 
18 
18 


30 
32 
34 
36 

38 
40 
42 
44 
46 


151 
166 
181 
196 
212 
229 
246 
264 
282 


1700 
1700 
1700 
1700 
1700 
1700 
1700 
1700 
1700 


14 
14 
14 
14 
14 
14 
14 


28 
30 
32 
34 
36 
38 
40 


83 
91 
100 
109 
118 
128 
138 


1030 
1030 
1030 
1030 
1030 
1030 
1030 


20 
20 
20 
20 
20 
20 
20 
20 
20 
20 


30 
32 
34 
36 
40 
42 
44 
46 
48 
50 


187 
205 
224 
243 
281 
300 
320 
340 
361 
382 


2100 
2100 
2100 
2100 
2100 
2100 
2100 
2100 
2100 
2100 





44 



SILOS: CONSTRUCTION AND SERVICE 



feed used daily, and the amount which should be used from 
a silo of any size, may be estimated. These tables are taken 
from Bulletin 100, Iowa agricultural experiment station, 
Table II being furnished by the Animal Husbandry Depart- 
ment of the Iowa State College. 

Table II. Amounts of silage required per day for various kinds 
of stock. 



Kind of stock 


Daily rations. 
Pounds 


BEEF CATTLE. 
Wintering calves, 8 months old 


15 to 25 


Wintering breeding cows 


30 to 50 


Fattening beef cattle, 18-22 months old 
First stage of fattening 


20 to 30 


Latter stage of fattening 


12 to 20 


DAIRY CATTLE 


30 to 50 


SHEEP. 
Wintering breeding sheep 


3 to 5 


Fattening lambs 


2 to 3 


Fattening sheep 


3 to 4 







Table I may be used in connection with Table II to 
determine the size of silo needed to fulfil various conditions. 
For instance, if the silage is to be fed to a herd of 40 dairy 
cattle, at the rate of 40 pounds per head per day, a silo 16 or 
18 feet in diameter will be satisfactory. In case a smaller 
type of cattle were kept, they would eat about 30 pounds each 
amounting to 1200 pounds per day. As seen from the right- 
hand column of Table I, this is not sufficient for a 16-foot 
silo; therefore a 14-foot silo should be used, unless some 
young stock is kept in addition to the 40 mentioned. 

It should be borne in mind that if the size of the herd is 
likely to vary from year to year, the diameter should be 
such that the smallest probable herd would still use 2 inches 



PLANNING THE SILO 45 

from the surface each day. In calculating the height, one 
must remember that the height should be such as to furnish 
the feed capacity for the maximum size of the herd during 
the required feeding season. 

The feeding season will vary. In many cases the silo is 
not opened until Christmas time, and silage is fed as needed 
until grass, which is usually early in May. Oftentimes it is 
desirable to feed silage from filling time, the middle of Sep- 
tember, until May 1. In many cases silage is fed every day 
in the year, and in most every case it is desirable to have 
silage to depend upon during the dry summer weather in 
August and September. Thus the feeding season varies 
from 130 to 365 days, and since at least 2 inches should be fed 
per day, for a 130-day season 22 feet or more (usually more) 
of silage will be consumed. The silage will settle at least one- 
sixth, or approximately 16 per cent, depending upon the time 
spent in filling. This indicates that a silo should seldom, 
if ever, be built less than 30 feet in height. If any silage is 
not used at the end of the winter season, no harm is done, as it 
will keep and will be found very advantageous during the 
dry summer months. In case the herd is larger than usual 
or the feeding season longer, a silo 40 feet in height above the 
ground is not too large. Blowers of the ordinary kinds will 
handle corn for silos 40 or 50 feet in height without any 
difficulty. 

The amount to be fed daily from the surface will vary 
somewhat with the condition of the silage and the time of 
year. The point is that no silage should be left exposed to 
the air long enough to permit the growth of mold. The air 
penetrates dry and poorly packed silage more rapidly than 
more moist and well packed silage. During the summer 
mold grows more rapidly than during the winter, so that the 
summer silo should be made small in diameter. In addition 



46 SILOS: CONSTRUCTION AND SERVICE 

to the rapid growth of mold, if the cattle have some pasture 
they will not eat as much of the silage as they otherwise 
would. 

At all times it is important to remove the feed evenly 
from the surface of the silage in order that no portion will 
be exposed to the air longer than necessary, not longer than 
a few days in winter nor longer than one day in summer. 

Excavations and Foundations. Every building should 
rest upon a foundation broad enough to prevent appreciable 
settling, and deep enough to rest upon earth which is never 
disturbed by frost. Excavating all the earth to the depth 
of the foundation increases the capacity of the silo. This 
space, however, costs somewhat more than equal space in 
other parts of the silo, on account of the additional labor of 
excavation. Thus it will be seen that it is not economical 
to extend the foundation deeper than necessary to get 
below the frost. 

In pits 14 feet or more in diameter, it is usually most 
economical to use a team and scraper in removing most of 
the dirt. In the case of monolithic concrete silos, the sides of 
the pit should be left smooth enough to serve as an outer 
form, if the soil is of such a nature as to permit it. For 
block silos the diameter of the pit should be such 
that the outer part of the silo wall will come within 
about 3 inches of the sides of the pit. This space gives room 
to work with the trowel, and should afterwards be filled in 
with concrete in order to protect the pit from soil water. It 
improves the appearance of the silo to carry this concrete 
up 8 or 12 inches above the level of the ground. This can be 
done very well by laying up blocks temporarily about three 
inches from the silo wall. These blocks make a very con- 
venient form for the concrete and may be removed before the 
concrete is set thoroughly. In the case of a stave silo, it is 



PLANNING THE SILO 47 

questionable whether or not a pit should be used, as the 
concrete wall forms a shoulder inside of the staves,causing the 
silage to draw away from the staves as it settles. Also, there 
is usually a leakage of air between the staves and the founda- 
tion. 

The foundation of the stave silo can usually be made 
most economically by simply digging a trench to the depth of 
2 or 3 feet. This trench need not be wider than 6 or 8 inches 
but the foundation should be extended above the ground 8 
inches or a foot. Usually thin lumber is bent around and 
secured to stakes set in a circle to make a form; but the 
stakes must not be driven into the ground until the pit is full 
of concrete, or the soil will be caved in. 

In case a pit is deemed advisable, the earth should be 
dug out as soon as the hardening of the concrete will per- 
mit, as the inner part of the foundation may then be 
trimmed smooth with a spade and plastered, if desired. 

Whether this pit is excavated or not, the foundation 
should be reinforced with considerable wire or enough steel 
rods to be the equivalent of at least a J^-inch rod. The 
amount of steel necessary for this, of course, depends entirely 
upon the size of the silo and the distance which the founda- 
tion projects above the ground. If there is any question as 
to the quantity to use, the reinforcing table shown for 
masonry silos should be consulted, using the quantity that 
is called for in this table. 

Drainage is important and should receive more consider- 
ation than is usually given in the construction of farm 
buildings, and especially of masonry silos. Any soil will 
support a greater load when dry than when wet. This is 
especially true of clay. The heaving motion of frost is due 
entirely to the moisture contained in the soil, which expands 
with an almost irresistible force upon freezing. Therefore, 



48 SILOS: CONSTRUCTION AND SERVICE 

unless the foundation lies in dry, well drained soil, a drain tile 
should be used to remove the ground water. The tile may 
be located around the lower edge of the wall. If gravel or 
cinders are used, they should be well tamped before the 
foundation is put in place. 

In the case of the wood hoop silo, the walls may be set 
flush with the inner part of the foundation of the silo pit, 
using a heavy coat of asphalt or tar on top of the foundation. 
The wood will then be protected from moisture of the foun- 
dation, also the joint between the wall and the foundation 
will be made perfectly air tight. In this case the pit is advis- 
able. 

In case gravel is expensive or scarce it may sometimes be 
economical to use brick or clay blocks for the foundation. 
If they are used exclusively for the foundation of a clay 
block silo, two 8-inch blocks may be laid side by side, making 
the first course 16 inches wide. The next may be laid 
crossways, making a 12-inch course. The third may then be 
laid on edge, starting the 4-inch wall. 

Details of Doors. In stave silos found on the market, 
very convenient doors are usually provided, so that little need 
be said concerning their construction. There will be found 
some difference in them, in that some are more nearly air 
tight, stionger, and less liable to stick than others. 

For masonry silos, a cheap and very good door is shown 
in Fig. 28. This door as shown is made of two thicknesses of 
ship-lap that lap onto each other about two inches, and are 
not beveled at the ends. The boards on the outer side are 
shorter than those on the inside. A wide cleat with beveled 
edges is nailed to the inner side of the door, on which the 
different doors meet end to end, thus offering little obstruction 
to the free settling of the silage. 



PLANNING THE SILO 49 

In order that any silo may fulfil its purpose, it is neces- 
sary that the joints between the doors and the door frames be 
air tight. It is difficult to obtain air-tight joints between 
doors and masonry drawn out of shape, thus causing the loss 
of as much as 4 or 5 cubic feet of silage at one door. Sealing 
with clay was found to be satisfactory where reasonable care 
was exercised in its use. This becomes a very simple matter 
by taking a quantity of fine clay or other fine soil, wetting it 
until sticky but quite stiff, and filling the shoulder of the 
door frame with it before pressing the door into place. If 
the mud is rather stiff it will hold the door to place until the 
silage is up high enough to secure it permanently. The 
moisture of the silage keeps the clay damp on the inside, thus 
making it air tight. This is one of the oldest and best meth- 
ods of sealing doors. It has been thoroughly tried and found 
to be very satisfactory. 

Roof Plans. There is in some localities a general impres- 
sion that a silo does not need a roof. In reality a roof is not 
absolutely necessary but is very desirable. It aids very 
materially in preserving the shape of a wood silo, and in any 
silo it is important to reduce the amount of frozen silage and 
to protect the feed from bad weather. Otherwise, with 
changes of weather the character of the feed will change. 

In building a roof it is desirable to make as rigid a struc- 
ture as is practical, at the same time obstructing the head 
room as little as possible. It is quite common to use timbers 
extending across stave silos from one side to the other. This 
is entirely dispensed with in the drawing shown in Fig. 4. A 
most economical roof for the wooden silo is generally made of 
rafters placed about 7 feet apart at the cornice and extending 
in to the center of the roof. Headers should be placed about 
three feet apart between these rafters. On a 16-foot silo roof 
with }/$ to J4 pitch, the rafter will be not far from 9 feet in 



50 SILOS: CONSTRUCTION AND SERVICE 

length, and two headers should be placed between each pair 
of rafters about equally spaced along the length of the rafter. 
These headers should be made of 2-inch material, and curved. 
To determine the curvature of these headers, take a radius 
equal to the distance from the rafter to the center line of the 
silo, measured on the line extending at right angles to the 
rafter at the point where the header is nailed to it. Then 
lumber should be bent around the silo for a frieze and the 
sheeting nailed securely to this, thus preventing the cold 
air from coming in. 

The sheathing is most conveniently made from sound 12- 
or 14-inch barn boards ripped diagonally. These should be 
nailed to the headers and to the top of the silo wall, so that 
only the sheathing boards project from the cornice. By 
covering this with a good grade of prepared roofing, a good 
roof is secured. Dormer windows in the roof are quite 
popular and perhaps add something to the appearance of 
the roof, but are more expensive than the trap door and do 
not serve so well. A glazed sash used as a trap door will let 
in more light than the same sash used as a dormer window. 
It should be covered with quarter-inch meshed galvanized 
screen in order to protect it from hail. 

The Chute. In order that the silage may be removed 
from the silo conveniently, it is essential that a chute or 
vestibule 3}^ to 4 feet square be built in front of the doors. 
In case of a wooden silo, the framework of the chute is 
nailed directly to the silo; in case of masonry, bolts should 
be placed in the wall so that 2x4's may be bolted to the wall, 
thus serving to connect the chute to the silo. The wood 
chute is more common than masonry, but masonry is some- 
times desired on account of its fire-proof qualities, being 
more permanent and warmer than the ordinary wood chute. 
If a monolithic concrete chute is to be attached to a mono- 



PLANNING THE SILO 51 

iitmc concrete silo, the two should be built up at the same 
time and securely tied together. Some reinforcing should 
be used in such a chute. 

If the chute is to be of clay blocks, it need not be built up 
at the same time as the silo, though it is usually found more 
convenient to do so. The chute must have a trap door or a 
dormer window in the roof extending out over the chute. 
At the bottom the chute should be connected to the feedway 
of the barn; sometimes, if considerable silage is fed outside 
the barn, it will be found advantageous to set the silo far 
enough from the barn so that a wagon can be driven under 
the chute between the barn and the silo, when large doors 
may be put in the bottom of the chute. 

Points on Floors. In many localities a special silo floor 
is not considered essential or even advisable. Every one 
agrees that the floor may be more often dispensed with than 
the roof. The floor, however, is a considerable advantage. 
It helps prevent water from seeping into the silo, and reduces 
the difficulty of cleaning out the silo before refilling. Con- 
crete is usually used for this, but it need not be made thick nor 
expensive. A three-inch floor is thick enough, but it should 
be made quite dense, generally 1 to 4, unless the gravel is 
exceptionally good. 

In some cases where gravel is expensive, paving blocks 
or even good hollow blocks may be used to advantage as 
flooring by simply plastering them with cement mortar. The 
floor should generally be slightly dished in the center, 6 to 10 
inches being common. 



CHAPTER VI 

ERECTION OF STAVE SILOS 

ERECTING WITH SCAFFOLD 

Inside and Outside Scaffolds. In the use of the scaffold 
two quite different methods have been followed. In one, 
the scaffold is built inside and in the other, outside of the silo. 
The former method is not common and is of questionable 
success, as an outside scaffold is most necessary for putting 
on the steel. The inside scaffold uses a little less lumber 
than the outside, but it is about as much trouble to build 
and does not have the advantage of being out where it is* 
needed for conveniently putting on the steel or hoops. 

Construction. As seen from Fig. 13, in building the out- 
side scaffold, place 2x6 uprights a short distance from the 
foundation and about 8 or 9 feet apart. Thus the number 
of the uprights will depend upon the size of the silo that is 
being built. Usually the scaffold is built 16 feet high, thor- 
oughly braced, and with brackets placed near the top of the 
uprights and extending in toward the silo. The uprights 
must be thoroughly braced, not only to one another, but to 
stakes in the ground, farther out from the foundation. 

Before building the scaffold, the door frame should be 
upended in place and thoroughly plumbed and guyed in 
every direction. 

If the silo is to be built in two sections with the lap only 2 
feet, it is convenient to build the silo to the height of the 
scaffold before extending the scaffold any further. A few of 
the lower hoops can be then put in place and the silo made 
fairly stable before extending it any higher. If the staves 



ERECTION OF STAVE SILOS 53 

are lapped more than 2 feet, or full-length staves are used, it 
will be necessary to build the scaffold full height before erect- 
ing any of the staves. The first thing to do is to erect the 
door frame. 

The uprights are then spliced to the lower ones and the 
scaffold built another section higher in much the same manner 
as at first. In securing the staves in place, it is necessary to 
have common plastering lath, 3-inch bats, or salt or lime 
barrel staves which have been soaked over night in order to 
get them to bend easily. As the staves are put in place nail 
these strips of lumber to them to hold them together. 

Handling the Staves. In any method of erecting it will 
be found most convenient to clamp three staves together 
before raising. A convenient method of doing this is to set 
saw horses upon reasonably level ground and match the silo 
staves together upon them. Then nail the convex or outside 
surface of the barrel staves fast to the inner surface of the 
silo staves, after the staves have been drawn reasonably 
close together. The barrel staves ought to be long enough 
to project 6 or 8 inches beyond the edges of the two outer 
staves so that as each section of these staves is upended, 
the projecting ends of the barrel staves may be nailed to the 
portion of the silo which is already erected. In this way 
crooked or warped staves do not give as much trouble as when 
set up singly; also clamping the staves together holds them 
better. 

The difficulty of lifting a heavy section is overcome by 
the use of a rope and pulley. The pulley may be attached to 
one branch of a "U" doubletree clevis, which is then hooked 
over the top of the last stave set up; by passing the rope 
through this pulley and taking a timber hitch around the 
three staves they can be easily raised by a man on the ground. 
The rope should of course be hitched a few feet from the end, 



54 



SILOS: CONSTRUCTION AND SERVICE 




Fig. 13. Erecting with outside scaffold. 



ERECTION OF STAVE SILOS 55 

but not so far that the man at the top will have difficulty in 
reaching down to unfasten it. 

ERECTING WITHOUT A SCAFFOLD 

While the most common practice is to use a scaffold, the 
author has had better success with no scaffold at all, and he 
very much prefers that method. This has been his experi- 
ence with silos of various sizes. 

The first step, as in the other methods, is to secure the 
door frame firmly in place. This makes it perfectly safe for 
one man who can work handily some distance from the 
ground, to go to the top of the door frame and manipulate the 
clevis and pulley, secure the top end of the sections when they 
are raised, and loosen the rope and pass it back down to the 
men below. As in the previous method, the staves are 
clamped together with three barrel staves if the silo staves 
are full length; if not, it will be necessary to use four barrel 
staves, one at the top, one at the bottom, and one at each 
joint. No scaffold is in the way to interfere with the raising 
of the sections. The clevis is simply hooked over the top of 
the door frame and a section drawn up. 

After the bottom of the section is put in place it is a very 
simple matter for the man above to loosen the rope, draw the 
section over and place one end of the barrel stave to the door 
frame for nailing. Nails should be set in the end of the barrel 
staves before raising, as it is sometimes difficult for the man 
at the top to get more than one hand free at a time. If there 
happens to be much of a wind blowing it is well to nail a 
scrap of 1-inch lumber on the ends of the staves and the top 
of the door frame so as to hold the two together more 
securely. The 1-inch pieces should extend pretty well across 
the door frame so that two or more nails may be placed well 
apart, thus stiffening the entire part that is already up. 



56 



SILOS: CONSTRUCTION AND SERVICE 




Fig. 14. Erecting the silo without a scaffold. 



ERECTION OF STAVE SILOS 57 

The second section may next be raised and secured to 
place with the barrel staves. After this is done, ordinarily, 
it is best to take the pulley and clevis to the other side of the 
door frame and set up two sections there in exactly the same 
manner. Next, a 2x6 or 2x8 (nearest door in Fig. 15) is 
placed across the silo and nailed to the top of the last stave 
on each side. If the wind is blowing seriously it will be advis- 
able to stretch No. 9 wires from the ends of these 2x6 's out 
to stakes driven in the ground some distance away and 
approximately in line with the 2x6's. Now two more sec- 
tions may be raised, and secured by means of one-inch scraps 
of lumber and nailed to the 2x6 in the same manner as the 
first section was secured to the door frame. These two sec- 
tions should be placed on opposite sides of the door frame, 
and another piece of 2x6 lumber placed across the silo as 
before shown in Fig. 15. 

Closing the Circle. It is usually rather difficult to decide 
just what size of circle to set the staves on* It is necessary 
to allow for the staves going together rather loosely, yet it is 
difficult to know just how much allowance to make. For 
this reason, when the silo is about half erected, some meas- 
urements should be taken to find out whether or not the 
staves remaining to be used will close the circle properly. 
If not, the staves must be set a little further out, or a little 
closer in, as the case may require. After the circle is closed 
by raising sections alternately on each side of the door frame, 
nail another scrap of lumber on top of the last staves erected, 
tying both sides securely together. This system of bracing 
is shown in Fig. 15. No. 9 guy wires should be used as 
needed, depending, of course, upon the weather. 

Putting on the Hoops. The staves are now ready for the 
hoops. Put them on, commencing with the second from the 
bottom. A short piece of hoop is always provided to use 



58 



SILOS: CONSTRUCTION AND SERVICE 



with the first, in order that it will reach around the first time. 
All nuts are then turned up, drawing the silo together 
snugly. The first and third hoops can then be connected 




Fig. 15. Erecting the silo without a scaffold. 



ERECTION OF STAVE SILOS 59 

without the use of the extra section. Put on each successive 
hoop up to as high as can be reached from ladders resting on 
the ground, being sure to mark the spacing of the hoops 
carefully. 

If a scaffold is used it is a comparatively simple matter to 
stand on the scaffold and put on the successive hoops, tight- 
ening them enough to hold the silo firmly in place. 

If a scaffold is not used, the steel may be put on in the 
following manner: Drive two spikes into the silo in such a 
manner that the hoops, which should first be properly bent 
to fit the silo, may rest upon these nails. The nails should be 
placed about J4 the length of the hoop from each end of it. 
Then place a ladder convenient to each nail and let a man on 
each ladder carry one end of the hoop section and place it on 
the nails. The entire hoop is put in place in this way, and 
then each man may go to a joint and put on the lugs and bars. 
In this way the lower half of the steel can be placed upon a 
30- or 32-foot silo. It is then a simple matter to hook the 
ladders to the top of the silo and finish putting on the steel. 
The permanent guy wires should be placed and the silo 
plumbed before thoroughly tightening the hoops or putting 
on the roof. It must of course be borne in mind that the 
lugs must not all be placed on one stave; they must be 
"staggered" around the silo. 



CHAPTER VII 
MONOLITHIC CONCRETE SILOS 

In the building of silos in which the concrete walls are 
moulded or as we generally say, monolithic silos, the common 
thickness of wall is 6 inches. This is plenty heavy enough 
for any reasonable size, up to a diameter of 25 feet and a 
height of 50 to 60 feet. The mixtures used will of course 
depend very largely upon the grade of gravel or other aggre- 
gate. Mixtures of 1 to 4 and 1 to -3^ are, however, usually 
found in the best silos. Stones should never be found in the 
wall larger than one-third the thickness of the wall. 

Reinforcement. Vertical reinforcement is commonly 
recommended for concrete silos, but it is of little or no impor- 
tance, as there has never been a failure due to lack of vertical 
reinforcement in any masonry silo, except where a very thin 
wall has " en built or the horizontal steel placed over 3 feet 
apart. 

The horizontal reinforcements may be determined from 
the table on page 78. If other sizes of steel are used than 
those shown in the table it will be a simple matter to 
determine the equivalent amounts. One 5/g-inch rod is equal 
to two ^-inch rods, while one J^-inch rod is equal to four ]/- 
inch rods. 

Forms. In the building of a concrete silo a scaffold may 
be arranged similar to that described in the building of block 
silos, but in addition to this equipment, forms will be neces- 
sary. Several kinds are on the market at present, and 
usually reliable information may be secured concerning them. 
The author has not had wide enough experience in their 



MONOLITHIC CONCRETE SILOS 



61 




COMPLETE FORMS IN PLACE 



Inner hoops qre made 
in one piece 



Outside hoops 
divided here 




'Hoops 



-Slaves 



[Steel 2" 
from door 
frame 



SECTION TROUGH 
FORMS SHOWING 
FORM FOR DOOR 

^^ IN PLACE 

rC-| Bolt with long thread 

PLAN OF FORMS 








DETAIL OF HOOP CLAMP 



M Pieces 
DETAIL OF HOOPS 

Fig. 16. Wooden forms for concrete silos. 



62 SILOS: CONSTRUCTION AND SERVICE 

actual use to compare them intelligently. In addition to 
this there are several types of homemade forms, all of which 
have been quite thoroughly tried out. The first is taken 
from Bulletin 100 of the Iowa agricultural experiment station. 
Illustrations of these forms are shown in Fig. 16; the descrip- 
tions are taken from the bulletin. 

"These forms resemble those used by R. L. Sollet, of 
Goldfield, Iowa, in the construction of his silos. Two sec- 
tions of staves 30 inches long are held in place by wooden 
hoops made of ^ to J^-inch lumber bent to the proper circle 
and nailed firmly together. 

"The staves rest on %-inch square cleats nailed to the 
hoops. The inner hoops are made solid ; and to remove them, 
one side is driven down and the hoops sprung out of round. 
The outside hoops are made with clamps by which they may 
be opened for removal as shown. Three outside and three 
inside hoops are required. The purpose of having two sec- 
tions of forms is twofold. First, the second set of forms is 
accurately located by the first before the second is moved, 
and also by using 30-inch staves 5 feet of wall may be built 
each day and the form need not be disturbed until the con- 
tained wall is at least 18 hours old. Second, no tamping of 
fresh concrete occurs on the unsupported wall, as there is 
always a section of the forms below the one being filled. The 
30-inch stave length was chosen because longer staves are 
likely to bend, and the length is handy for fitting the doors, 
which are 30 inches high inside and placed 30 inches apart." 

The same staves will serve for any diameter of silo and 
the hoops can be made adjustable within a limited range, so 
that a few sets of hoops will equip a contractor for any diam- 
eter of silo. This system of forms has been found to be fully 
as cheap as any. 



MONOLITHIC CONCRETE SILOS. 63 

With this type it is convenient to use scaffolding of the 
same plan as shown in the article on clay block silo con- 
struction. There are several patented systems embodying 
scaffold and forms. They are quite generally advertised and 
may be learned of in that way. There are several systems not 
patented. 

In some cases it will be found convenient to use thin sheet 
metal for outer forms, but the inner forms must be either of 
wood or quite heavy steel on account of the danger of collap- 
sing. If, however, a rigid inner form is used, the outer 
may be of light material and may be spaced accurately from 
the inner form. This secures a properly shaped wall of uni- 
form thickness. Any forms should be cleaned every time 
they are used, and usually it is well to coat them with grease 
or oil. This, however, leaves some grease upon the surface 
of the concrete and interferes with plastering in case it is 
desired. 

It is ordinarily advantageous to use two forms, the second 
being put in place and filled before the first is removed. With 
any system there should be separate forms for the door frame, 
that is, it should never be necessary to use a wooden frame in 
a concrete silo. After setting the forms they should be filled 
around evenly about six inches at a time. Concrete should 
not be dropped a great distance into them or any other rough 
handling done with them, as it is not advisable to go to the 
trouble of making forms that will stand much abuse. The 
concrete should be thoroughly tamped or rammed with a 
light rammer, and there should be sufficient water in the con- 
crete to work to the surface by this process. The concrete 
should be thoroughly spaded near the walls, in order to give 
it a smooth and even surface. 

In putting steel into the concrete, place it at a reasonably 
uniform distance apart and about half way between the inner 



64 SILOS: CONSTRUCTION AND SERVICE ' 

and the outer forms, but in no case put any reinforcing 
material closer than 1 inch from the surface of the concrete, 
also avoid any reverse curves in the steel. Where two pieces 
of reinforcing steel join they should lap at least 2 feet, to pre- 
vent slipping. Usually, good concrete need only to set over 
night, when the form may be removed and raised. 

One advantage of using two sets of forms is that in no case 
is it necessary to remove them until 18 hours after they have 
been filled. The common depth of a set of forms is 2J^ to 3J/ 
feet, but by using two sets, 5 or 6 feet can be added to the 
silo each day. 

Vertical reinforcement should be used on each side of the 
doorway. In any silo more steel should extend across the 
doorways than is found in other parts of the wall. Wall 
reinforcement ending at the doorway should be hooked to the 
vertical reinforcement. 

Plastering. In case it is necessary to plaster this silo it 
is most conveniently accomplished on the outside from a 
swinging scaffold either suspended from the forms, or, if the 
silo is completed, the scaffold may be supported from the 
cornice. On the inside, it is usually most convenient to 
remove the forms and plaster from the scaffold as it is low- 
ered. It is better, however, to plaster the silo if possible 
before it has thoroughly dried, as there is not much danger 
then of the plaster drying too rapidly. 

Methods of hoisting material will vary with different 
systems of forms, etc. In most outfits on the market a con- 
venient method of hoisting is provided. If, however, other 
means are not available, a gin-pole, shown in connection with 
block silos, Fig 22, will be found very convenient and 
strong enough to hoist at least 100-pound loads. 



CHAPTER VIII 
THE IOWA SYSTEM OF BUILDING BLOCK SILOS 

Construction of the Wall. The first course of blocks in 
an Iowa silo should be a trial course, the blocks spaced J/g 
to % of an inch apart, without mortar, in order to determine 
the proper diameter of the silo and the length of the guide. 
This will overcome the necessity of cutting blocks. Steel 
should be placed upon the outer half of the mortar course, 
in order that there shall be enough mortar inside to bear 
against the wire and hold the blocks. In case of a double 
wall the steel should, of course, be on the inner wall. 

Loose blocks may be placed temporarily upon the wall to 
hold the steel in place at intervals of 6 or 8 feet, as occasion 
requires. Steel reinforcement in the joints below and above 
the doorways should be long enough to lap past each other 
and be hooked, as shown in Fig. 19. 

The horizontal or bed joints should be thoroughly bedded 
to cover the steel reinforcement. The vertical joints at the 
block end should be made with care in order to insure per- 
fectly air- and water-tight joints. In order to do this the 
ends of both blocks should be mortared before pressing 
together. The outside joints should, for the sake of appear- 
ance, be struck neatly with the trowel as the work progresses, 
and for warmth they should of course be air tight. On the 
inside, however, this is scarcely sufficient, as there might still 
be an occasional opening left between the ends of the blocks, 
which would permit the air to enter. 

The Cement Wash. In order to close all such openings, 
leave the mortar hanging on the inside or cut it roughly; then, 



66 



SILOS: CONSTRUCTION AND SERVICE 



while still green, wash with a cement wash before the scaffold 
is raised or the work left for the night. This wash naturally 
brings to view any crevices which may exist. These may be 
then filled with mortar and thoroughly sealed on the inside 
of the wall. This wash is composed of cement and water 








Fig. 17. The clay block silo. 



THE IOWA SILO 



67 



mixed to about the consistency of good paint, and can be 
applied with a broom. The wash should be applied vigor- 
ously, in order to smooth 
down and fill the irregu- 
larities. 

Scaffolding. It is 
difficult to overestimate 
the advantage of con- 
venient, safe, and simple 
scaffold for any masonry 
construction. Three dis- 
tinct types have been 
tried by the author, and 
the one which is shown 
here was found to be 
superior to any other 
type tried. This and 
various modifications of 
it are in common use. 
This scaffold is shown in 
the drawing; all parts 
are lettered for^the sake 
of a clear description. 
The top side of the scaf- 
fold is shown in Fig. 20. 

This scaffold differs 
from most building scaf- 
folds in that the platform 
is movable. The plat- 
form itself consists essen- 
tially of a square frame- 
work of 2x8's or 2x6's 
for a small silo, of a rea- Fig. is. The clay block 




68 



SILOS: CONSTRUCTION AND SERVICE 




THE IOWA SILO 69 

sonably clear, stiff lumber. These are shown by the dotted 
line A. At the ends of these and flush with the bottom 
of each are securely nailed 2-inch pieces, B, of convenient 
length. Thus the bevel at the end extends through three 
2-inch pieces instead of one, and furnishes ample bearing upon 
the supporting pins, N. Instead of resting upon pins, the 
scaffold is sometimes hung by means of clevises and short 
chains. There should be at least 34 mc h of clearance all 
around the post, M . This framework is held together at the 
corners by an eye bolt passing through a 2x6, four feet long, 
approximately (L shown beneath at the right-hand corner) 
and by the outer planks above. The eye bolts should be 
made of % inch metal with a washer at each end. The diam- 
eter of the eye should be 1 inch inside. Four are required. 
A 2x8 or 2x6, F, is bolted at each end to blocks which in 
turn are nailed to the middle of the two opposite members, A. 
Upon this framework is placed a 2x10, indicated by (r, lying 
flat across the center of F and the two members, A. - Extend- 
ing at right angles from G and lengthwise but not central 
upon F are two 2xlO's, indicated by H. A block is nailed 
under the longer 2x10 not supported by F, and nailed to the 
inner end of these timbers, H, are blocks which extend two 
inches under G. By placing these blocks on each side of F, 
it is not necessary to nail H to F. It is highly desirable in a 
scaffold which must be used repeatedly that no nails should 
be drawn when taking it apart. Upon the corners of and 
diagonally to this frame are laid, inside of D, two widths of 
2x12 planks, lettered /; and connecting the ends of these and 
resting upon the ends of G and H are three 1x12 boards, five 
feet long, lettered J, beveled at the corners to fit the circle; 
also five 1x12 boards, lettered K, which are not beveled. 
The four 1x12 boards, lettered R, complete the upper part of 
the platform. 



70 



SILOS: CONSTRUCTION AND SERVICE 



If strong 1-inch hardwood lumber is at hand, it may be 
substituted for the 2-inch upper foot planks shown in the 
drawing. In fact, this plan may often be changed to suit 
the materials at hand, but in case all new materials are to be 
bought, the plan shown will be found to give general satis- 




Fig. 20. A scaffold for the Iowa silo. 



faction since all parts, having been used repeatedly, are 
known to be sufficiently strong. Four upright posts, M, 
secured to the wall at points approximately equally spaced, 
support the scaffold platform by means of %-inch round 



THE IOWA SILO 71 

steel pins 16 inches long, N, extending through 1-inch holes 
in the uprights. Eight of these are required, as one set 
should not be removed from a lower hole until the other pins 
are placed to support the scaffold in case any of the hoisting 
parts should break. As already noted devices and short 
chains may be used to suspend the scaffold instead of support- 
ing it from below. 

Each upright consists at first of a 2x6 eight feet long and a 
2x6 sixteen feet long screwed together with three 2^-inch No. 
14 or No. 16 flat-headed screws. It is necessary to use flat- 
headed screws in order that the head will countersink itself 
into the wood, thus not interfering with the raising of the 
scaffold platform. One of the bottom members of the up- 
right is 8 feet long and the other 16 feet long in order that the 
post may be added to as needed by simply screwing 16-foot 
2x6's on alternate sides. These upright posts are secured to 
the wall by means of light wires, P, which are placed about 
3 feet apart vertically. Every alternate time the scaffold is 
moved, 2-inch blocks, 0, should be placed snugly between 
the post and the wall and nailed to the wall. This places the 
post about three inches from the wall. Then it should be 
toenailed to the block, and the wires passing through the wall 
drawn tight. This holds the scaffold support rigid in all 
directions and enables the builder to keep them plumb. The 
distance between the holes in the upright will depend upon 
the kind of hoisting apparatus used, but usually 18 inches is 
most convenient. The most convenient device for raising 
the scaffold are ^-inch triple blocks. 

METHOD OF BUILDING 

The Guide Device. It is essentially important, for the 
sake of appearance, preservation of silage, and strength of 
wall that the silo be circular and plumb. It is highly desir- 



72 



SILOS: CONSTRUCTION AND SERVICE 



able that the guide be simple, easily used, and in the way as 
little as possible when not in use. A common board about 6 
feet long and cut to proper curvature also aids in getting a 
good, smooth, round wall. It is of course possible to build 
a circular wall by starting the circle, then using the plumb at 
intervals on the wall. However, the guide devised has been 




Nail to scaffold 
LTVumb line. 

GUIDE. 

for laying wall plumb and to true circle. 
Fig. 21. A guide device used in constructing the wall. 



found better for this purpose by men who have tried both 
ways. It is also advantageous, since, by means of ifc, the 
owner of the silo may in a very few minutes detect any 
faulty shape of wall. It is merely necessary to determine the 
proper position of the center-pipe by means of the plumb-bob; 



THE IOWA SILO 73 

then follow the end of the guide around the wall. All blocks 
should be within less than J^ or % inch of the guide, and even 
these variations should be gradual so as not to form shoulders 
in the wall. 

The device is shown in Fig. 21. A piece of 1-inch, or 
larger, straight gas pipe, indicated by A, 7 or 8 feet long may 
be secured as a center about which to revolve a light arm, B. 
The outer extremities of this arm, X, are hinged, in order that 
it may not interfere with walking around the scaffold. Also, 
when not in use, C may be placed in the position shown in the 
figure. It is not necessary to use the guide for each block, 
but it is convenient for determining whether or not the blocks 
are properly placed by means of this guide, before the mortar 
joints are pointed. 

The stand, D, is made of 2x4's or any convenient lumber 
by means of which the gas pipe may be held in a vertical 
position in the center of the scaffold. The collar and set 
screw, E, are used to raise the revolving arm to a level with 
the top of the course being laid. The upright, F, and two 
laths, G, serve the purpose of holding B in a horizontal posi- 
tion. 

It will be readily seen that this guide at once becomes use- 
ful not only in securing a circular wall but in making the 
course level, as the end of the arm, of course, revolves in a 
horizontal plane. This device has proven itself to be very 
convenient. In order that the pipe A may be in the center of 
the silo after each raising of the scaffold, it is only necessary 
to pass a plumb line from the center of the pipe through the 
board supporting the pipe to a nail in a stake in the bottom 
of the silo. With this as an indication of the proper location 
of the guide stand, the latter may be moved to place and 
nailed lightly. After raising the scaffold, the first thing to 
do, of course, is to drop wedges between scaffold and wall or 



74 SILOS: CONSTRUCTION AND SERVICE 

secure a scrap of lumber to the scaffold by one nail so the 
end, in turning about the nail, will strike the wall. 

Hoisting. Two general methods have been followed in 
hoisting materials to the scaffold. In one method a pulley is 
secured to the outer end of a 2x6 projecting over the wall and 
the material is hoisted by a horse. This method is found to 
interfere with the use of the guide of Fig. 22; therefore a der- 
rick after the plan of Fig. 22 has been devised. 

This derrick, 48 feet high, is built of three 2x6's 16 feet 
long, A, and six Ix6's 16 feet long, B, besides the pieces neces- 
sary for the arm at the top. As seen in the cross-sectional 
view in the center, the 1x6 V are nailed flatwise upon the 
edges of the 2x6's, thus forming an I beam. All of the mem- 
bers are so placed that no joints are closer than 5 feet 4 inches. 
Two short 1x6 struts, E, supports each end of the 1x6 pieces, 
C. Two No. 9 guy wires, F, are secured to the end of C 
toward the silo and fastened to stakes driven into the ground 
a considerable distance away from the bottom of the derrick. 
These prevent any side motion of the arm where the pulley 
is attached, while a third guy wire is fastened to the other 
end of C and secures the derrick in the other direction. This 
derrick has been thoroughly tried out with loads up to 400 
pounds. With the usual loads of less than 100 pounds it is 
entirely safe. The derrick itself is most easily raised by 
being constructed on the ground and raised after the guy 
wires, pulley and rope have been attached. 

DOOR FRAMES 

Reinforcement. The door frames are reinforced both 
vertically and horizontally with steel having a cross-sectional 
area equivalent to J4 square inch, or a square reinforcing 
bar % inch by y% inch. 



THE IOWA SILO 



75 



L ~^- _| 


r 

1 

i 




1 | 

1 |l 


3/oc* 




Fig. 22. An efficient derrick. 



76 



SILOS: CONSTRUCTION AND SERVICE 



Reinforcement 



The vertical reinforcing is bent as shown in Fig. 19, and 

wired in place, 
while crosstie 
steel is placed in 
the wall. The 
steel used for 
crosstie reinforc- 
ing is cut in 
lengths of 7 and 
11 feet and one of 
each length is 
placed in each 
half of the cross- 
tie extending, 
then into the wall 
on each side, ex- 
cept when ce- 
ment blocks are 
used. The No, 3 
wire used for 
horizontal rein- 
forcement of the 
wall is hooked 
around the verti- 
cal reinforce- 
ment of the door 
frame. 

The continu- 
ous doorway, 
shown in Fig. 23, 
consists essen- 
tially of a contin- 
uous door jamb 



Bolts for uooder : 
chute, or wall 
hes ir? each 
course if 
blocks arc 
used. 




Fig. 23. 



4"Droir? tile if needed- 
Elevation of the doorway. 



THE IOWA SILO 77 

on each side of the opening. These jambs are 
made of reinforced concrete and may be used with 
either clay or cement blocks. The horizontal reinforce- 
ments of the wall hook into the vertical reinforcements of the 
jamb. The jambs are tied together at intervals of 4 or 5 feet 
by steel within the crosstie block. This steel not only extends 
into the vertical jamb, but, in order to be more secure, 
extends several feet into the wall on either side of the jamb. 
As shown in Fig. 19, these crossties may be of steel and pro- 
tected from rust by being incased within the clay blocks 
filled with concrete or within the concrete alone. When the 
wall has been completed to the height at which it is desired to 
commence the door, two blocks are laid upon the wall across 
the doorway. These should be placed out far enough so that 
the door may be set down inside without touching the 
cross blocks. The shoulder or ledge thus formed should be 
1% inches wide. Through this crosstie, and extending into 
the hollow spaces in the blocks on either side of the door- 
way, should extend the reinforcing steel, unless cement 
blocks are used, in which case this is not practicable, and the 
reinforcing steel may simply be hooked into vertical steel. 
Upon this bottom crosstie must be placed the outer half of 
the continuous door form. Then the vertical reinforcement 
may be hooked to the lower crosstie and secured in a vertical 
position by tieing it to the form. Then the horizontal rein- 
forcement of the wall may be hooked to or placed inside of 
the vertical reinforcement. When the wall is completed to 
the top of this form, the inner portion of the form may be 
bolted to the outer. The form, crosstie, and the wall into 
which the steel projects should be then filled with moderately 
wet concrete made up of reasonably fine gravel. The second 
form may be secured to the first by means of 2x6's. The use 
of the second form is similar to the first. It will thus be seen 



78 



SILOS: CONSTRUCTION AND SERVICE 



T/3BLE 

or 




Fig. 24. Reinforcing 



that the door frame 
consists of inter- 
locking steel, thor- 
oughly set in ce- 
ment, which locks 
it, protects it from 
rust, and secures it 
in an air-tight man- 
ner to the hollow 
blocks of the wall 
by running into 
them a short dis- 
tance. 

Construction of 
the Door Forms. 
^ A detailed drawing 
4> of these forms, two 
of which are re- 
quired, is shown in 
Fig. 26. The up- 
per left-hand view 
shows the eleva- 
tion; the upper 
right-hand view 
shows the form as 
seen from the side, 
while the lower 
plan view presents 
the form as seen 
from above. 

One method of 
procedure in the 
construction of a 



THE IOWA SILO 



79 





Fig. 25. Concrete roof construction. 

set of these forms is as follows, each part being designated by 
letters and dimensions shown in the drawing. All surfaces 
coming in contact with cement should be dressed. First, two 
members, A, may be cut and pieces, lettered C, may be 
made from a 2x6. The edge nailed to B should be beveled so 
that the piece will be flared in order that it may be easily re- 



80 



SILOS: CONSTRUCTION AND SERVICE 



69 r "n 




Crosstie T 



2*- 

to Silo Wo 11 wth 
'x6" Dolf, IP, 
_f Mor-tor- Uoint" 




PLAN 



Flare to facilitate 
removal of -forms 
from concrete 



FORMS FOR CONTINUOUS 
CONCRETE DOOR FRAME 

Fig. 26. Door forms 

moved from the concrete. The outer edge of this member 
should be beveled about % m h in order to have it fit the 
circular wall against which it must be clamped. 

Two pieces, D, are required, and are cut from a 1-inch 
board. The corner of the piece where A and E join should be 
less than right angles, in order that each of the boards, E, may 



THE IOWA SILO 



81 



slant y% inch toward each other. This is also for conven- 
ience in removing the form from the concrete. The mem- 
ber E should be nailed back to D, as seen in Fig. 26. In 




Fig. 27. Perspective view of Iowa Silo. 



82 



: CONSTRUCTION AND SERVICE 



order that the crosstie blocks may be set into each side of the 
form, it is necessary to saw a notch in E. 

The length of these forms and the location of the notch 
cannot be determined accurately until the wall is built up to 
the top of the first form. Then the top of the form should 
be sawed so that it will be flush with the top of the crosstie 

when the top of the 
crosstie is level with the 
wall mortar joint. The 
notch will then be of a 
depth equal to the width 
of the block and wide 
enough to permit the 
crosstie block to rest 
loosely between the out- 
er and the inner form. 
The necessity of this 
will be readily seen in 
Fig. 27. The inside 
corners formed by B, C, 
and E should be filled 
with a three-cornered 
strip, which causes the 
concrete door frame to 
be chamfered, leaving 
smooth work. 

In the 2x6's, lettered 
F, Fig. 26, holes should be bored and J^-inch bolts used. 
Holes should also be bored in the end of members A and 
notches made as indicated. Holes should also be bored in A 
for a long bolt to extend through the inner portions of the form. 
The inner portion of the form is built as follows : Mem- 
bers, lettered G, are cut, and to them are nailed 10-inch 




Fig. 28. 



Wooden door for continuous door- 
way. 



THE IOWA SILO 83 

boards, H, which are placed 22 inches apart. The boards, H, 
should be beveled on the edge J4 mc h m two inches, to con- 
form to the curvature of the inner side of the silo wall. The 
edges need not be beveled thinner than % inch. The bev- 
eled strips, 7, are nailed to the end flush with the inner edge 
of H. Only a bevel of ^g inch is necessary here, as the lum- 
ber of the door extends horizontally, therefore there is little 
or no shrinking or swelling of the lumber in this direction. 
Holes must be bored in G to receive the bolts which hold the 
two parts of the form together. The cost of these forms need 
not exceed $12. 



CHAPTER IX 
SAFE STRENGTH OF MATERIALS 

The Factor of Safety. In the use of any material it is of 
course important to know how much force or pressure it will 
resist. In testing materials the actual weight necessary to 
strain, bend, break, or crush them is accurately determined. 
It is evident that the largest load which a given material will 
carry cannot safely be placed upon it. The fractional part 
of the greatest strength which it is considered advisable to 
use, determines what is generally spoken of as the " factor 
of safety." For instance, a steel rod one inch square, which 
of course has a cross-sectional area of one square inch, would 
probably support, without breaking, any load up to 60,000 
pounds, providing the load was suspended directly by it. 
But in case of silo building there should not be a force of more 
than 15,000 pounds placed upon it. This is called the safe 
strength of this material for this purpose, and is approxi- 
mately J4 of the ultimate or greatest strength. It is gener- 
ally spoken of as the use of a factor of safety of 4. If human 
life were more continuously depending upon this material, 
as is the case in residences, office buildings, or theatres, the 
factor of safety used would probably be 5 or 6. Thus the 
safe strength of this material would then be 10,000 to 12,000 
pounds per square inch. In masonry materials for silos the 
factor taken is not less than 8. 

Just what portion of its ultimate strength can be safely 
utilized, depends considerably upon the material and the seri- 
ousness of results in case a failure should occur. As already 



SAFE STRENGTH OF MATERIALS 



85 




Fig. 29. Elevation of water tank. 



86 SILOS: CONSTRUCTION AND SERVICE 

mentioned, where only property value is concerned, greater 
loads naturally are imposed than where human life is at stake. 
Causes of Failure. As to their strength, materials may 
fail in any one of three different ways, or by combinations of 
two or all three of them. 

First, pressure may be brought to bear which will crush the 
material; for instance, a block of wood may be put between 
the jaws of a vice and enough pressure brought to bear upon 
it to crush the fibers together. This is spoken of as failing 
in " compression." An example of this is a wall that is poorly 
built, of made too thin, and subjected to a greater weight 
than it will bear. In failing in this manner it simply means 
that the fibers or fine particles of the material have been 
crushed. 

Second, the force known as " tension" may cause failure. 
This is a force which tends to pull materials in two. The 
force tending to separate the ends of a straight piece of mate- 
rial may be sufficient actually to separate the fibers or parti- 
cles of the material. The intensity of this force is also given 
in pounds per square inch of cross section of the material. 

Third, a force known as shear may cause failure. As the 
name infers, portions of the material which fail in this respect 
are simply forced past each other sidewise. An example of 
failure in this respect is the unequal settling of a foundation. 
This simply means that the foundation is more thoroughly 
supported in one place than in another, and the rigidity of the 
material is not sufficient to support the pressure without 
breaking. Another illustration of this method of failure is 
in case of blocks pushed out of the wall, the shear occurring 
between the mortar and the block, causing the mortar to 
slide upon the block. The intensity of this force is generally 
spoken of as so many pounds per square inch, and indicates 



SAFE STRENGTH OF MATERIALS 



87 



bars 

Jo Ja</ 7/7 mor- 
Sca/e. /'= 




'Fig. 30. Detail of water tank. 



88 



SILOS: CONSTRUCTION AND SERVICE 



on fo 
base. ofl5//o - 

ib/aced '//? m&icf/ case 




Fig. 31. Further detail of water tank. 

the result obtained by dividing the square inches of fractured 
area of the material into the pounds of force required to frac- 
ture the material. 



SAFE STRENGTH OF MATERIALS 



In bending, there is a combination of all three of these 
forces. As an illustration of this take a green twig, cut it off 
square and bend it near the cut end. It results in the crush- 
ing of the fibers on the inner part of the curve, the failure by 
tension of the fibers on the outer part of the curve, and often 
that the portion of the stick between the bend and the end is 
split, indicating that the endwise compression on the inner 
side of the curve and the tension on the outer part of the curve 
have been so great, pulling in opposite directions, that the 
material of the twig shears through the heart. 

In this connection it is interesting to notice the impor- 
tance of the depth of a beam. For instance, an increase in 
the depth of a beam increases its stiffness more rapidly than 
the amount of material is increased. In fact, the ability to 
support a load increases as the square of the proportional in- 
crease in the depth of the material. That is, a 2x8 will sup- 
port 4 times as much as a 2x4, but contains only twice as 
much material. 

Safe Strength of Materials. The following table will 
show the safe strength of several materials: 

Table III. Safe strength of materials. 



Material 


Tension 
Lbs. per sq. in. 


Compression 
Lbs. per sq. in. 


Shear 
Lbs. per sq. in. 


Pine, G. yellow 


2000 






Pine, White 


1400 






California redwood .... 


800 






Douglas fir 


1800 






Hollow clay blocks 




80 




Brick 




200 




Mortar 




250 


60 


Concrete 
Reinforcing bars 


15 666 


200 


50 
7-10 000 











A No. 3 bright Bessemer steel wire will safely stand 1000 pounds in 
tension. 



90 SILOS: CONSTRUCTION AND SERVICE 

In the use of any material the possibility of destruction in 
time, by natural agencies, such as decay or corrosion, should 
be considered. The probable length of life of all parts should 
be taken into consideration, and that which will probably 
give out first should be planned with the largest factor of 
safety. Thus in building a structure of any kind it should be 
built so that each part will last as nearly as possible the same 
length of time as every other, and when it does submit to the 
agencies of time it should, like the "One-Horse Shay," all fail 
in a day. 

Splicing and Welding. The method of splicing materials 
should receive careful attention in order to make them as 
strong as other parts. Pieces of steel in concrete or mortar 
should hook into each other if the steel is smooth. The hooks 
should, of course, be thoroughly imbedded in the masonry. 
If twisted, corrugated, or other special reinforcing material is 
used, the ends should extend past each other a distance equal 
to at least 18 diameters of the material. Welding should be 
avoided where possible, as in general it is difficult to make sure 
that a forge weld is perfect. 

However, in cases of anchor rods, eye bolts, or similar 
parts, the hooks or eyes should, if possible, be welded, because 
the strength would then depend not only upon the stiffness of 
the material in the hook or eye, but also upon the strength of 
the weld. Hooked portions of any material should be 
welded unless the steel is held firmly by being imbedded in 
masonry. 

SPECIFICATIONS FOR STEEL 

Ordinary steel rods or wires do very well for silo building, 
and can be depended upon to withstand a pull of about 12,000 
pounds per square inch. Where steel is bought especially for 
this purpose it is best to buy reasonably high-carbon steel or 



SAFE STRENGTH OF MATERIALS 91 

hard wire. It is usually safe simply to specify bright Bes- 
semer or hard open-hearth steel wire. This will ordinarily be 
safe at 16,000 pounds per square inch. In other words, the 
No. 3 wire, which is a convenient size for silo work, will 
safely withstand a pull of about 1000 to 1200 pounds. For 
reinforcing rods to be used at the door frame, or for other 
general reinforcing work, corrugated or twisted bars will be 
found best; or, if smooth rods are used, they should be 
hooked at the ends so that they will not slip. 

CONCRETE MIXTURES 

The proper proportion for mixing material composing 
concrete will depend upon the kind of material used and the 
strength required by the service to which the concrete will be 
put. Concrete of the strength given in Table III is made by 
mixing 1 part cement with 2J/ parts of sand and 5 parts of 
crushed stone, or by mixing 1 part cement with 5 parts of 
bank gravel which, if sifted out, would give 1 part sand to 2 
parts stone. 

The theory is that the particles of cement should thor- 
oughly coat all of the particles of sand and stone, and at the 
same time fill in all spaces between the particles of sand and 
gravel which are not already occupied by smaller particles. 

It will be readily seen that if only sand and cement were 
mixed, it would be necessary, in order to get the same strength 
as before, to mix 1 part of cement with 2% parts of sand, thus 
giving only YT, the quantity of concrete otherwise obtained. 
This indicates the importance of knowing the grade of gravel 
or other aggregate. 

Testing the Concrete. It is easy to determine, in a prac- 
tical way, the amount of cement to make a dense concrete 
from any quality of aggregate that is available. A represen- 



92 SILOS: CONSTRUCTION AND SERVICE 

tative sample of the moist aggregate should be measured and 
the quantity of water determined which is required to fill to 
the surface of the aggregate. The proportion that this 
quantity of water, plus 10 per cent, is to the quantity of 
aggregate, is the proportion of cement to the aggregate which 
is required to make a dense concrete. 

Tamping. From this discussion it is easy to see why 
concrete should be tamped, or, more properly speaking, 
vibrated, as any motion of the mass will cause the finer parti- 
cles to settle more closely into the spaces between the larger 
particles. In all silo work a very dense concrete should be 
used. In order to remove forms promptly it is also very 
desirable to have a mixture rich enough to set quickly. This 
is especially true of the concrete used in the roof, 

The presence of clay or dirt prevents the union of the 
cement and the particles of sand and gravel. Small quanti- 
ties of dirt are usually present in bank gravel, but should not 
be more than 10 per cent. It is a simple matter to determine 
the quantity of dirt in gravel by simply washing a measured 
portion of the material. The wash water should be set aside 
to settle, and the quantity of dirt settling out should be meas- 
ured. The proportion of this to the quantity of gravel is 
determined. 

Storing Cement. It seems almost needless to say that 
cement should be very carefully stored in a dry place. Any 
cement having hard lumps distributed through it should not 
be used. Aside from what has been given, little or no testing 
seems advisable on the average job. 

If there is any question as to the quality of the cement, a 
trial sample may be mixed in the proper proportions with the 
gravel and allowed to stand a few days before the main 



SAFE STRENGTH OF MATERIALS 93 

quantity is to be used. If it sets up quickly it is, in all proba- 
bility, a safe cement to use. 

MORTAR 

Working Quality. In the mixing of mortar it is very 
important to get a mortar that will be conveniently plastic 
under the trowel. A good mortar is usually spoken of as 
tough. A sand and cement mortar is not tough, but very 
short. In order to improve the working qualities of such a 
mortar it is necessary to use some lime with the cement. 

Proportions. The proportion of 1 part of cement to 2 or 
2}/2 parts of sand and % P ai> t or 1 part of lime putty (slaked 
lime) , will result in a very good mortar. A good mortar saves 
time and sets up rapidly enough to permit the building of a 
considerable height of wall each day. 

CLAY BLOCKS 

Vitrified Brick. Brick clay is made up of two classes of 
materials, one which melts at a temperature within the kiln, 
and the other a nonfusible substance which does not melt but 
holds the brick in shape. The flux or fusible material, in 
melting, fills the pores between the other particles of clay and 
melts out over the surface, giving it a glassy appearance, that 
is, what is known as vitrified brick. If either the shale clay 
or surface clay tile have these materials properly propor- 
tioned, the result of thorough burning will be very dense or 
vitrified brick. 

The modern kiln is so arranged that the fire passes up the 
side of the wall and down among the brick or other material 
to be burned, so that the highest temperature occurs in the 
top of the kiln, and the most thorough burning occurs there. 
So even though the clay is right, only that portion located 
in the top portion of the kiln is right for silo construction. 



94 SILOS: CONSTRUCTION AND SERVICE 

Blocks for Silos. In silo construction we have two 
reasons for specifying hard-burned brick; one is that it must 
not absorb a great amount of moisture from the silage; 
another is that if soft or porous brick are exposed to the 
weather they are not durable, as moisture freezing in the pores 
of the brick expands and causes the block to disintegrate. 
This has been noticed by every one in the case of soft drain 
tile which have been allowed to lie in a slough over winter. 

In order to make sure that brick or clay blocks are right 
for silos it is necessary to buy only such brick or blocks as will 
absorb an average of 5 per cent or less of their weight of 
moisture. No block should be used that absorbs over 8 per 
cent. If this quality is secured the result will be a good 
durable silo, if it is put together with other good material by 
a good workman. 

In addition to this, it should be specified that all blocks 
fit the circle within Y% of an inch. When ordering blocks it 
should be borne in mind that uniform color of blocks is quite 
desirable and greatly increases the appearance of the 
building. 

Absorption Test. A convenient method of determining 
the amount of water these products will absorb is either to 
take the blocks hot from the kiln or place them in an oven 
where they will have a temperature higher than boiling water 
continually for two days. Then they should be weighed and 
placed in water for a couple of hours or until they cease to 
increase in weight. The increase in weight divided by the 
dry weight gives the percentage of the absorption. 

This same test will indicate whether or not there are lime 
nodules in the clay. Sometimes pebbles of limestone occur in 
the clay, which, when the clay is burned, become quicklime, 
and this exerts a swelling force when it comes in contact with 
water. This force is such as to chip off or split the material. 



SAFE STRENGTH OF MATERIALS 95 

If the concrete absorbs more than 10 per cent of its weight of 
water it should be plastered or coated with asphalt in order 
that it will not draw too much moisture from the silage. 



CHAPTER X 
BUYING AND CONTRACTING OF SILOS 

When to Plan. The man who gets what he wants is the 
man who looks the farthest ahead. Ordinarily a man can as 
well decide in January as in August or September whether 
or not he can profitably use a silo, and he should do so. It is 
important, in buying or arranging for the building of any 
kind of silo, that plenty of time be allowed for its delivery 
and other fulfilment of the contract. This is a matter of 
importance to everyone concerned, in securing a better 
grade of material and workmanship. It gives the farmer 
time in which to return any inferior material in case such is 
delivered. Even though a certain grade of material is speci- 
fied, it is difficult to secure a second shipment in exchange for 
inferior material when it is not delivered until late in the 
season. 

In buying wood, the kind and grade of wood should be 
specified. The choice of the grades of lumber will usually 
depend upon the amount of money which can be invested. 
It is also important, with most kinds of wood, to specify that 
little or no sapwood shall be found in the lumber; that is, it 
should be very largely heartwood. It should always be 
agreed in writing that any lumber not coming up to the 
specifications shall be replaced, with no cost to the pur- 
chaser, and that delivery shall be made early enough in the 
season to give opportunity for this replacement. 



BUYING AND CONTRACTING 97 

CONTRACT 

THIS AGREEMENT made and entered into this 

day of 191 . . , by and between 

, County of , State of 

, hereinafter called the 

"owner," and of 

Town of , State of , 

called the "contractor." 

WITNESSETH: That in consideration of the sum of 

dollars to be paid the contractor by the 

owner as soon as work hereinafter contracted for has been 
completed, said contractor hereby agrees to erect and con- 
struct, or cause to be erected and constructed for the above 

named owner on his premises, to-wit, on , 

in County, State of , 

a silo of the type known as Said silo 

to be in size and constructed as 

follows, to-wit : 

The foundation shall extend below frost feet and 

shall be at least 16 inches wide at the bottom. The top of said 
foundation shall be at least one foot above the surface of the 
ground, foundation to be made of concrete, mixed by taking 
five parts sand and gravel and one part cement, said founda- 
tion to be sixteen inches wide at the bottom and high, 

and to be wide at the top. On top of 

said foundation a wall shall be con- 
structed of to be used from the footing 



98 5/7,05: CONSTRUCTION AND SERVICE 

to the top of silo. The silo wall is to be securely and prop- 
erly reinforced with steel. On one side of said silo a door 22 
inches wide in the clear is to be constructed, commencing 
near the bottom of said silo and extending to within about 
five feet of the top of the silo. On each side of said door 
opening from the bottom of the first opening and extending 
to the top of the last opening, door-jambs are to be built of 
concrete, made by mixing four parts sand and gravel and one 
part cement. In said door space are to be placed horizon- 
tally reinforced concrete crossties about every four feet. The 
silo is to be covered with concrete roof conical in shape, prop- 
erly reinforced, and an opening of convenient size is to be left 
therein for the filling of the silo. 



INDEX 



Absorption test, 94. 
Acidity in silage, 11. 
Air spaces in wall, 20. 



Bacteria in silage, 11. 
Blocks, construction, 94. 
Block silo, 35, 65. 
Brick silos, 37, 93. 
Buying and contracting 
silos, 96. 



of 



Capacity of round silos, 43. 

Cattle, amount of silage to 
feed, 44. 

Cement block silos, 35. 

Cement, storing, 92; tamping, 92; 
testing, 91; wash, 65. 

Chute, 50. 

Clay blocks, 93. 

Clay products silos, 35, 65. 

Compression, 86. 

Concrete mixtures. 91. 

Concrete silos, 32, 34; mono- 
lithic. 60. 

Continuous doors, 8, 25, 28, 76, 82' 

Contract for silos, 96. 

Corn for silage, time to cut, 11. 

Cost of silos, 41. 

Cresote for wood silos, 24. 

Cro=stie of block silos, 68, 77. 

Derrick, 75. 

Doors, details of, 48; hinge, 30; 
improvement, 8; independent, 
27; Indiana, 29; wooden, 82. 

Door forms, construction, 78, 80. 

Door frames, construction, 74; 
improvement, 8. 

Drainage of silos, 47. 



Early development, 7. 
Ensilage, poisoning from, 13; 

preservation of, 11. 
Excavating, 46. 



Factor of safety, 84. 

Failure, causes of, 86. 

Feeding silage, amount, 44. 

Fermentation of silage, 11. 

Fire exposure, 17. 

Floors, 51. 

Forage or mold poisoning, 13. 

causes, 13; prevention, 16; 

symptoms, 15. 
Forms, 60. 
Foundations, 46. 
Frame silos, 24. 
Frozen silage, 18. 



Guide for wall, 71. 
Curler silo, 25. 
Guying the silo, 28. 



Heat, how lost in silo, 18. 

Hinge door, 30. 

Hoisting, methods, 64, 74, 75. 



Independent door, 27. 

Indiana door, 29. 

Influence of material on silage, 21. 

Interlocking block silos, 38. 

Iowa silos, 65; building, 71; 
perspective view, 81; scaffold- 
ing, 67. 



Location for silo, 39. 



100 



IND'E'X 



Masonry silos, advantages, 31; 

development, 10; kinds, 32. 
Material for silos, influence of, 

21; safe strength of, 84. 
Mold, cause of in silage, 12. 
Mold poisoning, 13. 
Monolithic concrete silos, 60. 
Motar, 93. 

Painting wood silos, 23. 

Planning the silos, 39, 96. 

Pit, 7, 46. 

Plastered silos, 34. 

Plastering concrete silos, 64. 

Poisoning from silage, 13. 

Preservation of silage, 11; air 
spaces in walls, 20; frozen 
silage, 18; influence of materials, 
21 ; nature of process, 11 ; moldy 
silage, 13; settling, 17. 

Reinforcement, 60, 63; of door 

frames, 74. 

Reinforcement table, 78. 
Roof construction, 79. 
Roof plans, 49, 79. 
Round silo, development, 8. 

Safe strength of materials, 84. 
Scaffolding, for block silo, 67; 

stave silos, 52. 
Settling of silage, 17. 



Sheathing, 50. 

Sheep, amount of silage for, 44. 

Silage preservation, 11. 

Shear stress, 86. 

Size of silo, 43. 

Splicing, 90. 

Square silo, 8. 

Stave silo, 21, 27; erection, 52. 

Steel, 63, 90. 

Stone silos, 32, 33. 



Tamping concrete, 92. 
Tension, 86. 
Testing concrete, 91. 



Unandilla door, 28. 
Vitrified brick, 93. 

Wall, air spaces in, 20; construct- 
ing, for Iowa silos, 65 ; materials 
of, 17, 21; quality of silage at, 
11. 

Water tank on silo, 85, 87, 88. 

Welding, 90. 

Wisconsin silo, 8, 24. 

Wood for silos, 23, 96. 

Wood hoop silo, 25. 

Wood silos, 23. 



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