THE WIRE 179
It often happens that a wire will travel slowly to one side of the machine
ind cling there, in spite of the guide roll being fully set to bring it into its
>lace. This is more inclined to be at the back side than the fore side, because
he guide roll has to turn on the back side as a pivot, and therefore has less
:ontrol of the wire at that side. There is very- great danger in this situation,
ind a machineman has to be very much on the alert lest the wire turn suddenly
ind come over too quickly, doubling up its edges on the guide-bar spades.
3ut assuming that no further alteration of the guide roll is possible, and the
wire shows an inclination to go too far, then the suction may be partly shut
)ff the last box, or the air valve opened a little. Then the wire will return to
ts place with a run, which can be quickly checked by again putting on the full
;uction and squaring up the guide roll. This will seldom take place if the
;ension from die boxes to the nip is properly adjusted, but it must be clearly
inderstood that the coucher must not be used to control the wire.
It may happen that a wire will run very well with the sides at the nip not
equally tight, so long as the paper and suction are on it; but couching will be
anequal, because the tight side has the least weight on it* In this case, if the
nachine is shutting down and the wire runs empty for a few turns, the heavier-
weighted side may slacken so much more as to run through the nip in wrinkles,
when the wire is rendered entirely useless.
For this reason it is very inadvisable to run the wire empty for more than a
:urn or two to clean it off, unless the machineman is very sure that his coucher
weights are perfectly adjusted.
The level of the guide roll to the last suction box has a very important
bearing on the steady and trustworthy guiding of the wire. If the guide roll
is too low, the suction box will control the wire in spite of the roll. This is
shown by a wire running to one side and coming back with a dangerous run
when the suction is eased off. The guide roll may work very far forward to
send the wire back, or vice versa, and this introduces another complication which
makes matters worse. The roll being too far advanced—say at the front side—
and the wire tending to come to that side, the wire is thereby tightened up
between the box and the coucher. This in itself ensures the tendency of the
wire to come forward, since a wire will always run towards the side on which
the wire is tightest, between the box and the couch roll. The guide roll should
in all cases be just so much under the level of the last suction box as not to
interfere with the suction; & inch is quite sufficient Most of the machine-
man's uncertainty as to the guiding of his wire will be eliminated if this vital
point is attended to.
The Tube H0/k—The tube rolls have two functions: First, they support
the wire from the breast roll to the suction boxes, and form a table widi die