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PHYSICAL   TESTS   FOR   THE   BLAST-FURNACE,    ETC.     51 r                      i
trated in the next Chapter, shows the design of flask,               ,
mould board and patterns, with the improved 4t whirl               ,
gate," which the author designed in the year 1895 for               '
" running " round bars cast on end.    The method com-                ;
plete is one which the testing committee of the West-               !
ern   Foundry-men's   Association  has  used   with   the
greatest success in obtaining perfectly solid bars.     As                l((
ftirnacemen   advance  in  the work 'of  physical tests,
many may desire to take up questions which the single
cast bar will not permit of investigation, requiring bars
cast  double,  plans for which  are  cited in  the next               , '
Chapter.     Whether the exact plans presented in this               <,
paper be adopted or not, the principles upon which              , j
they are based cannot be ignored in the   attempt to
secure true physical tests at the furnace or foundr}-.                   f
As a supplement to. this Chapter, the author desires to again call attention to the importance of the adoption               i ,
by the engineering and foundry world of test bars of a size that can establish a fair relation to the chemical              |
analysis of iron, or accord with the commercial value              ''i
which usage has given to degrees in its strength.     By              f
a study of Chapter LXIX., page 528, it will be seen              ''
that we should not use a bar smaller than of one square              '
inch area.* A few are still adhering to the use of one-half inch square bars, claiming that they have value in giving a'' sensitive test.'' I would ask such, after having              I''
studied pages 454, 467 and 484, if they have not drawn              '1
the wrong conclusions, or if this does not truly mean              ip
that bars as small as one-half inch square or round are                1
so '' sensitive '' to variations in the 4 'temper '' or damp-              ,| |
ness of sands and degrees in fluidity of metal, as to              jj I
make them very erratic, and hence valueless to be used              \ j
for a comparative test in any one single grade of iron.               'j
to say nothing about their inability to denote degrees of                I
strength in the various grades used in general founding.               ! j(
* The American Foundry men's Association recommends that                  jjl
bars should not be smaller than one and one-half inches diameter.                  j !
vSee pages487 to 573-                                                                                       lh\s .............................................................    8,860     "                               \,