36 BULLETIN 373, U. S. DEPARTMENT OF AGRICULTURE. 
hard machinery iron and should contain not less than 1 per cent of combined 
carbon. 
The staves shall be made of 6-inch medium steel structural channels 27£ 
inches long and weighing 15.5 pounds per linear foot. The staves shall have 
two holes it inch in diameter, drilled in each end, the center line of the holes 
being 1 inch from the end and If inches either way from the longitudinal center 
line. The spaces between the staves shall be as uniform as practicable, but 
must not exceed ife inch. 
The interior or flat side of each stave shall be protected by a liner | inch 
thick by 5£ inches wide by 19f inches long. The liner shall consist of medium 
steel plate and shall be riveted to the channel by three £-inch rivets, one of 
which shall be on the center line both ways and the other two on the longitu- 
dinal center line and spaced 7 inches from the center each way. The rivet 
holes shall be countersunk on the face of the liner and the rivets shall be 
driven hot and chipped off flush with the surface of the liners. These liners 
shall be inspected from time to time, and if found loose shall be at once re- 
riveted. 
Any test at the expiration of which a stave liner is found detached from the 
stave or seriously out of position shall be rejected. When a new rattler in 
which a complete set of new staves is furnished is first put into operation, it 
shall be charged with 400 pounds of shot of the same sizes, and in the same pro- 
portions as provided in Item 9, and shall then be run for 18,000 revolutions at 
the usual prescribed rate of speed. The shot shall then be removed and a 
standard shot charge inserted, after which the rattler may be charged with 
brick for a test. 
No stave shall be used for more than 70 consecutive tests without renewing 
its lining. Two of the 14 staves shall be removed and relined at a time, in such 
a way that of each pair one falls upon one side of the barrel and the other upon 
the opposite side, and also so that the staves changed shall be consecutive, but 
not contiguous ; for example, 1 and 8, 3 and 10, 5 and 12, 7 and 14, 2 and 9, 4 
and 11, 6 and 13, etc., to the end that the interior of the barrel at all times 
shall present the same relative condition of repair. The changes in the staves 
should be made at the time when the shot charges are being corrected, and the 
record must show the number of charges run since the last pair of newly lined 
staves was placed in position. 
The staves when bolted to the heads shall form a barrel 20 inches long, inside 
measurement, between head liners. The liners of the staves must be so placed 
as to drop between the head liners. The staves shall be bolted tightly to the 
heads by four f-inch bolts, and each bolt shall be provided with a lock nut, and 
shall be inspected at not less frequent intervals than every fifth test, and all 
nuts shall be kept tight. A record shall be made after each inspection showing 
in what condition the bolts were found. 
Item. 8. The frame and driving mechanism. — The barrel shall be mounted on 
a cast-iron frame of sufficient strength and rigidity to support it without undue 
vibration. It shall rest on a rigid foundation with or without the interposition 
of wooden plates and shall be fastened thereto by bolts at not less than four 
points. 
It shall be driven by gearing whose ratio of driver to driven is not less than 
one to four. The countershaft upon which the driving pinion is mounted shall 
not be less than lit inches in diameter, with bearings not less than 6 inches in 
length. If a belt drive is used, the pulley shall not be less than 18 inches in 
diameter and 6£ inches in face. A belt at least 6 inches in width, properly 
adjusted to avoid unnecessary slipping, should be used. 
