42 DEPARTMENT BULLETIN 1216, IT. S. DEPT. OF AGRICULTUPvE 
(&) A steel bearing piece one-half inch square and of a length equal to the 
full width of the specimen shall be placed between the upper knife edge and the 
specimen. 
(c) The speed of travel of the head of the testing machine, during the 
application of the load, shall not be more than 0.05 inch per minute. 
12. The modulus of rupture, R, in pounds per square inch shall be reported 
as calculated from the following formula : 
K 2bd 2 
where 
W=the total load in pounds at which the brick failed, 
/=the distance between the supports in inches, 
&=the width of the brick in inches, and 
d—the depth of the brick in inches. 
RATTLER TEST 
APPARATUS 
13. The machine used in the rattler test shall be of good mechanical con- 
struction, self-contained, and shall conform to the following details of material 
and dimensions, and shall consist of barrel, frame, and driving mechanism 
as described in sections 14 to 18. In Figure 14 is illustrated a rattler which 
will meet the requirements specified, and to which reference should be made. 
14. The barrel of the machine shall consist of the heads, headliners, staves, 
and stave liners conforming to the following requirements : 
(a) Heads. — The heads may be cast in one piece with the trunnions which 
shall be 2tV inches in diameter, and shall have a bearing 6 inches in length ; 
or they may be cast with heavy hubs, which shall be bored out for 2iVinch 
shafts and shall be key seated for two keys, each one-half by three-eighths inch 
and spaced 90° apart. The shaft shall be a snug fit and when keyed shall be 
entirely free from lost motion. The distance from the end of the shaft or 
trunnion to the inside face of the head shall be 15% inches in the head for 
the driving end of the rattler and 11% inches for the other head, and the 
distance from the face of the hubs to the inside face of the heads shall be 
5% inches. 
The heads shall not be less than three-fourths nor more than seven-eighths 
inch in thickness. In outline, each head shall be a regular 14-sided polygon in- 
scribed in a circle 28% inches in diameter. Each head shall be provided with 
flanges not less than three-fourths inch in thickness and extending outward 2% 
inches from the inside face of the head to afford a means of fastening the 
staves. The surface of the flanges of the head shall be smooth and give a true 
and uniform bearing for the staves. To secure the desired true and uniform 
bearing, the surfaces of the flanges of the head shall be either ground or ma- 
chined. The flanges shall be slotted on the outer edge, so as to provide for two 
three-fourths-inch bolts at each end of each stave, the slots to be thirteen-six- 
leenths inch in width and 2% inches center to center. Each slot shall be pro- 
vided with a recess for the bolt head, which shall act to prevent the turning of 
the same. Between each two slots there shall be a brace three-eighths inch in 
thickness extending down the outward side of the head not less than 2 inches. 
(&) Headliners. — There shall be for each head a cast-iron headliner, 1 inch in 
thickness and conforming to the outline of the head, but inscribed in a circle 
28% inches in diameter. This headliner shall be fastened to the head by seven 
five-eighths-inch cap screws, through the head from the outside. Whenever 
those headliners become worn down one-half inch below their initial surface 
level at any point of their surface, they shall be replaced with new ones. The 
metal of these headliners shall be hard machinery iron and should contain 
not less than 1 per cent of combined carbon. 
(c) Staves. — The staves shall be made of 6-inch medium-carbon steel structural 
channels 27 1 / 4 inches in length and weighing 15.5 pounds per lineal foot. The 
staves shall have two holes thirteen-sixteenths inch in diameter drilled in each 
end, the center line of the holes being 1 inch from the end and 1% inches either 
way from the longitudinal center line. The spaces between the staves shall be 
as uniform as practicable, but shall not exceed five-sixteenths inch. 
(d) Staveliners. — The interior or flat side of each stave shall be protected by 
a liner three-eighths inch thick by 5% inches wide by 19% inches long. The 
