16 
Transactions Texas Academy of Science. 
rattling chamber. Other machines may be used, varying in diameter 
from 26 to 30 inches, and in length from 18 to 24 inches; but if this 
is done, a record of it must be attached to the official report. Long 
rattlers must be cut up into sections of suitable length by the inser- 
tion of an iron diaphragm at the proper point. 
“2. Construction of the Machine: The barrel may be driven by 
trunnions at one or both ends, or by rollers underneath, but in no 
case shall a shaft pass through the rattler chamber. The cross sec- 
tion of the barrel shall be a regular polygon having fourteen sides. 
The heads shall be composed of gray cast-iron, not chilled or case- 
hardened. The staves shall preferably be composed of steel plates, 
as cast iron peans and ultimately breaks under the wearing action on 
the inside. There shall be a space of one-fourth of an inch between 
The staves for the escape of the dust and small pieces of waste. Other 
machines may be used having from 12 to 16 staves, with openings 
from one-eighth to three-eighths of an inch between staves, but if 
this is done a record of it must be attached to the official report of 
the test. 
“3. Composition of the Charge: All tests must be executed on 
^charges containing but one make of paving material at a time. The 
charge shall be composed of bricks to be tested and iron abrasive 
material. The brick charge shall consist of that number of whole 
bricks or blocks whose combined volume most nearly amounts to 
1000 cubic inches, or eigth per cent of the cubical contents of the 
rattling chamber. (Nine, ten or eleven are the number required for 
the ordinary sizes on the market.) The abrasive charge shall consist 
of 300 pounds of shot made of ordinary machinery cast iron. This 
shot shall be of two sizes, as described below, and the shot charge 
shall be composed of one fourth (75 pounds) of the larger size and 
three-fourth (225 pounds) of the smaller size. 
“4. Size of Shot . The larger size shall weigh 7 1-2 pounds about 
and be about 2 1-2 inches square and 4 1-2 inches long, having edges 
rounded to a radius of about 1-4 inch. The smaller size shall be 1 1-2 
inch cubes, weighing about seven-eighths of a pound each, with square 
corners and edges. The individual shot shall be replaced by new ones 
when they have lost one-tenth of their original weight.* 
“5. Revolutions of the Charge: The number of revolutions of 
the standard test shall be 1800, and the speed of rotation shall not 
fall below 28 nor exceed 30 per minute. The belt power shall be 
sufficient to rotate the rattler at the same speed whether charged or 
empty. 
*It has been proposed to use chilled steel shot, which have practically no wear, 
and thereby save the expense of replacing and frequently re-weighing the cast- 
iron shot. 
