SAMPLING AND TESTING HIGHWAY MATERIALS. 29 



separated by a partition. In event of some of the bricks being cracked or broken in 

 transit, the sample shall be disqualified if there are not remaining 10 sound undam- 

 aged bricks. 



(5) Storage and care of samples. — Samples shall be carefully handled to avoid 

 breakage or injury. They shall be kept in the dry so far as practicable. If wet 

 when received, or known to have been immersed or subjected to recent prolonged 

 wetting, they shall be dried for at least six hours in a temperature of 1.00° F. before 

 testing. 



THE CONSTRUCTION OF THE RATTLER. 



(6) General design. — The machine shall be of good mechanical construction, self- 

 contained, and shall conform to the following details of material and dimensions, and 

 shall consist of barrel, frame, and driving mechanism as herein described. 



(7) The barrel. — The barrel of the -machine shall be made up of the heads, head 

 liners, staves, and stave liners. 



The heads may be cast in one piece with the trunnions, which shall be 2| 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 2^-inch 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 of lost motion. The distance 

 from the end of the shaft or trunnion to the inside face of the head shall be 15f inches 

 in the head for the driving end of the rattler, and llf 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 be not less than three-fourths inch thick, nor more than seven-eighths 

 inch thick. In outline, each head shall be a regular 14-sided polygon inscribed in a 

 circle 28f inches in diameter. Each head shall be provided with flanges not less 

 than three-fourths of an inch thick and extending outward 2\ inches from the inside 

 face of the head to afford a means of fastening the staA r es. 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 machined. 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, said slots to 

 be thirteen-sixteenths of an inch wide and 2f inches center to center. Each slot 

 shall be provided with a recess for the bolt head, which shall act to prevent the turn- 

 ing of the same. Between each two slots there shall be a brace three-eighths of an 

 inch thick, extending down the outward side of the head not less than 2 inches. 



There shall be for each head a cast-iron head liner 1 inch in thickness and con- 

 forming to the outline of the head, but inscribed in a circle 28£ inches in diameter. 

 This head liner shall be fastened to the head by seven five-eighths-inch cap screws, 

 through the head from the outside. Whenever these head liners 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 head liners shall be 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 21\ inches 

 long and weighing 15.5 pounds per linear 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 If 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 of an inch. 



The interior or flat side of each stave shall be protected by a liner three-eighths of an 

 inch thick by 5J inches wide by 19| inches long. The liner shall consist of medium- 

 steel plate, and shall be riveted to the channel by three one-half-inch rivets, one of 



