VITRIFIED BEICK PAVEMENTS FOR COUNTRY ROADS. 33 



The heads shall be not less than f inch nor more than f inch thick. In out- 

 line each head shall be a regular 14-sided polygon inscribed in a circle 28 1 

 inches in diameter. Each head shall be provided with flanges not less than 

 f inch thick 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 must be smooth and must 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 must be either ground or machined. The flanges shall be slotted on 

 the outer edge so as to provide for two f-inch bolts at each end of each stave, 

 said slots to be 11 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 § 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 

 conforming 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 f-inch cap 

 screws through the head from the outside. Whenever these head liners become 

 worn down i inch below their initial surface level at any point of their surface 

 they must 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 27£ 

 inches long and weighing 15.5 pounds per linear foot. The staves shall have 

 two holes \% 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 tk inch. 



The interior or flat side of each stave shall be protected by a liner f 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 Hnch 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 proportions 

 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. 



