VITRIFIED BRICK 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| 
inches in diameter. Each head shall be provided with flanges not less than 
| 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 \% 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 \ 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 11\ 
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 i 5 e 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 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. 
