metal is to be strained the same as hereinafter specified for machinery operated by mechanical power under extraordinary conditions.

DETAILS OF MACHINERY.

OPERATING MACHINERY.

All gear-wheels are to be of cast steel with cut gears. To determine the size of any gear-wheel, the tooth-pressure on the pitch-circle is first to be found as follows:

For gears moved by mechanical power only,

where H.P. = horse-power to be transmitted by gear, v = velocity in feet per second at its pitch-circle, and P = tooth-pressure in pounds.

For gears moved by hand-power,

P = 120 NM

where N= number of men, M = multiple of lever over gear under consideration, and P = tooth-pressure.

Having thus determined the tooth-pressure, the pitch can be found by the following formula

for gears in which the face is equal to 2 1/2 times the pitch, where p = pitch, and P = total tooth-pressure.

This allows an extreme fibre-stress on the teeth of eight thousand (8,000) pounds per square inch, which is to be the standard intensity for all teeth under ordinary conditions of operation. Bevel-gears are to be considered as only three fourths (3/4) as strong as spur-gears of the same pitch and face. The use of bevel-gears with very thin teeth will not be allowed, even though they be of standard pattern; but special bevel-gears with thicker teeth than usual will have to be manufactured.