We may now convert the power at each pulley perimeter or circumference into inch pounds by multiplying the respective lbs. by the distance moved through in inches, as per the following table:

Distance moved.
Lbs. Inches. Inch lbs. of power.
Weight at b 10 × 32.2 = 322
„„c 5 × 64.4=322
„„d 5 × 64.4=322
„„e 21⁄2 × 128.8=322

If we require to find the power in foot lbs. per minute, we divide by 12 (because there are 12 inches in a foot), thus 322 inch lbs. ÷ 12 = 26.83 foot lbs. per minute.

Now suppose that b was moved by a belt, with a pull of 10 lbs. at its perimeter, and made 100 revolutions in a minute instead of one, then the pull at the perimeters of c, d, and e would remain the same, but the motion would be 100 times as great, and the work done would therefore be increased one hundred fold. It will be apparent, then, that the time is as important an element as the weight.

The velocity and power of gear wheels are calculated at the pitch circle.

Fig. 3355.

Now suppose the gear a in [Fig. 3355] has 30, gear b 60, gear c 10 and gear e 80 teeth, and that 5 lbs. be applied at the pitch circle of a; to find what this 5 lbs. would become at the pitch circle of e, we multiply it by the number of teeth in b and divide it by the number of teeth in c, thus:

Lbs.
At pitch of circlea 5
Number of teeth in b 60
Number of teeth in c10 ) 300
30
Answer, 30 lbs. at the pitch circle of e.