Exercise 30: Wall Box.—Draw the views of the wall box shown in fig. 30, and also a sectional plan; the plane of section to pass through the box a little above the joggles for the pillow block. Scale 3 inches to a foot.
Fig. 29.
Fig. 30.
VIII. PULLEYS.
Velocity Ratio in Belt Gearing.—Let two pulleys A and B be connected by a belt, and let their diameters be D1 and D2; and let their speeds, in revolutions per minute, be N1 and N2 respectively. If there is no slipping, the speeds of the rims of the pulleys will be the same as that of the belt, and will therefore be equal. Now the speed of the rim of A is evidently = D1 × 3·1416 × N1; while the speed of the rim of B is = D2 × 3·1416 × N2. Hence D1 × 3·1416 × N1 = D2 × 3·1416 × N2, and therefore