75 The gear train in Fig 724 shows the essential features th

7.5. The gear train in Fig. 7.24 shows the essential features the work drive for of a gear hobbing machine. Gear blank B and the worm gear 9 are on the same shaft and must rotate together. (a) the gear be driven clockwise, determine the hand of the hob A. (b) Determine the angular-velocity ratio to cut 72 teeth on the gear blank B. u an intermediate shaft

Solution

SOLUTION:-

(a) RIGHT HAND HOB-A WILL BE REQUIRED IF GEAR BLANK-B IS DRIVEN CLOCKWISE.

(b) > To cut 72 teeth on blank-B, gear-9 will complete one rotation (42 teeth) and worm gear-8 will rotate 42 times, which in turn indicates that gear-7 will rotate 42 times.

> At the same time hob-A will rotate 72 times for one rotation of blank-B. That is gear-2 will rotate 72 times. Gear-1 will rotate (30/16 x 72) = 135 times. Gear-4 which is driven by gear-3 will rotate 16/36 x 135 = 60 times. Gear-5 being on the same shaft as gear-4 will also rotate 60 times.

> So finally, w7 / w5 = 42 / 60 = 0.70 (ANSWER)