Six gears are mounted on four shafts as shown in gear train

Six gears are mounted on four shafts as shown in gear train below, determine Speed ratio of complete gear train For perfect motion of gear train shown in Figure the module of all gears must be same (True/False) To get the same speed ratio at shaft number 2 (as calculated in part a), what should be number of teeth on gear number 3 Which gear will be idle gear; which is not contributing in speed ratio, if gear number 5 is removed

Solution

N2 = 750 rpm

T3/T2 = N2/N3

84/14 = 750/N3

N3=750/6 =125 rpm = N4

N4/N5 = T5/T4

125/N5 = 84/14 = 6

N5=125/6 = 20.8333 rpm = N6

N6/N7 = T7/T6

20.8333/N7 = 70/14 = 5

N7 = 20.8333/5 = 4.1667 rpm

Speed ratio of gear train = N2/N7 = 750/4.1667 = 180 - ans (a)

For perfect motion of gear train module of all gears must be same - True ans (b)

To get same speed ratio at shaft 2 as calculated in part a,

T3/T2 = 180 = T3/14

T3 = 180 X 14 = 2520 - ans (c)

If gear 5 is removed, gear 4 does not mesh with any gear and it just rotates freely with the speed of shaft 2 and gear 3. So gear 4 does not contribute in any speed ratio. Thus gear 4 will become idle gear. - ans (d)