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N2 Fitting and Machining Theory|Hands-On! 143 No. of teeth on driver × revs of driver = no. of teeth on driven × revs of driven.
D A B
Figure 12.5 Simple gear train. Gears turn in opposite direction
Compound gears A gear system consists of more than two gears (more than one pair of gears engaged), where the intermediate shaſt has two gears fixed to it. It is called a compound gear train.
Te velocity ratio between gears 1 and 2 (meshing) is the same so for gears 3 and 4. Te rotational frequency (revolutions) for gears 2 and 3 are the same as they are secured (fitted) to a common shaſt. Because gear 2 is bigger than gear 1, the first reduction will take place. Te second reduction occurs between gear 3 and gear 4.
input first reduction + + second reduction Figure 12.6 Compound gear train
If more than two gears are used, the formula can be expanded as follows: NA × TA = NB × TB = Nc × Tc where TA = number of teeth on gear A NA = rotational frequency (revolutions) of gear A TB = number of teeth on gear B NB = rotational frequency (revolutions) of gear B