What is the purpose of an idler gear used in gear trains?

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ALP CBT 2 Fitter Previous Paper: Held on 21 Jan 2019 Shift 1
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  1. To increase the contact area of pulley and belt
  2. To obtain minimum center distance between driving and driven shaft
  3. To obtain maximum center distance between driving and driven shaft
  4. To have required direction of rotation

Answer (Detailed Solution Below)

Option 4 : To have required direction of rotation
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Detailed Solution

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Explanation:

Sometimes, two or more gears are made to mesh with each other to transmit power from one shaft to another. Such a combination is called a gear train.

When there is only one gear on each shaft, it is known as a simple gear train.

Since gear 1 drives gear 2, therefore gear 1 is called the driver and gear 2 is called the driven or follower.

The purpose of an idler gear used in gear trains is to have the required direction of rotation at the output shaft.

  • It may be noted that when the number of intermediate gears (idler gear) is odd, the motion of both the gears (i.e. driver and driven or follower) is like.
  • But if the number of intermediate gears is even, the motion of the driven or follower will be in the opposite direction of the driver.

gear train1

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