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RACK AND PINION EXAMINATION ANSWER

V. Ryan 2003

 

4. When the motor is turned on it rotates at 240 rev/min (rpm)

(i) How many times will gear X turn in one minute?

 

 

If gear Z rotates once then gear Y moves 3 times
 

 
As gear Y has more teeth than gear Z then rpm is reduced
 

 
Gear Y = 80 rpm
 
Gears X and Y are combined to form a compound gear. Therefore, gear X rotates at the same speed as Y
 

Gear X = 80 rpm

 
(ii) How far does the platform travel in one minute?
 
Gear X has 13 teeth. This number is multiplied by the 80 rpm giving the distanced moved in terms of number of teeth.

13 x 80 = 1040 teeth
 
The rack moves the same number of teeth as it meshes with gear X.
 
To convert this distance into millimetres
1040 (teeth) x 4mm (the pitch or distance between the teeth)
= 4160mm
 

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