# Gearing Question

#1
08-30-02, 04:57 AM
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A pinion with 21 teeth engages a gear...

A pinion with 21 teeth engages a gear rack having 14 teeth per inch. When the rack has moved 1 inch the pinion will have rotated through:
a) 120 degrees
b) 180 degrees
c) 240 degrees
d) 360 drgrees

This is homework and we are allowed to seek out the answers any way we can! Thanks!

#2
08-30-02, 05:02 AM
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Join Date: Feb 2001
Location: SW Fla USA
Posts: 11,566
240. If the rack moves one inch that means it moved 14 teeth.

14 teeth would be 2/3 of the number of teeth on the pinion.

2/3 of a revolution (360 deg) would be 240 deg.

#3
08-30-02, 05:10 AM
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the_tow_guy Thanks..1 more?

If a main gear having 45 teeth is revolving at 360 RPM, then the speed of a 15 tooth pinion driving this gear is?
a) 120 RPM
b) 180 RPM
c) 1080 RPM
d) 1800 RPM

Sorry I'm so lost this is all new to me!

#4
09-02-02, 02:49 PM
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Join Date: Feb 2001
Location: SW Fla USA
Posts: 11,566
Sorry about slow reply; gone for weekend.

1080 rpm. The gear ratio would be 3:1. It takes 3 revolutions of the pinion to make 1 rotation of the main gear. In any gear arrangement, the smaller of the gears is always turning faster.

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