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Old Apr 8th 2012, 01:26 PM   #1
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Join Date: Aug 2011
Posts: 7
Spur Gearing problem

Hi got a question and have no idea where to start it

A power tool will need a reduction gearbox giving two possible speeds. The input is from a 500W electric motor with a 3000 rpm speed. The two output speeds are about 950 rpm for the slow speed or at about 1900 rpm for the fast speed. I wish to use spur gearing. I have done a quick calculation on a spacing of about 25mm and this suggests that a spacing of exactly 27 mm will give me answers that give this result within the tolerances that I am happy with, using a module of 1. How many teeth are there on each gear and what are the precise output speeds?

Givens

Input Power = 500W @3000 rpm
Required Out speeds = ~ 950 rpm & ~ 1900 rpm
Spur Gearing 27mm spacing (? not sure what the spacing means)
Module = of 1

Unknowns
No. of teeth and exact speeds (rpm) of each gear.

Answer 13 41 low 951 rpm 21 33 high 1909 rpm

I know that I may have to change the rpm to rad/s and am able to do that. I also know how to calculate the torque produced from the input, but am pretty much lost after that.

I would also love to know what calculations may have been used where it says "quick calculation", but that just due to curiosity.

Thank you for any help in advance.
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