Gears - how much loss in general
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Posted by: Beeman ®

02/28/2006, 15:16:05
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Hi all,

I'm building a 8 wheel drive machine out of old gmc sprint parts, using the CV axles and Differential gears. The main gear on the differentials is approx 6" in diameter and each differential is roughly 24" away from each other. I had planned on using a 90 degree angle gear box in between the front two differentials and one between the back two. Attached to this 90 box would be two sprockets, one to hold a chain attaching the near by differentials (the differentials would have sprockets in place of the gear). This however needs tensioning and my setup won't allow for an easy tensioning system.

So, I am now thinking about using the existing gears on the differentials, put one gear on the 90 gear box, and two gears in between to attach the two together, all in a row (5 in a row, the center one being the driver and the outer ones being the driven and all gears being 6" diameter). I realise that the more gears you have, you get some sort of exponetial loss in power transfer.. but would this be a lot less than chains or minimal?

Thanks for your help,

Frazer RM Ross








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Re: Gears - how much loss in general
Re: Gears - how much loss in general -- Beeman Post Reply Top of thread Forum
Posted by: Dave Fowler ®

03/13/2006, 00:37:14
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The number of gears has nothing to do with losses! The number of gear sets that the power goes through to get from it's source to it's destination has a lot to do with it.

Each gear set that power flows through will reduce the power through it by a small percentage.
Typically one gear set will reduce the power through it to about 96 percent of the power that reached it. so whatever comes in, you will get about 0.96 of that going out.

If you are sending some power to wheel number 3 via 5 sets of gears then the power that gets to wheel number 3 will be ....
0.96 x 0.96 x 0.96 x 0.96 x 0.96 x the power you started sending for that wheel. i.e. 0.81 times the original power.

If you assume that one eighth of the total is going to each wheel (reasonable) then 0.81 / 8 times the engine power will go to each wheel...

So it is ideal to have the smallest number of gear sets in the path to each wheel. ... shafts do not take power.
You could have one shaft running full length along the vehicle with a gear on it driving each diff. Then for each wheel the path is... Engine-gearbox-shaft-local gear set into diff- diff gears- wheel.








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