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Author: Subject: Diff hight
Paul H

posted on 4/4/06 at 06:49 PM Reply With Quote
Diff hight

I am building a locost with IRS. Can anybody give details of the axle hight relative to bottom chassis rails?
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kb58

posted on 4/4/06 at 08:06 PM Reply With Quote
Normally you'd want it slightly higher then the center of the wheel. Take your tire diameter, divide by two, and add an inch. That's how high off the ground it should be. Where that is relative to the frame rails is a separate topic, since it depends on what ride height you set it to.

[Edited on 4/4/06 by kb58]





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britishtrident

posted on 5/4/06 at 08:34 AM Reply With Quote
With a live axle the diff centre must be the same distance off the ground as the axle centre line.


With irs or de Dion it can vary slightly but should be at around the crank centre line.

These drawings showing crank centre line positions should help

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kb58

posted on 5/4/06 at 02:23 PM Reply With Quote
While it should be "aimed" at the output shaft of the tranmission, it doesn't prevent the diff from being mounted at any height you want.

Slightly above 1/2 tire diameter...





Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book - http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html

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britishtrident

posted on 6/4/06 at 08:10 AM Reply With Quote
Actually the diff out put shouldn't be aimed at the gearbox but the diff flange set parallel to the gearbox output -- topic has been covered in depth many times before.

[Edited on 6/4/06 by britishtrident]

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Peteff

posted on 6/4/06 at 01:12 PM Reply With Quote
Take your tire diameter, divide by two

That would be the radius then .
why do you want it slightly higher than the centre of the wheel? Different circumstances would affect where you put it wouldn't they? How much suspension travel and your chosen ride height along with the driveshaft cv joints would all be contributing factors to take into consideration.





yours, Pete

I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.

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kb58

posted on 6/4/06 at 02:38 PM Reply With Quote
Because with the driver in the seat, it will compress the suspension bringing the diff into better alignment with the wheel hubs.

During hard acceleration with maximum torque fed through the CV joints, the suspension will compress even more. Having the diff slightly above half way makes everything self-align when it's needed most, during hard acceleration.





Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book - http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html

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