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Torque Multiplication in Gearboxes

To: land-speed@autox.team.net
Subject: Torque Multiplication in Gearboxes
From: ardunbill@webtv.net
Date: Mon, 2 Jul 2001 17:35:03 -0400 (EDT)
Hi Folks.  A few messages ago someone inquired whether gearboxes
multiply torque.  

Yes indeed they do, whether an automatic, a four-speed, or a rear axle,
they all multiply the input torque by any ratio they have, minus the
losses due to gears, bearings, seals and lubricants.  If you put 100
foot pounds of torque into a four-speed with a 3 to 1 first gear ratio,
you will get 300 foot pounds of torque out of it(in first gear, natch),
minus the said losses.  Ignoring the losses, your 300 foot pounds goes
down the drive shaft and runs into a 3 to 1 rear axle, which turns it
into 900 foot pounds to the rear wheels (say they are locked with a
spool).  So we've got 900 foot pounds at the rear wheels, and if we
deduct say 20% of it for all the friction of the gears, bearings, seals
and lubricants, that's 180 foot pounds to turn everything, but we still
have 720 foot pounds of torque to make the car go.  You would need a
long torque handle to make that much torque with those meaty arms of
yours, hence this is what it takes to make your car jump like it
(hopefully) does.  Actually, rather than 100 foot pounds of torque
input, unblown gas Arduns can easily do 300, fuel or blown Arduns
400-500, and all your other varieties pro-rata.  I think Keith said his
300 inch Rodeck puts out near 400 foot pounds.  That impressed me.

This is only an example, losses vary by designs of gearboxes and rear
axles.    

If anybody sees anything wrong with the above, don't hesitate to correct
it.  Your results may vary.  Cheers from Ardun Bill in the Great Dismal
Swamp, just back from Maxton and I had a good time.  Thanks to all the
organizers for their hard work.  We are VERY VERY LUCKY that there IS an
ECTA!!!!!

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