Gary Casey wrote:

I have to disagree somwhat with both Vance and Paul.  Having spent a few years
designing automotive planetary transmissions, I would have to say that one of the
big advantages of these gearsets the way they are typically implemented is that,
while the loads may not be EXACTLY shared between planets, the balance is so close
that it can be assumed to be matched.  The reason for this is that the carrier is
very precisely machined (the best reason for borrowing this component directly
from automotive manufacture) and the components - ring gear, carrier, sun gear -
are always floating in hydrodynamic bearings so they can seek their own center.
If they were not virtually matched there would be gear noise and durablility
implications that would not be acceptable for automotive applications.  All the
PSRU's I have seen retain this critical feature to some degree and that is the
main reason they can be expected to work fairly well.  By the way, the Heavy-duty
Hydramatic transmissions used in medium trucks use a similar planetary arrangement
that is used in the Ford transmission (called a "dual simplex" design) and they
use 4-pinion carriers with straight-cut gears capable of carrying a great deal
more torque.

Paul wrote:

Thanks Gary, for your input on this. I would love to publish a drawing or pictures
of the GM transmission planetary if you have one and can send it to me.
I have rather a poor drawing of the Powerglide. (Well at least I think it
is the PowerGlide.) Straight cut gears would certainly help simplify the PSRU
design.

Paul Lamar
 
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