Was looking though my latest MM&FF mag and there is an article on power
losses though the drive train. Unfortunately, no loss numbers are given. The
engine and chassis dyno people who were interviewed said nobody tries to use
factors. Then the article went on to say that, of course, my transmission of
choice is the worst of the lot! Naturally... Another fact jumped out and
that was that the efficiency losses are not linear! And it stands to reason
when thought about. Losses are greater the more horsepower being used. The
greater torque causes more load per tooth in the tranny and diff, hence more
friction.
Also while sitting in my new favorite Doctor's office I was reading a Road &
Track. It had an article on the old Chapparal cars of Jim Hall. An
interesting side bar was the "automatic transmission" used by those cars.
Turns out it wasn't an automatic after all. It was a GM hydromatic torque
converter tied to a manual box. They said the fluid got really hot and they
left the bottom of the bell housing off and welded some fins on the torque
converter to move cooling air. Also the tranny got rid of the synchro rings
and used three large dogs per gear. These were back cut so when engaged the
gears always had force to keep them engaged. Rounded engagement nose on the
moving dogs for easier engagement. Said just had to lift from the throttle a
tad the dogs would rotate apart a bit and Jim would then shift. So smooth it
was like an automatic. As I remember that tranny was never in need of a
rebuild and was never hurt in any of the racing activities. My thought is
that the torque converter multiplied the standing start torque by a factor
of maybe 2 and that during high power shifts was able to soak up the shock
of gear changes.
Just interesting stuff to me...
mayf
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