Subject: Re: Overdrives going backwards
> Message text written by "Nelson Riedel"
> >The unidirectional clutch normally transfers all the torque for all
> forward
> gears including jump starts in 1st. The sliding member clutch transfers
> torque
> when in OD --2nd 3rd & 4th, somewhat less torque then the 1st gear starts
> so my
> guess is if it is forced, the sliding clutch will slip. Backing up with OD
> engaged probably fells like the park brake is on real hard.
> <
>
> Nelson, look again. The cone clutch has two faces on it. One face is for
> overdrive and the other face is for direct. The Sprag clutch (one-way)
> comes into play only during the transition between the two modes.
>
> But you are right about the sprag clutch being robust enough to take quite
> a bit of abuse. I've seen one stall an idling Austin Healey engine (yes,
> we had it in backwards. We had reverse overdrive, just fine.) but one
> would have to think that somewhere there is a hill steep enough to apply
> enough reverse force to damage the clutch, doncha think?
>
> Dave Massey
Dave,
A few facts:
The force holding the sliding clutch in the rear position is about half the
force holding it in the forward position.
The torque reqirements in OD are less than half that of direct drive because OD
is not operation in1st.
>From this one can conclude that the designers were less concerned about the
torque capablilies of the rear position of the sliding clutch.
Yor are right that the unidirectional clutch carries the load when OD is
shifting as it does in direct drive.
The purpose of the rear position of the unidirectional clutch is carry the load
in reverse and deceleration (engine braking).
That is probably why they called the eight spring that hold the clutch in the
rear position "clutch release springs" rather than "direct drive springs".
I've written somthing up on how these work and how to overhaul them. Part of the
motivation was all the misinformation that is around. I plan to finalize it
after the summer party and put it on our club website. I'll mention it to the
list a that time.
Nelson
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