Corky Scott wrote:

On Tue, 21 Dec 2004 03:00:05 GMT, Dave S
wrote:


The glide distance has since been re-evaluated, but overall everyone is
glad it worked out ok.. and on a secondary personal note its refreshing
that the engine itself was not the point of failure

Dave


Dave, my feeling is that it does not matter that the engine did not
fail, the PSRU did and the result is the same: No engine and a forced
landging.

I wondered about using a transmission for a PSRU instead of a PSRU for
a PSRU. The problem with using a transmission is that the all the
gears except for fifth, are designed for light usage. In otherwords
they weren't designed to be used continuously with the engine pulling
50% or more power. George's transmission is not the first to fail
because of this.

Using the transmission for a PSRU is not necessarily a bad thing, but
the gears that will be used and the bearings that support the gears
may need to be re-evaluated.

I've not seen this before. This may be true for passenger cars, but for
pickup trucks, OTR trucks, off-road equipment, etc., each gear is
equally likely to be used and typically full throttle is more likely to
be used in the lower gears. I've never heard of any of the gears being
designed for "light" usage in any manual trans with which I'm familiar,
but I'm not that familiar with pax car manuals.

It used to be that 4th gear in most four-speeds was 1:1 and this was
often accomplished by simply connecting the input and output shafts
directly with a collar. So, I suppose this could have been more rugged
as the gears were just along for the ride at that point. However, some
new transmissions have the 5th or 6th gear as a overdrive gear, and
occasionally even the 4th, and may not even have a 1:1 ratio. In these
designs, every speed is being driven through the gear set/layshaft.

If you have a design reference for transmissions being designed to not
handle full torque in anything but high gear, I'd be interested in
seeing it. Also, if you have a list of such transmissions that would be
interesting as well.

Matt