Corky Scott wrote:

On Tue, 21 Dec 2004 11:46:46 -0500, Matt Whiting
wrote:


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.


Matt, it isn't a matter of being strong enough to withstand occasional
pulls at full throttle, it's the continuous use that appears to be the
problem, and also that this may be a problem endemic to transmissions
being used as PSRU's.

My curse is that I read a LOT. One of the many articles I read a
number of years ago was about a builder trying to use a Honda Goldwing
engine for his airplane engine. This engine has an integral
transmission which he used as the PSRU. He used second or third gear
for his output gear and the transmission failed, like George's.

That wouldn't be too surprising as airplanes require much greater
continuous power output than cars or motorcycles.


The reason for the failure, if I'm remembering this correctly, was
that the lower gears were not designed for continuous transmission of
power, at least not at the power levels required for flight. Whether
it was the width of the gears or the size of the bearings that
supported them, or even if there were bearings supporting the shaft, I
don't know. It could also have been a problem with prop loads on the
output shaft, not sure. But the transmission as a psru failed.

This is the part I don't buy as there is nothing different about the
lower gears than the higher gears. This is the part I think is a myth.
I believe that ANY gear selected in the GW transmission would have
failed under long-term high power output. I don't think this is an
issue preferential to the higher numerical ratio ("lower") gears.


It could be the gears that failed, or it could be that the output
shaft could not stand up to the prop loads, don't know how George
supported the output shaft.

In any case, George should be congratulated for safely landing an
airplane with a decoupled prop that has one of the higher landing
speeds for light airplanes around. Putting down after a total loss of
thrust is never easy unless you practice frequently and even then you
always know it's just practice and a blown approach can be salvaged by
advancing power and trying again.

But the real thing is the real thing, and while some people flying
Long E-Z's manage to be at around 60 mph when touching down, most I've
heard of are faster than that to prevent the nose from pitching down
prematurely and uncontrollably.

Absolutely. An E-Z would not be high on my list of airplanes to land
off-field.


PS, I hope George posts here what failed in the transmission. It
would be illuminating.

That it will.


Matt