What planetary gears are you referring to? I'm looking for something
from 100 hp to 500 hp.
Rob Miller
Ford C6 auto tranny and derivatives.
Paul Lamar
Thank you! From all that I've read most seem to prefer single spur
cut gears and there hasn't been much that I've found about the
planetary set ups, other than I know they were used in the big
radials, but most have said they aren't as reliable as spurs (but
just looking, there are alot of ford trans that have them and run
their lifetime just fine) the place I've found last fo info generally
doesn't like psrus...but my thought is every turboprop on the planet
runs behind one just fine. There shouldn't be any reason a rotary (or
any auto conversion) couldn't use similar set ups
Rob Miller
For a given gear width a planetary is six times stronger.
In fact there is an optimum ratio of width to diameter so spur gears cannot
be made much wider. In that case a planetary is the only solution.
All aircraft engines, with the exception of the V12s and rotax, have
been planetary
for the last 75 years. That includes the big corncob P&W 4360's.
Another problem with spur gears when the box heats up the tooth mesh
becomes less.
Here is what a high power spur gear box looks like. We call
it the rock crusher. It is HEAVY. You can imagine what it weighs.
These Ford planetary parts are used in the 650 foot pound Power Stroke
diesel
If you want a planetary stronger than the Ford you can go with an Allison
truck TX. Here is a picture.. Ford on the left Allison on the right.
Here is the Bell 47 helicopter final drive we are using in the TTC. It
is rated
at 1000 HP by Bell engineers. If you can find one they are $30,000.
Paul Lamar
Paul,
I have recently obtained a 600-7 Bell 47 transmission complete except
for the lower portion of the mast (rotor output shaft)........I am
now locating an un-airworthy mast to obtain the lower portion needed for
the output shaft to a propeller.........I sent a question about the
Bell 47 adaptation to Dave Garber's rotary engines to Jim Mederer and
received the opinion below.........
" In my opinion, Dave Garber's adaptation of the Bell 47 gearbox to a
rotary was poorly done. He used an adaptor from the engine
counterweight directly to the drive adapter that splines onto the sun
gear and ignored support for the output shaft rear bearing. He also
ignored the fact that the output shaft of a rotary gets "bent" off
center-line by the rear counterweight by perhaps .010" at high RPM, and
that run-out is transferred to the sun gear. The new drive system
supports the output shaft and uses a quill shaft and a sprung clutch hub
to isolate the run-out. Without these actions, I believe the assembly
would soon fail, even though the 47 parts are quite robust."
That said my question is this............Although Dave Garber's
conversion is/was not ideal what is your opinion on using his method of
supporting the rear bearing of the propeller shaft for a Rotary engine
of no more than 250 hp and not turned to more than 7000
RPM.............Although Jim Mederer stated the eccentric shaft of the
Rotary
is "Bent" off center-line as much as .010 thousands of an inch at high
rpm he did not define a number to "high RPM"...........In my humble
opinion 7000 RPM for the Rotary
is not high RPM and I wonder if there has been any information you have
seen about eccentric run-out at various RPM............I can fully
understand Jim's concern about
this run-out from 8000 RPM and up but all of the gear boxes (ROSS and
Tracy Crook's) built to date use essentially the same method of
supporting the Sun Gear shaft by piloting it into the eccentric
shaft..........
Best Regards,
Kelly Troyer
His concerns are exaggerated. He tends to be over concerned some times
with details.
He told me years ago a rotary would never work in an airplane :-)
I told him his RX7 would crash at Bonneville and he ignored me :-)
Of coarse about a 100 rotaries have flown some with well over a 1000
hours.
He does not fully understand how Dave supported the prop shaft on the
inner end.
He is kind of a negative guy :-) I have known him for near 45 years :-)
Never the less we modified Dave Garbers installation considerable. Jim
did not see those modifications.
Just about any rubber coupling design will compensate for any slight
bending of the e-shaft.
However I doubt his numbers on that as well. The E-shaft in that area is
very robust to say
the least as it has handled well over 1000 HP.
The pilot bore in the end of the e-shaft is not a close fit. Normally
there is a roller bearing
in there. It is not capable of imparting an angle deflection to any
shaft inserted into
the bore. Perhaps a slight run out. No mechanism is deflection free.
Here are some pictures of the modifications we made on the Dave Garbers
installation.
I would not do it exactly the way Dave G did it. I would get some sort
of rubber
coupling in there. Long term it would easier on the gear teeth.
You have a real jewel there. What did you pay for it?
Paul Lamar
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