The last line of my last message was the following:
"The bearing load on the output shaft near the ring gear is equal to the
force as calculated torque / radius, F = T / r = 1722 lbs."
Oops, that is not correct.
That would only be true if there would be only one planet gear or if it
would be a stationary spur gear arrangement.
Having several planet gears equally spaced around the circumference, the
various force components cancel each other out, so that theoretically,
there is no load due to torque on the bearing holding the planet
carrier. The same is true for the sun gear bearing.
Now I realize that I made another mistake. For the better however.
The force on the planet carrier bearings is output torque over the
radius of the planet carrier.
The radius of the planet carrier is in our case 3/4 of the diameter of
the ring gear. 234 / 2 *3/4 = 87.75 mm or 3.455 inches.
F carrier = 660 ft lbs * 12 / 3.455 inches = 2292 lbs. Divide by 6
carriers is 382 lbs.
The load on each side of the planet gear which is also the contact force
between the teeth is half of that or 191 lbs.
This also agrees with calculating the sun gear on its own.
F = T / r = 220 ft lbs * 12 / (234 / 4 /25.4) = 1146 lbs. divide that by
6 planets gear = 191 lbs per contact point.
Instead of 287 we have only 191 lbs or 2/3 of the load.
The stress is proportionally lower, instead being 12,000 psi it is only
8,000 psi, which is quite acceptable for hardened gear steel.
Sorry for the wrong calcs sent earlier.
Rolf
I thought about responding to that but I did not want
to prolong the agony :)
I still think the pitch line vel. is not so simple.
When you have a moving planet gear and planet gear
carrier moving around the sun gear at the the same
circumferential vel and direction as the teeth on the
sun gear the planet gear would not rotate at all.
The pitch line velocity would be zero.
Lets get off this subject as Doug is not likely
to put the money into this that WILL BE REQUIRED :)
He is in for a huge sticker SHOCK!!!
Right Francois?
Paul Lamar ...No rotor no motor.
Paul
With all due respect you assume too much:) Cost has never been the deciding
factor with me. If so I wouldn't be making a Seawind and attempting a
turbo-compound system. I know how much Mistral's unit cost and that is
still an option depending on the success of the turbo compound. The final
PSRU decision is an engine or two away. There are many variables to consider
in this project. Mass produced Ford or Allison units are neither good nor
bad weighted in this consideration at this moment. You know I am not
planning to go into business with this unit.
DougFir
I was taken by surprise when you were able to talk
Dave Garber out of those parts. I knew you were interested
in that gear box but I never thought anybody would
seriously consider it when you informed me the
used price was $30,000. I don't think Dave was aware of
that fact unless you told him.
BTW the big trouble with the Allison and all GM automatic
designs is the degree to which they integrate parts.
For example: The ring gear, ring gear bulkhead and shaft
can all be one piece in the GM or Allison while in the Ford/Jatco
design they are three separate parts. This makes it much easier to
incorporate the Ford parts and explains why the Ford parts are
so ubiquitous in PSRU's. It also lowers the costs of the
required parts as you are not paying for something you
are not using.
Paul Lamar ...No rotor no motor.
Paul,
Yes I found the Allison transmissions to be boat anchor heavy and that is OK
because they have a reputation of being bullet proof in their design use.
Of course I told Dave what the rebuilt unit was were worth months before I
met him. BTW $30K is the price quoted for a complete rebuilt 'like new'
Bell 47 box that contains both planetary units and a lot more upper and
lower stuff, not just the final drive. Still I am grateful to Dave for
selling me this unit and I have agreed to help get his story into one of
the aviation magazines and assist him to organize a team to give his 30 year
dream of racing at Reno a fighting chance.
Dave is an ex-Korean war jet jockey and ex Pan Am around the world course
pilot. He has flown the Connies and had good things to say about the
turbo-compounding systems as well. I believe he retired flying the 747s.
He still flies his Fuji made Bonanza painted up in Japanese military
markings in formation with other guys in doing bombing raids at air shows.
Their raids are followed by dog fights with American war planes.
Dave's race plane needs some upgrades. For instance, a new canopy, some
ducting into and out of his radiators, better inlets, and complete flight
testing. After that it needs painting in racing colors. I advised him to
stay in control of his project, keep it close at hand, and after all of the
bugs have been worked out, then move it out west. Two years to Reno is the
goal.
With Georgia Tech nearby his new home in Athens Georgia plus the numerous
EAA chapters around I think getting a student and local team together is
possible. IMHO he could use the moral and engineering support of this
newsletter as well because it would benefit 'the cause' (got ma hands
together here) to have a rotary engine entry at Reno.
When Dave starts to talk about racing he sounds 30 years younger. What can
I say? A lot of homebuilt aircraft pilots have these 'possible dreams'
right?
I haven't mentioned this yet but I promised my best did get his planetary
unit throughly checked out by some Fuji Heavy Industries engineers and
others to see if the unit can be made reliable for his top rpm as well as
functionally for his C/S props. If it is found to be unsafe then I'll be the
first to say so. Then maybe we have to go to plan B and use a Dodge
planetary unit:)
Did you know Jim at Racing Beat built his engines complete with a special
front housing to accept aircraft Magnetos?
Cheers
DougFir
Paul,
Opps correction is needed. I meant to say Kawasaki Heavy Industries. They
had the license to make the Bell over here. Fugi H.I. makes airplanes.
Doug
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