I finally got into the gear box today and found another issue.  In
addition
 to the sun gear pin failure inside the gear box, the flex plate came
apart.
 I found a piece of it in my cowl as a litte hint of what I was
 about tofind..

 Here are some pictures.  The plate was pretty badly broken up and
 was onlybeing held together by Tracys aluminum damper plate and
 the steel bolt  ring. Pin in sun gear was also broken.  No
 apparent serious damage, just what Iassume is cosmetic galling of
 the input shaft, adapter plate, and bellhousing from the loose
 pin floating around.

 Thinking back, I had an early sign of it at the Reno Pylon
 School.  Afterone of the races I noticed that my home made cover
 over the flywheel hadbeen marred by the flywheel but was not in
 contact with it.  I attributed  itto the high air speeds (205 Kts
 Indicated coming down "The Chute") somehowpushing my cover down
 onto the flywheel.  I put some creases into the  coverto make it
 stiffer which seemed to solve the problem, but perhaps the flex
plate had broken at that time.  With a mis-tracking flex plate it
 is easy  tosee that sun gear pins would be undergoing additional
 stress.  So I amcalling the underlying cause of both issues the
 flex plate failure.

 The large washers that covers the rubber dampers between the
 dampers and  theflex plate have made a significant groove into
 the aluminum of theattachment plate.  I have never noticed that
 before, possibly was a  functionof the twisting flex plate.
Question is, does it need to be replaced?

 My rubber dampers are noticeably worn and soft and need to be
 replaced.  Iam getting quite a significant amount of oil coming
 past either my rear  oilseal or the oil seal on the gear drive.

That oil may have done in therubber dampers, that got too sloppy
 and stressed the flex plate thateventually fatigued and broke,
which further lead to the pin failure.

 So I am undecided on what to do about the flex plate replacement.

I agreethat the iorn flywheel is not the answer.  The machine
 work would have to  bequite extensive, because the aluminum plate
 rides inside the ring.  Afterall that machining, it would have to
 be re-balanced but that would bedifficult because it has the rear
 counter weight built in.

 Using one of the aftermarket aluminum flywheels might work.  It would
still
 have to be machined to make space for the damper plate, but at
 least itwould be aluminum (easy to machine) and could then be balanced
symmetrically
 (perhaps even with the damper plate installed so it is all nicely
balanced.
That would not be a low cost solution, however!

 Paul, if I were to get an aluminum flywheel like this one:

 http://www.racingbeat.com/RX7-**1986-



1992/Flywheels/11465.html<http://www.racingbeat.com/RX7-1986-1992/Flywheels/
11465.html
 do you think that you could put it on your milling machine and
 mill in theresesses for tracys damper plate?  Then would you have
 any suggestion onwhere I could get it balanced?

 I am also wondering if I have any business trying to make that
 much HP.  Iwas about to install a water/methanol injection system
 to be able to usemore boost at Reno.  But it seems I may not be
 able to safely use the HPthat I already have...

 -
 --
 David Leonard

 Turbo Rotary RV-6 N4VY
 http://N4VY.RotaryRoster.net <http://n4vy.rotaryroster.net/
 http://RotaryRoster.net <http://rotaryroster.net/

 Wow Dave that is a game changer.

 I have a guy up here in SZP with a really big lathe that can make
 a new "flex plate" . As I recall the subject of flex plate run
 out came up recently. Perhaps your plate was warped. Everybody
 should check their plates for run out. Any run out puts a bending
 stress on the plate due to dynamic imbalance. All parts of the
 plate want to revolve in the same plane. If the plate does
 not track it will introduce a bending stress in the material.

 Also the alignment of the input shaft to the box must be
 perfectly in line with the e-shaft axis. This is not easy to
 check. Perhaps a low cost laser can be inserted into an empty
 gear box starting at the prop bearing end and see where the light
 spot falls on the counter weight. A holder for the laser can be made
 and checked in a lathe for an aligned axis. If you UPS your empty
 box,spacers and adapter plate  up I'll put Jim Poole on the job.

 One quick and dirty way is to assemble Tracy's damper on the
 input shaft with out bolting it to the flex plate. In fact
 leave the flex plate out and off for the moment. Use the engine block
 as an anchor for a dial indicator and check for damper plate run out.

 Then measure the distance from the block to all four quadrants
 of the damper plate.

 Paul Lamar

Dave if you look on the RX-8 flywheel as been redesign by Mazda
 and those 4  holes 1" dia plus are located further apart  as the
 center of the flywheel  and close to the ring gear It looks to me
 Masda had similar fatigue problem  with the RX-7 flywheel.The
 problem we can not fit  the Tracy damper plate  because it does not
 fit the attaching holes and are to close of the ring  gear unless
 someone have an other solution

Jean Prudhomme

 Yes, it is becoming pretty clear that any option other than the auto-
 tran flex plate is going to take considerable extra work to get it
 addopted.  I think the aluminum fly wheels are my first choice of
 alternative at this time, but I may just put in the flex plate and
 stop trying to make a lot of HP.
 --
 David Leonard

 Turbo Rotary RV-6 N4VY
 http://N4VY.RotaryRoster.net
 http://RotaryRoster.net

 I would not use aluminum Dave. IMHO a better way is use fatigue  resistant
 .065" thick  4130 sheet reinforcement tig welded in the center
 diameter. I'll build you one out of a spare plate I have if you will
 work on finding a replacement.

 Paul Lamar

Hi Dave,

I gather from your e-mail and web that you are a Naval Aviator. This
would
tell me you are used to aerobatics, which will put assorted higher
stresses on
the airframe. I was having a morning coffee and contemplating navel
lint when
I came to the idea to check your web and construction photos. Also this
came
to the forefront after the pylon school with high stresses.

Your PSRU mount on the plate has a fairly small diameter ring of bolts.
During
aerobatic manoeuvres, there will be a large torque on the prop that
will be
transmitted through the PSRU to the mount plate. I believe the flex
should be
determined and dealt with.

So, how to measure and calculate the flex force. A hydraulic cylinder
like
used with a pump for body work can be modified to have a pressure gauge
and
the cylinder diameter is easy to find.  This will tell the pounds
force. If
this cylinder is extended a bit (1/2 stroke) and a bottle jack is used
under
it to apply force, then a dial indicator will show the amount of flex.
Put the
hydraulic jacks under the front of the PSRU just behind the spinner. A
piece
of angle or channel iron bolted on the top of the engine (the lift
bracket
bolt hole) will provide a mount for a dial indicator, to read movement
on the
top of the front of the PSRU. Paul should be able to do a quick
calculation of
the force applied through the prop during turns.

You may need to install braces from the front of the PSRU back to the
engine
bellhousing bolts to stiffen it up. A small amount of flex is like a
misalignment and under load it will not take long to break the flex
plate.
Brace to the sides as well.

Dale Davies




 David I sent an idea of using the RX_8 flywheel with an additional
aluminum
 plate,the RX-8 look a stiffer design


 Jean Prudhomme

 Yes it does look stiffer Jean but it would require a new Tracy style
damper
 plate because I suspect it is larger in diameter.

 I think the cracks started in these holes.
 The 13B plate is only 1.5 mm thick or about .059".
 I think the holes could be filled in with .065" thick 4130
 and it would be much stronger. Also a 4130  doubler plate
 could be added to the center. This is all low cost.

 Aluminum is not a good material for this use.

 Paul Lamar

 --Hi, a flex plate will flex.  Our experiance with an odd fire Chevy V-6
on a dyno showed more than 1/2" deflection at the ring gear on a heavy duty
racing flex plate judging by the notches cut into the ribs at the back of
an expensive aluminum block. The ring gear is effectively the rim of a
gyroscope.  The unbalance of the V-6 excited it.  With the better balance
of the Wankel that would not be a problem but maneuvering in the aircraft
would be.  It needs to be stiffer to minimize deflection and fatigue.  Look
forward to seeing you all on Saturday.  Free lunch after meeting.

Murry Rozansky

Like some fast 2 G laps at Reno? :)
A one radian per second spin will bend a Lycoming crank shaft flange.
Good call Murry. Aluminum is not what you want when continuous bending
is present.

---------------------------------------------------------
Here is what the Skyranch Engineering Manual has to say about it.


It is obvious from this point of view Tracy's large nuts and bolts
out near the rim add to the moment of inertia. Helicopters deal with
this by putting hinges in the blades near the hub. Obviously it is not
a good idea to use a solid and stiff disk such as an aluminum
or steel flywheel as that adds a lot of weight. Stresses in the solid hub
go up to high levels. It is better for the rim of the flex plate and ring
gear to find its own plane of rotation and allow the plate to flex. If it is laminated from two or more thin spring steel  plates the cyclical bending
stress on any one plate will be lower.

Does anybody wish to comment on this analysis or scenario?

* Sky Ranch Engineering Manual. This book presents an excellent
overview of the problems of aircraft engines. It is 500  pages and a
bargain at only $23. There are many details on the materials and
processes used to build a successful aircraft engine. There is a
very good and exhaustive discussion of destructive  torsional
vibrations and fatigue. The telephone number  to buy this book is
(916) 421 7672. The author is John Schwaner. John is highly thought
of in the experimental aircraft community.


Paul Lamar