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 to
  find..

  Here are some pictures.  The plate was pretty badly broken up and was only
  being 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 I
  assume is cosmetic galling of the input shaft, adapter plate, and bell
  housing from the loose pin floating around.

  Thinking back, I had an early sign of it at the Reno Pylon School.  After
  one of the races I noticed that my home made cover over the flywheel had
  been marred by the flywheel but was not in contact with it.  I attributed it
  to the high air speeds (205 Kts Indicated coming down "The Chute") somehow
  pushing my cover down onto the flywheel.  I put some creases into the cover
  to 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 to
  see that sun gear pins would be undergoing additional stress.  So I am
  calling the underlying cause of both issues the flex plate failure.

  The large washers that covers the rubber dampers between the dampers and the
  flex plate have made a significant groove into the aluminum of the
  attachment plate.  I have never noticed that before, possibly was a function
  of 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.  I
  am getting quite a significant amount of oil coming past either my rear oil
  seal or the oil seal on the gear drive.  That oil may have done in the
  rubber dampers, that got too sloppy and stressed the flex plate that
  eventually fatigued and broke, which further lead to the pin failure.

  So I am undecided on what to do about the flex plate replacement.  I agree
  that the iorn flywheel is not the answer.  The machine work would have to be
  quite extensive, because the aluminum plate rides inside the ring.  After
  all that machining, it would have to be re-balanced but that would be
  difficult 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 it
  would 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
  do you think that you could put it on your milling machine and mill in the
  resesses for tracys damper plate?  Then would you have any suggestion on
  where I could get it balanced?

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

  -
  --
  David Leonard

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


I don't think that is the problem. There are several 3 rotors running
with that flex plate. Tom Parkes is a turbo 3 rotor no less and
Mark Steitle's is a p-port 3 rotor with over 300 HP. Please check your flex plate for cracks Mark and Tom.

This is the first time in 12 years we have a reported failure in the flex plate.

I think it is some kind of alignment or heat problem.
The rubber bushing can be replaced by fabric reinforced
silicone rubber washers from McMaster Carr good to 500 F instead
of only 200 F.

Paul Lamar