I am looking for these dimension from the flywheel 13-b RX-7 if someone
 have one on hand uninstalled i would really appreciate those informations
 see photo
 Jean Prudhomme

Which dimensions? hole spacing? Diameter? Hole size? How exact do you
need... I happen to have one off the plane right now :-)
-- David Leonard

Dave you are insured. Sky Smith had the info on you. You are famous.
As far as I can tell you can fly the RV4 anytime.
Apparently two successful off airports counts for a lot :)
I need a medical and and bi annual. Both have recently expired. I got them
 for
flying in Oz.

Paul Lamar
 Hi David i will need all holes diameter and holes circle so i can compare
 with
the RX_8 flywheelThank's for your assistance
 Jean Prudhomme

 Jean, I received the damper plate today. All is well. Thanks.
If someone hasn't already given them to you, I picked up my RX-7 flex
 plate from
the hangar today. I will measure it tomorrow if you still need them.
C. Smith


C. Smith Thank's for your response of received the damper plate,yes i still
 need the holes dimensions on the RX-7 flywheel just to compare if both are
 interchangeable, but i found an idea to use the RX-8 flywheel and the
 standard Tracy damper but Paul recommend 4130 instead of aluminum plate but
 it will add a few pounds, you see the rx8 one  is design differently then
 the rx7 with those big holes away of center holes and closed to the ring
 gear and by using a bolted plate to the original holes 12mm the Tracy damper
 plate by attaching the rubber bushing holes and are line up with the rx8 big
 holes for the bolts head clearance.There is a sketch for this additional
 plate no welding and no balancing i guess it worth to try.
Jean Prudhomme
 Jean when you took these measurements did you measure the outter ring
diameter and teeth to make sure they were the same as the 13B flex plate?
If not, could you?

Thanks,
--
David Leonard

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

  Yes David there is those dimentions you are looking for

 Jean Prudhomme
Now if Tracy would make a damper to fit we would be home almost free :)

 BTW Jean when you scan something or export a dwg please use
 jpg instead of pdf as they show up directly in most email programs.

 Paul Lamar



Yes Paul i will do next


Jean Prudhomme


I am going to attempt to get an estimate of the shear stress in the flex plate.
Lets do the 1.5 mm or .060 thick flex plate first.

Look at the attached dwg. The highest shear stress is in a strip adjacent
to the clamping plate. The clamping plate is 4.5 inches in diameter
so the length of this strip is pi times 4.5 inches or 14 inches.

The peak torque on the flex plate is 500 foot pound or 6000 inch
pounds. Therefore the shear force on the strip is that number
divided by 4.5 inches or 1,333 pounds. The area of the strip is
.060 times 14 inches or .84 square inches. 1,333 pounds divided by
.84" is only 1,590 psi. On the face of it that does not appear
to be the problem. The strength of even mild steel is 30,000 psi.
The .060: thick flex plate should work. Even if one put holes in the
flex plate near the clamping plate and reduced the effective length
of the shear strip by  half the stress would still only be 3,180 psi.

Check my arithmetic. It seems like I must have made a mistake.

Perhaps something  else is going on like the plate is vibrating
in some weird mode. Bonding on carbon fiber or fiberglass
as Joe Berki suggested would damp all vibrating modes.

Perhaps Dave's PSRU is out of axial alignment with the e-shaft.
That will be a cyclical bending load on the flex plate as Tracy's
damper will be fighting the flex plate. One is rotating in one
plane and the other in a slightly different plane.
That will do it for sure. One quick and easy way to check for that is
loosen the bolts holding them together and rotate the engine.
The damper plate rubber bushing holders will get closer and
further away from the flex plate  as the engine rotates.

BTW here too is the diameter of the 20B flex plate.

Paul Lamar