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 themfor  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 bigholes

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

Yes, if the e-shaft isn't concentric that would be bad..  That's why
I was asking if the nose of the damper fit into the tail of the e-shaft.

If the plate isn't perfectly flat (is dented), you'll have the same
problem. Thicker material will handle this better.

I'm not ecstatic about epoxy being used in this application..  It
thermal cycles a lot, is subject to significant vibration, and may
make things a pain to inspect. Would you be able to see cracks in
the plate if it's under a layer of composite?  Significantly
different CTE between metal and fiberglass/carbon. Warps the plate
or fails the bond..  Metal plates sandwiching a composite
reinforcement might be ok..

Matt-

Yes but out of alignment would also be bad. That was what Iwas trying
to describe. In other words if the GB shaft did not come out of the
e-shaft stright.

The epoxy would  be on one side only. You would still be able to see
cracks.

Paul Lamar


To check alignment:
1: With the PSRU completely off the engine but the flex plate on, mount a dial
indicator on a bolt in a bellhousing  bolt hole. Put the indicator on the side
of the ring gear where it will not touch the teeth. Pry the e-shaft front or
back and zero indicator. Rotate engine 45 degrees and pry the shaft the same
as zero operation. Read any runout. Repeat until all the way around. If not
straight within 0.005" replace flex plate.

2: mount the PSRU adapter without the PSRU installed. A magnetic base stuck on
the flex plate will work this time if it can be mounted so it does not wobble
at all. Other wise a bolt with a rod welded on in a flywheel bolt hole is
required. Now set up the indicator to read the inside diameter of the mount to
verify it is concentric to the e-shaft/flex plate. Loosen mount bolts and tap
lightly until it is concentric. Remeasure with the bolts tight.

3: Now with the same setup, the face flatness to the back iron can be
measured. If it is not 0.000" the prop flange end is not 100% parrallel to the
e-shaft. Shimming or sanding the spacers will be required in that case.

We had to do this almost every time we had a transmission out of a hi-way semi.

Dale Davies

Good plan Dale. Do you have a dial indicator Dave?

Paul Lamar