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Regardless of the method used, you will
discover that those teeth are hard! And there are many of them!
I also think you will need to spot weld or
something the two plates together so that they become one in order for this to
work. Especially since the rubber bushings allow the bolts to wiggle?
side to side, putting opposite forces on the two plates.
Bill B
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Kelly Troyer
Sent: Saturday, July 16, 2011
12:06 PM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Re: Flex
Plate Failure - Improvements
In the interest of maintaining flexplate balance I would probably rig up some
way
to
grind the ring gear tooth bevel with a tool post grinder perhaps either on
the lathe
or
milling machine..........I would bet your
friend Bob D. could come up with a method
to do
this...................<:)
Kelly
Troyer
"DYKE DELTA
JD2" (Eventually)
"13B
ROTARY"_ Engine
"RWS"_RD1C/EC2/EM2
"MISTRAL"_Backplate/Oil Manifold
"TURBONETICS"_TO4E50
Turbo
From: Mark
Steitle <msteitle@gmail.com>
To: Rotary
motors in aircraft <flyrotary@lancaironline.net>
Sent: Saturday, July 16, 2011 9:04
AM
Subject: [FlyRotary] Re: Flex
Plate Failure - Improvements
Bill,
That's a good
point. The 20B flexplate, which appears to be the same as the Renesis,
has a small bevel on the engine side of each tooth, 180* opposite of the 13B
flexplate. My thought is that this could be duplicated using a dremmel or
die grinder.
Mark
S.
On Sat, Jul
16, 2011 at 8:39 AM, Bill Bradburry <bbradburry@bellsouth.net>
wrote:
The RX-8
flywheel/flexplate is designed to have the starter gear enter from the front as
related to the engine. The RX-7 has the starter entering from the rear as
related to the engine. As a result the RX-8 flywheel will not work with
the RX-7 starter. That is my opinion as I remember the
layout. I am willing to stand corrected by more knowledgeable folks.
From: Rotary
motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Tracy
Sent: Friday, July 15, 2011 2:41
PM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Re: Flex
Plate Failure - Improvements
I'm still in
analysis mode on this myself.
So far the possibilities are:
1. The flex plate may have been warped when installed ( I bought several
that were) I think the standard should be close to zero runout or wobble
on the flexplate in view of this failure.
2. The flexplate could have had cracks when installed (I also
bought several that had cracks and they were not visible unless you looked
closely)
3. The dang things (RX-7 flexplates) are not strong enough for boosted
13Bs or 20Bs.
I do NOT think the problem is fore & aft travel of the input shaft.
The RD-1x drives have had thrust bearings from day one. There is no
thrust load at all on the damper, flexplate or crankshaft imposed by the
drive. This was not the case with the Ross drive I used at first.
I have over 1000 hours on the same flexplate on my NA 13B. I have only 55
hours on the 20B. But I'll be checking both. I did inspect
both flexplates VERY carefully before installing.
If I found that a change were necessary, I would consider two possibilities.
1. Use a modified aluminum racing flywheel used with an auto
counterweight. (Or possibly a lightweight steel one if there is such a
thing)
2. Use an RX-8 flexplate with an adapter plate made of aluminum or steel
sheet to go between the flexplate and damper. The RX-8 version looks
stronger than the RX-7. I briefly studied this when good RX-7 flexplates were
getting hard to find. I did not develop a formal procedure for doing
this but it looked like it would be pretty easy. Anybody with spare time
out there want to take a closer look? Hint: The damper bolt
pattern would be offset 45 degrees from the RX-8 torque converter bolt pattern.
Tracy Crook, RWS
Bill summed up what
I’ve been thinking the last few days. I’m not changing anything
until Tracy
makes a recommendation. It could be fore and aft movement on the shaft, flex
plate out of round, worn rubber isolators or a combination of all these items.
We may need a scheduled maintenance plan to replace items like the rubber
isolators or other items that wear and loosen tolerances.
I will however be
inspecting for this problem before most flights.
(playing
with fiberglass again)
From: Rotary
motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Bill
Bradburry
Sent: Friday, July 15, 2011 10:03
AM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Re: Ok Here
are the important flywheel measurements
I can’t help but
think that you may be fixing something that is not broken. I realize that
the flexplate came apart on your plane, but that doesn’t mean that the
flexplate is the cause of the problem. That flexplate holds up quite well
in the car with a heavy torque converter attached to it. Think of the
forces when a car under heavy acceleration changes gear! As long as the forces
are along the plane of the plate it is very strong. Not so much in the
forward/rearward directions. In fact that would cause metal fatigue and
cause it to break just like yours did. I think that what ever is causing
the endplay is what you should be looking at. I suspect that if you check
out the transmission on the car you will find that the endplay of the input
shaft is controlled by thrust bearings or some such device. Lynn may know the answer
to this??
That msg from Al Wick
really resonates with me. Tracy
had to install a thrust bearing to prevent the drive shaft from hitting the
bottom of the pilot bearing and causing an eccentric shaft failure on the
engine. Maybe you now need to add a cage similar to what Al was
discussing that will trap the shaft end play completely. That, to me,
makes more sense than adding a bigger flywheel. If you strengthen the
weak spot, you will then discover where the next weakest spot is because that
will be the next failure!
This is a real
opportunity for you and the rest of us with the same drive. Please study
this a little more before you begin the fix!
From: Rotary
motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of David Leonard
Sent: Friday, July 15, 2011 12:42
AM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Ok Here are
the important flywheel measurements
I finally got
to the hangar and measured out my S5 turbo flywheel and the remains of my S5
flexplate. The results are very encouraging, even as good as the possibly
could be to make the swap, but I only had ten min at the hangar before I had to
leave to pick up my daughter from daycare, so they are one try and slightly
sloppy... I make no guarantees. The height measurements of the flex plate
were particularly suspect because, well, mine is all warped and broken.
Ring Gear Diameter - Perfect
fit. As we suspected, same size, same tooth spacing.
Ring Gear Fore-Aft Placement - As
measured from the underside of the big nut. (for all further reference, aft
means aft in the CAR). The flex plate puts the aft side of the ring gear
1.290 inches from the front of the big nut. The flywheel puts it 0.913.
So the flex plate puts the ring gear (appx) 0.377 in. further aft. This
is actually fortuitous because it just so happens that the ring gear thickness
is .365 ... So all we have to do to fix the discrepancy is
weld and extra ring gears onto to the flywheel ring gear and there will be
teeth that the starter can reach:(bottom of the page.. the cost $80)
http://mazdatrix.com/flywheel.htm
It may also be possible to fix the discrepancy by changing the starter... will
look into that.
Damper Plate Placement - On the
flywheel, the mounting surface is proud (or aft) of the ring gear. On the
flex plate, the mounting surface is recessed (or forward) from the ring gear.
And it all pretty much works out. That position on the flywheel will vary
somewhat depending on which flywheel you have and how much wear you have on the
clutch slip surface. But on my (I assume well-worn) flywheel the placement was
0.965 while the flex plate was 0.950. Pretty damn close and given
measurement error it might me meant to be right on. Or, any difference
could be made up by trimming down the spline on the damper plate or removing or
adding spacers between the two.
So in my mind, a flywheel is the way to go. Stout, easy to get, pick your
weight, only mods seem to be drilling the mounting holes and welding on a
second gear ring.
--
David Leonard
Turbo Rotary RV-6 N4VY
http://N4VY.RotaryRoster.net
http://RotaryRoster.net
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