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There's a lot of history of this type of drive
plate failure. It occurred on the Lou Ross psru with some frequency. I did
measurements and analysis of the Lou Ross, then some experiments to prove cause
and effect. Here's what I learned:
The drive plate has tremendous strength in the
rotational axis, but very susceptible to fore/aft movement. All of the cracks
are consistent with fatigue failure fore aft direction. In addition, the Lou
Ross had symptoms which forecast drive plate risk. The width of the spline
wear on the input shaft was a direct measure of how far the shaft moves fore
aft. So if the spline on the drive plate had 1" of contact with the mating
spline, yet you saw spline wear on shaft to be 1.25" wide, that was proof of
1/4" movement. In addition, this movement rapidly caused grease to be extruded
from the little pilot bearing at the end of the input shaft. So you'd see grease
streaks after only 5 hours of use. Looks like you don't have these same
predictors, but I thought it was valuable to explain all of the supporting
evidence.
Fuel combustion causes explosion which sends high
energy pulse to drive train. Since the gears are helical, a portion of that
energy is transferred into fore aft movement of the input shaft. Excessive
clearance at the end of that shaft allows greater inertia of shaft. Beating on
drive plate like a hammer. The input shaft is steel, the psru housing is
aluminum. They don't expand the same amount when heated. As a result, the Ross
psru had excessive clearance during operation. Getting rid of this excess
clearance dramatically improved Ross design. No more loss of grease on that
little pilot bushing. No more wide wear pattern on the input shaft spline. No
more failure risk.
I think you guys are using a pretty good psru. Very
likely you have this same problem.
----- Original Message -----
Sent: Tuesday, July 12, 2011 4:17
PM
Subject: [FlyRotary] Re: RD-1B
failure
David, I have
seen this multiple times in the auto repair business, as far as a cause,
on cars that someone had removed trans & did not reinstall all the
retaining bolts, improper alignment of trans/eng., guide pin missing, trans
bolts loose, damaged when trans installed (pry bar nicks all over the flywheel
caused cracks) found a rag installed between trans & eng., & also on
NEW cars with low miles no previous repairs
performed. I also found three
Mazda auto trans flywheels as Tracy did, with very fine cracks around the
lightening holes ( not the bolt holes ) when we were looking for one to
use on our RV6A rotary. I even asked the salvage yard guy to check
for me & he missed them & shipped me that junk
flywheel. David R. Cook RV6A
Rotary, Lansing MI.
From: "David Leonard" <wdleonard@gmail.com> To: "Rotary
motors in aircraft" <flyrotary@lancaironline.net> Sent:
Tuesday, July 12, 2011 6:27:57 PM Subject: [FlyRotary] Re: RD-1B
failure Left over pieces of flex plate - we being held together
by ??? -- David Leonard Turbo Rotary RV-6 N4VY http://N4VY.RotaryRoster.nethttp://RotaryRoster.net-- Homepage:
http://www.flyrotary.com/ Archive and UnSub:
http://mail.lancaironline.net:81/lists/flyrotary/List.html
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