From: "Stephen Izett stephen.izett@gmail.com" <flyrotary@lancaironline.net>
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Subject: Re: [FlyRotary] RD1-C damper
Date: Tue, 8 Dec 2020 06:12:30 +0800
References: <list-1017879@logan.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
In-Reply-To: <list-1017879@logan.com>
Message-Id: <F6D0544B-05D5-422C-99E0-4FB294AC376F@gmail.com>

Thanks Charlie
Steve

> On 8 Dec 2020, at 5:03 am, Charlie England ceengland7@gmail.com =
<flyrotary@lancaironline.net> wrote:
>=20
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> On Mon, Dec 7, 2020 at 8:20 AM Ernest Christley echristley@att.net =
<flyrotary@lancaironline.net> wrote:
> The temperature in that area will range from around 180F to well below =
freezing on a cold night, resulting in a lot of differential expansion.  =
Epoxy is basically plastic.  It is going to soften in use, when its =
strength is needed most.
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> This is something I'd probably try, but I wouldn't bet money that it =
would work.
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> On Monday, December 7, 2020, 5:29:25 AM EST, Le Roux Breytenbach =
breytenbachleroux@gmail.com <flyrotary@lancaironline.net> wrote:
>=20
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> Hi : It was mentioned on P.L. newsletter a couple of years ago - what =
if the flexplate center are reinforced with say 6 layers of carbonfiber =
on both sides ?
> The carbonfiber can be vacumebag and really good cured if doiing it =
from both sides.
> The carbonfiber will lock from both sides face to face threw the =
bigger holes and will secure more than just on the metal itself.
> Doiing the flexplate as a complete unit and then just cut and machine =
the holes.
> It will be ridged and light as well and counter the gyroscopic forces =
ect.that leads to cracks from the holes=20
> Then the rubber dampener could still be put in place.
> I am goiing to replace the center on this clutchplate with a rubber =
dampener
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> Regards Le Roux
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> Sent from my iPhone
> Le Roux Breytenbach=20
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> > On 07 Dec 2020, at 09:07, Stephen Izett stephen.izett@gmail.com =
<flyrotary@lancaironline.net> wrote:
> >=20
> > =EF=BB=BFSee below what Tracy wrote in Feb 2012.
> > Also found a note in the archive where Tracy mentions only producing =
a few of the RD-2 boxes before retiring.
> > So how many hours does Tracy=E2=80=99s RV4 with the damper removed =
now have on it.=20
> > Sounds from what some have said that he may have installed this mod =
to his 20B RV8 which may have more time, however thats a 3 rotor. What =
difference would that make I wonder?=20
> > I take it the torque reversal and pulses will be the same magnitude =
but the sum of those pulses may have a different outcome for anything =
connected.
> >=20
> > Cheers
> >=20
> > Steve Izett
> >=20
> >=20
> > email from Tracy back in Feb 2012 -
> > "Finally got around to flight testing the aftermarket flywheel setup =
for the RWS redrive.=20
> >=20
> > The cracked flexplate issue some builders experienced came up at the =
same time as my CNC source for input shafts lost the ability to make =
them anymore due to loss of specialized spline making machinery.  Since =
I had to line up a new source I took this opportunity to review the =
design from the input shaft back to the engine.  Because the damper has =
been such an expensive and labor intensive part, it was looked at as =
well.  As a result, there have been enough changes to warrant a change =
in the name so the new drives will be RD-2B & RD-2C.
> >=20
> > In rethinking the drive I had the thought that since the relatively =
low frequency primary resonance range of the drive train is taken care =
of by the system lash, that left only the high frequency harmonics that =
the damper is responsible for.  This high range is the factor that =
creates the red zone in rpm ranges found on some certified engines and =
metal prop combinations.  As far as I know, no one has used a metal prop =
on an RD-1x drive so I decided that it was an unneeded requirement.  The =
new design has no damper at all and consequently it has a "No Metal =
Propeller" restriction.
> >=20
> > Replacing the damper is a flanged spline that is bolted directly to =
the flywheel using the same bolts (longer bolts required) that attach =
the flywheel to the counterweight.  The spline is a different spec (15 =
splines instead of 30) so it is not compatible with the RD-1 damper but =
the new shaft itself is backward compatible with the remainder of the =
drive.  I retrofitted the same RD-1C that was on my RV-4 for these =
tests.
> >=20
> > The flywheel was an aluminum racing flywheel with the replaceable =
iron friction surface unbolted and removed.  Really looks pretty and =
professional compared to the flexplate.  Any of the aftermarket RX-7 & =
RX-8 racing flywheels (steel or aluminum) that utilize the auto =
counterweight may be used.=20
> >=20
> > As David Leonard found, these flywheels place the ring gear about =
.2" closer to the engine than the flexplate.  To compensate, I milled =
.2" off the front surface of the adapter plate where the starter mounts. =
 No changes were needed to the starter itself.  I did not bother to =
grind the lead-in bevel on the ring gear teeth as discussed earlier.  =
Starter engagement was smooth anyway.
> >=20
> > The RV-4 drive had over 700 hours on it and everything looked =
beautiful inside.  No signs of wear other than a shallow groove (~.002") =
on the input shaft where the 1mm thrust bearing race between the two =
needle bearings rides.  Others have reported more than this in fewer =
hours so this is an area to inspect carefully.  The new input shaft is a =
harder alloy (post machining through hardened 4340) than the the RD-1 =
which was pre hardened 4140.  This should reduce the wear in this area.  =
The old flexplate with over 1000 hours was still crack free.  The input =
shaft oil seal still looked and felt new so it was not replaced as =
planed.  Others have reported these leaking in much fewer hours.  Don't =
know the reason but I suspect that oil temperatures out of range may be =
a factor.  NEVER allow oil temps to exceed redline.  If they go higher, =
back off the power then land and correct the cooling system.
> >=20
> > Only 1 hour of flight testing so far but all indications were good.  =
Operated the engine through the full range of rpm up to 7100 looking for =
tell-tale signs of resonance.  I was sort of expecting to feel, sense or =
hear some indication of increased harshness in the drive with no rubber =
anywhere in the system but if anything, it felt smoother.  There was =
none of the 'Waaa --- Waaa' warbling sound (like a twin engine with the =
engines out of sync) that I had with the Ross drive years ago.  So far =
I'm very satisfied with the results but it's still early in the =
tests.=E2=80=9D
> >=20
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> >> On 7 Dec 2020, at 9:47 am, Stephen Izett stephen.izett@gmail.com =
<flyrotary@lancaironline.net> wrote:
> >>=20
> >> Thanks Lynn.
> >>=20
> >> Steve
> >>=20
> >>=20
> >>>> On 7 Dec 2020, at 9:04 am, lehanover lehanover@aol.com =
<flyrotary@lancaironline.net> wrote:
> >>>=20
> >>> If you have picked up a stock manual transmission flywheel for a =
rotary, you must know that "Houston we have a problem". So the worst =
pick for a car engine becomes the best pick for smoothness at idle. That =
flywheel is the answer. The less flywheel effect available the more =
powerful the reversals near idle. The more powerful the reversals the =
shorter the flex plate life. The flex plate drives the car through a =
hydraulic damper. So it is with the aircraft. No damper, short life. =
There are companies who make little tiny shock absorbers. I thought that =
4 such shocks on a racing flywheel pushing a driven disc should do the =
job. Even stock flex plates from piston powered cars get cracks. Few =
fail completely.
> >>>=20
> >>> I think Tracy's pucks are adequate. Just double up the flex plate =
to just outboard of the puck housings. No welding. Use nuts and bolts.  =
It also adds actual flywheel effect which reduces the stress. =20
> >>> For the racer I made a steel button flywheel. Just large enough to =
support a 2 disc 5 1/4" clutch. I bolted this on over the stock flex =
plate. The flex plate was just used to start the engine and nothing =
else. I turned down the face of the counter weight so as to provide a =
taller spigot to locate the flex plate and the flywheel. Piece of cake.=20=

> >>>=20
> >>> The racer used a straight cut gear dog ring style gear box from =
Saenz in Argentina. The gears had enough clearance so as to agree with =
various RPMs. As on start up form a stand still the RPMs would drop =
below 2,200 and the car sounded like a Brush Hog running over a pile of =
hammer heads. That is what you want to avoid.=20
> >>>=20
> >>> Also when unloaded even at higher RPM. The same thing. So when =
feathering the throttle like in third gear. When the engine is not =
driving the wheels and the wheels are not driving the engine. Maybe as =
on final you might get into this situation. So a bit more power, or, a =
bit less power will save the day.
> >>>=20
> >>> The teem had a very competent engineer. My hands are still =
dirty............... Lynn E. Hanover =20
> >>>=20
> >>> In a message dated 12/6/2020 5:28:22 PM Eastern Standard Time, =
flyrotary@lancaironline.net writes:
> >>>=20
> >>> Thanks Dave.
> >>>=20
> >>> Did you do away with your damper after your flax plate =
disintegrated/failed over time, or was this still before Tracy changed =
his mind about the need for the "higher frequency=E2=80=9D isolation =
provided by the damper?
> >>>=20
> >>> I was trying to think about the forces at work on that thin steel =
plate apart from the torque of your boosted 300 hp.
> >>> I was wondering about the gyroscopic (is that the right word) =
force created by that extra mass bolted to it, travelling at much higher =
velocity, and then being asked to change direction with the subsequent =
=E2=80=9Cflexing=E2=80=9D forces at play.
> >>> Steve Boese=E2=80=99 science/engineering mind or Lynn Hanover=E2=80=99=
s hands dirty experience appreciated at this point!
> >>>=20
> >>> Thanks also to Dave Leonard for what we have learnt from your need =
for speed, and Neil Unger=E2=80=99s relentless work on gearboxes.
> >>>=20
> >>> So there being evidence of failure outside of aircraft use, I'll =
look into another stronger starter ring gear.
> >>>=20
> >>> BUT more to the point. what experience do we now have of removing =
the damper altogether?
> >>> I thought this was the important question, because if not =
required, appears to save significant: weight, cost, and maintenance.
> >>>=20
> >>> Has there been further word from Tracy or anyone else flying the =
RD2 or other no-isolator setups?
> >>> Tracy=E2=80=99s initial testing appeared promising but thats now =
some years back.
> >>>=20
> >>> Thanks heaps everyone. Couldn't have got this far without your =
brains, pain, cheque book, experience etc.
> >>>=20
> >>> Cheers
> >>>=20
> >>> Steve Izett
> >>>=20
> >>>=20
> >>>=20
> >>>=20
> >>>=20
> >>>=20
> >>>=20
> >>>=20
> >>>=20
> >>>> On 7 Dec 2020, at 12:52 am, David Leonard wdleonard@gmail.com =
<flyrotary@lancaironline.net> wrote:
> >>>>=20
> >>>> Steve, you are right.  The Issue is cracking og the auto-tranny =
flex plate.  Mine failed entirely.  I highly recommend making the change =
sooner rather than later.
> >>>>=20
> >>>> Dave Leonard
> >>>>=20
> >>>> On Sun, Dec 6, 2020, 12:48 AM Stephen Izett =
stephen.izett@gmail.com <flyrotary@lancaironline.net> wrote:
> >>>> Hi Charlie
> >>>>=20
> >>>> I thought people moved to the race flywheels because the flex =
plates were cracking.
> >>>> I hadn=E2=80=99t heard of the Engine/Drive/Prop needing a =
flywheel mass.
> >>>> I found some info on the forum archive but nothing to draw it all =
together.
> >>>> I=E2=80=99ll have a good look at the flexplate when I pull the =
drive and check for cracking, but unless I hear otherwise I plan to =
reuse the flex plate.
> >>>>=20
> >>>> Thanks
> >>>>=20
> >>>> Steve
> >>>>=20
> >>>>=20
> >>>>=20
> >>>>=20
> >>>>=20
> >>>>=20
> >>>>> On 6 Dec 2020, at 8:58 am, Charlie England ceengland7@gmail.com =
<flyrotary@lancaironline.net> wrote:
> >>>>>=20
> >>>>> On 12/5/2020 6:35 PM, Stephen Izett stephen.izett@gmail.com =
wrote:
> >>>>>> Hi team
> >>>>>>=20
> >>>>>> Having completed phase #1 testing of the Glasair Super IIRG =
power by Renesis and RD1-C redrive, I=E2=80=99re going to pull the =
redrive for its 25 hourly initial inspection.
> >>>>>>=20
> >>>>>> Tracy deleted the damper assembly from the last rendition of =
his design and I=E2=80=99m considering removing ours by creating a new =
adapter plate from the existing splined
> >>>>>> part that is currently riveted to the damper and adding some =
longer bolts and spacers.
> >>>>>>=20
> >>>>>> Has anyone heard anything further in regard to RD receives with =
the damper removed?
> >>>>>> Has Tracy given any further updatess?
> >>>>>> All I have read was after initial tests some years ago.
> >>>>>>=20
> >>>>>> Cheers
> >>>>>>=20
> >>>>>> Steve.
> >>>>> Best I remember is that you need either an aluminum or steel =
racing flywheel, to get more mass on the engine side of the system.  =
IIRC, it's also limited to low mass (wood, etc) propellers. The ones he =
sold had a different input shaft, but I think Dave Leonard modified his =
RD1-C & to use a steel racing flywheel which was only slightly heavier =
than the aluminum version. Search for Dave's posts, if he doesn't chime =
in. I've been wondering if Guibo/Rototflex couplers could be a viable =
alternative to the aluminum plate/rubber discs. Probably would weigh =
more, and definitely cost more.
> >>>>>=20
> >>>>> Charlie
> FWIW, in the car, the torque converter seems to be bolted to the =
flexplate using the same holes that Tracy's adapter uses. Looking at the =
RX8 service manual, there may be a narrow sheet metal adapter ring =
between the flex plate bolt circle and the torque converter, but not =
much else in the way of structural reinforcement. (Of course, the torque =
converter housing itself may act as stiffener.) It *seems* logical to me =
that if there were going to be stress cracks caused by flying the =
assembly, they'd show up in the aluminum adapter plate before the steel =
flex plate. And cracking usually starts where there's a 'stress riser'; =
a notch or deep scratch in an edge. The only plates I've observed have =
un-dressed, sharp edged punched holes where the cracks seem to =
originate. I don't know whether it will help, but I attacked my =
uncracked flex plate with a die grinder & files to clean up all the =
accessible edges of holes, etc, as we do with any aluminum parts, before =
assembling everything.
>=20
> Again, just my opinion, but I think that the real benefit of the extra =
mass of a flywheel is pulse isolation from the gearbox.
>=20
> Charlie