From: "Stephen Izett stephen.izett@gmail.com" <flyrotary@lancaironline.net>
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Subject: Re: [FlyRotary] RD1-C damper
Date: Mon, 7 Dec 2020 15:06:51 +0800
References: <list-1015467@logan.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
In-Reply-To: <list-1015467@logan.com>
Message-Id: <604B9DD9-24A7-4BD2-AF87-2708C19D39BC@gmail.com>

See 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.

Cheers

Steve Izett


email from Tracy back in Feb 2012 -
"Finally got around to flight testing the aftermarket flywheel setup for =
the RWS redrive.=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.

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.

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.

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

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.

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.

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


> 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=99s=
 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
>>>>=20
>>>> --
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software.
>>>> https://www.avast.com/antivirus
>>>>=20
>>>>=20
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>=20
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