From: "Stephen Izett stephen.izett@gmail.com" <flyrotary@lancaironline.net>
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Subject: Re: [FlyRotary] Flexplate cracks
Date: Sun, 12 Jan 2025 15:03:34 +0800
References: <list-3785185@lancaironline.net>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
In-Reply-To: <list-3785185@lancaironline.net>
Message-Id: <1C72A6ED-5E29-43AF-B4D9-D3DF29D44764@gmail.com>

Thanks very much Steve

I recall something about concern over the material and the soft rivets.
Thanks

Steve

> On 12 Jan 2025, at 2:38=E2=80=AFpm, Steven W. Boese SBoese@uwyo.edu =
<flyrotary@lancaironline.net> wrote:
>=20
> Steve,
>=20
> The same splined part is in the larger photo and the smaller photo =
with the spacer.  It was cut from a C4 drum.  Tracy used soft rivets to =
attach the splined part to the aluminum damper plate because he was =
concerned with the strength of the splined part material.  I didn=E2=80=99=
t turn down the flange to 5=E2=80=9D in order to maintain as much =
strength as possible although that may not be necessary.
>=20
> Steve Boese=20
>=20
>> On Jan 11, 2025, at 9:56=E2=80=AFPM, Stephen Izett =
stephen.izett@gmail.com <flyrotary@lancaironline.net> wrote:
>>=20
>> =EF=BB=BF=E2=97=86 This message was sent from a non-UWYO address. =
Please exercise caution when clicking links or opening attachments from =
external sources.
>>=20
>>=20
>> Thanks for the resonance data and photos Steve.
>>=20
>> A questions. I=E2=80=99m thinking the larger photo of the original C4 =
splined female part was what I was thinking of doing.
>> Ie. Removing Tracy's rivets and turning it down before drilling the 6 =
holes to match the Eccentric shaft.
>> Is the original splined part from the C4 also in the photo with a =
spacer? Or is this another different part?
>>=20
>> Thanks Steve
>>=20
>>=20
>>=20
>>> On 12 Jan 2025, at 8:43=E2=80=AFam, Steven W. Boese SBoese@uwyo.edu =
<flyrotary@lancaironline.net> wrote:
>>>=20
>>> When the Flexplate is bolted to the eccentric shaft without the =
damper plate it rings with frequencies of around 320 and 1340 Hz.  It =
doesn=E2=80=99t ring with the damper attached.
>>> This gives the possibility that the Flexplate without the damper may =
resonate being excited by the engine harmonics at rpm ranges normally =
used in flight.  Such resonance could accelerate Flexplate cracking.  =
For this reason, I would be reluctant to eliminate the damper while =
retaining the Flexplate.  Converting to Tracy=E2=80=99s recent solid =
coupling design may best be done by also replacing the Flexplate with a =
manual transmission flywheel.
>>>=20
>>> The photo shows a couple of possibilities to convert to a solid =
coupling while retaining the original splined input shaft.  The =
thickness of the aluminum spacer or the steel part can be adjusted to =
accommodate the thickness of a flywheel.
>>>=20
>>> Steve Boese
>>>=20
>>> <image0.jpeg>
>>=20
>>=20
>>=20
>> --
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> 	=20
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