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[105.245.235.50]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38a8e4b80d4sm3973004f8f.85.2025.01.10.01.44.42 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 10 Jan 2025 01:44:42 -0800 (PST) Content-Type: multipart/alternative; boundary=Apple-Mail-01B10EC8-B7FB-408A-9C8C-305FF9292A59 Content-Transfer-Encoding: 7bit Mime-Version: 1.0 (1.0) Subject: Re: [FlyRotary] Re: Flexplate cracks Date: Fri, 10 Jan 2025 11:44:30 +0200 Message-Id: References: In-Reply-To: To: Rotary motors in aircraft X-Mailer: iPhone Mail (21E236) X-SPAM-LEVEL: Spam detection results: 2 BAYES_00 -1.9 Bayes spam probability is 0 to 1% CBJ_GiveMeABreak 1.75 Messages with consecutive break characters DKIM_SIGNED 0.1 Message has a DKIM or DK signature, not necessarily valid DKIM_VALID -0.1 Message has at least one valid DKIM or DK signature DKIM_VALID_AU -0.1 Message has a valid DKIM or DK signature from author's domain DKIM_VALID_EF -0.1 Message has a valid DKIM or DK signature from envelope-from domain DMARC_PASS -0.1 DMARC pass policy FREEMAIL_FROM 0.001 Sender email is commonly abused enduser mail provider FREEMAIL_REPLY 1 From and body contain different freemails HTML_MESSAGE 0.001 HTML included in message KAM_MXURI 1.5 URI begins with a mail exchange prefix, i.e. mx.[...] MIME_HTML_ONLY 0.1 Message only has text/html MIME parts MIME_QP_LONG_LINE 0.001 Quoted-printable line longer than 76 chars MPART_ALT_DIFF 0.79 HTML and text parts are different RCVD_IN_MSPIKE_H2 -0.001 Average reputation (+2) SPF_HELO_NONE 0.001 SPF: HELO does not publish an SPF Record SPF_PASS -0.001 SPF: sender matches SPF record WEIRD_PORT 0.001 Uses non-standard port number for HTTP --Apple-Mail-01B10EC8-B7FB-408A-9C8C-305FF9292A59 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: quoted-printable What i can rember was this also a topic on t= he late Paul L group discussion.
Maybe Dave Leonard can chime in - think= more that it was gyroscopic forces that craked the plates
Maybe i= can find the photos and topic in my old mails

Sent from my iPhone
Le Roux Bre= ytenbach 

On 1= 0 Jan 2025, at 08:13, Andrew Martin andrew@martinag.com.au <flyrotary@lan= caironline.net> wrote:

=EF=BB=BF
Maybe some of the cracking= flexplates are resulting from starting issues, the starter motor can hammer= the ring gear if not meshing correctly or if engine misfires on start. may e= xplain why so many flexplates come pre-cracked from the wreckers.
=
Andrew




On Fri, 10 J= an 2025 at 11:32, Stephen Izett s= tephen.izett@gmail.com <flyrotary@lancaironline.net> wrote:
Hi M

I was wondering the same thing.

What I discovered first of all was that flex plates are designed to flex (fu= nny that) and cracking is not limited to our setup.
There are companies that specialise in stronger flex plates, particularly fo= r modified and higher horsepower engines.

Since our engines are being used at a higher horsepower per unit time and th= erefore higher stress (assumption) perhaps our setup could be likened to rac= e applications.
But then our hours of use would be significantly lower (assumption) than an a= verage vehicle, but perhaps not a race application.
Is the cracking we are seeing consistent with race applications? But they do= nt race automatics, do they?

So my take on this is that perhaps the flexing of the plate in our setup is t= o some extent higher than OEM.

Our options seem to be:
1. Replacing the OEM flex plate with a stronger part. Steve B being the late= st going down that track and in his case also removing the rubber isolation i= n the process.
2. Connect direct to the eccentric shaft and therefore taking the stress off= the Flex Plate doing away with the damping mechanism which Tracy did, and p= erhaps is still doing. Would be real nice to know.

Like M, I would appreciate hearing what others know or are thinking or doing= .

Steve Izett












> On 10 Jan 2025, at 2:15=E2=80=AFam, Marc Wiese cardmarc@charter.net <flyrotary@lancaironline.= net> wrote:
>
> Has the cause of these cracks been uncovered, and if so, what is the cu= rrent thinking on it? An AL racing plate?
> M
> Sent from my iPhone
>
>> On Jan 9, 2025, at 1:31=E2=80=AFAM, Steven W. Boese SBoese@uwyo.edu <flyrotary@lancaironline.n= et> wrote:
>>
>> =EF=BB=BFSteve,
>>
>> I didn=E2=80=99t see the cracks prior to disassembly and doubt that= they could have been seen on the counterweight side very well -if at all- w= hen assembled.
>>
>> I replaced the Flexplate with a steel flywheel about a year ago.&nb= sp; Since then, I replaced the four rubber dampers with machined aluminum di= scs giving a solid connection and then dynamically balanced the system. = ; This was done because maintaining a dynamic balance wasn=E2=80=99t possibl= e with the dampers.  Only a few hours of flight have occurred in this c= onfiguration so far and there has been no indication of problems resulting f= rom this change.
>>
>> Steve Boese
>>
>>> On Jan 8, 2025, at 11:03=E2=80=AFPM, Stephen Izett stephen.izett@gmail.com= <flyrot= ary@lancaironline.net> wrote:
>>>
>>> =EF=BB=BF=E2=97=86 This message was sent from a non-UWYO addres= s. Please exercise caution when clicking links or opening attachments from e= xternal sources.
>>>
>>>
>>> Hi Steve
>>>
>>> Is this recent then?
>>>
>>> I=E2=80=99m not able to get to my aircraft at present to check m= y flex plate which has probably seen 50 hours of service.
>>>
>>> Was it possible to see these cracks assembled?
>>>
>>> I would appreciate your reflections on Tracys latter choice to r= emove the damper, and particularly when using a timber/glass prop such as an= MT.
>>>
>>> It would be great to have an update and current info from Tracy= regarding his no damper hours if anyone can contact him.
>>>
>>> Very helpful, thanks again Steve
>>>
>>> Steve
>>
>> --
>> Homepage:  http://www.flyrotary.com/
>> Archive and UnSub:   http= ://mail.lancaironline.net:81/lists/flyrotary/List.html
>
>
>
> --
> Homepage:  http://www.flyrotary.com/
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