Charlie,

A 3/16” thick disc would place the female spline in the original position and would most likely stabilize the Flexplate greatly.  An accurately machined hole in the center would engage the hub of the splined part and still allow that hub to protrude enough to engage the spacer.  In that way, one would not be depending on the bolts to maintain alignment.

Steve Boese 

On Jan 12, 2025, at 2:53 PM, Charlie England ceengland7@gmail.com <flyrotary@lancaironline.net> wrote:



◆ This message was sent from a non-UWYO address. Please exercise caution when clicking links or opening attachments from external sources.

Thanks for those images. Looks like a larger AL disc could replace part of the spacer's thickness and bolt to the holes where the damper plate mounted. Does that look reasonable 'in person'?

If feasible, I'm thinking that it could serve two purposes; raise resonant freq of the flexplate to a safe area, and add mass close to what would be in an AL flywheel (they're getting hard to find used, and new ones are really expensive).

I suspect the extra rotating mass on the Eshaft is needed (or at least a good idea). 

Charlie

Virus-free.www.avast.com

On Sat, Jan 11, 2025 at 6:45 PM Steven W. Boese SBoese@uwyo.edu <flyrotary@lancaironline.net> wrote:

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’t 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’s recent solid coupling design may best be done by also replacing the Flexplate with a manual transmission flywheel.

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.

Steve Boese 

<image0.jpeg>