From: "Neil Unger 12348ung@gmail.com" <flyrotary@lancaironline.net>
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Subject: Re: [FlyRotary] Re: cushion drive - retrofit questions.
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
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Date: Thu, 8 Nov 2018 07:20:48 +1100
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Bobby,

                   There is no need to replace the input shaft on the 
RD1-C just to fit my cushion drive.  My input shaft is identical except 
it is machined from solid and a one piece shaft.--- and much dearer!

Bearing stack,  if you use my shaft exactly the same stack required.

Yes snubber washer thickness is unique as distances vary slightly.  I am 
happy with 5  - 10 thou clearance as the washer is to only contact when 
the prop is driving the engine which  allows the input shaft to move 
forwards.  The snubber washer simply prevents metal to metal contact in 
that situation.  I do know of one redrive that is operating without the 
washer at all and all it seems to do is allow oil leakage from the seal 
on the input shaft as it travels back and forth, (if it actually does?)

End play I believe is difficult to check as drag on the parts, when 
stationery, seem to make shaft movement impossible.  But it is possible 
in theory for the shaft to move, hence the nylon washer.  As you say 
gear lash is simple.

Neil.


On 11/8/2018 1:34 AM, Bobby J. Hughes bhughes@qnsi.net wrote:
> Neil,
>
> I've got a few questions about the input shaft replacement.
> Does the replacement input shaft use the same thrust washer stack at the RD1-C?
> If a replacement shaft was retrofitted how does that affect the molly infused snubber washer tolerance? I believe it would be unique for each drive. Not sure what the acceptable tolerance range is.
> 0.50 - 1" movement seems like a lot. There may be some movement in my RD1C but I'm not aware of it. I check lashing and endplay before each flight but never noticed any movement other than lashing.
>
> Thanks,
>
> Bobby
>   
>
> -----Original Message-----
> From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net]
> Sent: Wednesday, November 07, 2018 12:15 AM
> To: Rotary motors in aircraft
> Subject: [FlyRotary] cushion drive
>
> Charlie,  Photo attached,.  Should the rubber fail then the inner drive block will simply lock up on the outer square giving metal to metal which should last quite some time (hours) before wearing either away. The rubber is "engine mount" rubber so will only deteriorate slowly and not just explode and disappear completely. To test for wear you simply rock the prop and any more than 1 inch movement would suggest a problem as in deterioration in the rubber.  I can only get a half inch movement which is in the gear drive train.  The rubber can be re-vulcanised if it is ever necessary.  I have now in excess of 50 hours with the rubber insert for no visible wear..
>
> Neil Unger.
>
>   
> --
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