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: Fri, 9 Nov 2018 07:34:32 +1100
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Bobby,

                    Welcome to my world.  No engineering shop wants to 
change what they do without effort.  That is unless you want to buy the 
shop in "set up" fees.

The prop movement of up to 1" is normal as the planetry gears are not 
"pressed" into the ring gear, so have the usual tolerances which allows 
movement.

Yes bearing stack is the same, but if you wish to put a larger thrust 
washer as in a 3mm instead of the 1mm, it is simply a matter if you have 
my input shaft, to simply machine off another 2mm from the input shaft 
to accommodate the extra thickness.  The shaft is "tough" but not 
brittle.  The normal carbide tips will cut it successfully.  Going from 
memory you should be able to do the same with Tracy's shaft.  The gear 
is hardened but I am sure another 2mm could be accommodated with 
grinding and machining.

The alternative is your costs as quoted which I feel will end up very 
expensive by the time the washer is finished.  I know of nothing like 
what you are looking for.  If you can get just the larger washer and 
drill the mounting holes is the only cheaper option.  There ae drill 
bits that easily drill a metal file.

Neil.


On 11/9/2018 12:42 AM, Bobby J. Hughes bhughes@qnsi.net wrote:
> Neil,
>
> So the 0.5 - 1" movement is the normal gear lashing plus any deterioration of the rubber flex coupling?  That would make more sense than how I originally interoperated the prop movement.
>
> "Bearing stack,  if you use my shaft exactly the same stack required."
>
> I have an inquiry in to Tracy about the feasibility of changing the bearing stack order. I've inspected four C model gearboxes and two of the units have some input shaft wear where the 1mm thrust washer is contacting the shaft. It has been suggested that swapping the 1MM and 3MM thrust washers should eliminate the shaft wear between the two thrust bearings. However the 1MM thrust washer will not capture on the input shaft for assembly. I have been unable to locate a 1MM / 35MM shaft thrust washer large enough to mount to the aluminum plate. I've attached a possible design that I have sent out for quote. One change is that the mounting tabs cut at the washer would need to include a radius to minimize stress fractures. Problem is the company has a $200 minimum setup fee.
>
> Bobby
>
>
> -----Original Message-----
> From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net]
> Sent: Wednesday, November 07, 2018 3:21 PM
> To: Rotary motors in aircraft
> Subject: [FlyRotary] Re: cushion drive - retrofit questions.
>
> 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.
>>
>>    
>> --
>> Homepage:  http://www.flyrotary.com/
>> Archive and UnSub:   http://mail.lancaironline.net:81/lists/flyrotary/List.html
>
> --
> Homepage:  http://www.flyrotary.com/
> Archive and UnSub:   http://mail.lancaironline.net:81/lists/flyrotary/List.html
>
>
> --
> Homepage:  http://www.flyrotary.com/
> Archive and UnSub:   http://mail.lancaironline.net:81/lists/flyrotary/List.html


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    <p>Bobby,</p>
    <p>                   Welcome to my world.  No engineering shop
      wants to change what they do without effort.  That is unless you
      want to buy the shop in "set up" fees.</p>
    <p>The prop movement of up to 1" is normal as the planetry gears are
      not "pressed" into the ring gear, so have the usual tolerances
      which allows movement.</p>
    <p>Yes bearing stack is the same, but if you wish to put a larger
      thrust washer as in a 3mm instead of the 1mm, it is simply a
      matter if you have my input shaft, to simply machine off another
      2mm from the input shaft to accommodate the extra thickness.  The
      shaft is "tough" but not brittle.  The normal carbide tips will
      cut it successfully.  Going from memory you should be able to do
      the same with Tracy's shaft.  The gear is hardened but I am sure
      another 2mm could be accommodated with grinding and machining.</p>
    <p>The alternative is your costs as quoted which I feel will end up
      very expensive by the time the washer is finished.  I know of
      nothing like what you are looking for.  If you can get just the
      larger washer and drill the mounting holes is the only cheaper
      option.  There ae drill bits that easily drill a metal file.</p>
    <p>Neil.<br>
    </p>
    <p><br>
    </p>
    <br>
    <div class="moz-cite-prefix">On 11/9/2018 12:42 AM, Bobby J. Hughes
      <a class="moz-txt-link-abbreviated" href="mailto:bhughes@qnsi.net">bhughes@qnsi.net</a> wrote:<br>
    </div>
    <blockquote type="cite" cite="mid:list-11853395@logan.com">
      <pre wrap="">Neil,

So the 0.5 - 1" movement is the normal gear lashing plus any deterioration of the rubber flex coupling?  That would make more sense than how I originally interoperated the prop movement. 

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

I have an inquiry in to Tracy about the feasibility of changing the bearing stack order. I've inspected four C model gearboxes and two of the units have some input shaft wear where the 1mm thrust washer is contacting the shaft. It has been suggested that swapping the 1MM and 3MM thrust washers should eliminate the shaft wear between the two thrust bearings. However the 1MM thrust washer will not capture on the input shaft for assembly. I have been unable to locate a 1MM / 35MM shaft thrust washer large enough to mount to the aluminum plate. I've attached a possible design that I have sent out for quote. One change is that the mounting tabs cut at the washer would need to include a radius to minimize stress fractures. Problem is the company has a $200 minimum setup fee. 

Bobby


-----Original Message-----
From: Rotary motors in aircraft [<a class="moz-txt-link-freetext" href="mailto:flyrotary@lancaironline.net">mailto:flyrotary@lancaironline.net</a>] 
Sent: Wednesday, November 07, 2018 3:21 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: cushion drive - retrofit questions.

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 <a class="moz-txt-link-abbreviated" href="mailto:bhughes@qnsi.net">bhughes@qnsi.net</a> wrote:
</pre>
      <blockquote type="cite">
        <pre wrap="">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 [<a class="moz-txt-link-freetext" href="mailto:flyrotary@lancaironline.net">mailto:flyrotary@lancaironline.net</a>]
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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</pre>
      </blockquote>
      <pre wrap="">

--
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</pre>
      <br>
      <fieldset class="mimeAttachmentHeader"></fieldset>
      <br>
      <pre wrap="">--
Homepage:  <a class="moz-txt-link-freetext" href="http://www.flyrotary.com/">http://www.flyrotary.com/</a>
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