Mailing List flyrotary@lancaironline.net Message #64470
From: Charlie England ceengland7@gmail.com <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: 1mm thrust washer
Date: Mon, 12 Nov 2018 17:00:05 -0600
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Just so everyone's on the same page, Bobby's talking about wear on *the shaft* from the 1mm washer, which currently rides between the two thrust bearings. The goal is to get a 3.5mm washer in that central spot.

On 11/12/2018 4:39 PM, Bobby J. Hughes bhughes@qnsi.net wrote:
image1.png

Steve,

I think the C drive bearing stack is different than the A series. I have observed a small amount of wear on the aluminum’s plant from the 3.5 mm rotating but it’s not measurable except by feel. For the C drive, reordering the bearing stack and locking the 1mm thrust washer should eliminate potential wear at both locations. I’ve inspected four drives and 2 have some wear at the 1mm washer. 

Bobby 


Sent from my iPad

On Nov 12, 2018, at 5:25 PM, Steven W. Boese SBoese@uwyo.edu <flyrotary@lancaironline.net> wrote:

As a result of following the messages concerning the input shaft thrust bearing, I disassembled the RD1A reduction drive that was installed on my test stand after spending 610 hours of flight time with a fixed pitch prop.  The input shaft thrust bearing setup on this unit appears to be similar those recently discussed.

The attached photo shows the mounting plate having a pocket 0.006" deep worn into it by the thrust bearing.  As recommended, conditions where the prop was driving the engine were deliberately minimized.  Possibly I wasn't conscientious enough about this.  In any case, it would seem to be a good idea to fix the thrust washer to the mounting plate to avoid the wear I observed.  "Stickum" or a pressed fit into the proposed cup might be effective.  If the wear rate I encountered was typical, a 2 mm deep pocket would be the result after about 8000 hrs of operation thus requiring no additional machining. 😉 The photo also shows that the other end of the thrust bearing has been turning on the shoulder of the input shaft.  This appears to be cosmetic as the amount of bearing wear here was not measurable.  The plastic snubber did not show obvious damage.


The RD1A uses a single thrust bearing.  I have found references to stacked thrust bearings being used to increase the axial load capacity of the bearing assembly, but this involves more than simply stacking normal individual thrust bearings:

https://www.tackpoint.com/stacked-thrust-bearing-gallery/jtqo7l8j741jy1zvu8abos9hziflyw

If the stacked thrust bearings are used to extend the reliable RPM range of the assembly, I have found no references to this being standard practice.  There doesn't seem to be any guarantee of the relative speed of each bearing in the stack.  What am I missing?


Steve Boese




    

  


From: Rotary motors in aircraft <flyrotary@lancaironline.net> on behalf of Neil Unger 12348ung@gmail.com <flyrotary@lancaironline.net>
Sent: Monday, November 12, 2018 1:48:32 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: 1mm thrust washer
 

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


Charlie,

                 Sounds simple, but to cut the depression in the plate accurately will take a lot of setup time.  Then whatever depression you cut will have to be added to the nylon snubber washer and the whole gear train will be moved backwards as well.  Couls end up time consuming and very messy IMHO.

Neil.


On 11/13/2018 2:53 AM, Charlie England ceengland7@gmail.com wrote:
Could the same effect be achieved by milling a depression in the 1/2" plate? How thick are the thicker washers; 2 mm? If so, mill a 1mm depression in the plate, and replace the thin 1 mm washer with a 3rd 2 mm washer. IIRC, Locktite makes a 'stickum' that could keep the washer embedded in the plate, so it doesn't un-nest when the shaft is unloaded. Would this excessively compromise the strength of the plate?

Charlie

On 11/12/2018 7:10 AM, Bobby J. Hughes bhughes@qnsi.net wrote:

Neil,

 

Looking good. The cup ID may need to be a few thousands over 52mm so not sure if there’s room for a mounting spigot. Depending on material thickness,  the cup will fully enclose one of the 2MM bearings and part of the 3.5mm thrust washer. Possibly add oil path grooves to the front and rear of the cup at 45 degree clocking. Depending on the material thickness the channels may need to be offset. Oil channels may not be necessary.

 

Too early for wine but well caffeinated!

 

Bobby

 

 

From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net]
Sent: Monday, November 12, 2018 2:26 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: 1mm thrust washer

 

Kelly,  I really should not draw freehand --- see if you can make sense of the scribble.  Neil.

 

On 11/12/2018 4:15 PM, Kelly Troyer keltro@gmail.com wrote:

Neil and All,

    Not sure I am visualizing the shape of the of the cup to encapsulate the 

1mm thrust washer but would certainly be a customer if Randy Kempf were

to gear up to produce them........How about sketch of the proposed shape

for those of us that are somewhat mechanically inept...........<:)

 

Kelly Troyer 

 

On Sun, Nov 11, 2018 at 6:52 PM Neil Unger 12348ung@gmail.com <flyrotary@lancaironline.net> wrote:

Bobby,

                        Sorry I misunderstood you.  By all means contact
Randy as he may be able to fit you in.  He has a complete reduction
drive of mine there to measure,  and certainly has the machinery to make
same.

Neil.


On 11/12/2018 7:41 AM, Bobby J. Hughes bhughes@qnsi.net wrote:
> Neil
>
> I was asking if Randy would consider making the 1mm washer mounting cup. I have a chip detector but removed it due to the 1mm washer / shaft wear creating fuzz every few hours and setting off an alert.  I also measure the gearbox oil temp output.
>
> Bobby
>
> Sent from my iPad
>
>> On Nov 11, 2018, at 3:15 PM, Neil Unger 12348ung@gmail.com <flyrotary@lancaironline.net> wrote:
>>
>> Bobby,
>>
>>                       Another way is what I did, was to put a temp sensor in the pSRU which will let you know if all is not well with elevated temps.  This is standard in heavy trucks,  One in the gear box, and one each in both diffs.  Simple and effective.
>>
>> Neil.
>>
>>
>>> On 11/12/2018 6:58 AM, Neil Unger wrote:
>>> Bobby,
>>>
>>>                       I put a magnet in the return line to catch any metal, but only got the "fuzz" you are talking about so simply removed it.
>>>
>>> Will discuss with Randy re stocking a chip detector.  That will be his commercial decision.
>>>
>>> Neil.
>>>
>>>
>>>> On 11/12/2018 3:29 AM, Bobby J. Hughes bhughes@qnsi.net wrote:
>>>> Neil,
>>>>
>>>> That should work. I believe Tracy has suggested the same solution. It would allow for replacing the 1mm washer if needed. I’m thinking aluminum instead of steel to minimize any wear on the washer outer edge if it rotated. I would like to start using my gearbox chip detector again. The 1mm washer shaft contact caused enough fuzz to activate it every few hours so I removed it. Would this be an item Randy Kempf would consider supplying? We need four in Austin TX and I’m sure others would retrofit if the part was available.  The cup OD would need to increased but I think we have plenty of room to accommodate modification.
>>>>
>>>> Thanks,
>>>> Bobby
>>>>
>>>> Sent from my iPad
>>>>
>>>>> On Nov 10, 2018, at 4:01 PM, Neil Unger 12348ung@gmail.com <flyrotary@lancaironline.net> wrote:
>>>>>
>>>>> Bobby,
>>>>>
>>>>>                     Tried my bearing blokes with no joy, over that size they are all 1.5mm.  There is another way however if there is room.  I suggest a small alloy (or steel) "cup" with mounting flanges like the washer you want, except in the middle the 1mm washer fits flat against the mounting plate as usual, and the cup then tapers upwards (after the 1mm thick retaining hole at the bottom ) and out slightly (for say another 3mm?) to prevent the 1mm thrust washer to "jump out of bed" and moving sideways. If it does move forward the taper will force it back into place when the load comes on again.  My $0.02 worth,
>>>>>
>>>>> Neil.


 

 

 



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