Steve, The two bearings are required as both have an upper rev
limit of approx 6000 RPM each, so with one thrust bearing the
engine is limited to 6000 rpm or if exceeded it will drag and
bore a hole in the back plate. THe thrust washer in the middle
is to separate the two thrust bearings that may well turn at
different speeds. The thin thrust washer is more likely to saw
its way through the input shaft due to being 1mm instead of 3mm.
The front thrust washer should be a light press fit on the input
shaft, and if the rear washer is also held then wear is highly
unlikely. Then nothing is perfect!!
Steve, just what turbo are you using? Many choices on the
market, but then all perform differently, so need figures from one
that is working on the Mazda to see what can be adapted. WE have
XR7 turbos here for $300 USD from China that fit most Fords - up
to 5 litre engines. Have you any details to clear the fog?
Neil.
Thank you Bobby for the
RD1C image.
Since there is no fixed
relationship between the relative motion of the two stacked
bearings (one of the bearings may not be doing anything except
taking up space), my question is: What is the advantage of
having the bearing stack with the center washer trying to saw
off the input shaft as opposed to using a thicker single
thrust bearing as in the RD1A?
Steve Boese
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:
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
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
◆ 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.
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.
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...........<:)
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,
>>
>> Â Â Â Â Â Â Â Â Â Â Â Â Â
        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.Â
Simple and effective.
>>
>> Neil.
>>
>>
>>> On 11/12/2018 6:58
AM, Neil Unger wrote:
>>> Bobby,
>>>
>>> Â Â Â Â Â Â Â Â Â Â Â
          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,
>>>>>
>>>>> Â Â Â Â
          Â
    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.
<thrust bearing s.jpg>
image1.png
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