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Home✈️Aircraft🚁HelicopterHelicopter Main Discussion › Thrust Washer question..why?
05-27-2007 07:44 PM  13 years ago
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tauscnc

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Joliet IL

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Thrust Washer question..why?
*** POST FIXED***

Why do thrust bearings...washer have one larger hold in one and one smaller hole in the other.

Why must they be put on a certain way?

Only thing I can think of is some binding issues??

thanks,
taus
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05-27-2007 07:54 PM  13 years ago
AirWolfRC

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Yes, it's a binding issue. The smaller ID goes on the side that is not expected to rotate relative to the shaft and the larger ID goes on the side that IS expected to rotate relative to the shaft.

Brings up the question, why not make both ID's large ?
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05-27-2007 08:50 PM  13 years ago
tauscnc

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I wonder if the smaller hole is to keep the thrust bearing centered??
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05-27-2007 10:48 PM  13 years ago
wuzofoz

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Brisbane,Queensland- Australia

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the washer with the smaller ID should also have a smaller OD.
I wonder if the smaller hole is to keep the thrust bearing centered??
thats about right with the thrust bearings we use in helis.
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05-27-2007 11:43 PM  13 years ago
balsabasher

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Central Ohio, USA

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The washers are the races for the ball bearings between them.
Look at it this way, smaller id hole washer = inner race, larger id hole washer = outer race. Yes, the smaller hole is to hold and center the bearing to the shaft.
Normally used in blade grips to take side loads while allowing grips to turn freely.
And yes, they must be installed correctly.
Blades; what goes around, comes around!
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05-28-2007 12:00 AM  13 years ago
swheli

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cornwall uk

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thrust washers
They have different size holes so that when you have assembled blade grips you have to take them off again just to make sure you put them on correctly the first time !!!
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05-28-2007 04:11 AM  13 years ago
dkshema

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Cedar Rapids, IA

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Those would be thrust BEARINGS, not thrust washers. You'll find thrust WASHERS on the front end of your crankshaft.-----
Dave

* Making the World Better -- One Helicopter at a time! *

Team Heliproz
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05-28-2007 04:49 AM  13 years ago
jschenck

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La Vista, NE.

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I did some thinking about this recently trying to truely grock the how and why. What I came up with is basically the object is to let the thrust bearing to continue to work even if one side is locked against the spindle due to side load on the grips.

So in the case of our main rotor grips you want the spindle to lock against the outside plate of the thrust bearing so that the pull of the blade and thus the weight/pull of the assembly is on the inside plate of the bearing which can still rotate on the caged thrust bearings without locking against the spindle shaft.

This is why we need to make sure that the larger I.D. plate goes toward the middle and the smaller I.D. plate goes toward the blades.

Sound about right?
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05-28-2007 06:24 AM  13 years ago
uragem

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Indianapolis, IN - USA

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I have a related question. Which way should thrust bearing races face. Exposed ball section facing in or out (towards the blades)?Indy Jeweler
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05-28-2007 06:26 AM  13 years ago
Dennisu

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Langley, B.C. Canada

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tauscnc

If you are talking about Thrust Bearings then each race of the bearing has to be anchored to something at each side/end but NOT to the same thing. The outer bearing (small ID) is attached to the feathering spindle and stays fixed to it and must therefore be separate from the grip (small OD). The inner bearing is taking the centripetal load of the grip and blade and passing that to the outer bearing race and so must be fixed to the grip (large OD) and not drag on the feathering spindle (large ID).
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05-28-2007 06:29 AM  13 years ago
Dennisu

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jschenck
What I came up with is basically the object is to let the thrust bearing to continue to work even if one side is locked against the spindle due to side load on the grips.
No that is not the reason. See the explanation in previous text.
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05-28-2007 06:33 AM  13 years ago
Dennisu

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uragem
I have a related question. Which way should thrust bearing races face. Exposed ball section facing in or out (towards the blades)?
Both races, with the balls in between, make up the complete bearing. Would not work any other way. See previous post of mine to explain which races go where and why.
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05-28-2007 01:24 PM  13 years ago
ProModeler

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Sanford, FL (Orlando area)

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uragem,

It doesn't really matter how the balls face, but as a matter of personal preference, I place the unit into the grip such that it cups the grease under centrifugal force - the theory being it helps retain grease better.

My 2¢

John Beech
AMA # 47381
IRCHA #745
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05-28-2007 01:30 PM  13 years ago
z11355

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New England

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I think most of the greases are a bit too light and they tend
to spread and migrate. you want a really sticky, high-pressure
type of grease like MolyB but I agree w/ Mr. Beech on orientation.
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05-29-2007 01:17 AM  13 years ago
Dennisu

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Langley, B.C. Canada

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uragem

Did not know that you were referring to the ball cage and not the races of the bearing.
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05-29-2007 01:36 AM  13 years ago
Yug

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UK. Herts

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Bosch Ft1v27 works well and the ball cage 'cups' hold it pretty well when facing inwards. As for the ID of the outer, it helps maintain centering as well as the fact that the larger ID of th inner will always maintain some clearence on the spindle and hence wont wear or bind.
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05-29-2007 03:57 AM  13 years ago
jschenck

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La Vista, NE.

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as well as the fact that the larger ID of th inner will always maintain some clearence on the spindle and hence wont wear or bind.
That's what I was trying to say, perhaps not as clearly.
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