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Date: Wed, 09 Feb 2005 09:31:20 -0500
From: Ernest Christley <echristl@cisco.com>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: PSRU - hub/prop end
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George Lendich wrote:

>Ernest,
>Timken Taper Bearings are the best there are, but I'm surprised there is
>only one - there's not one on the other end of the shaft?
>They are in fact overkill for this application.
>
>  
>

Did some research last night, and I am now very comfortable with the 
taper bearing.  There is in fact one on the other end, but I was not 
considering it, because I view all the forces trying to pull the hub off 
the shaft and the rear bearing won't see much stress in that situation.  
Now I realize that the rear bearing will be important to keep the hub 
aligned properly, and this won't happen unless the correct preload is 
applied.  I also understand that the correct term for the load forces 
are axial and radial, not longitudanal and lateral.

>The nut will be for preload, remember when you put it back on, that you know
>the preload number.
>
>  
>

Unfortunately, the nut was finger tight and the keyed lock washer had 
never been bent to lock it in place.  I have no idea what the preload 
number is or how to determine it.  On cars, we always just tightened the 
nut till there was no side play in the wheel but it still spun freely.  
I would think that I'd want it a little tighter in this application, 
since the forces will be trying to open up the rear seal and the only 
thing stopping that will be the preload...but I don't have a number to 
attach to 'little tighter'.

>Again go to a bearing supply company, I have no doubt that there would be a
>standard seal to fit. Who ever made this PSRU would look for standard seal
>sizes.
>
>George ( down under)
>  
>

Thank you, George.  I looked over Tracey's website (thank you, Tracey), 
and several other places.  I think in the application that this hub was 
meant for (a racecar wheel), that the car's wheel was the seal.  I have 
a 1/4" plate that will sandwich nicely between the prop and the hub.  I 
can easily machine a recess into it for a standard seal (I think).