But, Dave.....
if the distance piece is put into compression by torquing the nut, the stub
axle will see exactly the same amount of TENSION, yes? This would move the
tensile loads on the stub axle closer to its ultimate tensile strength, and
reduce any margin available to resist bending loads from driving. Any
up-bending loads on the axle are translated into tensile loads on its bottom
surface.
This is another one of those discussions that comes up on the list
periodically. I respectfully submit that the distance piece does not add
any strength to the stub axle. It is there only to preload the bearings.
Steve Byers
HBJ8L/36666
BJ8 Registry
Havelock, NC USA
-----Original Message-----
From: owner-healeys@autox.team.net
[mailto:owner-healeys@autox.team.net]On Behalf Of Dave & M
Sent: Monday, May 22, 2006 5:56 PM
To: jerry adams
Cc: Healey list
Subject: Re: Re; Front wheel bearings BN2-BJ8
Hi folks,
My take on the front axle "distance pieces".
The Austin stub axles are a bit small/weak for the Healey applications.
Since the distance pieces are considerably larger in diameter than the
stub axles & installed in compression, 50 to 70 ft/lb of preload, they
act to effectively increase the stub axle diameter & greatly reduce the
bending moment on the axles. Stiffen/strengthen the axles, if you will.
A bearing is never intended to have this much side/end load, so the
distance piece assembly is shimmed to reduce the bearing side load while
still maintaining a good deal of compression on the distance pieces to
increase the axle strength.
A very clever if somewhat unknown advantage of this feature.
Dave Russell
BN2
jerry adams wrote:
> List,
>
> Just to add to what Steve said. Donald and Geoff were good well
> grounded engineers with lots of practial and racing R & D. The BN1
> had ball bearing type front wheel bearings and probably had stub axel
> or bearing failures which cause them to go the Timken tapered roller
> bearing for the front. Since the front wheels and axels receive a
> lot of both radial and axial loads I can understand why the Timken
> tapered roller bering was selected. For these bearings to preform as
> designed the must have preload so that the races are not damaged from
> shock loads during driving. The ideal preload would be exactly 0
> lbs, so that the bearing would not move during any axial load since
> the cars weight has already loaded the radial load. (Actually the
> Timken design has both radial and axial loading built in when the
> bearing is install and weight is put on the bearing, with 0 lbs.
> preload). The distance piece and the shims were added to give the
> bearings as colse to 0 lbs of preload as possible. In actual
> practice you can't get 0 lbs unless you are very lucky, so the next
> best thing is to try for a few ozs. of preload. A few ozs. of
> positive preload is better than a slightly negative preload, since
> the negitive preload will give you some slack and cause some small
> load shock during axial loading. Too much preload will cause
> brinelling and premature bearing failure. When installing the
> bearings and setting up preload, set up with light oil on the
> bearings and without the grease seal, some say set up the bearings
> dry. After preload is set then grease bearings and install grease
> seal. This is a lot of work but should be done right.
>
> Jerry BN2
|