I have to agree about the structural question, but have some further
comments on the spacer issue.
First I think the distance piece and shims were included as much
because it was the Austin standard as anything else.
Secondly, if done properly, the shimmed method provides the optimal
point at which the bearings (Tapered rollers) provide no detectible end
play with no thrust loading.
That would seem to be the best running condition for this type of
bearing and the fact that so many of them are still in use after 40 or
50 years would seem to bear that out.
Using the "tighten and slacken to feel" method works also, but is it
"RIGHT"?
Bill Lawrence
On May 26, 2004, at 5:06 PM, BJ8Healeys wrote:
> Yes, Mike, we did knock around the question for a while, and we DID
> come to
> conclusions, only not the same ones!
>
> First, the credentials: although I am no longer a practicing,
> slide-rule
> wielding structural engineer, that was my origin in the military
> aircraft
> world.
>
> From a structural analysis point of view, the bearing/spacer/bearing
> stack
> adds no strength to the stub axle because it is not structurally
> connected to
> (bolted, welded, or an integral part of) the stub axle, and
> consequently
> cannot resist either bending or shear loads applied to the axle by the
> wheel.
> Bending loads are the maximum at the root of the axle (that's why
> cracks
> appear here first), and the spacer stack merely "sits" here. It is not
> attached, no matter how much it is compressed against the butt of the
> axle by
> the axle nut.
>
> There seems to be very little actual technical information available on
> exactly why the spacer and shims are used in the Healey application.
> However,
> bearing engineering books indicate that ball bearings have inherent
> axial
> freeplay between the inner and outer races. In order to eliminate this
> freeplay, which could cause some lost motion in steering (my
> assessment), the
> spacer and shims are used to pre-load the bearings and remove the
> freeplay.
> This arrangement may not be necessary for tapered roller bearings,
> which have
> less inherent freeplay.
>
> I can't remember whether my BJ8 has ball bearings or tapered rollers,
> but I
> used the spacer and the shims, and I set up the wheels according to the
> manual. I believe they are necessary for ball bearings and couldn't
> hurt for
> rollers.
>
> To have your Healey opinions respected by Mike Salter is quite an
> honor.
> Thank you, Mike!
>
> Steve Byers
> HBJ8L/36666
> BJ8 Registry
> Havelock, NC USA
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