Well, I'm not a GM automotive engineer, but I am an aircraft structural
engineer with some experience in stress analysis of landing gears. My
previous statement that the spacer adds no strength to the axle was based
on the conclusion, from looking at the system design, that its purpose is
merely to ensure that a load on one ball bearing in the "non-thrust"
direction is reacted by the other bearing in the "thrust" direction, but
mostly by the point that Crash makes.
Crash is exactly right that putting a tension load on the stub axle
actually will reduce the capability of the axle to take a bending load.
When the axle is bent upwards, for instance, the upper surface of the axle
is in compression, while the lower surface is in tension. I think that
would be pretty evident to most people. The tensile stresses from pure
tension and bending moment are additive, so that bending the axle upwards
with a tensile load already on it would move the total tensile stress on
the bottom surface closer to failure, while the bending moment would
relieve the tensile stresses on the top surface.
It is also not intuitively obvious to me that the amount of torque applied
to the axle nut will place the 1-inch diameter hardened steel axle under
significant tensile stress at its base.
I have a spare stub axle and bearings to take some measurements from, and
plan to do some more investigation into this. My reference materials are
at work, but I hope to be able to do a stress analysis of the axle and
bearing system. I'll report my results later (if they prove my point!
:-) ).
Steve Byers
Havelock, NC USA
'73 Midget GAN5UD126009G "OO NINE"
"It is better to remain silent, and be thought a fool
than to speak, and remove all doubt" -- Mark Twain
----------
> From: David Ramsey <dwramsey@worldnet.att.net>
> To: Angela Hervey-Tennyson & Peter Westcott <toobmany@bigpond.com>
> Cc: spridgets@autox.team.net
> Subject: Re: Front Wheel Bearings...
> Date: Sunday, May 09, 1999 4:49 PM
>
> Please ask your GM engineer why placing the axle in a state of tension
reduces the bending moment stresses? Also why placing the hardned bearing
races in a state of compression with a spacer adds strength to the system?
This goes against everything I learned in strenghts of materials or in
Mechanics of Materials, 3rd Ed Gere/Timoshenko. If anything an axle in
tension has less resistance to bending moment stresses! Racers have broken
axles for years, thats why they buy the high strenght axles, it has nothing
to do with if they have spacers or not. The repeated high bending moment
stresses that they place on the axles with big sticky tires is why they
break. By the way I have run timken tapered cone rolller bearings with no
spacer in my street bug-i for many years with no problems. Sorry guys,
just had to say it!
> Crash
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