I'd like to share this explanation on the front bearing spacer and shims
topic that we've been beating to death lately, it sounds logical. It's an
answer to a question I sent to Mike (a Sprite racer who's not on the list
and lives in South Carolina) and I don't know his last name.
And BTW... I just talked to Don at Mini Mania, they don't sell the front
wheel spacer shims. Don also told me that they are moving to Grass Valley.
Drats!!... no more lunch time visits to MM.
-Drew
Drew,
Yes, these spindles/stub axles have broken in the past. A fellow out on the
west
coast (British Masters) recounts a tale of a serious accident and long
recovery
time due to a broken stub axle. For the most part, the failures are due to
stress fatigue for the materials used. Magnafluxing during the winter hiatus
from racing is a good preventive maintenance. Another solution is to upgrade
to
the 4340 steel spindle that has been machined from an extrusion and is then
pressed into the swivel portion of the stub axle and welded in place. The
factory steel is of the EN17 variety which falls into the common variety
3000
series steels here in the US.
I have run the BTA746 and BTA747 stub axles for many years using the
assembly
method outlined without a failure (knock on wood). In discussing this matter
with one or our stress engineers here on site, our conclusion was the
installation helps insure 1) the inner races won't turn, 2) ensure the
bearing
loads are consistent at known application points to the stub axle and 3)
prevent
any slop (loosness) in the installation for increasing the bending moments
at
the inner bearing root of the spindle.
The installation won't make the stub axle any stronger, it only assures the
loads are consistent due to a better installation.
We probably could have spent an hour discussing the materials, the
installation
and all the various conditions, brought in a couple more engineers and still
come up with about the same conclusion. Maybe tomorrow.
I will e-mail you with the cost for shipping the parts on Friday. I have
some
time to go to the UPS shipper and get the information.
Hope my discussions help.
Mike,
You had mentioned before that I should use the center wheel bearing spacer
even though I've converted to the tapered roller bearings, but I'm having a
hard time figuring out why.
With the spacer in place, correctly shimmed and the caster nut torqued to 90
Lbs., the end result would be an outward pulling on the axel and a
compression force on the inner bearing races locking them on the axel with
the spacer between them. I don't see how this would make the axel stronger
or is the objective to keep the inner bearing races from turning on the
axel? Do these cars have a history of axel problems when the wheel bearing
spin on the axel creating a stress line for a future failure?
Thanks,
-Drew
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