The axle shafts in Spridgets fail on street cars at the spline. The root
cause of the failure is coming off of slick pavement (such as ice) onto
dry pavement with your wheels spinning. This causes the axles to twist
at the splines. Later they will fail at the weakened area. If you are
buying used axles, avoid any axles that show twisting at the splines. If
you have your brake drums off, you should pull the axles and check for
signs of twisting.
On race cars, the axles fail at the outside plate. The hub and bearings
have enough play that they will pass on the flexing movement during
cornering. This causes the axles to fail at the outside plate. This is
just like flexing a piece of metal until it breaks.
When I raced a Sprite in the 70s, I had to replace axles every 2 races
to prevent failures. Since the wire wheel axles are 2 piece units, I
tried to use the wire wheel hubs by machining off the splined area where
the wheels attach. That way, I could relieve the stress concentration on
the solid axle. I discovered the difference in axle length the hard way.
I ordered axles and found out they wouldn't fit because the length was
different. My best recollection is that wire wheel axles were about 3/4
of an inch shorter. When I checked the parts book, I discovered that the
axle housing had a different part number (oops). I tried to find a
machine shop to make axles that would fit the splines on the wire wheel
hubs and the splines at the differential. I was unable to find a machine
shop that could perform an acceptable job.
I also tried to fit double roller bearings to limit the flexing. I found
double roller bearings that it was possible to use, but I got out of
racing before I completed the modification to the hubs. Later on,
someone was making 2 piece axles for about $500 each in 1970 dollars.
You could buy a very nice street Spridget in 1970 for $500.
Tech tip
When the axles fail on street cars, you can remove the broken piece from
the differential without pulling the differential. Just remove both
axles and use a 1/8" steel rod from the other side to tap the axle out
of the differential. I used a support rod from a floral display. You can
use a magnet to remove the broken spline after it is out of the
differential. Takes about 20 minutes total and you don't have to pull
the differential.
I had an axle break on the way to high school in 1965 in my Bugeye. I
replaced the axle on the street and was only an hour late for class.
That included walking to the dealer for the part and talking him into
driving me home for tools (small towns are great). I was giving my
father a ride to work at the time. He was able to catch a ride the rest
of the way with someone he knew that was passing by. When he got home
that night, he was impressed that I didn't have to call a wrecker. He
had to have his Plymouth towed-in about a year before when it broke an
axle (I was probably responsible but he never found the connection). My
axle cost less than $20, his axle costs about $175 including labor and
towing.
A.J. (Jim) Seippel
jim.seippel@siemenscom.com
>-----Original Message-----
>From: Mike Gigante [SMTP:mikeg@vicnet.net.au]
>Sent: Saturday, December 20, 1997 3:16 PM
>To: Patton Dickson; John Nelson; Spridget List
>Subject: Re: Converting to Steel Wheels (plus Warning on half shafts)
>
> (snip)
>The standard half shafts do fail, even on standard, non-comp cars. They are
>not
>over-engineered - remember that the mechanicals were originally out of a
>baby Austin
>and they didn't change over the years but the engines and (especially) tyres
>have
>changed a great deal... However, that doesn't that they fail all the time.
>I'd be happy
>using a second-hand pair of half shafts.
>
>
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