Hot topic on MG list: Interesting answer here.
----- Original Message -----
From: "David Pennington" <racerx23@earthlink.net>
To: "MG List" <mgs@autox.team.net>
Sent: Friday, December 29, 2000 7:48 AM
Subject: Fw: wire wheel discussion
> I recieved an excellent explanation from a Sunbeam racer who seems to have
a
> good handle on the mysterious locking action, his name is Carl
McLelland...
>
> ==================================
> Hi David,
> Geez, I had forgotten all about that letter I put out on the vintage race
and
> Alpine nets...... As it turns out, another physicist wrote a thread that
> explained what's happening. It was so simple I was ashamed that I didn't
see
> it right away. What causes the knockoff to tighten instead of loosen is
the
> same principle that allows a train to go around a curve.
>
> Picture in your mind a cross section of railroad track, and the wheel on a
> train car. (Remember, the wheels on a train are part of the axle.... the
> 'inside' wheel turns at the same rate as the 'outside' wheel). Thus, when
a
> train car goes around a curve the inside wheel is turning the same rate as
the
> outside wheel. Which means(!!), one of the wheels must be sliding/skidding
on
> the track because you have a different radius for the inside track and the
> outside track. SO, how does the train go around a curve?
>
> The top of the track is curved and the wheel surface is slightly slanted
> (larger diameter on the inside of the wheel and smaller diameter on the
> outside of the wheel). As the train goes into a (for example) left curve,
> centrifugal force pushes the train axle(and wheels) to the outside of the
> curve. The outside of the "left wheel" is in contact with the "lower" edge
of
> the track and the inside of the "right wheel" is in contact with the
"center"
> edge of the track. This results in a slight increase in the mathematical
> radius of the inside wheel and decrease in the mathematical radius of the
> outside wheel, which makes the radius for inner and outer wheels nearly
the
> same, which allows BOTH wheels to "roll" on the track rather than slide.
>
> If your still with me, if you haven't fallen asleep and your eyes glazed
over
> (!!!!!), the same basic thing is happening between the knockoff and the
> "knockoff mating surface" of the wheel. They are both slightly curved,
thus as
> the axle rotates with the knockoff on the axle and tight against the
mating
> surface on the wheel, there is just enough difference in radius' to
> effectively be constantly tightening the knockoff.
>
> DON'T EVER REVERSE THEM!! (Left on right and right on left)! You would not
be
> able to tighten them enough to prevent the knockoff from coming off the
> axle!!!!! The knockoff WILL COME OFF and you will lose the wheel..... just
> before becoming the first person to the scene of the accident!
>
> I was safety wiring the knockoffs because I had this fear of losing a
wheel.
> I've since lost that fear. If the knockoff is tighened properly to begin
with
> it cannot come off. As an experiment, I beat on my knockoffs with a lead
> hammer until they wouldn't tighten any more. I safety wired them with the
> safety wire TIGHT! After a 20 minute practice session at Thunder Hill I
> checked and sure enough, they had tightened! I retied the safety wire
(again
> TIGHT), and after a 20 minute race they had tightened more!! The same
occurred
> on the next days practice and race. A couple months later, at Sears Point
(I
> had not removed the wheels between races), I went throught the same drill,
and
> after each session the knockoffs had tightened. Two weeks later, again at
> Thunder Hill (I had intentionally NOT removed the wheels between races) I
went
> through the same drill, and SAME SCENE, TAKE THREE! After each session
they
> had tightened!
>
> Lastly, Thunder Hill is a counter clockwise course and the fastest corners
> (which means the greatest wheel loading) occurs in left hand corners. I've
> noticed that the right side knockoffs tighten more than the left side
> knockoffs, which would be consistent with greater loading on the right
side of
> the car.
>
> I hope this answers your questions.
> Carl
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