I am new to this list, but I have been on the triumphs list for some time.
Interestingly, I just read an explanation that may address this area.
(unfortunately, I deleted the original e-mail but saved that text to a
column I edit for our British Cars of NH (USA) newsletter.
'67 TR4A, '72 XJ6 & '74 MGB
Dave
ps Credit given below:
"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)!"
Edward
fogbro1@home.com
"David Pennington" <racerx23@earthlink.net>@autox.team.net on 12/29/2000
12:58:08 PM
Please respond to "David Pennington" <racerx23@earthlink.net>
Sent by: owner-mgs@autox.team.net
To: <mgs@autox.team.net>, "Barrie Robinson" <barrier@bconnex.net>
cc:
Subject: Re: wheel hubs on the "wrong" side
Barrie,
Thanks for the note. Please let me be clear, I do believe in the mysterious
locking action of the stock setup. Sufficient examples have been presented,
with but one counterexample (perhaps) under investigation. I don't yet
understand why it works, but the number of theories I have seen leads me to
conclude that I'm not alone in this. Your theory is one I have heard, but I
don't think it stands to reason. I will attempt to explain my thinking on
this.
Looking at the left rear wheel, (it has a RH thread) imagine the car doing
a
fast accelleration. During the accelleration, your theory would be working,
the shaft would be trying to screw itself into the spinner. However, during
braking (which is a sharper accelleration curve by far) the reverse would
be
enacted. Just like your drill example. Imagine the wheel, spinning rapidly
(counterclockwise). Suddenly the shaft/wheel stops. The nut/hub will at
that
point try to keep spinning counterclockwise, which with a RH thread of
course
unscrews it. Since this twisting force force during braking is much greater
than during accelleration, the net effect would be the reverse of the
desired
effect, so this theory cannot be what is causing the spinner to tighten. We
have to look elsewhere for the mysterious locking force.
that's my 2 cents anyway
- Dave
----- Original Message -----
From: Barrie Robinson
To: David Pennington ; mgs@autox.team.net
Sent: Friday, December 29, 2000 1:29 PM
Subject: Re: wheel hubs on the "wrong" side
David,
We all know that we are talking splined wheels not bolt on wheels. yes?
It is all very simple if you have engineering training.....Image the wire
wheel and its wing nut.. The wing nut is reluctant to rotate (Newtons's
first law of motion). As the half/stub axle rotates it screws itself
into
the wing nut because the nut is resisting movement This screwing-into
or
tightning continues as the nut always resists being moved. Conversely
when
the car drives backwards there is a tendancy for the winged nut to
unscrew.
The force applies is not large as one can imagine - but given time it
will
get loose and then will unscrew rapidly. If you want to see this work
just
put a bolt in your electric drill, put a nut on the end and see what
happens when you turn the drill on - in both directions.
At 01:17 PM 12/28/00 -0500, David Pennington wrote:
>I am not trying to be obstinate, but why would a spinner get tighter
from
>driving the car forward as opposed to backward? Stopping and starting
torques
>have been discussed. My experience has been that stock spinners tend to
>gradually loosen with use. I also know from experience the stock setup
can
and
>will unscrew if the splines fail, and I have proposed a theory as to why
they
>do so. But what possible force could be twisting the spinner if the
splines
>are not spun? Am I missing something here?
>
>I can imagine a tiny amount of play may exist between the splines which
could
>allow the wheel to twist the spinner, and this could/would/will
eventually
>loosen the spinner. But this play would be exceedingly small with good
>splines, if it exists at all. And if it does exist, it will tend to undo
ANY
>spinner, regardless of its LH-RH thread type. This is why ALL spinners
need to
>be checked periodically. BTW, a fine thread spinner is less subject to
>loosening than the coarse, due to the increased force the fine thread
spinner
>applies to the wheel if both are equally torqued. This explains the
switch
>from 8 TPI spinners to 12 TPI spinners found on later models.
>
>I don't follow your reasoning here, and would very much like to
understand
if
>there is a mechanical principle I am overlooking.
>
>thanks again,
>
>Dave P
>70B
>
>----- Original Message -----
> From: Dave Quirt
>
> David:
>
> Don't do it. To do so is a definite death-wish. The main draw-back is
> that extended reversing WILL eventually unscrew the hub-nuts when they
> are on their proper side - they tighten (or keep tight) during forward
> motion. If put on the wrong side, they will be reversing whenever you
> are moving forward. Get the picture now??
>
> Dave Q.
> As and Bs
>
>
Regards
Barrie Robinson
barrier@bconnex.net
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