Since Rudge-Whitworth taper mounted wire wheels do indeed self tighten their
knockoff when installed properly, there is absolutely no need to safety wire
the knockoffs. However if the wheels are pin drive like Halibrands and some
Jag wheels, they are not selftightening and the knockoffs must be safety
wired. John Harden
----- Original Message -----
From: Simon Favre <simon@mondes.com>
To: Brian Evans <brian@uunet.ca>
Cc: Carl McLelland <carlmcle@saturnnet.com>; Vintage list
<vintage-race@autox.team.net>; Alpine list <alpines@autox.team.net>;
<clark@dnf.com>
Sent: Thursday, April 20, 2000 3:51 PM
Subject: Re: Wire Wheels
> OK, OK, OK. I think I've got this figured out. It has nothing to do with
> the inertia. It has nothing to do with braking or accelerating. It has
> everything to do with the taper fit at the knockoff and the wheel hub,
> as Brian pointed out. Here's what's happening.
>
> Let's start out assuming the knockoff is absolutely tight. This means
> everything is moving at the same RPM, nothing is getting looser or
> tighter, all is well. Now let's assume the knockoff is a little loose.
> Since the fit between the inner piece (wheel hub) and the outer piece
> (knockoff) is a taper, when it's loose, the taper joint will only be in
> contact at one point. In this case, the wheel rides up and the contact
> is at the top. At this point, at the top of the wheel hub, you have a
> smaller diameter circle in contact with a larger diameter circle. In
> order for the two circles to be turning at the same RPM, the outer one
> would have to be traveling at a higher LINEAR surface speed. Since they
> are in contact at one point, the outer piece is only traveling at the
> same linear surface speed as the inner piece. Therefore, the outer piece
> isn't turning at full RPM, and is therefore "precessing" backwards on
> the end of the spindle, which tightens it up as you drive! At some point,
> the taper fit becomes tight enough, the circles become concentric, and
> effectively the same diameter, and no more tightening occurs.
>
> If you want to see the "Mr. Science" demonstration of this, roll a tennis
> ball around in a large bowl. The ball is traveling around the bowl one
> way, but the ball is actually turning the opposite direction. Better yet,
> tip the bowl towards you and rotate the bowl. The ball rolls over one
> whole turn long before the bowl has. The outer piece travels backwards
> with respect to the inner piece because the inner piece turns faster.
>
> If the taper went the other way, as in having a nut that holds the wheel
> on with the outer taper being the wheel, you would want it to tighten IN
> the direction of rotation, because the smaller circle still turns faster
> when loose.
>
> Class dismissed.
>
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