Rick:
One of the most important things to understand in any form of
machinery is that nothing is static. There is stretch and give in any form
of mechanical movement. This holds very true for fasteners. Momentum works
down to a molecular level.
A knock off nut is never tight. The surface area that it seats upon
is conical and of very large area. The wheel itself seats upon a conical
surface and does move slightly between the knock off nut and the hub
mounting face. Even with perfect, new splines on hub and wheel there is
always some movement, which is one reason why grease is important.
The knock offs are handed so that the momentum of forward movement
will tend to tighten them. This system works well unless you decide to
drive in reverse as one list member pointed out. I hope the list member
does not attempt this with a traditional American car, as the self adjusting
brakes on such a vehicle may also cause problems. Not to mention the
possible chiropractic bills.
Lug nuts have a much smaller fastening surface and are under far
higher clamping force. The frictional force between wheel and nut is far
higher than that of a wire wheel. Check out how much metal is damaged on a
typical steel wheel nut surface. Compare that to the lack of damage to the
much softer wire wheel nut and wheel taper. The momentum effect on the much
smaller wheel nuts is also much less, so the non-handed lug nut became
industry norm.
Metallurgy and design have come a long way, and clamping forces and
torques are now very different from when our cars were originally designed.
Case in point is the difference between the handed axle nuts on the Banjo
rear end and the non-handed nuts used on the Saulsbury rear end. Torque and
clamping force are very different between these two designs.
Working in a British scrap yard, you get to see about as many
failure modes as are possible. I have had a number of calls from people who
had installed their wire wheel hubs on the wrong side. Mostly TR people
where the hubs bolt on. The calls usually resulted in sales of replacement
wheels, hubs and nuts.
The other customers who come to mind were the tow companies who
usually had to replace major suspension components as the cars were dragged
down the road, trailing sparks.
Hope this explanation makes sense.
Always keep in mind momentum is a very moving experience.
Kelvin.
> -----Original Message-----
> From: REwald9535@aol.com [mailto:REwald9535@aol.com]
> Sent: Tuesday, April 20, 1999 6:04 PM
> To: doddk@mossmotors.com; mgs@autox.team.net
> Subject: Re: Towing Warning (Was Dropping Drive Shaft)
>
>
> Kelvin et al,
> OK, I believe you guys about towing a wire wheel car backward.
> However there is something that has always bugged me about
> this. Back in
> the old days Chrysler used right handed thread lugs on one
> side of their cars
> and left haned thread lugs on the other side. The theroy
> being, I suppose,
> the same as the knock off that they would not come loose when
> driving. OK
> fine, I'll buy that. Every other car maker in the world only
> uses right hand
> thread studs on both sides of the car. Now since we don't
> see the road
> littered with wheels off just one side of all the cars made
> EXCEPT Chryslers,
> and LBC's with wires, it must mean that the Left handed
> threads aren't as
> necessary on cars as Chrysler thought.
> Agreed?
> So why do knock offs come off when towed backward? On a car
> with all right
> handed thread lugs, at any one time, half of them are going
> in the "wrong"
> direction and should be comming loose. I can tell you from personal
> experience that if lug nuts get a little loose the studs (all
> of them) will
> break. Ask me how I know this<G>. The only answer I can
> think of is that a
> properly torqued fastner won't come loose. Am I missing
> something here?
> Not trying to start a flame war, just want to understand.
> Rick Ewald
> 67 MGB
>
>
> In a message dated 4/20/99 4:30:24 PM SA Eastern Standard Time,
> doddk@mossmotors.com writes:
>
> > > DO NOT DO THIS WITH A WIRE WHEEL CAR! Towing a wire wheel car
> > > backwards will
> > > cause the knockoffs to loosen and spin off.
> >
>
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