This maybe the blind leading the almost blind - but I'll try.
Tightening/loosening has to do with "precession". When two parts fit together,
whether tapered or not, the outer HAS to be marginally larger than the inner.
When both rotate at the same rpm they move at slightly different linear
(circumferential) speeds. Vice versa - if they move at the same linear speed
they
move at slightly different rpm. The differences are of course VERY slight - but
it is this difference that causes the tightening or loosening.
If you don't understand - think of two very different diameter pieces. If the
inner piece is half the diameter of the outer pieces then it would rotate at
twice the rpm for the same (linear) speed at the point of contact. Now reduce
that concept to microns of difference and you have the wheel nut situation.
Derek
Brian Evans wrote:
> There was a complete explanation of this in Racecar Engineering a year or
> two ago. it seems that the taper is the trick - even the taper center lock
> bolts that modern race cars use exhibit this tightening /loosening to some
> degree. Per the article I recall that there are two modern designs, with
> the taper acting in different ways, so that the tightening action is
> opposite so that the threads have to be opposite for each design to get the
> desired effect. So it's likely that inertia of the ears has nothing at all
> to do with the effect - especially since the article also noted that at
> constant speeds (ie no acceleration) the nuts would tighten up if loose,
> when on the correct side of the car.
>
> Nice bit o'calculation, tho...
>
> Brian
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