On Fri, 16 Aug 1996 13:04:32 -0700 Michael Marr <mmarr@execpc.com>
writes:
>ArthurK101@aol.com wrote:
>>
>> In a message dated 96-08-15 14:33:40 EDT, twakeman@scruznet.com
>(TeriAnn
>> Wakeman) writes:
>>
>> << Using a lead hammer, not copper, pound the living daylights out
>of the
>> knockoff untill it refuses to turn any more. >>
>>
>> NO! NO! definitely not the way to do it. This is not necessary and
>can
>> result in damage to the hub or wheel. The correct way is:
>>
>> With the tire off the ground
>> 1) Ensure that the knockoff is on the correct side of the vehicle
>(the
>> knockoffs and the hubs are threaded differently for the right and
>the left
>> sides).
>>
>> 2) Screw the knock-off on snugly by hand then, then give about 5 or
>6 medium
>> strength taps with the lead hammer.
>>
>> 3) Then drive several miles. The centrifugal force on the knockoffs
>will
>> tighten them down properly.
>>
>> They are designed to tighten as you roll. That is why they are "side
>> sensitive".
>>
>> Art Kelly '64 TR4 CT33118L
>
>Because centrifugal force acts radially, it will NOT tighten the nuts
>as
>you roll. I remember reading a long series of correspondence on this
>subject in an English engineering magazine, I believe, in which
>several
>theories were offered but none were agreed upon as being true. One of
>
>the points that was agreed upon was that relative movement between the
>
>wheel and the hub would tend to tighten or loosen the nut. The
>question
>is, is the relative movement predominantly in one direction or the
>other?
> In other words, does braking torque or acceleration torque
>predominate?
> If braking torque is the predominant torque, then the nuts on the
>left
>side of the car (driver's side in the USA) should be threaded
>counterclockwise and the right side clockwise. If acceleration torque
>is
>the greater, then the opposite would be true. If I were designing a
>car,
>I would assume that braking torque would be the predominant torque
>experienced by the knock-off nuts, because I think we tend to brake
>harder than we accelerate, so I would put counterclockwise threads on
>the
>left and clockwise on the right. I can't for the life of me remember
>which way my TR3 is set up - I shall check it out tonight!
>
>As for the degree of pounding required, I think I would agree with
>TerriAnn. The tightening torque for a 2.5" diameter bolt has got to
>be
>in the 250-300 ft-lb range (I shall look it up in my "Machinery
>Handbook"
>tonight) and, without doing the math, I bet the impulse of a 2lb
>hammer
>swung through a 2 ft radius at 5-6 ft/second acting on the ear of a
>knock-off would result in a tightening torque approaching those
>values.
>
It seem that I have opened up a can of worms; and a rather spirited
discussion. My personal feeling, as an engineer, is that the knockoffs
will not self tighten and therefore should be tightened securely
(probably with the wheel off of the ground, for proper seating), and
retightening after several miles of driving seems like a good idea too.
Jack Brooks
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