Re: Thud in the parking lot

["Rossato, Bob HSD" <ROSSATR@hsd.utc.com>]

>> Interestingly, Carroll Smith says that the nylon-locking nuts *can*
>> be reused.  Bentley disagrees.  I'm not sure why.
>
>Bentley disagrees because Bentley is a direct translation of the
>German manual.  Audi AG says that all self-locking nuts and bolts must
>be renewed whenever they are removed.  Period.  Capital letters.
>"Unbedingt".  "Grundsaetzlich zu erneuern".  No argument.  During the
>clutch master cylinder removal procedure for RHD cars, this comment
>is repeated three times.
>
>Good enough for me.  Anyone who's seen Ingolstadt, Neckarsulm and
>Porsche Weissach will know that these guys know a bit about building
>cars that belt up and down Autobahns day after day at 150+.  The last
>thing I want, when I'm going round a corner with my family in the car,
>is the brake pedal assembly or the steering column detaching itself
>from the car.  The damn nuts are 60 cents each.
>
> Phil Payne

Being in the aerospace business we use locking bolts & nuts everywhere,
and they can be reused.  Of course this is providing that they meet a
_minimum_ running torque during installation.  After 2-3 cycles most
bolts will fail to meet the required running torque.  Conversely,
sometimes you can get too much running torque from the inserts.  We have
some applications where a new bolt will be beyond the specified running
torque range and we will run it in and out of a threaded block a few
times before we install it on the actual hardware.  Our hardware is
required to have a minimum life of 15 years and withstand 100 Space
Shuttle launches.

Keep in mind that Audi and presumably all other car manufactures have
the big "liability" picture in mind.  While locking nuts or bolts can be
reused to a minimal extent, the manufacturer has no way of controlling
it because in this case they really aren't dealing with rocket
scientists.  Most people (everyone on this list excluded of course)
wouldn't even know what to do with a torque wrench, never mind knowing
that a locking nut must provide some minimum level of running torque for
it to do its job.  Therefore, it is to Audi's best interest to state
that they should never be reused.

Personally, I feel perfectly comfortable in reusing a locking nut once
or twice if I have to, as long as I can feel a fair amount of resistance
while threading it.  But as you stated, new nuts are cheap.  Do whatever
you feel comfortable with.

Bob