Nut backed off ball caused accident
I was heading up to santa cruz ca. in my 40' american eagle I had my motorcycle in tow on a utility trailer. Before I left I had tighten the nut on the ball with an air impact driver the kind that you...
Forum Discussion
schlep1967 wrote:
To the OP, thanks for posting this. Looks like you made an expensive mistake and by posting this you may keep others from doing the same thing.
Ditto that...many thanks for the OP for posting and getting the spears
and arrows in the back... :S Hope you stick around
In case folks didn't understand why asked what PSI/age/etc of the
impact gun...is that all air impact guns torque is at a specified
PSI and CFM. Oiled or not too. Over time the gun wears. More so if
not taken care of properly (oiled is the biggie) and will lose it
ability to meet torque spec. All my air tools get oiled before hooking
up and during their use
Some depend on torque sticks, which I have and use, but do NOT trust
them. Recheck with a properly set torque wrench and often find not
up to torque (most likely dirt/grim/etc on the mating surfaces)
Lock washer, nylon slug, etc assumes already tightened to spec. This
kind of 'back up' is no different than wired fasteners on airplanes,
race engines, nuclear plant stuff, military stuff, etc and more etc
All are tightened to spec by trained professionals who either know
what they are doing, or under threat of losing their jobs if they don't
Plus super critical will have a 2nd person double check the torque
Of course not rocket science here, but life and limb is on the line
Some of you 'Farmer Tight' folks have the risk of over tightening and
that then will have the stud and/or nut not able to hold...even at
lesser torque...some will actually get it right...but...how would one
be able to tell?
The way of it is that all things have harmonics (vibration) and either
matches the natural harmonic and/or amplitude so high...as to stretch
the stud to even the threads ever so SLIGHTLY.
The nut can and will back off a bit. Over time, the torque (clamping
force) is no longer able to provide enough clamping force to withstand
lesser vibration & amplitude
Back to the OP...again, say much appreciate your posting for 'some'
who might learn from your near disaster experience.
