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
BenK wrote:
Fastening science stuff...cotter pin & castle nut are for different applications
They are for 'not' too tight, but just enough for bearings or some such that needs
to be allowed to 'move'.
Clamping force is NOT the goal, but maintained 'gap' is
Yes that is their role in that specific application but not always.
Look at the head bolts on a radial aircraft engine. All of the bolt heads have a hole drilled parallel to the top and from flat to flat, like this:
Two step fastening process: First the bolts are torqued to spec, second a long loop of safety wire is run through the head of the bolt, the two ends twisted as a pair and then onto the next bolt like this:
On a radial aircraft engine this goes all the way around the perimeter of the engine and includes all of the bolts fastening the head on.
In the case of studs, the nuts are castled and wired in the same fashion.
This NOT a replacement for the correct torque but in addition to. insures that the bolts don't come loose from extreme vibration, cold temps at altitude, etc.
So back to the hitch ball....rather than relying solely on torque to hold the fastener in place, why not use a safety mechanism? Instead of a torque-only spec of 400+ ft/lbs, why not a more attainable 150 ft/lbs with a castle nit and cotter pin?
