Beyond the above two incidents, I'm not sure if I can see any way to improve the
fixture beyond what methods are used in prepping it for a show and what might be a
nut that might be better as a different part if not just replaced if it fails as similar to a stripped screw on something that gets removed a lot should you de-yoke the
fixture.
If of any help, I don't see any problem with the parts used on the
fixture, only in it not noticed to have failed before use of it. Sorry you got hit, but often something failing is a wake up
call to something needed to be added to the before used checks. Definately something to inspect it would seem.
From what I see from the parts
manual, one side has a knob (12-0020-25), washer (32-FW375), and screw 24-0225). I expect that given the
hand knob, this is the side that did not come un-done since knob adjustments are something the end user is charged with making tight or loose.
The other side has what seems by PDF picture like a
nut (31-HF500),
cone washer (32-FW500) and screw (30-HT50016). (Left my actual parts descriptions in saying what they are at work.)
Not a lot of room for a longer
bolt in the assembly thus if it is using a nylock
nut, perhaps a thread deforming side lock
nut might be a better option if the nylon locking
nut came loose. Such nuts lock in a similar way but instead of using the nylon to prevent un-screwing, use a deformed thread to grab onto the screw attached to. Such nuts thus are not much effected by heat and how much used unlike the nylon. This
nut given the
fixture will not be removed from it's
yoke. A thread deforming
nut does just that in that it screws up the threads of the screw it is locking to. For the most part, it's a one time deal and if you remove it, the screw needs to be considered for replacement. Nylock nuts on the other
hand don't damage the screw thread so if the
fixture needs to be de-yoked, it might be a better option. Just keep in mind that this
nut will need occasional replacement.
Should this
fixture have it's nylon locking
nut removed a few times or get too hot, given it is only nylon it will
grip less and less with time. The Nylock
nut with heat or repeated tightening or movement can fail still as if a normal
nut in not gripping. Toss out old nylock nuts that don't
grip sufficiently, they will never work as needed again. You should not be able to tighten a nylock
nut with your fingers, much less one will notice a difference between a new one and one that's been used a lot. When a nylock
nut fails to maintain it's tension on the screw thread, it needs to be replaced.
In other words, it becomes more like a normal
nut at that
point and somewhat easy to un-screw. The thread deforming
nut or simply replacing the nylock with a new one might be an option.
Otherwise and always now, as part of the prep of the
fixture for a show, checking that the right side was sufficiently in tact it would not fail might be a better option.
A further option might be Thread Llocker compounds such as a #242 which might help the
nut in not coming loose.
I have often found that the screws mounting the
fixture mounted sub-yoke (#20-3154) on similar fixtures, it either becomes un-welded or un-screwed as a more design flaw than maintinence issue. Given this part is still attached, I can't see much that could be done to change the problem other than when I occasionally work on similar fixtures, me also doing the above in checking if the right side of the
yoke mount is able to come loose on it's own. I would
call it the Left side but what ever the case is dependant upon knob adjustment side verses
bolt side. Again, should the knob become un-done that's the operator's fault.
Thans for noting something to inspect when I also service
call similar fixtures. On the other
hand, sorry to say but I can't see anything wrong with the design given proper inspection before use. You should be able to note when an exposed
nut comes loose.