Yeah, vibration, knocking etc.
In Australia our main type of globes are not screw in but bayonet. (push in
& 1/4 turn).
Most globes here for household type use only have 3 supports holding the
element up. It is possible to get ones that have 7 or 8 supports & these can
take much more rough treatment. They are designed for "trouble lights" for
mechanics etc.
Another recent type of globe has just recently taken over the trucking scene
here in Aussie is a type of LED light but I doubt if it would be bright
enough for your purposes. They last "forever" on truck side light useage.
BruceM


"Leanne" wrote in message
...

"Tom Best" wrote in message
om...
I would appreciate some help with a 12 volt question.

I would think it would be from excessive vibration if they were
originally for fixed service in the yard.

Leanne