In article ,
Steve wrote:
I have an up & over metal garage door that stays up when I open
it most of the time. The problem is that every now and again it
drops down again, by anything from about 6 inches to 2 or 3
feet. This often happens some time I have opened it and carried
on, happily believing it has decided to stay open. It's already
taken a lump out of the top of my head and it's only a matter of
time before it drops on to the roof of the car as I back it out.
This would not be a good thing.

When it is up and horizontal our garage door seems
to be held there more by balance than the springs.
A downwards pull on the bottom edge seems to be
needed to tilt the balance. In which case it might
be worth experimenting with weighting the top edge.

--
Tony Williams.