On Sat, 08 Dec 2012 09:26:49 -0800, Oren wrote:

Following the threads here, I learned some things.

Since this is a lessons-learned thread, another not-so-obvious result
is to understand the differences when a torsion spring breaks nearer
to one end than to the other in a single torsion spring system.

Until I read Dan Musick's web site, I hadn't realized that the part
that spins violently is the winding cone end because that's the end
bolted to the torsion rod itself.

The other end just spins inside its bearing.

So, the implication is different if the spring breaks nearer to one
end than to the other. If the single torsion spring breaks nearer to
the winding cone, the violent spin on the torsion rod is apparently
much LESS than if that same spring breaks nearer to the stationary cone.

This, of course, has implications if the door was moving upward at the
same time. This particular detail, to my knowledge, has never been
discussed on a.h.r, and therefore I add it as an additional lesson
learned.