Re: Garage door help! (Off topic but begging for help!)

Bruce L. Bergman writes:

The aircraft cable isn't just winding onto a plain spool, it's
following a varying radius tracking snail groove so that the force
goes down as the door goes up and approaches the end of the run, to
equalize the assistance needed.

You've got it quite inside out. The spiral drums create a net *constant*
force by mirroring the torsion decline as the springs unwind. And these
are not used on a standard residential door, since the spring torsion and
weight to be lifted both decline linearly as the door goes up (consider why
those are both the case). Spiral drums are used on straight-lift
commercial doors.
.