Richard,

When the door is mostly up as I had suggested The rollers on the door are
still in the track. Your *huge* force is still constrained. By the way,
how many pounds of force are exerted when the door is half way up? Seems to
me the force on one cable would be slightly less than half the weight of the
door in the vertical position. Since these sections are ordinarily
assembled by one person the *huge* force might not be so *huge*.


--

Roger Shoaf

About the time I had mastered getting the toothpaste back in the tube, then
they come up with this striped stuff.
"Richard J Kinch" wrote in message
. ..
Roger Shoaf writes:

Now please explain to me why you claim my suggestion is a foolish death
wish?

I gather it isn't obvious to your mechanical intuition.

A sectional garage door is normally a system containing a balance of two
huge forces, the weight of the door versus the lift of the lift cables,
drums, and torsion springs. This balance gives the illusion that the door
is approximately weightless and that no forces are involved, when in fact
hazardous forces are merely being kept at bay, like two giants in a
stalemated tug of war. This is a very dangerous illusion when it comes to
naive tinkering with the mechanisms. Releasing certain constraints
(setscrews, cable brackets, tracks) permits the potential energy of these
opposing forces to convert into kinetic energy of large masses in violent
motion.

For example, if the track does not constrain the door movement (imagine
the
track were to just suddenly disappear by magic), in the down position, the
door will fold on its hinges. BOOM! The lower panel(s) will be lifted by
the lift cables and fly up violently, while the upper panel(s), no longer
supported by the lower panels, will fall by gravity, also violently.