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taking garage doors for granted
Tuesday, August 5 2008
Since respringing the southern garage door (the one whose bottom-most panel I rebuilt), it has been difficult to open and close. At some point I realized what the problem was. I'd failed to stretch-tension the torsion spring (the one that cancels the door's enormous weight), so, whenever the spring twisted to a certain point it would run out of room for more twists and the coil's shape would begin to flex out of its normal cylindrical form, eventually rubbing on the pulley rod running down its center. This would hinder the action of the moving door, making it stick in various positions. In the abstract simulation running in my brain, I realized that all I had to do to prevent this problem was to stretch the torsion spring along its axis, putting spaces between each of its coils. Then, as it wound tighter and tighter, there would be room to absorb the additional metal.
Today I managed to fix the torsion spring problem by moving the garage door to the top of the track, the position where the torsion spring is under the least amount of tension. Then I loosened the pulleys on one of the torsion rod and used clamps to pull it (and the spring) until I'd added over an inch to its length. Then I fixed the pulley back in place. After I'd done this, the action of raising and lowering the garage door was exceptionally smooth.
I'm still wrapping my brain around all the things I've learned about garage doors after working with this one. Even a non-automated garage door (like this one) is an exceedingly dangerous device, something that hadn't once occurred to me. The danger is masked by the torsion spring, which cancels out the hundreds of pounds of potentially-lethal weight. In so doing, though, it concentrates enormous forces within itself, forces that could easily kill someone standing nearby should it break. Aside from our cars, there are no moving objects in our household as heavy as our garage doors, and yet we've accepted them as benign seasonal walls, opening them in early spring and closing them in mid autumn, but otherwise paying them no mind whatsoever.
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http://asecular.com/blog.php?080805 feedback
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