On Wed, 30 Oct 2013 23:40:19 -0400, micky wrote:

In your picture, especially the close-up, what is the role of the coil
spring? It's either two springs with 3 or 4 inches in between, or one
spring that has broken in two.

Heh heh. That's a broken spring.
http://farm4.staticflickr.com/3682/1...ccf1e6c8_o.gif

The spring is attached at both ends so neither end can move.
When you wind a spring 7-1/2 turns, it "grows" by the thickness of 7-1/2 coils.
Plus, you manually stretch it outward another coil thickness to prevent binding.

If your wire gauge is, say, 1/4 inch, then that's about 8 coils (roughly) that
the spring will expand when wound and set. That's about 2 inches that the spring
grows.

Since the spring is bolted down on both ends, when it breaks, there will be
that distance between them.

In my picture below, the spring on the left is broken. The spring on the right
is intact:
http://farm8.staticflickr.com/7329/1...e2064872_o.gif

These are the replacement springs from DDM Garage Doors (which arrived only one
day after they were shipped):
http://farm8.staticflickr.com/7442/1...e0f14be0_b.jpg

You'll notice the new (upgraded) springs are black (galvanized isn't worth
anything, in reality); one winding cone has red paint on it (the RHW spring);
there is a blue line painted straight (which will coil 7 times); and that
the dimensions are painted on it, which are 35-1/4 inches long, with a wire
gauge of 0.243 inches.