Richard J Kinch writes:
Everett M. Greene writes:

The number of turns = door height / (drum diameter * pi).
Should be about 5 for most doors.

WRONG.

And what's wrong with it?

If you start with the door in the full up position, you
can get everything connected without tensioning the
springs.

WRONG AND HAZARDOUS.

Everything is hazardous to life. I'll be you don't have
the blade guard installed on your table saw.

At:

http://www.truetex.com/garage.htm

See the section on "Why Can't You Install the Springs Unwound, with the
Door in the Up Position?".

Having done it, I wonder why I couldn't.