"Bryce" wrote in message


All of the torsion spring doors I have worked on used a solid shaft
that mount the springs and take-up pulleys. The pulleys turn in
unison and throwing slack at one end means unequal effective
diameters ... unless the OP has encountered a local variation in the
value of pi.

Omigosh, I'll have to keep track of that! Good catch! What's the most
accurate way to measure pi anyway? My protractors always give me
somewhere between 2.5 and 4.5 on my half-inch diameter circles! The
stupid center keeps moving around!

G ! :^}[