Eric R Snow writes:

On 05 Oct 2005 00:19:27 -0400, Greg Menke

Sorry didn't catch the previous post. One way to avoid the cable
walking is to set up a parallel shaft nearby and turn a couple
"windlasses"- bigger collars on each shaft so the cable can bear more on
each. Wouldn't hurt to put notches on the collars to help guide the
cable. So the coil goes around the first, then around the second, then
back around the first. Not wrapping all the way around each shaft, but
looping around the pair of shafts. The aux shaft should be free to
spin. Then as the cable drives the shaft (or vice versa), the cable
won't walk or slip. Maybe you only need a few loops around the shafts &
can keep things fairly compact.

Gregm
Greg,
I can't quite see waht you are describing. Maybe I'm too tired. The
encoder shaft cannot get any bigger. This shaft is 1.000 in
circumference. This is so the encoder outputs 10,000 pulses per
revolution. Could you explain your idea more clearly so I can
understand it? I'm sure everyone else here has already visualized the
setup but my brain is fogged this morning.
ERS

Take your encoder shaft, put a 2nd parallel one "nearby", maybe 1
diameter away. On each shaft put in a series of notches, not deep, just
enough to help guide the cable- no more than 1/2 the diameter of the
cable. Align the shafts so the notches on one shaft are in line with
those on the other. The cable comes in, goes around the outside of one
shaft (in the notch), over and around the other shaft (again riding in
the notch), then back to the 2nd notch on the first shaft and so on
until it has traversed each notch on both shafts- looping around them
all the way. With tension on the cable, it will get nice and tight, but
it won't walk since its not taking a helical path along the shafts. You
should pack in the turns as closely as you can to reduce how far the
cable has to shift down the shaft to make the next notch.

I suggested the bigger diameter collars because this approach loses 1/2
of the engagement on each shaft- since its only bearing on the outside
surfaces of the shaft pair. Maybe you could cross the cables over as
they lead between the shafts & get more engagement that way.

Frictional loss is greater with the 2nd shaft, though maybe you could
make the 2nd shaft bigger to reduce the loss a bit.

Greg