On Tue, 4 Oct 2005 23:31:42 -0400, Ned Simmons
wrote:

In article ,
says...
I ordered some fine cable today from
McMaster-Carr today. It will be wrapped a few turns around the encoder
shaft. I hope that this will provide enough friction while at the same
time have low enough tension to keep the friction low in the pulleys
the cable will travel over.
ERS

What concerns me about using a wrapped cable is that the turns of cable
want to walk across the drum as a result of the helical wrap. This will
cause the cable to be pulled out of line with it's attachment points,
which changes number of pulses per inch of carriage travel. If the
stroke is long relative to the drum's circumference the cable may either
slip back into line, cross over itself, or walk off the end of the drum.

I've done this, and even with a fairly short stroke, large drum, and low
accuracy requirement, it was a real pain to get working reliably. I
don't mean to be discouraging, but I haven't heard, or thought of, any
idea yet that gives me the warm fuzzies.

Ned Simmons
Ned,
I've considered this. And I'm not quite sure how to keep the cable
where I want it. But I think I have figured it out. I'll let everybody
know when the cable arrives.
Eric