Threaded Rod/Cable Driven Encoders

Gents,
If I followed the thread correctly on threaded rod backlash isn't a
problem if you use a plastic nut. The problem seems to be cumulative
cyclic error. It seems to me that you could get around this problem
pretty easily with a http://www.usdigital.com/products/ S2 or H3 2K
pulse/revolution encoder driven by a cable streched along the axis
and wrapped around a capstan attached to the encoders shaft. I recall
seeing something about this last year where someone was using this on
a lathe but can't find it now.

Do any of you have any long term experience with cable driven
encoders? Are they working out and staying accuarate?

I'm still dreaming about builing a realy big router...

Roger

PS. My 3d laser stripe digitizer is coming along pretty well. Its now
controlling the mill for automated scanning. I hope to post software
and a tutorial in the next couple of months.