Re: [CAD_CAM_EDM_DRO] Building A Cheap DRO

I "was" worried about the tension issue until I designed the housings that
I used that include ball bearings. Not only will this allow greater
tension, it lowers the friction required to turn the shaft.

I thought about using the multi-turn idea but quickly discarded it for the
very reasons you mentioned. The result was to build the system to maximize
the amount of cable around the shaft (and keep a simple design) so the
contact angle is 180 degrees. I am always trying to think of better ways
and one that I recently thought of was to add a pressure roller (again with
a ball bearing) similar to what is done on a tape recorder capstan. This
should increase the pressure on the encoder axle without increasing the
cable tension further. However, right now there are other projects on my
plate and the darn thing works as is!

At 09:42 PM 3/18/02 -0800, you wrote:

>I'd be greatly concerned about the amount of tension you need to have in
>the wire that's wrapped around the encoder shaft. Most rotary encoders are
>designed to handle only very light "side-loads". Also, even at 1 inch of
>wire wrapped per rev, how many turns of wire can you even put on the
>shaft?? You probably only get 20" of travel, max. And don't forget about
>the "sweep-angle" error that would be induced. Also what keeps the wire
>from "piling up" as the sweep angle gets greater. I'd worry more about
>these things than the dia of the "pulley" (shaft), or the uniformity of the
>wire dia. There must be better ways of doing this ...for what it's worth.
>
>RayHex
>

Bubba

OLDER THAN DIRT
Country Bubba
(Actually the inventor of Country and Bubba)

axtein@...
LaGrange, GA

http://members.dicomm.net/~axtein


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