wrote:
On Nov 23, 10:33 am, wrote:
Can anyone point me to possible sources for this critter?

Thanks,
DOC


No idea where you can get such a gear. You could try to make one.

That's the hard and expensive way.

The smart way is to use a 63 tooth gear which is much cheaper to get,
I believe.

I worked out the arithmetic for use of such a gear some years ago and,
while the conversion is not exact, it is so close that the inaccuracy
would get lost in the accumulated tolerances of the lead screw and
gear train.

If you are interested in pursuing this let me know and I will dig out
my scribbles.

Wolfgang

33/13 = 2.5385, -0.06% error
127/50 = 2.5400, 0% error
94/37 = 2.5405, 0.02% error
61/24 = 2.5417, 0.07% error

My Smithy, which is a brand that is world-renowned for quality* uses the
33/13 trick, and does OK.

0.06% error would require 1666 threads to be off by one; if being off by
1/20th a thread makes you bind up that's still 83 threads, or over four
inches for a 1/4-20 screw.

* I didn't say _good_ quality!

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html