Re: Crayford construction

Robert Beer (r-beer@onu.edu)
Mon, 1 May 1995 11:43:59 -0500

At 10:06 AM 5/1/95, Mitch Berkson wrote: >I recently looked up an old S&T article on the Crayford focuser. It
>seems straightforward, but I have a question about the JMI
>implementation. In the JMI focusers in which ball bearings are used for
>the focusing rod, how is the tension provided to prevent the draw tube
>and eyepiece from slipping?
>
>The drawings I saw had simple metal bearings which pressed against the rod
>with a spring to provide this force. Thanks.

I took a look at one of these before I built a Crayford and JMI's also had a plastic locking screw to the barrel.

I think I would investigate a set screw with a nylon tip that could provide adjustable friction to the rod (no the barrel). 

---
Bob Beer, Ohio Northern Univ., Academic Computer Services, Ada, OH  45810
r-beer@onu.edu