[ATM] Focuser speed reducer

[GARY FUCHS]

Thanks Don - I'm still figuring out the split-nut method but the two-nut approach looks like something I could manage.

Gary Fuchs

---- Original message ----
>Date: Mon, 16 Apr 2007 17:02:44 -0700
>From: "Don Clement" <don_clement at charter.net>  
>Subject: Re: [ATM] Focuser speed reducer  
>To: <atm at atmlist.net>
>
>Gary,
>
>
>
>There are many ways  to eliminate backlash in leadscrews. A common way is to
>use a tapered split nut such as are found in almost every micrometer head.
>Here is a link to that might help:
>http://www.liutaiomottola.com/Tools/Backlash.htm
>
>
>
>Don
>
>
>
>
>
>> Don,
>>
>> Could you explain more about the "zero backlash nuts". I'm working on a
>focuser that would benefit from them - it's strictly for personal use!
>>
>> Thank you,
>>
>> Gary Fuchs
>>
>>
>>
>>
>> >
>> >I don't use or need speed reducers. Just use a single fine pitch
>leadscrew
>> >with zero backlash nuts.  The advantage is no backlash or play from an
>added
>> >gear (or similar type) reduction mechanism. There is also excellent
>> >repeatability and ultra-smooth movement because the leadscrew nuts
>average
>> >over many threads and have a very large contact area. Of course fine
>focus
>> >is inherent with leadscrew focusing whereas the Crayford design has  the
>> >inherent coarse focusing limitation in which a focus reduction mechanism
>> >must be added for any type of fine focus. Also the contact area of the
>> >Crayford is very small, a point or line contact at best so there is also
>a
>> >limitation on maximum load before slipping occurs.
>> >
>> >
>> >
>> >Don Clement
>> >
>> >Running Springs, California
>> >
>> >
>> >
>> >
>> >
>> >> I've seen lots of great focuser plans out there, but I've never seen
>> >> plans or even a commercial source for a speed reducer like the ones
>used
>> >> on feathertouch and moonlite focusers to get dual speed focusing.
>> >> Anybody have plans or a source for such a beast?
>> >>
>>
>
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