Re: [ATM] Mirror Cells - Springs vs. Push/Pull

["Don Clement" <clement.focuser@verizon.net>]

Rod,



Nylon would probably work for this purpose. I used 303 SS 1/2" hex stock
because it is what I had in hand. Brass or Delrin would have been better
than SS for the split nut because SS on SS will gall. Also I machined a
round bearing surface in the Hex split nut that fits in the aluminum split
housing and SS will also gall with aluminum.



-Don



-Don

> Dumb question, could you make a fine thread nylon locknut by tapping a
block
> of nylon with a 3/8 - 32 tap, then slitting the block and somehow
> compressing the block so as to snug up the ID?
>
> Do you think the threads would put up with the mirror getting jounced
well,
> say from hitting a good bump on that gravel road?
>
> Thanks,
>
> Rod Shea
>
> ----- Original Message ----- 
> From: "Don Clement" <clement.focuser@verizon.net>
> To: <atm@atmlist.net>
> Sent: Thursday, November 24, 2005 10:26 AM
> Subject: Re: [ATM] Mirror Cells - Springs vs. Push/Pull
>
>
> >
> >>  Don't forget some obvious but often overlooked ways to
> >> make adjustments finer.  These may be easier to implement.
> >>
> >> 1. design your collimation screw locations as far apart as possible.
> >>
> >> 2. Buy fine thread screws.  The standard US inch size screws usually
> >> come in at least two different pitches, e.g 1/4-20 and 1/4-28.  Use the
> >> higher pitch number.  (Of course you have to get nuts to fit.)
> >
> > The Standard 3/8-32 UNEF thread size could be substituted for 3/8-24 UNF
> > size previously mentioned. Taps are readily available for UNEF sizes.
The
> > larger diameter 3/8" is much stronger that 1/4"  diameter used for
> > support.
> > Three 3/8" diameter collimation bolts are located at each apex of 9"
long
> > triangular sides of the moving mirror focuser and adequately supports
the
> > focuser with 14" mirror.
> >
> > Also there must be some sort of allowance for the angle change or
tip-tilt
> > of the bolt during collimation. That is what the  flexure machined  into
> > the
> > bolt if for. To allow for tip-tilt but be axially  and radially rigid.
> >
> >
> >
> > Another advantage of larger diameter fine pitch bolts is the thread
helix
> > angle is smaller so that given the same coefficient of friction of the
> > threads there is less of a tendency for overdrive or loosening to occur
> > after collimation.
> >
> >
> >
> > Don Clement
> >
> > Running springs, California
> >
> > Happy Thanksgiving.
> >
> > _______________________________________________
> > ATM mailing list http://www.atmlist.net/
> >
>
>
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