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

["RodShea" <RodShea@comcast.net>]

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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