ATM [Fwd: BOUNCE atm@shore.net: Non-member submission from [Paul Shankland <pshankla@jiatfe.org>]]

[Mel Bartels <mbartels@efn.org>]

owner-atm@shore.net wrote:

> Sender: pshankla@truman.jiatfe.org
> Date: Tue, 09 Sep 1997 10:29:50 -0400
> From: Paul Shankland <pshankla@jiatfe.org>
> To: atm@shore.net
> Subject: Help with securing Truss tubes to lower cage
>
> I am again re-modifying my 16" f/5 Newt and am having a bit of a
> stable
> mechanical "connection" problem... Any advice will be immensely
> appreciated! This is the problem:
>
> I originally built a truss tube assembly (the upper cage is light,
> too),
> and connected the upper to the lower cage with the standard 8 stiff
> aluminum poles. The upper ends are attached by a plate common to 2
> poles
> apiece and a "speed-knob", making 4 connect points. No problem there.
> At
> the lower cage, I followed the advice in a back issue of AA (was it
> one
> of Kreige's or Clarke's works?) and made 8 clamp blocks (of the
> less-likely-to-split variety, hole in top & 2 horizontal slices so the
>
> middle third of the block can be "pulled" tight to the cage wall &
> clamp
> a pole).
>
> It got complicated when I changed my mind. The knobs are/were on the
> outside of the otherwise smoothly formica'ed (over a 20" sonotube
> section 2 ft long & with plywood end rings). And after alot of debate
> over making my already built upper cage into a turning cage, or to
> rotate the whole truss tube, I chose the latter (for optical reasons
> and
> for building reasons - I always struggle when generating reliable,
> precision motions... :-)  ). So, I needed to remove those knobs on the
>
> lower truss from the exterior (so I could make a viable rotating
> system
> there), and I couldn't put the knobs on the inside (protrude into the
> light path; no "corners" for such leeway in a round tube vice square
> dob
> box.)
>
> So I went back to another AA article in which was made fancy,
> slip-lock
> mechanisms for the poles (like those paint-roller extention poles,
> etc).
> After an expensive trip to the machine shop, alot of time drilling
> offset holes in my press, I put together 8 "cams" of hard plastic....
> which didn't work: primarily because it is way too hard to twist the
> pole in its socket (the old clamp block sans bolt/knob), so it aligns
> just right to bolt down at the upper cage. And they loosen too easily.
>
> And nothing was so rigid as those clamp blocks.
>
> SOOO, any ideas on:
> 1- how to improve those slip-lock cams?
> 2- or, probably better, how to make a reasonable clamp-block that
> somehow pinched the truss tube and does not require a bolt/knob
> renetrating the lower cage wall or the light pathe (IE a vertical knob
>
> action do-thingy...)
>
> I hate to return to ground zero too ( my boss insists he wants to see
> this thing by Xmas... :-). Nor do I have much access to novel or
> exotic
> fixes, especially if they cost the bucks... But the optical tube now
> sits on my living room floor (to the chagrin of my patient wife),
> taking
> up alot of space while I ponder, and each time I lift an end, the
> meager
> connections mentioned above (cams) just have the whole thing flex
> shakily to kingdom come. Not even to balance the thing to find a
> balance
> point to work on a fork...
>
> Thanks in advance! Any ideas are most welcome all!
>
> Clear Skies,
> Paul Shankland
> Key West, FL, USA
> Pshankland@flakeysol.com
> +++++++++++++++++++++++



--
Clear skies, Mel Bartels    Programmer/Analyst, amateur astronomer
Eugene, Oregon, USA         homepage: http://www.efn.org/~mbartels
mailto:mbartels@efn.org     atm, atm-digest list-owner
Motorize A Dob: http://zebu.uoregon.edu/~mbartels/altaz/altaz.html