Re: Slide Bar

[P3D George Gioumousis <georggms@xxxxxxxxxx>]

Stephan Miller wrote
> 
> I would like to do some macro and MF stereo with a slide bar.  I know of
> only one commercially available bar made by Hama which is selling for $110
> at Hunt's near Boston.  I have been using some of the methods suggested on
> this list in recent months but I would like to graduate to the flexibility
> of a real bar.  Are there any alternatives to the Hama bar?  Has anyone
> used the Hama bar?  Any helpful hints will be appreciated.
> 
> Stephan Miller
> 
> **************************************************************************
> Stephan Miller                                Cambridge, MA  02142
> Molecular Genetics Group                      (617) 679-3323
> Biogen Inc.                                   smiller@xxxxxxxxxxxxx
> 14 Cambridge Center                           Stephan_Miller@xxxxxxxxxx
> 

Recently, I built a slide bar that works quite well using only hand
tools, plus a radial arm saw. A table saw or a router would have worked
as well. The design is sophisticated, but unless there is an outpouring
of demand, I'll save it for tech-3D. I don't have pictures, so I'll
just have to describe what I did.

I started with a 16" by 16" piece of 3/4" thick particle board and
three 1" pieces of 5/16" diameter maple dowel rod. I cut the particle
board in half, and used one of the 8" by 16" pieces. [The other one is
waiting in case I go into mass production.]

I cut a V-groove 1" from the long edge deep enough that the doweling
can rest in it about half-way down, then I cut the particle board so
one piece (the base) is 10" by 8" and the other (the camera support) is
6" by 8". Now I glued one of the dowels in the center of the V-groove
on the small piece. I laid wax paper in the V-groove on the other
piece, placed the dowels on the waxed paper, then placed the flat part
of the small board on the dowels and adjusted the dowels so that their
ends were just even with the small board. I then removed the small
board carefully, smeared glue on the two dowels, and replaced the small
board so that everything was square.

When the glue dried, I drilled a 1/4" hole in the small board, and used
a 1/4 20 bolt from beneath to attach the camera. A small ruler screwed
to the lower board, and an index mark on the matching edge of the
smaller board finished the project.

The camera support moves smoothly parallel to itself; the maximum
left-to-right distance is 4", which is not bad. It is easy to adjust
the distance to hardly anything for macro stereo slides. So far I've
gone as far as one-to-one, and the half-a-dozen pairs I've done which
chanced to be in focus look pretty good.

The support is a small tripod, which is the reason it works so
smoothly. I read a book on machine design once, probably while in
college, and I remember this technique as kinematic design. The
president of my company, who started out as a mechanical engineer,
remembered it as kinetic design, while John Berkovitz, when I showed
him the gadget, said "Oh, kinematic design!"

I built this as a proof of concept. The next version was going to use
Teflon bearings on pebbled Formica, just like Dobsonian telescopes.
Then I was going to have stop blocks adjusted by left and right handed
screws, so I could have a reproducible interocular distance.  However,
it works so well that I just might not bother with a second version.
However, if I make a new base out of the 8" by 16" piece, I would have
a 10" lens spacing, which could be fun.
-- 
                           Stereo                Stereo
George Gioumousis           /---\        |       /---\ 
                             o o         |       o o  
georggms@xxxxxxxxxx           |          |         |   
(415) 494-6276              \===/        |       \===/ 
                        Photographer          Photographer


------------------------------