[NLRS] Elevation rotators for small stuff

[Doug Reed]

Notice how this thread has changed from generic elevation rotors to
10GHz dish roving specific?

Here are some links for the Dobson telescope article Ray mentioned.
Look near the end for "Making the mount" in links 2 and 3.

<http://www.sfsidewalkastronomers.org/index.php?page=building-telescopes>
<http://www.raycash.us/sfsidewalk/intro.htm>
<http://www.cdcc.usp.br/cda/telescopios/tie-jpl-nasa/>

The third link is a Chilean site copy of the NASA TIE program
telescope plans that were mentioned in the second link. I'd guess that
NASA didn't have the funds to keep their web site active.... :-)  It
also looks like the SF Sidewalk Astronomers site hasn't been updated
in 3 years.

I like the mount design for its simplicity. It provides some direction
that I'd otherwise lack. Think of it as a homebrew Lazy Susan with
Teflon bearing surfaces. I liked the comment about using a Formica
sheet or countertop because an old LP record might be hard to find. He
obviously hasn't visited many thrift shops recently... The "furniture
sliders" they sell at "dollar stores" might be an alternative for the
Teflon bearing points.

It would probably work OK to mount the dish directly to their tube box
so it is more or less centered and supported by the box. Or treat it
like a 20" tube for design purposes. For our purposes, I could see
making the mount out of 2x10 treated lumber for the box and cradle,
but it will be heavy! I'm fairly happy with whatever we need to do to
make it strong and stable.

But I keep mentally adding metal parts; bearings, shafts,
strengthening members, etc, to the design, in an attempt to "improve"
things.... Eventually I'd be back to that 3-box design that John
mentioned. The only real issue with the 3-box design is that at some
azimuths the dish would be pointing through the fixed frame member.

I'll end up needing a hoist to lift it to the car roof.... Maybe that
3' diameter fiberglass radome isn't such a bad idea..... :-)

If you have a vehicle with a strong roof rack you might mount it to
that. I'm thinking of my sedan without a roof rack. I can use a
temporary strap-on ski rack (was $3 at a garage sale) to attach two
frame members to the vehicle roof and bring them together at a third
mounting point where a perforated square steel tube comes up from my
trailer hitch. That should be fairly low impact and easy to remove.
I'd use ratchet straps from the strap-on rack through the car door
opening and tighten the ratchet inside to hold it to the car roof.
Should work but probably not completely water tight....

You could even use perforated steel tube to make the strap-on rack if
you take some pains cutting 2x4 wood spacer blocks that fit the curve
of your roof. Use a piece of leather belt or rubber sheet to protect
the paint from the wood. Probably easiest to cut with a band saw but
could be done with a coping saw or even a wood rasp.

The two frame members can be the same perforated steel tube and the
pieces can all easily bolt or pin together. The steel tubes are
available at Menards, unless you want to buy galvanized instead. Maybe
could use galvanized Unistrut instead? Comes in 8' or 10' lengths so
one or two pieces might be enough. It is strong, HEAVY, and has an
assortment of clamps that might make life easier...... Could be worth
a look.

I'd need to mount a flat plate in the triangle to act as the turntable
bearing support. The Formica turntable surface can ride on Teflon
patches attached to the triangle surface. It would be cute to run a
cogged or toothed belt all the way around the outside of the turntable
and use a stepper to rotate it. Bicycle chain? That would take care of
the azimuth part of the project. So far this is all pretty much bolt
together stuff.

The tilt mechanism will need pretty sturdy uprights for the dish tilt.
Or there is nothing to stop us from going back to a simple vertical
pipe to mount the dish on the turntable and modify the existing dish
tilt mount for motor adjust. Yup, I can reinforce the vertical pipe
and just use the dish tilt mount with an electric screw driver or
possibly one of the $15 linear actuator units from Surplus Center.

Might be worth considering.... Except for the DIY Lazy Susan, it is
all the way back to the original designs we were discussing, similar
to what Jerry mentioned and what Bob W0AUS tried 10 years ago..... My
only complaint is that the dish can't be laid horizontal very easily.
I'd have to settle for turning the dish edge-on to direction of
travel.... Pins or clamps to hold it on that direction while in
motion?

Anybody with an ENG (Electronic News Gathering) van they are not using? :-)

73, Doug Reed, N0NAS.