Cave drive motors

Hi Don

I have found the Hurst motors on Ebay.  They seem to pop up quite often.  You just need to be sure that they are 1 RPM and that they are not a configuration that will not fit under the motor box cover.  Larger hurst motors will work and have a lot of torque but are not necessary. 

Drive correctors are pretty complicated and have caused a few restorers some nightmares (including me!)  You can find them selling on Cloudy nights and Astromart for about $90 - 100.  They tend to be hit or miss sometime.  I own 4 of which one has never worked and has several people puzzled over the electronics.  That said, you may not need them as much anymore as they did in the 50's and 60's.  Power is pretty much stabilized to 60 hz. and is very accurate.  Your RA axis should run quite well without one.  The corrector changes the frequency of the AC current to "correct" for deficient current that has increased or fallen from the 60hz it is supposed to be.  Todays AC current is very stable.  Correctors are not really used to drive the RA axis for searching the skies.  The reversible hurst and bristol motors for the DEC axis can drive the mount for searching.  There is a schematic on my Cave-astrola website on how to hook up both motors.  When operating the reversible motors with the two button control box, avoid pressing both buttons as it will create smoke in the motor and you probably know what that means.  : )

Turk

Hello

I'll buy one of the motors off you.  Let me know how you want paid.  Paypal gift would be the easiest.

Let me know.

Can you post a picture of the motor?


Turk

Oh, I realize my last post was ambiguous. That'd be one motor--Don

Hello Again,

Hey Tom, 'thought I'd fill you in on some details:

My mount is a Cave but the 10" telescope mounted on it is homebuilt as-follows:
--tube rings: parallax systems
--tube: Hastings Irrigation 12" aluminum tube w/Protostar flock board
--focuser: JMI NGF-1, manual focus
--spider+diagonal: Cave
--mirror: by John Hall, full thickness, 1/20th wave P-V at 0.64 um, 98% reflectivity coatings over the visual band (no scattering detected, BTW)
--mirror cell: University Optics, 3-point
--finder: 8 x 50 Meade
--counterweight w/slide on lower tube for eyepiece weight variation compensation.
--mount: Cave, w/1.5" shafts, RA drive (no original corrector), and DEC slew
--additional mount counterweights (2" hole diam. barbell weights with a 1.5" ID PVC pipe sleeve to minimize clearances)
--Argo Navis digital setting circles in addition to original Cave anodized 6" circles

Like many others, I've found the original polar axis adjustment on the Cave mount to be both difficult and to slip. To solve both problems, I mounted a stainless
turnbuckle attached using two stainless U-bolts: one for the RA drive plate (attached to the polar axis) and the other on the pedestal. BTW, I found
turning the lower (pedestal) turnbuckle eye outward, out of the plane of the loop, allows for removal without complicated topology problems. Adjustments are now
easy and can be done with near-micrometer precision just by turning the turnbuckle.

My total telescope weight is 182 lb. I can easily roll the mount (thank God for casters!) out onto my patio and carry the tube (61 lb) out separately. I find
the telescope to be transportable to remote sites but hardly easily portable. I must disassemble the legs from the pedestal, remove the equatorial head from the
pedestal, remove the tube cradle from the head, and of course remove all the counterweights to fit the mount in my 3-series BMW trunk. I can fit the tube
in the passenger seat by reclining the seat all the way back, using towels for padding, and exercising great care to ensure the leather is not damaged.

My house is in a typical light-polluted suburb. My sixty year-old eyes can see to mV=4.3 on the best nights, after midnight when many lights are off. Also,
our city recently replaced the old high pressure sodium street lighting with LED lights. They emit lots of blue light, which scatters terribly. So I tend to concentrate
on the planets, asteroids, double stare, and some old chestnut brighter deep sky objects.

I am the original owner of the mount (since 1972!). It is in perfect shape mechanically and is both tight and glass-smooth. The paint is a bit scratched
on the equatorial head and tube rings, and I have repainted the telescope pedestal and legs. Performance is more important to me than appearance,
although I appreciate all the hard work many of you have put into making your telescopes visually gorgeous. Still, mine is quite decent looking. The
performance of the optics is superlative and the Cave mount is reasonably steady. However, I note the following flaws:
--despite lots of effort, I never fully succeeded in removing all the backlash from the drives. It turned out the aluminum Cave worm gear
(a one-piece elongated U-shaped hunk of coarsely-cut aluminum) flexes and
--I never did find a replacement 1/3 Hz reversible synchronous Hurst AC motor for my DEC axis. Instead, I replaced the non-working original with it's 1 Hz equivalent. As
Tom has pointed out, these are still available for reasonable prices from time-to-time on eBay. The DEC drive is a bit fast for astrophotography, which is OK by me but needs
to be noted.

I want to be able to control both axes electrically. This would, of course, allow slews in pure RA and pure DEC, which would facilitate me locating objects as well as minimizing vibrations. That means I needed an AC drive corrector for the RA axis. Guess what, no one makes them anymore! Looking for a used JMI dual-axis controller for a few months on Astromart was futile. Fortunately, I have a friend who gave me his homemade one-axis drive corrector, built based on an S&T article from 1975. After cleaning it up a bit and resoldering a detached ground wire, it worked perfectly, hooray! So I have three projects left:

(1) replace the Cave drives with Byers drives. I have already obtained the Byers drives:(9" for RA and 7" for DEC). As luck would have it, they are both suck fits to the 1.5" mount shafts! I need to fabricate the sundry mounting plates and enclosures. I can fabricate the parts myself and 'will send them out for powder coating (see, I like beautiful telescopes too). I intend to use the AC motors Mr. Byers supplied, not DC servo motors, because I am not interested (given the poor quality of my observing site) in long-exposure astrophotography that requires an autoguider, nor do I want or need a "goto" telescope. For those of you who do want these things, I suggest having a look at Sidereal Technologies website, they can help.

(2) The input power to the DEC drive is AC while the inout power to the RA drive corrector is 12V DC. I intend to have a removable mini-rack located on the pedestal with the following:
--terminal lugs to hook up DC 12V battery power to telescope electronics (for the Argo Navis and the AC drive corrector)
--an AC-to DC power converter
--an outlet to accept an AC power cord and outlets for the DEC drive and the AC-to-DC power converter
--the RA drive corrector
--and perhaps an DC-to-AC inverter, to allow the DEC axis to run on battery power at remote sites, and

(3) At the least, combine RA and DEC controls into a single "paddle". Additionally, would be nice to somehow incorporate the
Argo Navis readout box as well, I'm still thinking about how to do this.

So anyway, that is what I'm up to. There is a chance when I finish (in many months?) that my old and very much working Cave drive parts will become
available to the community.

Best,

Don Ferguson