Bob Myler
sage
Reged: 05/18/06
Posts: 224
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Folks, at the end of this thing, I really do have a question. I own an Exploradome and I have little desire at this time to invest big $$$'s in a system that synchronizes the motions of the dome and shutter, to that of a driven telescope. Maybe someday, but not now. For now, "dumb-slewing" the dome CW and CCW (at somewhere around one rpm) is all this visual observer wants or needs. There's no use re-inventing the wheel here. Exploradome offers a proven system tying their hardware to the dome. Rotation Kit #1 (AM-0188 - $158.70) consists of a large acorn sprocket gear, - now available in 6" AND 8" diameters - matching gear track, and screws to fasten said gear track to Exploradome's wheel channel. As many of you know, reversible 12 vdc motors with enough starting torque sufficient to rotate something like an observatory dome, are extremely expensive ($400+), plus the cost of "controlling" it. And there's precious little to be found on the surplus gear motor market. Buy the wrong used gear motor, and chances are you will be stuck with something that you will never find a use for. So here's one poor man's "solution": Dan Johanneck of Exploradome will custom-ream the center hole of his acorn sprocket to fit any size shaft up to 1" diameter. Harbor Freight sells a portable 12 vdc utility winch, complete with corded hand control (to switch from power in to power out), for only $60 bucks (item #92860-2VGA). This puppy has a rated capacity of 2000 lbs., so starting torque would not seem to be a problem. Rotation speed would just about be right on. Obviously, I'd have to find a way to mount - and spring load - this 14 pound hunk onto ED's top wall ring (without deforming it), AND modify the spool shaft to fit Dan's gear socket. Even if all this didn't work, I would hopefully still have myself a working utility winch!
So here are my questions: I know NOTHING about powered winches. Perhaps some of you do. When the specs on a winch call for "Power In and Power Out," is that the same as fully reversible? Would the dome power-rotate in both directions? Anything else you can think of that might cause this $219 cheapo combination not to work?
Edited by Bob Myler (01/28/09 10:13 PM)
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Pedestal
Post Laureate
Reged: 03/11/06
Posts: 3857
Loc: Smoggy Bottom, Baytown,Texas
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"Power in and power out" means, yes, it is reversible, and there is probably no "freewheel" setting. (Something you might want to do to deploy a long winch line)
Hubert
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Hubert
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www.smoggybottom.org
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rodney
Vendor - Explora Dome
Reged: 03/08/05
Posts: 812
Loc: Asbury, NJ
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Bob,
Looking at that winch at Harbor Freight it should work. Without actually having it in hand it is hard to tell. I currently use an AC motor in my Explora Dome. That winch surely has enough power and since it is a winch it is reversible.
Hope this helps some.
Clear skies,
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Explora Dome information can be found here:
www.exploradome.us
Rodney
Meade 10 SCT
AT 8/F4 imaging scope
13 Truss
C8-NGT
Orion 80mm/F11
Canon 300D
Canon XSi
Two AS-GT mounts
Extremely happy Explora Dome home observatory owner
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Bob Myler
sage
Reged: 05/18/06
Posts: 224
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Rod and Hubert, I appreciate your feedback. I plan to pull the trigger on this thing - and I'll keep the Forum informed with photos on how it all works out. Thanks again! Bob
Edited by Bob Myler (01/28/09 10:32 PM)
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Remy Bosio
Zeit-Meister
Reged: 03/02/04
Posts: 10358
Loc: Kenner, LA.
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All you need is a gear reduction motor combo and a go-cart tire. The motor mount is on a spring plate and it rubs against the lower lip of the dome. Observadome has used this method well and I personally can attest to it working extremely well for years without failure. that is unless you forget to inflate the tire to proper pressure each year.
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REMY
Meade ETX 125PE
102mm.F-7 Ref.
Sears 60mm.Ref.
UCNROSN
Member: Baton Rouge Ast.Soc.
"Life Member" Pontchartrain Ast. Soc. Inc.
President:Beachview Heights Civ.Assn.
American Legion,Post 0133
http://pasnola.org/
"Pay no attention to that man behind the curtain!"
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Bob Griffiths
Postmaster
Reged: 10/10/05
Posts: 6583
Loc: Frederick Maryland
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Morning Bob...
Like you I have absolutely no plans to automate my ED... and to be honest I have no plans to even power the dome or shutter ..its just too easy to rotate by hand..
However I have been looking at winches ...to HOIST ME .... up into my ED..
My ED is elevated 7 foot off the ground so I climb up a built in ladder (4x4's with 2x4 rungs) .. and enter via a trap door in the floor...
Climbing up is not a problem... but due to a severe drug reaction last February I lost the feeling in my toes/feet...(nerve damage).. BUT climbing down a ladder is an experience to say the least because I can't feel the darn rungs...have to visibility check that my feet are in fact firmly planted on each rung as I climb down. not as easy as it sounds...
A simple 12V winch, 2 garage door tracks and a platform should be all I need to fabricate my own elevator... you do not want to price commercial residential elevators or even hydraulic lift tables or motorcycle lifts ..these things cost more then my 2 lifts I have in the garage for my cars...
Neurologist tells me that nerves rejuvenate about 1 inch per month and I am 6'1 ...doing the math tells me I'll get back to normal in 5 more years.. Heck I'll be into my 70's by then .. and I have never been one to waste any time...!
Bob G.
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CPC1100
Nexstar 8i + GPS & Rays Brackets
Denk S1 power switch
Orion 100 mm Refractor
Meade LXD 55 ...AR-5 127 mm Refractor
Exploradome Observatory S.I.E. (Smiling Irish Eyes)
Gerbring Heated Motorcycle clothing in the winter
39*21'03" N
77*28'12" W
The sky over my head....
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Chris Rowland
sage
Reged: 02/28/05
Posts: 269
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My astro society's dome is motorised using a windscreen wiper motor and gearbox (Ford I think). The drive is with a cam sprocket onto cam shaft belts that have been cut up and nailed to the dome ring. It takes about 5 amps at 12V from a jump start battery pack.
Currently it's controlled using a car door window switch.
This works fairly well. I've plans to automate it using an Arduino microprocessor, a relay, power FETs and some software. The biggest problem has been the azimuth sensor but I hope that I've cracked it by using the innards of an old potentiometer and a couple of slotted opto switches.
Chris
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Bob Myler
sage
Reged: 05/18/06
Posts: 224
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Thanks for all the great ideas guys. Bob, I know where you are coming from when you speak of the body rebelling against you. I just tried my daughter in law's Wii exercise game. It judged my aerobic health to be that of a 125 year old douglas fir - with rotted roots and significant fire damage...
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Tom Clark
sage
Reged: 11/14/07
Posts: 248
Loc: Chiefland, Florida
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Bob,
This is overkill for your project, but still the idea is worth passing on. For a drive wheel I used a solid rubber tire from a bush hog mower. It costs $34, and you never have to worry about a flat tire. This single wheel drives my 24' dome easily at one RPM. The gear motor has enough power to drive a 100' dome.
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Bob Myler
sage
Reged: 05/18/06
Posts: 224
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Tom, thank you for your feedback and the photo - an interesting setup you have there! In addition to NOT losing air; -as the flap-style mower wheel's diameter decreases over the years (would it EVER wear?), those two compression springs would ensure consistent upward contact. A wheel as opposed to a cogged sprocket just might be the way to go. As for me - Harbor Freight's #92860 portable winch is really sized and "geared" to pulling ATV's, lawn tractors, and floating boats - not cars or trucks. Thru many searches, I have found that easily-adaptable, low rpm, reversible 12 vdc gear motors - with sufficient oomph to drive a dome - are virtually unavailable on the used or surplus gear motor markets. I don't know why. And something close - might prove to be practically unusable for ANYTHING - and not returnable. A new unit - say from Grainger - would cost big bucks, and a dedicated system to control it would only add to that. Today, I just picked up the above unit on sale - complete with remote hand control to reverse directions - for only $49.99! The cast metal housing for the motor is robust and approx 3" in diameter - and together with its planetary gear box - approx. 7" long overall. Removing the mounting frame, 50' of wire cable and the drum it's spooled on, probably brings the weight down to 10 or so pounds (if we exclude the hand control and power cables). It IS a hunk and it will require some supplemental support when mounting on the dome wall. At the very least, even if it were to prove unusable in my observatory, I will NEVER be stuck in mud again! - Clear Skies
Edited by Bob Myler (02/01/09 12:30 AM)
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rodney
Vendor - Explora Dome
Reged: 03/08/05
Posts: 812
Loc: Asbury, NJ
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Bob,
It's funny you mention how tough it is to find just those 12v reversible motors. Someone once told me they could be had for dirt cheap. They never got back to me on that supplier. Dan's supplier will only sell them to Dan since they are made just for his application. Not by Dan's choice either. I had my concern about that winch motor but without it being right in front of me it is hard to tell.
The sprocket being used on ED's is off a piece of farm equipment and they are available online. I forget where at this time. The reason the sprocket was used is to ensure there is no possilbe way the dome will slip and cause any issues with automation. Rotation is one thing, automation is another. A slip of a tire would cause parameter issues within the software controlling automation. Hence the use of the sprocket again.
Bob, when I tell you a lot of thought has gone into what will and will not work on these Explora Domes I am not making up the hours involved. I have more hours involved than I would care to repeat out loud.
Keep us posted on your progress and options,
Clear skies,
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Explora Dome information can be found here:
www.exploradome.us
Rodney
Meade 10 SCT
AT 8/F4 imaging scope
13 Truss
C8-NGT
Orion 80mm/F11
Canon 300D
Canon XSi
Two AS-GT mounts
Extremely happy Explora Dome home observatory owner
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Bob Myler
sage
Reged: 05/18/06
Posts: 224
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OK, I may have reduced the price of "dumb slewing" down to $25 bucks. After tearing apart the above ATV winch, I think I might limit its use to winching - at least for now. I just received a reversible gearhead motor, yielding 21 rpm @ 12 vdc. (Item #16779 MD at www.mpja.com) It's output shaft measures 8mm x 51 mm. Under load - using a 4" bearing wheel - an ED dome would rotate @ the ideal speed of approx one rpm: IF - and this is a big IF - 4.5 stall amps are enough to do the job. Stated another way, is 1/14th HP (hopefully I calculated this right) enough power to start and move a 180 pound Exploradome requiring average operating force?
If ONE is insufficient, would TWO work - on opposite sides of the dome? If I were to double the line voltage to 24vdc (reducing the diameter of the bearing wheel of course) would THAT give me enough stall amps? Folks, any suggestions here would be greatly appreciated!
And please remember that I'm cheap...Bob Myler, St Louis
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kiwisailor
Pooh-Bah
Reged: 01/07/04
Posts: 1221
Loc: Lyttelton, New Zealand
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G'day Bob
Take a look at the formula and calculators Engineers Edge plug in the various dimensions and you'll get the info you need.
I visited a home brewed wooden dome last month that had three motors spaced around it to rotate it.
Steve
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Don't wait until tomorrow, start procrastinating today!
Sky-Watcher 8" F5 Newt
Mmmm Moonlite CR2
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Bob Myler
sage
Reged: 05/18/06
Posts: 224
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Thanks, Steve, for that heads up. I did find out that, at 12 vdc and 21 rpm, the above motor puts out about 4 ft/lbs of torque. At 24 vdc and 42 rpm, torque increases to 7 ft/lbs...
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Mr.päivinen
sage
Reged: 07/29/06
Posts: 272
Loc: Rajamäki Finland
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Hi!
Just if you are interested to see my design of the rotation motor here is the image of it.
HERE IMAGE OF THE MOTOR!
I have done same kind of motor systems using car wiper motors. They are usually very strong and sometimes you can find them at old car for free.
More images of my dome systems can be seen HERE!!!
Mikko Päivinen
Finland
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MP-observatory finland http://www.kolumbus.fi/jappervokki/
C11".
ST-2000XM/AO-7.
CFW-8A.
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Bob Myler
sage
Reged: 05/18/06
Posts: 224
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Nice setup you have there, Mikko! I notice your system uses inline roller blade wheels similar to Exploradome's. Are you able to power your dome with the use of only one windshield wiper motor?
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Mr.päivinen
sage
Reged: 07/29/06
Posts: 272
Loc: Rajamäki Finland
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Yes one motor is enough becouse the dome rolls so easily and it also keeps the shape well and does not bend at all. I did also get better grip for the wheel when i did put it in the 45 degrees angle (Then one wheel have two contact areas of the dome.)
Mikko
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MP-observatory finland http://www.kolumbus.fi/jappervokki/
C11".
ST-2000XM/AO-7.
CFW-8A.
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