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looking for source for gear racks

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#1 Tom Clark

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Posted 03 December 2012 - 09:39 AM

Before starting construction of my own dome, I visited many home observatories, taking photos for ideas later on.

Somewhere I took this photo of a shutter opening mechanism. Now I am looking for a source for the motor and gear rack similar to what is shown in this photo. If anyone can help or recognizes it, please let me know.

I was planning to use a commercial garage door opener, and make my own gear, just purchasing the rack, but all my internet searches are getting nowhere fast.

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#2 mikey cee

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Posted 03 December 2012 - 10:51 AM

Because of different curvatures this rack may have been custom bent. Might only be able to find straight stock ones when you do find a supplier. ;) Mike

#3 Tom Clark

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Posted 03 December 2012 - 02:13 PM

Mike,

This material is only about 1/8" thick, and will be easy to bend to a large radius by hand. My radius is 12', so in answer your comment, yes, I am looking for flat stock.

Tom

#4 stmguy

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Posted 03 December 2012 - 02:38 PM

Looks a little like stuff I saw on a farm long ago , perhaps Tractor Supply might have something similar ??

Norm

#5 Scott Horstman

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Posted 03 December 2012 - 05:05 PM

Tom, the picture you posted is an Ash Dome shutter motor set up, They use the same sort of track for the rotation but it's horizontal not vertical so couldn't be bent easily on site to fit your radius. If you mounted it vertically so you could bend it, you'd have to do some sort of "capture" to keep the gear in the rack. You might check with them or Dan at Exploradome. They put a pretty good system together. It's similar and I'd bet it'd be cheaper.

#6 Mary B

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Posted 03 December 2012 - 07:08 PM

That track looks like shelf support material.

#7 Starhawk

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Posted 03 December 2012 - 07:49 PM

Have you looked at Grainger and McMaster-Carr?

-Rich

#8 Christopher Erickson

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Posted 03 December 2012 - 08:05 PM

Tom, the picture you posted is an Ash Dome shutter motor set up, They use the same sort of track for the rotation but it's horizontal not vertical so couldn't be bent easily on site to fit your radius. If you mounted it vertically so you could bend it, you'd have to do some sort of "capture" to keep the gear in the rack. You might check with them or Dan at Exploradome. They put a pretty good system together. It's similar and I'd bet it'd be cheaper.


I'll confirm that the pic is of the shutter drive system of an Ash dome.

You might consider calling Ash and see if you can buy the parts you want from them. No guarantee that you can get what you want but it might be worth a shot!

Ash is a quality manufacturer of tough, reliable steel domes.

#9 Scott Horstman

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Posted 03 December 2012 - 11:59 PM

I'll confirm that the pic is of the shutter drive system of an Ash dome.



Thanks Chris. Always makes one feel good to be verified by the experts. :jump:

#10 Tom Clark

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Posted 05 December 2012 - 08:31 AM

Update:

I looked at Grainger and McMaster-Carr, no dice. Called Ash Domes, they were nice but said that they would not sell components. Tractor Supply has a light-duty metal with round holes in 6' lengths. I bought some to experiment with, but gut feeling is that it is too light duty. (I am a retired machinist.)

Haven't called Dan at Explorer Dome yet. Will call today. Looked at their web site but didn't see much but little domes.

Will next looking into using chain drives. Anyone have any photos of a working solution along those lines?

Thanks for all your input and help. The quest goes on. Mike Lockwood is now working on my 42" mirror refiguring. I need to get the dome ready in a month or so…

Tom

#11 Tom Clark

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Posted 05 December 2012 - 04:33 PM

Thank you everybody! Problem solved!

Scott, thanks for recommending Dan at Explorer Dome. He was very helpful, and led me to the right place on their web site. At first all I saw was their small domes. but hidden in there are many pages of info and parts.

I got my gear rack and main gear for a very reasonable price. they also have the rest of the parts to finish the job if you don't want to make them yourself.

The gear and rack are made with poly-something. When I asked about durability Dan said that they come with a lifetime guarantee. That works for me. Here is a link to the page of their web site I was on. Yes, it says it is for dome rotation, but the rack comes straight and has to be bent to rotate a dome.

You can check on the other thread to watch the completion of the dome over the next month or so.

#12 Scott Horstman

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Posted 06 December 2012 - 08:57 AM

No problem Tom, glad I could help. Dan and clan are great folks. I hope it does the trick.

#13 Starhawk

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Posted 07 December 2012 - 10:08 AM

Egad- I've been at the large dome for the 60" scope on mount Lemmon- it has a working drive for the dome shutter, but I didn't take pictures. It's about the size of what you are doing, though. I'll ask around.

-Rich

#14 Starhawk

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Posted 07 December 2012 - 10:16 AM

Just in food for thought, a drive chain can be laid out so it acts like a rack. This would be the inverse of your picture, with the chain underneath with guides to keep it from moving side to side and the sprocket on top (outside of the shutter). I would suggest supporting the shutter with roller-blade wheels. But a rack made this way wouldn't need to be the perfect curvature- a support roller would make sure the local separation was correct, or the chain could be picked up on each side by small guide sprockets.

-Rich

#15 Christopher Erickson

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Posted 07 December 2012 - 12:40 PM

Just in food for thought, a drive chain can be laid out so it acts like a rack. This would be the inverse of your picture, with the chain underneath with guides to keep it from moving side to side and the sprocket on top (outside of the shutter). I would suggest supporting the shutter with roller-blade wheels. But a rack made this way wouldn't need to be the perfect curvature- a support roller would make sure the local separation was correct, or the chain could be picked up on each side by small guide sprockets.

-Rich


Drive chains can be found with 90-degree mounting tabs on every or every-other link. Also, you can buy bicycle chains with hollow links that can be mounted with small nails or screws. Bicycle chains are more than strong enough for amateur observatory applications.

However be warned that thermal expansion and contraction can make drive chains rather problematic over time. They can get too tight in cold weather and too loose in warm weather. And the regular thermal expansion-contraction can potentially loosen up your fastening system rather quickly.

I hope this helps.

#16 Retsub

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Posted 09 December 2012 - 07:28 PM

Hi Tom, fine looking dome ! Glad you found a simple rack for a drive. I was about to suggest that you look for some country parts meaning looking at the square link chains that are used on farm implements. Would have been easy for you to bend some small steel tubing to the correct radius and tack weld it on both sides of the chain to make your rack by the foot. Always is another way but maybe not the best. Keep at it! Regards. *BW*

#17 Tom Clark

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Posted 14 January 2013 - 08:38 AM

As a follow up to this post from the beginning of December, the rack and pinion gear finally arrived and are mounted to the shutter. The parts are solidly built, reasonably priced, and have a lifetime guarantee from Dan at Polydome. The shutters will soon be mounted and the dome finished.

So for anyone else looking for these gears here is a link:
http://explora-dome....me_Rotation.cfm

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