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Building a 24' Dome

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#126 Peter L.

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Posted 28 January 2013 - 07:57 AM

Absolutely incredible!

#127 stevecoe

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Posted 09 February 2013 - 03:43 PM

Tom and Jeannie;

I am in the RV park in Wickenburg and there is snow on the ground and the temperature is 34 degrees last night. I am glad I got some observing done during the week.

The dome looks great, I am glad that the shop we built has some usefullness;-)

Looking forward to seeing it for myself;
Steve Coe

#128 Tom Clark

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Posted 17 February 2013 - 07:40 PM

Update.

Since the last photo was three weeks ago, nothing has been done except for waiting for the guy with the crane. This huge door has been hogging all the space in the shop, and the scope hogging all the space in the garage.

The crane man said he would be out in about two weeks, so any day now. Once the roof is finished the scope can be moved in. Lots of photos to follow. Just got a new fisheye lens that makes it easy to post interior photos.

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#129 brave_ulysses

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Posted 17 February 2013 - 07:47 PM

championship shop! sorta reminds me of the new yankee workshop.

maybe you could wake up this thread with a couple of pix:
"Post a Picture of Your ATM Workshop !"

http://www.cloudynig...5587593/page...

#130 tclehman1969

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Posted 20 February 2013 - 01:06 AM

Incredible!

#131 Tom Clark

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Posted 26 February 2013 - 04:59 PM

When you are building your own project you are able to work at your own pace, but once you are dependent on someone else, all falls apart. We started the dome in Sept, and by January we were nearly finished, other than waiting first for the gears and shutter motor.

I wanted all those parts on hand before having the shutter lifted up in place. Then we had to wait nearly a month waiting for the crane guy to show up. At first he said two weeks, and then he said another week and he would call. After another week of waiting, I got mad and started looking around. Finally found an air-conditioning and heating guy with a small crane, and when I spoke to him he said he would be out in an hour. An hour and a half later the shutter was up and in place!

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#132 Tom Clark

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Posted 26 February 2013 - 05:06 PM

Of course that is when I discovered that the engineering designer for this project was not too sharp. The shutter was about 6" too short. It was supposed to overlap the bottom shutter. Oh well, things like that are easy to fix. I'll just add 6" to the bottom shutter so it goes under the top like it was planned. I think I must have used the radius for the shutter opening instead of the radius for the top of the shutter in my calculations. Duh!

I would like to thank everyone for their kind comments all through this thread. They really do help to make the job easier. It should be obvious that I am just a telescope maker, not a contractor - but the whole project wasn't that hard to do. You just take it one step at a time and before you know it we are nearing completion.

As soon as the shutter is working it will be time to get the scope installed. More photos will be posted then.

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#133 Mary B

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Posted 26 February 2013 - 07:17 PM

Looking good even with the error. Maybe just some flashing that is Z shaped to cover the gap?

#134 dmdouglass

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Posted 27 February 2013 - 12:07 AM

How cool is that !!

You are going to enjoy that facility sooooooo much!
One minor little problem to fix... and you already have a plan.
And then it will be time for "first light"...

We await your report.

#135 Mirzam

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Posted 27 February 2013 - 07:34 AM

The trick in engineering design is to make the mistakes look like they were "done on purpose".

JimC

#136 Tim Gilliland

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Posted 27 February 2013 - 08:33 AM

The trick in engineering design is to make the mistakes look like they were "done on purpose".

JimC


Or as My wife says of my errors in woodworking, it gives it Character.

I really have enjoyed following this thread. Congratulations on a beautiful Observatory. Can't wait to hear first light on the refigured mirror.

#137 Smack

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Posted 27 February 2013 - 07:43 PM

The trick in engineering design is to make the mistakes look like they were "done on purpose".

JimC


It's what we aerospace engineers like to call "a feature".

Steve

ps before you get too scared, we aren't allowed to leave the features unfixed :)

#138 Peter L.

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Posted 28 February 2013 - 07:30 AM

It's what we aerospace engineers like to call "a feature".

And I thought only us software guys used that term. "It's not a bug, it's a feature". I even have a coffee mug with that saying on it...

Peter

#139 EdTheEdge

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Posted 28 February 2013 - 12:18 PM

This is a most fascinating project, thanks for sharing!

#140 frolinmod

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Posted 28 February 2013 - 11:21 PM

Bugs only become features after other programmers write code that is dependent upon them and will break if you fix them.

#141 BluewaterObserva

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Posted 06 March 2013 - 04:04 PM

I'm not to far away from you. Mine is a .8 meter under a 6 meter dome in the Zuni Mtn's, NM.

The weather is warming up, My wife and I and perhaps our well behaved little Beagle would love to see your setup down there. Once the snow melts I think there are some back roads that would make it a fairly short distance between us. Your welcome to come up here some time as well if interested.

#142 Tom Clark

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Posted 07 March 2013 - 12:28 PM

PM sent.

#143 Tom Clark

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Posted 20 March 2013 - 07:12 PM

Haven't posted lately, as have been trying to figure out how to get our big sliding shutter to open and close properly. I hate to admit it, but getting the twin shutters to slide sideways was a lot easier to build and adjust…

The first motor I put on the dome was just too small. It would open the shutter a bit, but as soon as the open button was released the door would come crashing back down.

The door needed a more powerful motor that would hold the door in position. I ended up getting an electric winch gear motor, and taking it all apart, then building brackets so it could be mounted to the dome. It works, but seems to be too powerful and moves the door much faster than I would like.

Anybody know how to slow down an AC motor without doing it by gearing?

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#144 Tom Clark

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Posted 20 March 2013 - 07:15 PM

The door does go up and down, but I am still adjusting the support wheels to try to end up with a shutter that is trouble free. The simple truth is I just don't know what I am doing and could use a little help.

Building everything else on this project was actually quite easy, but solving this new problem is taking a bit of work.

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#145 John Jarosz

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Posted 20 March 2013 - 08:21 PM

If you use a worm drive then the weight of the shutter can't backdrive the motor after it's turned off. Worm drives have a high reduction which slows the output speed down AND gives you much more torque. It might be something to think about.

John

#146 John Jarosz

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Posted 20 March 2013 - 08:26 PM

There are a zillion of them

#147 stmguy

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Posted 21 March 2013 - 05:35 AM

You should be able to control the speed with a PWM control
http://www.ecrater.c...switch-ac?gps=1

this one is for 220 volts , not sure what you have for a motor
Norm

#148 Mike Lockwood

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Posted 21 March 2013 - 11:27 AM

Anybody know how to slow down an AC motor without doing it by gearing?

There are a variety of solutions, but really you should know what type of AC motor it is before you choose a speed control method.

What other info do you have about the motor?

#149 Jeff B

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Posted 21 March 2013 - 11:45 AM

Would it be possible to have a hanging weight with a rope snaked over pullies along the ID of the dome, like an elevator? The weight could be removed so you could rotate the dome and only attached when openning the shutter.

Just an idea.

Jeff

#150 Rustynuts

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Posted 24 March 2013 - 08:48 PM

Tom, what you need for controlling ac is a frequency inverter. they are industrial ac motor controllers. they worked like the drive correctors worked for the synchronous motors used in the older eq mounts. I am surprised that you decided to use a ac motor system because the only way to slow down a ac motor is to lower the frequency connected to it. Jon






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