Thought on dome wheels and track please

[Cam99 (Campbell)]

I am building a dome and mulling over the options for track and wheels. I want to drive it with automation eventually. It seems to me that grooved (V or U) wheels of some sort running on a track (perhaps rolled tube or a strip of 4mm steel or Al) will stabilise the dome laterally and have less rolling friction than castors on a timber ring. But is this extra structure (a track) really needed??



I would be very interested in any wisdom that those of you who have been down this track could impart.


Thanks
Campbell

[LonelySpoon (Neville)]

Hi Campbell,
After trying various roller systems for my 3m dome, I settled on skateboard bearings onto a rolled steel tube.

Getting the tube rolled (2 of 1/2 circles 5m X 30mm) cost less than $200.

The bearings are mounted onto short pieces of angle aluminium as the picture shows. There are 12 sets.

I can rotate the whole dome with one hand, but usually use two wiper motors to do it.

If you go to https://homemadeplans5.wixsite.com/lsobservatory
you can see the whole construction story.

I will also be doing a presentation at next years NACAA in Parkes about this style of dome.

Good luck with your project.

Neville
LSO

[Cam99 (Campbell)]

Thanks Neville.
Really useful information.

The rolled tube and bearing assemblies look like a great solution. I note that you opted for horizontal shutters rather than a vertical one. I am interested in how you have found this - has weatherproofing been difficult?
And your dome structure is an interesting twist on the usual as well. I may have a few more questions as I get my head around this.
Cheers
Campbell

[LonelySpoon (Neville)]

Hi Campbell,
LSO is my third dome, and the first one I have used horizontal shutters on.

The shutters don't leak, but the hatch I installed on the back slope does, slightly.

I've also had them freeze shut once, but I can't specifically blame the design for that. Probably wouldn't be an issue where you are!

I've found that differential heating and cooling of the horizontal shutter leads to occasional sticking, to the point that I've disconnected the motor for now and open/close manually.

I may still rip them off and go vertical. I'm too lazy though...

Happy to help in any way.

Cheers,

Neville
LSO

[Cam99 (Campbell)]

Thanks again for the comments, Neville.
Do you need a hatch behind the horizontally rolling doors to expose the zenith or is it possible to extend them back sufficiently? Or is this yet another 'suck it and see' question?
Campbell

[LonelySpoon (Neville)]

The hatch is for access to that part of the dome.

The slot extends past the vertical to allow the scopes to point straight up.

I figured because the dome is already 2m off the ground at the base it was safer to come at the top runners from the inside, especially if I had to do some major work like removing them.

Having said that, if I made another one I wouldn't put the hatch in.

Neville
LSO