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A pier question for my next project - Help please...


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With the arrival of baby number two, we are now planning to relocate to a bigger house at some point over the next few years. I am planning to make good use of this opportunity to begin planning the construction of an observatory.

I have my heart set on a 3m scopedome http://www.scopedome.com/en/default.aspx

Does anyone here have experience of them?

Ideally I’d like to build a flat-roof, wooden framed building to support the dome. The problem I have, is in the purchase (ideally) of a suitable pier to allow for the telescope to be mounted so far from the ground. Would a six foot tall brick built chimney type construction be suitable to support an off the shelf pier, or a cement filled pipe etc?

Any pointers would be gratefully received!

Kind regards, Andrew :)

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I made my own domed obsy. many years ago. The 4" steel upright ring that supported the dome on grooved wheels, sat on the four walls of the building via L brackets bolted to the walls.

The problem I had was keeping a good waterseal between the flat roof and the dome ring. Almost impossible to maintain. In the end, I gave up trying to prevent water ingress, and decided to catch it in a sealed ducting which I suspended below the dome ring Inside the Obs. The collected water flowed around the ducting, and hence through a pipe in the Obs wall. Worked a treat.

--------------------

I have to say, my dome was 3 metres in diameter and fabricated onto a steel superstructure, and skinned with Galvanised steel sheets cut to shape. It weighed a great deal, so not surprising the sealing couldn't hold up.:)

Steel piers are sold , but they are not all that cheap. A steel fabrication shop will make you one to specification. A steel one would be the best option perhaps, as it may need to be moved at a later time, should you decide on a change of scope/ Mount.

You should aim for a good solid concrete base. 75 cm deep x 45cm square.

Ron.

Edited by barkis
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Cheers Ron - I was thinking of something like a steel pipe to run from below ground (3 feet?), and then six or so feet up into the flat roof - where I would then fix a shop made pier for my mount. Do you think this would work ok, or is there a better way?

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Is there a typo in there Ron at a guess you meant to say 75cm deep x 45cm square

Billy...

HehHeh!! You don't miss much Peter.:)

I did mean 75cm, but I thought I'd give Catanonia something to laugh at.

He'll laugh on the other side of his face when I don't put his future Sky at Night imges in the Published Section :):D.

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Cheers Ron - I was thinking of something like a steel pipe to run from below ground (3 feet?), and then six or so feet up into the flat roof - where I would then fix a shop made pier for my mount. Do you think this would work ok, or is there a better way?

Steel pipe is fine Andrew. You should fill it with concrete, it will prevent bell ringing :).

You can cap it with a circular steel plate, on to which your mount base can be bolted. Provision should be made to allow levelling of the Mount.

:)

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I just had visions of someone digging a very deep hole... Ok for us Welsh boyos of my generation as we were born with picks in our hands...

Billy....

HehHeh! I'm so pleased you can spell OK Peter, you could have been banned for an unfortunate error.:):)

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Get them to weld a few pieces of 25 or 50mm flat about 300mm long along the bottom of the tube .. that way once its set in concrete there's no way it will twist either...

I always like driving a few lengths of Re-bar at an angle into the foundation hole before pouring the concrete...

Had to be careful with that on Ron as the spell checker wouldn't have "flagged" up an error...

Billy...

Edited by Psychobilly
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Thanks Barkis, Billy and all.

I'm surprised that a nine foot pier, mount and telescope would remain wobble free with only 75cm of cement. Thats good to know! Much cheaper than building a block of bricks too.

Thanks once again :))

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