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Old 07-08-2019, 10:54 PM
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StarChildDazee (Dazeford)
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Question New Elivated Peir Construction Q's

Hi all, this is my 1st post here and I only joined recently.
I need to replace the end part of my house length Patio which is of timber construction.

What I'd like to do is construct a Viewing deck on top of the end part of the Patio, and then with a concrete pier prob made from concrete blocks (Bessa Blocks) up to the deck level then have either a concrete filled Storm Pipe (200mm) or a steel pipe up the remaining of the height required to take my telescope a Celestron Nexstar SE8. Currently AltAz but will later make a Wedge for it).

At the base at ground level there is concrete which I'm thinking of cutting a 1msq hole then digging a cubic meter hole below and filled with reinforcing and concrete to steady/brace everything.

For the Pier, up from the ground I am thinking 1 and a 1/2 blocks square filled with concrete and reinforcing rods.
Deck height above ground is about 8 feet, then approx. another 4 foot to the scope baseplate.

My Q is, is this over kill or not enough to keep my scope steady when viewing and imaging and from vibrations?
The ground in general is Clay.
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Old 07-08-2019, 11:33 PM
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xelasnave
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Welcome Dazeford.
Sounds good but is there any chance of getting down to bed rock ? Clay although reasonable dies expand and contract. If that's what you have perhaps keep it moist. I was in real estate an old houses on clay would get cracks in protracted dry spells but an architect client told me his truck with his oldie as to not let the ground dry out.
Perhaps the important thing would be to make sure the pier is isolated from the deck so that walking on the deck will not carry to the mount. But I am not an expert so hopefully someone who has done similar can share their experiences. I would drive in star pickets and pour your concrete so it holds onto say 18 inch of the star picket....probably over kill but hey here is nothing wrong with overkill...good luck and let us know how you go...maybe a thread so others can learn from your hopefully successful venture.
Alex
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Old 09-08-2019, 02:21 PM
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StarChildDazee (Dazeford)
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Thank you Alex for your input...
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Old 09-08-2019, 06:39 PM
Sunfish (Ray)
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You may find that digging hole and filling with concrete is no better than bolting steel to existing slab if it is reinforced correctly and is on good footings.

I have a steel pier on a slab on filled and reinforced concrete block work, again on footings and piers in clay. I can walk around while imaging.

The problem is the additional weight you are adding with a tall concrete pier unless it is above existing concrete footings of a reasonable standard. And then , in clay , it would require deep drilled concrete piers to keep stable over time and moisture levels depending on slope and clay depth. Only an engineer with a drill log report could answer these questions more exactly.
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Old 10-08-2019, 11:26 AM
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StarChildDazee (Dazeford)
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Quote:
Originally Posted by Sunfish View Post
You may find that digging hole and filling with concrete is no better than bolting steel to existing slab if it is reinforced correctly and is on good footings.

I have a steel pier on a slab on filled and reinforced concrete block work, again on footings and piers in clay. I can walk around while imaging.

The problem is the additional weight you are adding with a tall concrete pier unless it is above existing concrete footings of a reasonable standard. And then , in clay , it would require deep drilled concrete piers to keep stable over time and moisture levels depending on slope and clay depth. Only an engineer with a drill log report could answer these questions more exactly.
Hello Ray, ok then sounds like sound advise.
The concrete patio floor I would expect is as per standard concrete laying. its been down some 30yrs.
I now have to decide what size steel pipe to use.
It has to go up about 2.3m to the proposed deck height then I am anticipating going up another 1.4-1.5m for the scope and mount to sit upon.
For this I am also thinking 200mm dia.
Any suggestions??
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Old 10-08-2019, 03:01 PM
Sunfish (Ray)
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For that height the bigger the better. I think you would have to add two or three diagonal pipe braces and perhaps fins from the slab up to to below the next level in different directions to prevent movement and perhaps fill part of the steel to dampen it down. Still easier than cutting a cubic meter hole in the slab. Perhaps you can find a calculation for the size and thickness required above the braces to get vibration to an acceptable level. It is a challenging height for mounting a scope.

The cost of the steel and welding and bolting may be more expensive than a new location higher on the site.
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Old 10-08-2019, 04:13 PM
Wilso (Darren)
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I like the steel pier option myself, a lot easier to manufacture and you could also add three stainless steel turnbuckles and wire to stabilise the pier . Perhaps fill 1/3 with sand.
Sounds like a fun project!
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