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Pipe Pier Plan. Possible? Probably.

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#1 Cotts

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Posted 21 September 2012 - 11:06 AM

Planning for my backyard observatory is well under way. I would like to have a metal pipe pier rather than concrete. A friend of mine made his as follows. The pipe was 6" iron (I forget the exact I.D. and O.D.) At the top, which had been machined as square as possible, an adapter was attached with three 3/8" bolts through the side of the pipe at 120 degree spacing into a ring which fit inside the pipe and then had the wedge for his C11 attached on top of that. The pipe was about 8' long, 4' of which went below ground.

A hole about 12" in diameter was dug with an auger to a depth just over 4'. A 10' diameter patio stone was lowered into the hole to prevent the pipe from 'drilling' further down into the soil. The pipe was then put in the hole, made vertical and guyed in place very securely. Concrete was poured around the pier to ground level. Everything was left to dry for a few days.

The pipe was filled almost to the top with beach sand 'liberated' from a Provincial Park nearby which helped damp resonance and vibration.

This pier has functioned perfectly, he says, for the past 20 years. When I have observed at his observatory I tried the rap test. I gave the top of the pier a good smack while looking through the eyepiece. The damping time was well less than one second! He also told me he has not had any problems with the pier tilting over time.

The question is, should I copy this design? I'll be mounting a 6" f/8 APO on a Mach 1 GTO on my potential pier. Any caveats?

Dave

#2 DeanS

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Posted 21 September 2012 - 11:42 AM

No reason it wouldn't work as well as his. Mine are made from steel pipes, 8" & 10" diameter with bottom and top plates welded on. They are bolted down to a concrete floor with heavy duty anchor bolts. Very solid, but I can remove them, or move them if needed. Something to consider if you think you might ever need to remove it.

Dean

#3 Keith Howlett

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Posted 22 September 2012 - 02:49 AM

IIRC the pipe diameter is the main determinant of the pier stiffness. Moving up from 6 inches to nearer 10 inches diameter might make a significant difference.

Cheers,

Keith

#4 rick barnaby

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Posted 26 April 2013 - 02:44 PM

IM DEBATEING WEATHER TO GO WITH PIPE 6" WELL CASEING & PLATE STEEL WELDED TO BOTTEM & TOP OF PIPE , SAND IS A GOOD IDEA IN PIPE FOR DAMPING VIBRATIONS , ALTHOUGH IT MUST BE KEPT DRY TO WORK , THEN BOLT TO CONCRET FOOTING (BELOW FROST LINE) OR 12" CONCRET TUBE WITH FOOTING BELOW FROST LINE TIED TOGETHER. CAN ANYONE TELL ME ESTIMATED COST DIFFERENCE? CLEAR SKYS.....RICK

#5 stmguy

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Posted 26 April 2013 - 03:54 PM

I'm very happy with my 6" well casing about 40" long with a weldable pipe flange on the bottom. This is bolted to a 12" concrete pier (bigger here wouldn't hurt as anchor bolts are pretty close to the edge) It supports my 10" F4 Meade reflector just fine
Norm

#6 Kraus

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Posted 30 April 2013 - 06:49 PM


If you see and know it works, why not go with it. I made mine of concrete. Rap test? No vibration. 18 years now.






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