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#1 Cotts

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Posted 12 August 2014 - 07:42 AM

......to hold an AP Mach 1 and TEC 202mm Mak Cass for visual and video only...    I'm looking at a 6" steel pipe, 1/8" wall thickness, 8' long with 5' underground encased in concrete and filled with sand.   Should be good, yes?

 

I'm building an 8'x8' ROR in my Toronto backyard to house the above equipment to carry on video imaging of double stars and, occasionally, planets or the moon...  There will be no deepsky, long-exposure photography thanks to my mag 3.3 skies...

 

Some of you may remember that I had erected a SkyShedPod here last year.  It ended up being too small for my equipment and 6'6" me so I sold it.  I will be using the existing base (see pic) minus the circular wooden plinth which went with the Pod.

 

DaveAttached File  IMG_4235.jpg   68.13KB   3 downloads



#2 Orion58

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Posted 12 August 2014 - 08:00 PM

Hello David - the pier sounds more than adequate.  A friendly word of advice - check the pier for plumb several times after the concrete and sand are in place - things tend to move until the concrete reaches it's initial set.  Good luck with the new observatory!



#3 tomcody

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Posted 12 August 2014 - 08:18 PM

Dave,

I would suggest a 18" x18" x 48" deep ( depending on your freeze depth) poured base with J,bolts on top and a steel or aluminium   pier bolted to the base so you  can adjust for level if the ground heaves. You can just dig a square hole and form the top 12" for the pour. The ATS website has some good guidelines on piers. 

Rex



#4 rkayakr

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Posted 12 August 2014 - 10:14 PM

Dave,

I would suggest a 18" x18" x 48" deep ( depending on your freeze depth) poured base with J,bolts on top and a steel or aluminium   pier bolted to the base so you  can adjust for level if the ground heaves. You can just dig a square hole and form the top 12" for the pour. The ATS website has some good guidelines on piers. 

Rex

ATS website?



#5 drollere

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Posted 13 August 2014 - 05:46 PM

dave, a local scrap metal yard will have dozens of pieces of tubular steel to choose from. you can have the rest fabricated for a few hundred dollars.

 

i would bolt the pier to a flat concrete base, and have a leveling plate on the top. the base doesn't have to be deep in order to give the necessary support, provided it is wide. the leveling top will take care of any issues that come from settling over time.

 

i have read that incorporating sand can accelerate internal rust, because the sand is never really dry. i've also heard that sand doesn't really add that much to stability or vibration suppression, because all that is in the diameter of the tube. and square may be better (and cheaper) than round for the same dimensions; see the comparative calculations here: http://www.handprint...ry02.html#june9 and photos on the following page.

 

take your time with the design and consider things like cord wrangling and equipment overhang. make sure the height, plus mount, puts the scope in the most comfortable position. an adjustable tripod helps identify that to the nearest centimeter.

 

good luck! planning is half the fun.


Edited by drollere, 13 August 2014 - 05:47 PM.


#6 stmguy

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Posted 14 August 2014 - 05:29 AM

I used about a 4 ft length of 6" well casing welded to a flange bolted to a 4 ft 12" concrete pier and it is rock solid. I did not fill it with sand

 

Norm



#7 jazle

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Posted 14 August 2014 - 02:51 PM

I have a steel pier made from junk yard materials.  The pier tube is 12" dia, 3/8" thick, 3.5' tall with a 16" dia, 1/2" thick bottom flange and a 1/2" thick top mounting ring.  When mounted on top of a concrete pier base, it rang like the Liberty Bell when struck.  These frequencies of oscillations would probably interfere with any video AP work by blurring some of the super-fine detail you are trying to capture.  For visual or long-exposure AP, I don't think your eyes could tell and long-exposures are going to average everything in those frequencies anyways.

 

The vibrations are not a problem after filling with sand.  Our climate is extremely dry so I haven't seen or expect to have any problems with rust.  You could always drop in a few bags of dessicant beads and cover the top with a rubber membrane if you wanted to try to prevent moisture.

 

I think your plan is sound.  You can always put the leveling plate on top of your pier -- weld a square piece of steel with a hole cut in the middle to inject your sand.  Put three holes in a triangular shape to mount three bolts.  And fix another plate over this one to accept the bolts with washers and nuts to allow leveling. 

 

If you decide later on to go with a base plate above the conrete pour, that shouldn't be too tough -- cut the pipe a little bit above the ground and weld a mounting plate with bolts to the top of it.

 

Depending on how much concrete you are set into, you might have some shift over time.  You'll have less shift if the center of mass of the entire pier + telescope is below ground level.



#8 John Fitzgerald

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Posted 06 September 2014 - 08:47 AM

Dave,

I suggest welding the steel pipe to a flange and bolting that to a concrete stub with j-bolts sticking out of the concrete.  The sand will be unnecessary.  My pier is 56 inches high and only a 4 inch nominal pipe with 1/4 inch wall.   No problems at highest powers with a six inch refractor.  The adjustability afforded by the flange is well worth the extra trouble.

John



#9 JJK

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Posted 06 September 2014 - 12:37 PM

Dave, I thought Woodhenge would have been completed by now.



#10 Starman27

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Posted 07 September 2014 - 02:52 PM

Dave,

I use steel piers in my ROR that were fabricated at the local blacksmith (welder). They are bolted to concrete stubs that go down 4.5 feet. I have a second steel tube that tightly fits inside the pier. This allows me to change the pier designs simply by altering the interior pier. I do use sand inside the piers.

#11 Cotts

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Posted 10 September 2014 - 08:28 AM

There's been a bit of a pause in my project.   I ended up going with a 6" steel pipe 7 feet long which, at $80 from Metals supermarkets, was actually considerably cheaper than the 4x4"x4" and the large bolts to hold it together!  The pipe will be 4' into the ground and stick up 3'.  Concrete to hold it in the 12-inch hole.....

 

I have also made a 3-bolt pair of levelling plates which I'm having welded on to the top of the pier today.   I will be digging the hole and installing the pipe either tomorrow or Friday, depending on the weather.  The levelling plates and bolts add about 2 inches to the height 

 

I will be filling the pipe with sand which I will dry on a tarpaulin in the sunshine.

 

And, since this thread was about piers, I'd like to close it and have folks drop by my 'build' thread,  "Blackwater Observatory, v. 2.0" ...

 

Next, the world's largest skateboard!!

 

Dave








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