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Suggestions on changing out pier?

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#1 thj

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Posted 03 December 2012 - 04:39 PM

When I first built my simple Observatory I created a concrete footer and put a simple wooden pier on it: see here

This works great for my smaller imaging scope (102mm refractor) but my 10" Newtonian (for visual use) makes the whole thing shake too much. I simply dealt with the shakiness until now but want to change out the pier to eliminate as much as I can for good.

I looked into replacing the wood pier with a steel version but that's a bit pricier then what I had in mind. I was quoted around $250-$300.

Does anybody have any suggestions what I could do? Instead of a steel pier I was thinking of simply making a concrete pier but then the question becomes how do I take the existing footer and "extend" it. I guess I could hammer some of the concrete away to expose the rebar I have in there and then pour a concrete pier from there or would I be better off to rip the whole footer out and start over?

Thanks a bunch in advance.

#2 nytecam

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Posted 03 December 2012 - 05:18 PM

DON'T swap out that existing wooden pier - your equat mounted 102 refr is producing superb images and should continue so :grin: Build another pier for the Newt if you must ;)

#3 mikey cee

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Posted 03 December 2012 - 06:17 PM

I can't believe you cannot find a salvaged piece of boiler pipe, a square piece of steel plate and a welder who can weld it together for roughly $100 give or take a cheap eyepiece. Dig another hole and it's history...with both scopes available at the same time. I can see another spot where the step ladder sits. Looks like plenty of wood along the back fence to build another "shed" too! How much gooder can it get!! :shocked: Mike

#4 Mary B

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Posted 03 December 2012 - 06:57 PM

Hammer drill holes into the existing footer and epoxy in rebar. Add your sonotube form and pour away.

#5 JJK

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Posted 03 December 2012 - 08:33 PM

I would not make the pier out of a fresh pour of concrete. When you consider the hassle to drill the footer, add rebar, make the form, schlep the concrete, sand, and aggregate, mix the stuff, pour it, level/smooth it, make a form for the mounting bolts, etc. it just isn't worth the bother.

Get a wide scrap pipe, have it cut & ground square, and have two plates welded to it.

#6 thj

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Posted 04 December 2012 - 02:04 AM

Thanks for the quick feedback everyone.

A second pier and shed, although tempting :grin:, unfortunately isn't an option. Our yard has gotten a lot more "busy" since I took those pictures. But, if I can get a steel pier built for around $100 I'd definitely prefer that route over concrete. JJK, you have a good point - it would be a lot of hassle to prepare, mix, etc. compared to simply putting 4 new anchors and plopping down a new pier.

I guess the hunt for some steel pipe is on :)

#7 opticsguy

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Posted 04 December 2012 - 10:16 AM

Could not get your website open so making a guess here.

IF you have a boxed wooden pier, I would try filling it with sand first. Cost you about $10 and then if this does not fit your needs you could move onto another design. The sand will provide a lot of mass.

#8 Gastrol

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Posted 04 December 2012 - 01:10 PM

Hammer drill holes into the existing footer and epoxy in rebar. Add your sonotube form and pour away.


For me, this would be the easier and cheaper option than to locate a steel pipe and fabricator to work on it.

#9 thj

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Posted 04 December 2012 - 01:26 PM

Well, I saw a 6" square tube with a wall thickness of 3/8th of an inch on craigslist. That sounds pretty massive.

Let me confirm that the dimensions are what they sound like but would a 6" square tube be large enough for a pier in your guys' opinion? The pier itself would be about 22 inches tall so it's fairly short.

#10 stmguy

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Posted 04 December 2012 - 04:11 PM

I have my 10" F4 Newt on a pier I made from 6" well casing and it is rock solid . I don't see any reason that 6" sq tube wouldn't work especially only being 22" tall.
Norm

#11 Aquarist

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Posted 04 December 2012 - 06:50 PM

I enjoyed the website a lot. Thanks for sharing. A steel pier sounds preferable to doing anything with concrete IMO.

#12 Mirzam

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Posted 05 December 2012 - 07:25 AM

There was a link here a few weeks ago that discussed the analysis of pier deflection based on pier diameter and wall thickness. I read the link carefully because I'm also using 6" steel box tubing for my pier (about 41" high). I wish I could find the link, but the bottom line is that you won't have much deflection at 22". One thing that does help though is to add reinforcing members at the baseplate, which is the point of maximum stress.

JimC

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#13 JJK

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Posted 05 December 2012 - 09:01 AM

There was a link here a few weeks ago that discussed the analysis of pier deflection based on pier diameter and wall thickness. I read the link carefully because I'm also using 6" steel box tubing for my pier (about 41" high). I wish I could find the link, but the bottom line is that you won't have much deflection at 22". One thing that does help though is to add reinforcing members at the baseplate, which is the point of maximum stress.

JimC


That's a nice looking pier. It looks very robust.

I second the thought on adding substantial reinforcing batwings at the base.

#14 thj

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Posted 05 December 2012 - 10:08 AM

That is one good looking pier! Good point about those reinforcement pieces at the bottom. I will make sure to add some. What thickness are you top and bottom plates?

BTW, I remember reading an article similar to the one you mentioned years ago when I wasn't even planning to build an observatory. It discussed how much a pier would deflect when pushed at the top with a certain force.

/ThJ

#15 Mirzam

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Posted 05 December 2012 - 02:44 PM

If memory serves the top and bottom plates are 5/8". The gussets are 1/2".

The holes are there to aid in lifting the pier, which weighs about 120 pounds. The idea is to run a piece of rebar through the pier so that 2 people can maneuver it over the mounting studs, which are set in concrete. I also have a hole in the top plate for adding sand in case there is a need for vibration dampening. The pier will be supporting an AP1600 mount and a 15.5" astrograph of my own design sometime next Spring.

JimC

#16 thj

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Posted 06 December 2012 - 02:57 PM

Prefect. Thanks Jim. I was wondering if those holes had a purpose :)

I am going to pick up the 6" square tube today :jump: - just need some plates now.

#17 Tom and Beth

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Posted 06 December 2012 - 06:15 PM

Prefect. Thanks Jim. I was wondering if those holes had a purpose :)

I am going to pick up the 6" square tube today :jump: - just need some plates now.


Many of the Steel scrap yards around here will not only have the plates you can use, but for a few extra bucks will weld them together for you. Never hurts to ask if those near you would do the same.

#18 astroRoy

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Posted 06 December 2012 - 06:21 PM

Be careful welding the plates to the pier-post. The plates will warp if not welded correctly. The bigger the plate, the more the warp.

Roy

#19 JustinO

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Posted 07 December 2012 - 03:09 PM

Make a steel pedestal. I'd look for a "full service junkyard" or ornamental iron place that has a scrap heap for materials, an acetylene torch for cutting, and a buzz box for welding. Make it out of 1/2. It is amazing how strong and stiff you can make something with really crude chunks of scrap. Take the wooden pedestal as a template so they get the hole patterns right -- they're all that matters.

#20 thj

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Posted 07 December 2012 - 10:28 PM

Thanks for all the suggestions guys. Looks like I got my work cut out for myself. All this metal work is brand new to me :).

Anyhow, I am now the proud owner of a 6" square tube that's about 40" long and has 3/8" inch walls. Now that I see it in my yard I have no doubts that it'll be more then strong enough, especially once I get it cut down to 22".

I have some scrap metal in my backyard I've been meaning to take to a junkyard anyhow and I'll keep my eyes and ears open for some 1/2" or 3/4" plates and somebody to weld it all for me.

Take the wooden pedestal as a template so they get the hole patterns right -- they're all that matters.

I definitely will. Especially the top plate has to be an exact match. I'm going to put new anchors into the concrete footer so those holes will be in a different spot anyhow.

#21 Mary B

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Posted 08 December 2012 - 07:15 PM

You can compression mount your plates with threaded rod running from top to bottom if you can't find a welder.

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#22 Mirzam

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Posted 09 December 2012 - 07:26 AM

Mary--That compression mount idea is an interesting one. I'm curious how you came up with it? Is this method used in some other application? Or is it just your own ingenious solution for telescope piers?

JimC

#23 thj

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Posted 09 December 2012 - 07:41 PM

That is an interesting idea!

I don't think finding somebody to weld my pier will be an issue, though. I notice welding places all over now that I'm looking for one; never noticed them before. Funny how that goes sometimes.

/ThJ

#24 Mary B

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Posted 10 December 2012 - 06:35 PM

Saw it on a post here and nobody around here can weld aluminum. I had the 8 inch diameter 1/4 inch wall tube on hand from another project so I re-purposed it.






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