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Exposed piers and pier materials

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#1 dghent

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Posted 06 October 2020 - 10:46 AM

I went through this subforum and I couldn't find much on this topic, so forgive me if I missed an existing thread.

 

I'm contemplating (semi)-permanent pier to give me a much better experience than the tripod on the sloped turf of my yard, but the only place I can image from is not conducive to a full-blown observatory. We're also planning on moving in a few short years so I want something good enough until it's time to pull up and move. So a fabricated pier would be great - I can unbolt it and sledgehammer+cut the top few inches of the footer then throw down some dirt and seed when it's time to go.

 

I've read up on the Pier Engineering thread and have settled on a footer design, but I'm wondering about the pier itself. There are the SB and Sky Shed piers which are steel. There are the ATS piers which are 6061 aluminum. Since this pier will be exposed to the elements, something is telling me I ought to be wary of the painted steel piers and favor the power coated+urethaned aluminum one. I do plan on reusing the pier in a proper home obsy in the future, so I want it to last and not turn into a rust bucket over time. Are my fears unfounded? If price were not a factor, would one be favorable over the other, or does it even matter?



#2 Couder

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Posted 06 October 2020 - 11:04 AM

I saw someone selling pieces of aluminum light poles for piers - seems like that would fit your needs.

 

https://www.cloudyni...aluminum-piers/



#3 robbieg147

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Posted 06 October 2020 - 11:44 AM

The Altair Astro steel piers are powder coated which should last long time 15 - 20 years? Don't think I would buy steel pier which has just been painted.



#4 macdonjh

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Posted 06 October 2020 - 01:09 PM

A couple of things to keep in mind:

 

  • A coat of good paint, properly applied, will last for several years during which time the steel will not rust.
  • It is pretty simple to clean and then repaint a steel surface when the original paint eventually does fail.  Even easier if you repaint prior to the paint actually failing.
  • Rusting under normal conditions (I'll exclude marine conditions, salt makes everything except steak and fries worse) is on the order of 0.005-0.006" per year.  If you start with 8" sch 40 pipe it will take fifty years or so to rust through even if it's not painted.

Of course, rust is ugly to most of us and makes it look like the builder either doesn't know or doesn't care what he's doing.  So painting or powder coating or galvanizing is the route most of us take.

 

From an engineering stand point, steel is 3x stiffer than aluminum: E = 30 x 106 vs 10 x 106 psi.  Obviously, there are other engineering knobs to turn to make aluminum piers equally stiff as steel piers. 

 

From a fabrication stand point, anyone who can weld can weld steel, aluminum takes a special welding machine and better-than-average technique.  That makes it easier to have a steel pier fabricated to your specifications out of materials you might be able to find cheap or free.



#5 dghent

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Posted 06 October 2020 - 02:24 PM

The Altair Astro steel piers are powder coated which should last long time 15 - 20 years? Don't think I would buy steel pier which has just been painted.

That's nice but I'm not going to pay to ship a pier from the UK ;)



#6 tjay

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Posted 06 October 2020 - 03:24 PM

I think the Altair Astro piers are the same as the Skyshed ones.  

 

I looked at having one made and powder coated when I had my first observatory built.  It was more expensive than buying one from Skyshed, but I'm close enough that I drove to pick up the one I'm going to use for the observatory I'm building now.

 

Where are you located?  You may be able to get away with stripping, priming and repainting it every year or two, so you might not have to do it that many times before you move.



#7 DSOGabe

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Posted 06 October 2020 - 03:57 PM

Another alternative is to make a pier out of cinderblocks (a Todmorden pier). Make the footing so its just below ground level. When its time to move a sledgehammer will make the pier disappear. All that is needed is to grind down the mounting bolts and cover the footing up. You can build another one at the future house or go for a permanent concrete one there. 


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#8 PeteM

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Posted 06 October 2020 - 11:38 PM

I recently had the pier footing thread and have the SB pier on order. For roughly $680 at a number of different heights, you cannot go wrong. Especially considering it is a 10" diameter steel pier with 1/2" plates on each end. Just need to get an adapter for your AP mount. I order the AP flat adapter for my currently ordered 1100GTO.



#9 Travellingbears

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Posted 07 October 2020 - 07:04 AM

Dghent

 

If you’re using Mach 1 (in your signature) I’ll mention option to consider. I’m using SB pier (since have Paramounts) but also have ‘off the shelf’ adapters for A-P Mach 1 mount as cost-effective solution. I bought the A-P ADATRI for Mach 1 and added SB’s MyT pier adapter plate as intermediate plate vs drilling extra holes in top of SB pier. The MyT pier adapter flat plate has set of pre-drilled holes on 5.11” circular pattern which fit the three holes on bottom of ADATRI. Then the ‘ADATRI/MyT pier adapter’ combo rests on SB pier using pre-drilled MyT holes on top plate of SB pier.

 

My SB piers (42” ME and 48” MX) had exposure initially to weather and only place where saw ‘rust’ start quickly was within pre-drilled holes on top plate when I had pier exposed (no mount on it) for several weeks. Squirted WD-40 in holes and cleaned out before putting mount on. So think that SB production must have prepped coating on pier and then tapped top plate (inside threads were not well ‘protected’). Seemed like profile inside four elongated/slotted holes on base plate was similar if I recall. The 42” ME pier is now enclosed within observatory. The 48” MX pier will get repositioned to new location (exposed) in my yard when I get energy to dig pier foundation.

 

So as PeteM said SB pier (in any height) was $680 plus ship. I had around $900-925 involved when accounting for the two other adapter plates ($80 ADATRI and $100 MyT adapter plate) for Mach 1. So best plan for SB piers might be to spray these vulnerable areas ‘pro-actively’ with black rust-preventative (but pricing is not bad).

 

Dave


Edited by Travellingbears, 07 October 2020 - 07:16 AM.



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