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Pier Planning Advice

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#1 CMS1288

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Posted 30 June 2022 - 05:38 PM

I’m looking to build a simple pier for equipment in my signature.

I live on Florida’s Suncoast where the soil is hard clay a few feet deep. In the rainy season, the ground can get saturated.

Any general advice as to go about this? Concrete or wood? How far deep? I was thinking about 3’ deep with a 6’ diameter foundation to minimize settling. I have iOptron’s pier adapter on order in the meantime (I know about the center bolt issue I may have to drill it out wider).

#2 Broz22

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Posted 30 June 2022 - 06:14 PM

You would still need the concrete foundation for the pier, but I have been very happy with the Skyshed 8" steel pier that I have bolted to a 42" deep (Maryland) 18" concrete base. You can get an adapter plate for the top to fit your mount, and the adapter plate is rotationally adjustable to get the mount within range for polar adjustment. Very well built and strong.

John



#3 ram812

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Posted 30 June 2022 - 06:42 PM

You may want to look at one of the solar imagers pier build that's here on CN ( MalVeauX), he's in the sunshine state and has dealt with that very issue you're facing. Good luck😁!

CS, Ralph

#4 speedster

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Posted 30 June 2022 - 07:19 PM

Settling is not an issue.  Our loads are very light in terms of what even poor soil will support.  Clay +  seasonal saturation often times = soil movement.  Going deeper gets you farther below the more active surface soils.  Best of luck with your project!



#5 macdonjh

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Posted 01 July 2022 - 07:58 AM

A long thread to be sure, but lots of good information: 

https://www.cloudyni...n#entry11928916

 

Good luck with your project.



#6 CMS1288

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Posted 01 July 2022 - 09:00 AM

Yep found that thread great info!! I also found this if I want a bit easier project:

https://digitalstars...kyard-pier/amp/

How stable would this be?

#7 macdonjh

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Posted 02 July 2022 - 09:12 AM

Yep found that thread great info!! I also found this if I want a bit easier project:

https://digitalstars...kyard-pier/amp/

How stable would this be?

That's a Todmorden pier. My personal opinion is I don't like them, but others disagree with me. The reason I don't like them is they are just as much work as a concrete pier and not as "secure". By that I mean: in the video you linked the builder only dug a couple of feet below grade, I used an auger and drilled a bit more than six feet down. If my area had frost, I'd be below the frost line, and I have lots of contact area with undisturbed soil to resist movement from expansive soil at my site.

Note he also dug a hole bigger than his CMU so he could set the blocks and get them plumb. That means more digging, plus backfilling. That's more work than simply digging a hole and pouring concrete against the undisturbed soil. The latter technique also provides a foundation which will move less over time since the surrounding soil is as compacted as possible. Mother Nature and Time are the best compactors around.

He set his CMU on end and bolted them together with adhesive as well. I had a bad experience with concrete adhesive (it failed) and installing all those bolts requires a lot of time drilling and assembling. Besides, having those blocks on end is the least-stiff orientation.

Of course, setting the blocks the other way, running a couple pieces of rebar through the height of the pier and then filling it with concrete makes most of my objections moot. Except, you've traded a single piece of Sonotube or PVC drain pipe for several blocks which have to be set and plumbed individually- more work to me.

It's also harder to route conduit through a pier made from CMU for wiring through the pier since you'll have to drill a big hole in a CMU to get the conduit out/ exposed.

So my preference is for a poured concrete pier. As I said, others have had good success with CMU, with wood, with steel. I think more important than which material you use, is to choose materials you have the ability and tools to work with and execute your design well.

Good luck with your project.

Edited by macdonjh, 03 July 2022 - 07:29 AM.


#8 kathyastro

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Posted 02 July 2022 - 10:01 AM

I built a plywood pier.  It is very stable: vibrations damp out in 1/4 second or so.  It is currently mounted on a concrete foundation, but I previously had it standing on hard-packed ground, just pinned to the subsoil with steel rods.  That was also a successful setup.



#9 mackiedlm

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Posted 02 July 2022 - 06:25 PM

Yep found that thread great info!! I also found this if I want a bit easier project:

https://digitalstars...kyard-pier/amp/

How stable would this be?

The Todmorden pier is a great easy to build option. I am really not very good with my hands but I managed to build one earlier this year with no difficulty whatsoever. Making the former, digging the holle (I did no back fill, just a simple hole) Laying the foundation, drilling and painting the blocks took half a day, total, and attaching the pier to the fixing bars after the crete had dried was a matter of minutes a few days later. I followed the details of that linked page pretty closely, following his reccomendation to make the hole a little larger. Having looked at the alternatives this was way easier.

 

The charge that is often laid against the Tomorden is that its unstable because of the size of the foundation. So before I did mine, with a 20"x20"x"20" hole I contacted some other folks who had done these piers and asked how they had faired. Some had smaller foundations - like the one in the page you linked, none had bigger than mine and all had been in place for several years without any type of movement. Several of them stated that in their opinion, many of the bigger heavier piers are hugely over engineered.I'd point out that the page you linked to is Charles Brackens page - He is the author of what is one of the most often reccomended books on astrophotography so I'd say he has some idea what he's doing.

 

I've only been able to use mine a few times since building but PA has remained spot on each night. It is rock solid.  - I am checking PA each time just to monitor for movement but will stop that fairly soon.

 

So, for me anyway the Todmorden Pier was the perfect solution.

 

pier.jpg



#10 speedster

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Posted 02 July 2022 - 06:35 PM

Todmorden construction can have some construction pitfalls.  You can use a gun-grade glue that is "waterproof" but that waterproofness is the glue and not the whole joint assembly.  A saturated block can eventually float off the adhesive.  This is just a fundamentally flawed use of construction adhesive.  Thin set adhesive is truly waterproof, stronger than the block, unaffected by freeze/thaw and moisture or water, expands and contracts at the same rate as the block,and is cheap and available in any big box store.  Look in the floor tile section.  In other words, there is a product made for gluing a Todmorden together.  Then, one 1/2" bolt between blocks and one anchor bolt into a foundation and you've done about all that can be done to make the thing last reliably.  I'm recommending a Todmorden but everything has its place and if a Todmorden is is your thing, there are some things you can do to increase its long-term reliability.


Edited by speedster, 02 July 2022 - 09:55 PM.



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