Concrete pier


Howard Ritter
 

I want to put my upcoming AP 1600GTO on a concrete pier. My plan is to dig a 24” circular pit a foot deep, auger a 12” hole 3-4’ deep in the middle of this, put a 7-8’ Sonotube down to the bottom, pound some rebars into the ground at the bottom to fix them in place, fill the pit with concrete as a stabilizing collar, and then fill the Sonotube with concrete for a pier about 42” high.

So, a small pit, a hole, an 8'Sonotube and 30’ of rebar, a few cubic ft. of concrete. Do it myself? Sounds like a fair amount of work, plus renting an auger and an electric mixer. Contract it out? How expensive can that be? Sounds like a better deal to me!

Well. The estimate from the neighborhood landscape contractor – if I dig the 2’ x 1’ pit - was $4450! He didn’t itemize the estimate, but I just cannot conceive of how such a figure was attained. I looked at it twice, and it’s not $445.00 with a zero missing.

This is now a DIY project after all. Advice?

—howard


steve.winston@...
 

On Fri, Nov 5, 2021 at 08:42 AM, Howard Ritter wrote:
The estimate from the neighborhood landscape contractor – if I dig the 2’ x 1’ pit - was $4450!
That's crazy :-/.   I dug a 3x3 pit myself and put a 12" sonotube with some rebar in.  Rented a mixer from Home Depot and had it done in half a day.   I'd recommend doing it yourself, or at least getting a second estimate ;)


Jeff B
 

Go slowly.  

A suggestion.  Find a small local steel fabricator who does small jobs and have them weld up a nice, custom pier.  Then have them or a vendor powder coat it, or even a local body shop prep and spray it.  I've done that a couple of times and they can look great!!  Yeah, it might cost about a kilo-buck or so...but it looks great!!

Some standard features I incorporate are pre-drilled and tapped holes in the top plate to take your pier adapter, an ~6" diameter hole in the top, and a 4" hole with bolted on cover at the south side bottom.  Why?  Because I completely fill up the pier with dry play sand once it has been aligned and bolted to the concrete pad it sits on.    The sand adds mass and  completely deadens the structure and if you wrap your knuckles on the side of the pier after its been filled with sand, it WILL hurt. 

A fabricated pier made from steel pipe with gussets at the base is also an option but may not be any cheaper that one fabricated from flat stock, it would be worth asking about.

One interesting thing is that when I explain what my projects are for, the shops typically find that really pretty cool.  

Jeff

Jeff

On Fri, Nov 5, 2021 at 11:42 AM Howard Ritter via groups.io <howard.ritter=mac.com@groups.io> wrote:
I want to put my upcoming AP 1600GTO on a concrete pier. My plan is to dig a 24” circular pit a foot deep, auger a 12” hole 3-4’ deep in the middle of this, put a 7-8’ Sonotube down to the bottom, pound some rebars into the ground at the bottom to fix them in place, fill the pit with concrete as a stabilizing collar, and then fill the Sonotube with concrete for a pier about 42” high.

So, a small pit, a hole, an 8'Sonotube and 30’ of rebar, a few cubic ft. of concrete. Do it myself? Sounds like a fair amount of work, plus renting an auger and an electric mixer. Contract it out? How expensive can that be? Sounds like a better deal to me!

Well. The estimate from the neighborhood landscape contractor – if I dig the 2’ x 1’ pit - was $4450! He didn’t itemize the estimate, but I just cannot conceive of how such a figure was attained. I looked at it twice, and it’s not $445.00 with a zero missing.

This is now a DIY project after all. Advice?

—howard







W Hilmo
 

Construction prices are completely insane right now.

I just finished building a 40 x 60 garage on our property a few months ago.  This is a basic, metal building with no amenities added by the builder (I subcontracted the electrical myself).  The total price came to more than double the budget, was well into 6 digits.

The site prep folks left a huge mess at the completion of the project.  There was supposed to be a gravel driveway leading to the garage, but they left it with a significant drop off from the garage floor to the ground.  It was far too high to get a vehicle in and out of the garage.

We solicited several bids for a concrete apron at the garage entrance.  It would have been 240 square feet, averaging about 4" thick.  All of the bids that we received were right around $10,000.

We found a way to finish the project with gravel, so that the garage is at least usable.  Hopefully, in a few years, prices will resume some kind of sanity.  If an when that happens, we'll look at an apron.

I do have plans to build an observatory in 2022.  I contacted Scott Horstman earlier this year.  He's asked me to contact him after the first of the year to solidify the plans.  So I will be needing to do both a slab and two piers for the observatory.  I'm cringing at the thought of what it might cost.

-Wade

On 11/5/21 8:41 AM, Howard Ritter via groups.io wrote:
I want to put my upcoming AP 1600GTO on a concrete pier. My plan is to dig a 24” circular pit a foot deep, auger a 12” hole 3-4’ deep in the middle of this, put a 7-8’ Sonotube down to the bottom, pound some rebars into the ground at the bottom to fix them in place, fill the pit with concrete as a stabilizing collar, and then fill the Sonotube with concrete for a pier about 42” high.

So, a small pit, a hole, an 8'Sonotube and 30’ of rebar, a few cubic ft. of concrete. Do it myself? Sounds like a fair amount of work, plus renting an auger and an electric mixer. Contract it out? How expensive can that be? Sounds like a better deal to me!

Well. The estimate from the neighborhood landscape contractor – if I dig the 2’ x 1’ pit - was $4450! He didn’t itemize the estimate, but I just cannot conceive of how such a figure was attained. I looked at it twice, and it’s not $445.00 with a zero missing.

This is now a DIY project after all. Advice?

—howard





richard payne
 

Call a fence company to drill the hole
maybe $200?  do the rest yourself, a Harbor Freight mixer, easy!


On Nov 5, 2021, at 9:16 AM, Jeff B <mnebula946@...> wrote:


Go slowly.  

A suggestion.  Find a small local steel fabricator who does small jobs and have them weld up a nice, custom pier.  Then have them or a vendor powder coat it, or even a local body shop prep and spray it.  I've done that a couple of times and they can look great!!  Yeah, it might cost about a kilo-buck or so...but it looks great!!

Some standard features I incorporate are pre-drilled and tapped holes in the top plate to take your pier adapter, an ~6" diameter hole in the top, and a 4" hole with bolted on cover at the south side bottom.  Why?  Because I completely fill up the pier with dry play sand once it has been aligned and bolted to the concrete pad it sits on.    The sand adds mass and  completely deadens the structure and if you wrap your knuckles on the side of the pier after its been filled with sand, it WILL hurt. 

A fabricated pier made from steel pipe with gussets at the base is also an option but may not be any cheaper that one fabricated from flat stock, it would be worth asking about.

One interesting thing is that when I explain what my projects are for, the shops typically find that really pretty cool.  

Jeff

Jeff

On Fri, Nov 5, 2021 at 11:42 AM Howard Ritter via groups.io <howard.ritter=mac.com@groups.io> wrote:
I want to put my upcoming AP 1600GTO on a concrete pier. My plan is to dig a 24” circular pit a foot deep, auger a 12” hole 3-4’ deep in the middle of this, put a 7-8’ Sonotube down to the bottom, pound some rebars into the ground at the bottom to fix them in place, fill the pit with concrete as a stabilizing collar, and then fill the Sonotube with concrete for a pier about 42” high.

So, a small pit, a hole, an 8'Sonotube and 30’ of rebar, a few cubic ft. of concrete. Do it myself? Sounds like a fair amount of work, plus renting an auger and an electric mixer. Contract it out? How expensive can that be? Sounds like a better deal to me!

Well. The estimate from the neighborhood landscape contractor – if I dig the 2’ x 1’ pit - was $4450! He didn’t itemize the estimate, but I just cannot conceive of how such a figure was attained. I looked at it twice, and it’s not $445.00 with a zero missing.

This is now a DIY project after all. Advice?

—howard






<AP 1100 and pier.jpg>
<With 7 F9 Starfire.jpg>
<Pier.jpg>


Mike Dodd
 

On 11/5/2021 11:41 AM, Howard Ritter via groups.io wrote:
I want to put my upcoming AP 1600GTO on a concrete pier. My plan is to dig a 24” circular pit a foot deep, auger a 12” hole 3-4’ deep in the middle of this, put a 7-8’ Sonotube down to the bottom, pound some rebars into the ground at the bottom to fix them in place, fill the pit with concrete as a stabilizing collar, and then fill the Sonotube with concrete for a pier about 42” high.
I don't see the need for a 2-foot collar at the top. It might sound like a good idea and it might help stabilize the pier a bit, but I think your pier would be fine without it.

I have a 1200 mount on top of a 12" concrete pier that (reduces to 10" near the top, but that was unnecessary). The pier extends about 5 feet above the ground. This page describes and illustrates how my wife and I cast the pier: <http://house.mdodd.com/proj_obs_prep.html#PierPour>

Our auger has an 8" bit, so we bored three holes side-by-side, and slightly overlapping, ending up with a 16"-diameter hole 28" deep after cleaning it up with a shovel and post hole digger. We dug out the hole bottom to provide a small base for the pier.

After the concrete cured thoroughly, I cut away the Sonotube as far down as I could reach, then back-filled around the pier with dirt. I tamped it down with the 2"-wide handle of a heavy metal root chopper. I left this dirt exposed to the weather for several weeks, then added and tamped more dirt as it settled.

Some notes:
1. We bought a two-person earth auger years ago, and use it for all sorts of projects. I estimate we've bored 150+ holes, not including those to prepare the soil for landscaping bushes. (We call this "vertical tilling." We bore 3-4 holes close together, then swivel the auger around to break down the walls between to make a large single hole. The final step is to dump a bag of composted manure, and use the auger to mix that with the soil.)

2. We rented an electric concrete mixer, and it was a godsend. On other projects, we've mixed 80-pound bags of concrete in a wheelbarrow with a shovel and a mortar hoe (I figure we've mixed over 2 tons this way). The concrete mixer definitely was the way to go.

3. We own a subcompact tractor, and used the front bucket to raise the concrete mixer above the Sonotube, to make shoveling easier. But shoveling concrete from a mixer on the ground to the top of a 5-foot Sonotube is doable -- just not easy.

My advice is to do the job yourself:

* Rent a two-person auger and USE two people. Pulling it up with a load of dirt to clear the hole is hard for one person. Plus, two people make it much easier to control the auger when it encounters a rock and tries to rip your arms off.

* I recommend a single hole with an enlarged foot, and no top collar.

* Your idea of a 12" hole for 12" Sonotube might work, but I suggest boring a slightly larger hole. You could fill the hole with concrete, then place the Sonotube on top of the concrete as it nears the top. Use a level to plumb the Sonotube, and BRACE THE SONOTUBE SO IT STAYS PLUMB AS YOU SHOVEL-IN CONCRETE.

* Figure out how you'll attach the mount to the pier before you mix concrete! I attached four 5/8" threaded rods to my A-P SPA pier adapter, then shoved those into the wet concrete, leveled it, and blocked it in place until the concrete cured. Here's the result: <http://astronomy.mdodd.com/observatory.html#PierBolts>

Hope this helps.

--- Mike


richard payne
 

I had a fence company drill an 18" hole 6' deep, built the rebar cage and ouored it myself. maybe 2 hrs mixing the concrete. I built an
18x18 form 6" deep around the hole and bolted a pier on top, this allows a different pier height for the future.


On Nov 5, 2021, at 9:47 AM, Richard Payne <rpayne85392@...> wrote:

Call a fence company to drill the hole
maybe $200?  do the rest yourself, a Harbor Freight mixer, easy!


On Nov 5, 2021, at 9:16 AM, Jeff B <mnebula946@...> wrote:


Go slowly.  

A suggestion.  Find a small local steel fabricator who does small jobs and have them weld up a nice, custom pier.  Then have them or a vendor powder coat it, or even a local body shop prep and spray it.  I've done that a couple of times and they can look great!!  Yeah, it might cost about a kilo-buck or so...but it looks great!!

Some standard features I incorporate are pre-drilled and tapped holes in the top plate to take your pier adapter, an ~6" diameter hole in the top, and a 4" hole with bolted on cover at the south side bottom.  Why?  Because I completely fill up the pier with dry play sand once it has been aligned and bolted to the concrete pad it sits on.    The sand adds mass and  completely deadens the structure and if you wrap your knuckles on the side of the pier after its been filled with sand, it WILL hurt. 

A fabricated pier made from steel pipe with gussets at the base is also an option but may not be any cheaper that one fabricated from flat stock, it would be worth asking about.

One interesting thing is that when I explain what my projects are for, the shops typically find that really pretty cool.  

Jeff

Jeff

On Fri, Nov 5, 2021 at 11:42 AM Howard Ritter via groups.io <howard.ritter=mac.com@groups.io> wrote:
I want to put my upcoming AP 1600GTO on a concrete pier. My plan is to dig a 24” circular pit a foot deep, auger a 12” hole 3-4’ deep in the middle of this, put a 7-8’ Sonotube down to the bottom, pound some rebars into the ground at the bottom to fix them in place, fill the pit with concrete as a stabilizing collar, and then fill the Sonotube with concrete for a pier about 42” high.

So, a small pit, a hole, an 8'Sonotube and 30’ of rebar, a few cubic ft. of concrete. Do it myself? Sounds like a fair amount of work, plus renting an auger and an electric mixer. Contract it out? How expensive can that be? Sounds like a better deal to me!

Well. The estimate from the neighborhood landscape contractor – if I dig the 2’ x 1’ pit - was $4450! He didn’t itemize the estimate, but I just cannot conceive of how such a figure was attained. I looked at it twice, and it’s not $445.00 with a zero missing.

This is now a DIY project after all. Advice?

—howard






<AP 1100 and pier.jpg>
<With 7 F9 Starfire.jpg>
<Pier.jpg>


Howard Ritter
 

That’s encouraging, Steve, thanks.


On Nov 5, 2021, at 12:13 PM, steve.winston@... wrote:

On Fri, Nov 5, 2021 at 08:42 AM, Howard Ritter wrote:
The estimate from the neighborhood landscape contractor – if I dig the 2’ x 1’ pit - was $4450!
That's crazy :-/.   I dug a 3x3 pit myself and put a 12" sonotube with some rebar in.  Rented a mixer from Home Depot and had it done in half a day.   I'd recommend doing it yourself, or at least getting a second estimate ;)


brian close
 

see if someone can weld a rebar cage 

I adapted the tube mount for my AP800 and just used a base plate as opposed to having all that concrete sticking up

Bet Clay can design and  make that for you

On Fri, Nov 5, 2021 at 9:43 AM Howard Ritter <howard.ritter@...> wrote:
I want to put my upcoming AP 1600GTO on a concrete pier. My plan is to dig a 24” circular pit a foot deep, auger a 12” hole 3-4’ deep in the middle of this, put a 7-8’ Sonotube down to the bottom, pound some rebars into the ground at the bottom to fix them in place, fill the pit with concrete as a stabilizing collar, and then fill the Sonotube with concrete for a pier about 42” high.

So, a small pit, a hole, an 8'Sonotube and 30’ of rebar, a few cubic ft. of concrete. Do it myself? Sounds like a fair amount of work, plus renting an auger and an electric mixer. Contract it out? How expensive can that be? Sounds like a better deal to me!

Well. The estimate from the neighborhood landscape contractor – if I dig the 2’ x 1’ pit - was $4450! He didn’t itemize the estimate, but I just cannot conceive of how such a figure was attained. I looked at it twice, and it’s not $445.00 with a zero missing.

This is now a DIY project after all. Advice?

—howard



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Howard Ritter
 

OK, that’s another idea to put in the mix. Advanced Telescope Systems wants over $2600 for a painted and overcoated aluminum pipe with a gusseted baseplate and hundreds more for the J-bolts and mount plate.

On Nov 5, 2021, at 12:16 PM, Jeff B <mnebula946@...> wrote:

Go slowly.  

A suggestion.  Find a small local steel fabricator who does small jobs and have them weld up a nice, custom pier.  Then have them or a vendor powder coat it, or even a local body shop prep and spray it.  I've done that a couple of times and they can look great!!  Yeah, it might cost about a kilo-buck or so...but it looks great!!

Some standard features I incorporate are pre-drilled and tapped holes in the top plate to take your pier adapter, an ~6" diameter hole in the top, and a 4" hole with bolted on cover at the south side bottom.  Why?  Because I completely fill up the pier with dry play sand once it has been aligned and bolted to the concrete pad it sits on.    The sand adds mass and  completely deadens the structure and if you wrap your knuckles on the side of the pier after its been filled with sand, it WILL hurt. 

A fabricated pier made from steel pipe with gussets at the base is also an option but may not be any cheaper that one fabricated from flat stock, it would be worth asking about.

One interesting thing is that when I explain what my projects are for, the shops typically find that really pretty cool.  

Jeff

Jeff

On Fri, Nov 5, 2021 at 11:42 AM Howard Ritter via groups.io <howard.ritter=mac.com@groups.io> wrote:
I want to put my upcoming AP 1600GTO on a concrete pier. My plan is to dig a 24” circular pit a foot deep, auger a 12” hole 3-4’ deep in the middle of this, put a 7-8’ Sonotube down to the bottom, pound some rebars into the ground at the bottom to fix them in place, fill the pit with concrete as a stabilizing collar, and then fill the Sonotube with concrete for a pier about 42” high.

So, a small pit, a hole, an 8'Sonotube and 30’ of rebar, a few cubic ft. of concrete. Do it myself? Sounds like a fair amount of work, plus renting an auger and an electric mixer. Contract it out? How expensive can that be? Sounds like a better deal to me!

Well. The estimate from the neighborhood landscape contractor – if I dig the 2’ x 1’ pit - was $4450! He didn’t itemize the estimate, but I just cannot conceive of how such a figure was attained. I looked at it twice, and it’s not $445.00 with a zero missing.

This is now a DIY project after all. Advice?

—howard






<AP 1100 and pier.jpg><With 7 F9 Starfire.jpg><Pier.jpg>


Howard Ritter
 

Thanks for the additional info, Mike. I had already adopted your idea from your previous response of sinking the allthread rods after tapping threaded holes in their ends and screwing them to the AP mount adapter plate.

On Nov 5, 2021, at 12:49 PM, Mike Dodd <mike@...> wrote:

On 11/5/2021 11:41 AM, Howard Ritter via groups.io wrote:
I want to put my upcoming AP 1600GTO on a concrete pier. My plan is to dig a 24” circular pit a foot deep, auger a 12” hole 3-4’ deep in the middle of this, put a 7-8’ Sonotube down to the bottom, pound some rebars into the ground at the bottom to fix them in place, fill the pit with concrete as a stabilizing collar, and then fill the Sonotube with concrete for a pier about 42” high.
I don't see the need for a 2-foot collar at the top. It might sound like a good idea and it might help stabilize the pier a bit, but I think your pier would be fine without it.

I have a 1200 mount on top of a 12" concrete pier that (reduces to 10" near the top, but that was unnecessary). The pier extends about 5 feet above the ground. This page describes and illustrates how my wife and I cast the pier: <http://house.mdodd.com/proj_obs_prep.html#PierPour>

Our auger has an 8" bit, so we bored three holes side-by-side, and slightly overlapping, ending up with a 16"-diameter hole 28" deep after cleaning it up with a shovel and post hole digger. We dug out the hole bottom to provide a small base for the pier.

After the concrete cured thoroughly, I cut away the Sonotube as far down as I could reach, then back-filled around the pier with dirt. I tamped it down with the 2"-wide handle of a heavy metal root chopper. I left this dirt exposed to the weather for several weeks, then added and tamped more dirt as it settled.

Some notes:
1. We bought a two-person earth auger years ago, and use it for all sorts of projects. I estimate we've bored 150+ holes, not including those to prepare the soil for landscaping bushes. (We call this "vertical tilling." We bore 3-4 holes close together, then swivel the auger around to break down the walls between to make a large single hole. The final step is to dump a bag of composted manure, and use the auger to mix that with the soil.)

2. We rented an electric concrete mixer, and it was a godsend. On other projects, we've mixed 80-pound bags of concrete in a wheelbarrow with a shovel and a mortar hoe (I figure we've mixed over 2 tons this way). The concrete mixer definitely was the way to go.

3. We own a subcompact tractor, and used the front bucket to raise the concrete mixer above the Sonotube, to make shoveling easier. But shoveling concrete from a mixer on the ground to the top of a 5-foot Sonotube is doable -- just not easy.

My advice is to do the job yourself:

* Rent a two-person auger and USE two people. Pulling it up with a load of dirt to clear the hole is hard for one person. Plus, two people make it much easier to control the auger when it encounters a rock and tries to rip your arms off.

* I recommend a single hole with an enlarged foot, and no top collar.

* Your idea of a 12" hole for 12" Sonotube might work, but I suggest boring a slightly larger hole. You could fill the hole with concrete, then place the Sonotube on top of the concrete as it nears the top. Use a level to plumb the Sonotube, and BRACE THE SONOTUBE SO IT STAYS PLUMB AS YOU SHOVEL-IN CONCRETE.

* Figure out how you'll attach the mount to the pier before you mix concrete! I attached four 5/8" threaded rods to my A-P SPA pier adapter, then shoved those into the wet concrete, leveled it, and blocked it in place until the concrete cured. Here's the result: <http://astronomy.mdodd.com/observatory.html#PierBolts>

Hope this helps.

--- Mike





Worsel
 

Howard

It is common to use J- or L-bolts, rather than straight threaded rod to avoid the rods twisting over time in the concrete.  Unlikely, but why take the risk.

For example, http://www.physics.sfasu.edu/observatory/10-inch/dome/index.html

Bryan


Brian McFarland
 

I have that same AP blue refractor! I love that thing.

Brian


dan kowall
 

Hello Howard,
You haven't told us some pertinent information such as your soil type and the frost line in your area.  Plans will be different if your digging in sand vs. clay for instance and you definitely want the base of your pier below the frost line.
Your collar is a definite no-no.  If the base of the collar is above the frost line any frost heave will lift your whole pier.
The bottom of your pier should be on undisturbed soil and the wider the better.
I know a lot of people do it differently but you can skip the rebar.  Concrete is immensely strong in compression, not so much in tension.  Rebar is added when tensile forces are strong but the tensile forces in an amateur's pier just aren't that great.  Pounding the rebar into the ground at the bottom of the hole is also not called for.  Standard rebar needs to be completely enclosed by concrete.  If left exposed it will rust, expand, and crack the concrete.
If you use a sonotube remove the tube after the concrete has set.  It just unwinds.  When you backfill do it in stages and compact the fill as you go.  Watering the fill will help it compact.
Stainless steel threaded rods can be used as your anchors but trap a large washer between two nuts at the bottom to resist any pulling force on the anchor.
Follow good concrete procedures such as 'working' the mix when it's still fluid to remove entrained air and keeping the mix damp while it cures.  Also, a stiff mix is stronger than a watery one.

dan kowall


Astrobob
 

This is what I did 20 years ago and it’s still working perfectly. I dug an 18" round hole 5' deep with a post hole digger and   put a 10' sonotube (or whatever height you want) In the center. Then I placed four 10' rebar equally spaced inside the sonotube. Then I filled the 18" hole and sonotube equally 3 1/2 feet with concrete. The sonotube was then heavily roped around the outside perimeter to avoid bursting from the concrete filling. Over the next few days I filled the tube 2' more each day until I got the height I wanted. Then I was able to remove the rope. The reason I filled the 18" hole only 3 1/2 feet with concrete was to fill it the rest of the way with dirt. This avoids stepping directly on any concrete that might shake your telescope with your feet.

I used 60lb bags of Redimix concrete in a wheelbarrow and shoveled in in where and when necessary. The whole job took me 3 1/2 days and even with todays costs, it shouldn’t cost more than 2-3 hundred dollars. Readmix is not expensive.

 

Good luck,

Bob

 

Sent from Mail for Windows

 


Howard Ritter
 

Thanks, Bob. More appealing ideas to think about. For one, I hadn’t considered the effects of the hydraulic pressure exerted by hundreds of pounds of wet concrete on freestanding Sonotube. I wonder if a big hose clamp every 6” or so would hold the pressure. But aren’t all those cylindrical pillars you see in outdoor applications everywhere all poured with Sonotube, and not roped? 

Maybe I’ll go with an aluminum pier after all! 

After reading all the suggestions and reports I’ve gotten, I’m thinking that maybe all I need is a 2’ hole 3’ deep filled with concrete, no rebar or Sonotube, and the metal pier bolted onto that. Anyway, that would give us flexibility compared to a concrete pillar if we ever move again.

I just looked at the Sonotube website. Supplemental banding is NOT needed.

—howard

On Nov 5, 2021, at 7:31 PM, Astrobob <imager1940@...> wrote:

This is what I did 20 years ago and it’s still working perfectly. I dug an 18" round hole 5' deep with a post hole digger and   put a 10' sonotube (or whatever height you want) In the center. Then I placed four 10' rebar equally spaced inside the sonotube. Then I filled the 18" hole and sonotube equally 3 1/2 feet with concrete. The sonotube was then heavily roped around the outside perimeter to avoid bursting from the concrete filling. Over the next few days I filled the tube 2' more each day until I got the height I wanted. Then I was able to remove the rope. The reason I filled the 18" hole only 3 1/2 feet with concrete was to fill it the rest of the way with dirt. This avoids stepping directly on any concrete that might shake your telescope with your feet. 
I used 60lb bags of Redimix concrete in a wheelbarrow and shoveled in in where and when necessary. The whole job took me 3 1/2 days and even with todays costs, it shouldn’t cost more than 2-3 hundred dollars. Readmix is not expensive.
 
Good luck, 
Bob
 
Sent from Mail for Windows
 


weems@...
 

It depends on the type of tube. Some are rated for above ground fill up to a fair height. Others, especially the cheap ones that big box stores sell, may only be rated for 24” free standing. When I did mine, there was a shortage, so I got two of the cheap tubes that fit snugly together and reinforced them with ratchet straps, to get up to the height I needed. Probably not necessary, but having had concrete forms burst in the past, I didn’t want to take any chances.

If you can pour a wider base below the frost line, it will reduce heaving even more. Steel piers are nice, but if you know the height you need, concrete is much less expensive, and even more stable. Literally rock solid. I can kick it hard and not see any vibration, even at high powers.

Chip


vk3cjk
 

Howard, I dug a 2 cubic metre hole by hand, constructed a reo-bar cage in it, and also attached 8 upright reo-bars to form the pier.  After the cube base was poured an 18" Formtube was placed over the uprights and readymix concrete was poured.  The 2.2 metre high concrete pier is as solid as a rock and supports 100 kg of scope and AP 1200 mount (which are actually on top of a 1.2 m steel pier bolted to the top of the concrete pier).  It was straightforward to do myself but I wouldn't want to mix the concrete by hand.   
Cheers, Chris

On Sat, 6 Nov. 2021, 02:42 Howard Ritter via groups.io, <howard.ritter=mac.com@groups.io> wrote:
I want to put my upcoming AP 1600GTO on a concrete pier. My plan is to dig a 24” circular pit a foot deep, auger a 12” hole 3-4’ deep in the middle of this, put a 7-8’ Sonotube down to the bottom, pound some rebars into the ground at the bottom to fix them in place, fill the pit with concrete as a stabilizing collar, and then fill the Sonotube with concrete for a pier about 42” high.

So, a small pit, a hole, an 8'Sonotube and 30’ of rebar, a few cubic ft. of concrete. Do it myself? Sounds like a fair amount of work, plus renting an auger and an electric mixer. Contract it out? How expensive can that be? Sounds like a better deal to me!

Well. The estimate from the neighborhood landscape contractor – if I dig the 2’ x 1’ pit - was $4450! He didn’t itemize the estimate, but I just cannot conceive of how such a figure was attained. I looked at it twice, and it’s not $445.00 with a zero missing.

This is now a DIY project after all. Advice?

—howard







Astrobob
 

 

 

Sent from Mail for Windows

Hi Howard,

 

Back in my day it was wise to rope the sonotube. The bigger commercial construction sonotubes are much sturdier today and some are made to become part of the structure. I looked in my notes of 20 years ago it took me 3days, a lot of digging and it cost me less than $100 to build my pier. Probably not much different today if you consider inflation.

 

Good luck with your project,

 

Bob


Glenn Wallace
 

Here’s my pier design, with lots of help from Ajai Sehgal.
It was designed for an AP1200. Ground doesn’t freeze (Seattle).

We dug a square hole 4’x4’ and gave up at about 3.5' deep. We laid a short layer of small gravel, maybe 1”.

I used a 12” Sonotube, with enough height to come up to my desired height in observatory.
I made an Excel model of observatory roll off roof height and overall parked scope height and determined a “pier plate height above grade”.
My observatory is on threaded pier blocks too I also have some height adjustment there too.

I created a form/frame to hold the sonotube off the ground at the desired height holding the cut to length sonotube.
I created a dummy pier plate from marine ply with 4 1/2” J bolts mounted in it. This later became a template to drill my metal pier plate.
It is stood off the cement pier using two nuts and two flat washers per J bolt, so height and level can be adjusted.

We poured the concrete in one session, used one of those vibrating noodles to get the air out.
We filled the 4’ square almost to grade, to the bottom of the tube, and then filled the tube and inserted the J bolt and pier plate form.

I made a 12” circular pier plate (I think 3/8” thick) and drilled J bolt holes from form and drilled and threaded holes to take one of the AP flat surface adapters, aligned with North of course.

The observatory floor has an oversized pier hole to disconnect floor from pier and a flexible foam rubber floating collar to keep most critters out.

There’s no movement of the pier.

The biggest issue in the whole project was breaking a tap in the pier plate and having to eat it out with special acid.
(yes I used cutting oil and carefully tapped forward and back, stuff happens)