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Midnight Dan
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Reged: 01/23/08

Loc: Hilton, NY, Yellow Zone (Bortl...
Re: Brainstorming dream obs which will become real! new [Re: Starhawk]
      #5838588 - 05/03/13 03:14 PM

HunterofPhotons hit the nail on the head. Contractors are thinking about very different things when they look at building techniques.

I'm getting ready to have my pier built in the next month or so. I was showing the contractor the pier plate assembly with the 3/4" stainless J-bolts on the bottom to sink into the concrete. He was telling me there's no way I need bolts that big - he's built houses that attached with smaller bolts than that.

I explained that it didn't really matter how strongly the bolts were holding the pier plate to the concrete. The issue is that the the pier plate needs to be suspended above the pier so that there is room to adjust the height and level the plate. The bolts need to be thick and solid so that the suspended plate and attached scope/mount are held rigidly without vibrations. These are things a contractor has no experience with and could care less about.

Similarly, the design of the concrete part of an astronomical pier has to meet different requirements than normal structural concrete work. Your contractor won't be taking those requirements into consideration so take what he says with a grain of salt.

-Dan


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corpusse
scholastic sledgehammer


Reged: 04/11/10

Loc: Mississauga, Ontario, Canada
Re: Brainstorming dream obs which will become real! new [Re: Midnight Dan]
      #5838696 - 05/03/13 04:21 PM

First of all I know he doesn't know about piers for astrophotography. He knows about regular building stuff and is somewhere between 90 and 100% done. I have not inspected the site yet but from what I can tell he did an amazing job. He also was get accommodating as far as getting the dome off the truck for me, not charging extra for a forklift to put the dome on top when originally we didn't think it was needed ect.

I'm simply consulting him about the pier not using him to build it. I come here for the pier advice and everything I'm reading less considering using another guy I agree with. Cinder blocks and chimney blocks it will be. I am now thinking I will use cinder for the first few feet and below the floor so rebar can go through it with ease and then possibly switch to the chimney blocks as it gets higher. Unless its better to go cinder all the way. I will then switch to either a sonotube or steel pipe when I get to the second level. This part will be narrower to avoid having to resupport the floor.

I'm so excited to get there.


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stmguy
sage


Reged: 10/11/12

Loc: Western NH
Re: Brainstorming dream obs which will become real! new [Re: corpusse]
      #5838712 - 05/03/13 04:32 PM

It's looking good. I'd go with the concrete blocks and top it off with a steel pier (I used 6" well casing and I'm very happy with it)
Norm


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HunterofPhotons
Pooh-Bah


Reged: 04/26/08

Loc: Rhode Island, USA
Re: Brainstorming dream obs which will become real! new [Re: corpusse]
      #5838786 - 05/03/13 05:28 PM

Look at what Russ Croman did.

Go about halfway down and find the plans.
It will give you an idea of how to build a cinder block pier.
A mason and a helper could easily build something like this in a couple of days, maybe a bit less.
There's nothing wrong with a sonotube pier for lower heights, but they become problematic for high piers.

dan k.


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corpusse
scholastic sledgehammer


Reged: 04/11/10

Loc: Mississauga, Ontario, Canada
Re: Brainstorming dream obs which will become real! new [Re: HunterofPhotons]
      #5839284 - 05/03/13 11:04 PM

Good news everyone, the dome is up. Everything is done as far as what the contractor was supposed to do. My Dad is at the house this weekend and said it looks great. He'll send me some pics tomorrow.

Thanks for the link Dan, I think I will be doing something similar, although that pier looks MASSIVE. I understand I want the pier to weigh somewhere between 25x and 50x maximum load on top, but is that about the only guideline I have to go by as to how big it should be? I was planning a 40x40 slab but that's not set in stone (yet). I can certainly go bigger, that number just seemed good to me but I will make sure it's good before I start..

Initially the load on the top will be less then 100lbs however as I am hoping to use this for the rest of my life there could one day be a paramount or ap mount and 14" HD or 16" RC, so I'd like to build this so it will be good for a 200-300 LB load just in case. I plan on living a while and doing imaging the rest of my life.

Edit some rough calculations :

If I do a 40x40x60" pad that will require 7380lbs of concrete. If I use the 16x6x8 blocks HD sell and make the pier 36x32 I would need 12 pier level. I don't have the ceiling height but I guess it's around 10 feet maybe slightly less I'd need a 180!! blocks x 40lbs per block that is 7200lbs + the 7380 for the pad puts me at 14380 + the rest of the pier should bring it past 15000 which would allow for a 300lbs load and still maintain the 50:1 ratio.

edit again, so the blocks apparently weigh 45lbs now.

http://www.homedepot.ca/product/10-inch-standard-concrete-block/981814

On the US home depot they are 28lbs. Either weight should work though.

Edited by corpusse (05/03/13 11:40 PM)


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Midnight Dan
Postmaster
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Reged: 01/23/08

Loc: Hilton, NY, Yellow Zone (Bortl...
Re: Brainstorming dream obs which will become real! new [Re: corpusse]
      #5839778 - 05/04/13 09:30 AM

Hi Andrew:

Not sure where the 25-50x came from, but seems reasonable as a guideline. I think it just highlights the fact that you want a big mass for the base. There are other things to consider.

If you have roughly 14K pounds in a pier, you want to be sure the soil underneath it will support it without it sinking or tilting to one side over time. Digging down to a reasonable depth helps because the soil is more stable and compacted. But still, you need to know what the load bearing capacity of the soil in your area is so you provide enough surface area for the pier.

For example, clay is rated at about 2K pounds per square foot. To support the load you'd need about 7 square feet. Your 40" x 40" base provides 11 square feet so you should be good to go if your soil is clay. Most soil types are at least 2K pounds per square foot or more, so you're probably fine, but you might want to check on the soil types in your area from your local building department.

-Dan


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corpusse
scholastic sledgehammer


Reged: 04/11/10

Loc: Mississauga, Ontario, Canada
Re: Brainstorming dream obs which will become real! new [Re: Midnight Dan]
      #5840959 - 05/05/13 12:00 AM

Just reading other threads on large piers it seems people are using that number, there was one in particular but I closed it otherwise I'd link. I`ve been reading about big piers as much as I can. I can always reduce the size if this ends up being too much weight. I highly doubt there is a "building department". We are talking about a place that has no police, garbage pickup ect. I remember reading the Mayor takes home a salary of $700 a year or something silly like that. All I can do is dig and find out. Unless I really want to get crazy and bring someone in from further away..

The dome is up and it looks exactly exactly how I wanted it to. Having something come together like this really is amazing. Obviously there is a lot to do still but it's going better then I could have hoped.



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stmguy
sage


Reged: 10/11/12

Loc: Western NH
Re: Brainstorming dream obs which will become real! new [Re: corpusse]
      #5842127 - 05/05/13 05:42 PM

looks fantastic

Norm


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Midnight Dan
Postmaster
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Reged: 01/23/08

Loc: Hilton, NY, Yellow Zone (Bortl...
Re: Brainstorming dream obs which will become real! new [Re: stmguy]
      #5842273 - 05/05/13 07:12 PM

Wow! Looks wonderful! Should have a great view of the sky at that height. Now for that last pesky detail - the pier!

-Dan


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corpusse
scholastic sledgehammer


Reged: 04/11/10

Loc: Mississauga, Ontario, Canada
Re: Brainstorming dream obs which will become real! new [Re: Midnight Dan]
      #5846974 - 05/08/13 12:46 AM

Quote:

Wow! Looks wonderful! Should have a great view of the sky at that height. Now for that last pesky detail - the pier!

-Dan




Yes the pesky pier.

Small bit of good news. I found a company who does excavation. I can likely get them to dig down to the frost line. Even better good news is its the same guy who plows the driveway so he already knows the house / my Dad. I'll give him a call friday and see if he can come by on the weekend. I still have to cut the concrete of course, at least this is someone who can do it whenever I won't have to be there. He's one of those island guys who doesn't have a computer. Such a different world there, no wonder there is no light pollution.


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csa/montana
Den Mama
*****

Reged: 05/14/05

Loc: montana
Re: Brainstorming dream obs which will become real! new [Re: corpusse]
      #5847399 - 05/08/13 09:40 AM

Your dream observatory is really materializing beautifully! The dome looks great!

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corpusse
scholastic sledgehammer


Reged: 04/11/10

Loc: Mississauga, Ontario, Canada
Re: Brainstorming dream obs which will become real! new [Re: csa/montana]
      #5855230 - 05/12/13 11:10 AM

Just catching my breath on my cell phone with barely a wifi signal but I wanted to share my findings. This weekend has been tough I forgot a bunch of stuff I needed. My camera lens and a part for my skill saw. I took the blade off and just bought a concrete blade here but it's too lose without the spacer.

I decided I'll break up the middle of the concerete anyway. The sledge hammer route is so hard! I consider myself pretty strong but this is wearing me out. I have abou an 8" round hole in the middle of my 40x40 area. The good news is under the building it's just sand. Sand and a lot of rocks. With my gloved hands and a pry bar I've been able to get about 18" deep. I should have no time digging down to the frost line. I was thinking breaking the concrete would be easier then digging. I do want to do some of the work myself. In part to save money in part because id like some of my own sweat but hopefully not blood to be put into the construction of this observatory. This is the one for life.

Also I bought 12 concrete blocks just to visualize my pier. They had 3 sizes I stuck with the 16x6x8 ones I assumed I was going to work with. They have 8" and 12" wide ones as well. Now for the 12" ones id use a lot less blocks but in concerned they will be too heavy to work with especially at higher heights. I can also put more rebar in more blocks. I'm not sure if I will fill them all the way but at the bottom for sure and probably the top.

Do you think I should stick with my 280 or so 6" wide blocks or drop the number and use bigger blocks? Just trying to make sure I do everything as right as I can.

Also it's amazing to be under the dome! It's actually snowing now despite the fact it was 25 degrees here earlier in the week. I saw a ton of turtles when I got here yesterday but now it's back to winter. I've never seen snow this late in the year in my life!


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Midnight Dan
Postmaster
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Reged: 01/23/08

Loc: Hilton, NY, Yellow Zone (Bortl...
Re: Brainstorming dream obs which will become real! new [Re: corpusse]
      #5855277 - 05/12/13 11:32 AM Attachment (23 downloads)

Quote:

Do you think I should stick with my 280 or so 6" wide blocks or drop the number and use bigger blocks?




Not sure I understand the question. Why would wider blocks reduce the number? Seems like wider blocks would just make the wall thicker.

The most commonly used size is the 8" wide block, mostly because it is half the length of the block which makes it easier to turn corners and have everything line up when the blocks are laid out in half-block overlapping layers. So, if you use 2.5 8-inch blocks per side, that would take up your 40 x 40 area as shown below. Was that your plan?

-Dan


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corpusse
scholastic sledgehammer


Reged: 04/11/10

Loc: Mississauga, Ontario, Canada
Re: Brainstorming dream obs which will become real! new [Re: Midnight Dan]
      #5855337 - 05/12/13 11:58 AM

Dan that makes a lot of sense. My original "plan" if you can call it that was a 36x32 on the 40x40 slab using 12 blocks per layer just continuously stacking them up. Obviously crossing them like you illustrated will further strengthen the pier. This is why I'm asking every step of the way I want to make sure it's done right.

I was also under the assumption I had to fill the middle with blocks is that not correct? This would mean I'd need a lot less blocks. This is why I thought wider blocks would mean I will need less.

The 8" wide now seems like the way to go.


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Gardner
scholastic sledgehammer
*****

Reged: 01/19/04

Loc: New Hampshire
Re: Brainstorming dream obs which will become real! new [Re: corpusse]
      #5855371 - 05/12/13 12:20 PM

Andrew,

Congrats on your observatory project! Looks like you're getting close and it's exciting to see it come together.

I helped a friend build an observatory that was high up like yours. Thankfully it was well documented here on CN. You might want to see how we did the pier before you start constructing yours.

Here is a the link to the archived observatory thread.

Good luck with your project!

Edited by Gardner (05/12/13 12:24 PM)


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Midnight Dan
Postmaster
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Reged: 01/23/08

Loc: Hilton, NY, Yellow Zone (Bortl...
Re: Brainstorming dream obs which will become real! new [Re: Gardner]
      #5855664 - 05/12/13 02:56 PM Attachment (13 downloads)

Quote:

I was also under the assumption I had to fill the middle with blocks is that not correct?




Ah, that explains the issue with the number of blocks. No, I would not fill the middle with blocks. Usually that is just filled up with dirt, rocks, rubble, whatever.

The tricky part is dealing with the top and the transition to the next part of the pier, which is smaller. Since I haven't done this, I can only offer some ideas. One would be to make the top few layers a little smaller than the one below so you get a stair-step effect and fill the center with concrete. But that would require cutting blocks and I'm not sure how strong it would be.

I would probably criss-cross some rebar across the last layer, drilling some holes into the interior of the blocks, and then fill the top with concrete to make a flat surface on which to mount the top part. You'd probably want that top layer to be at least a foot thick. The drawing below shows this idea.

The top part would be a concrete cap about 4" thick that covers the entire top of the base including the blocks. The center of the base would be filled with concrete another 8-10" deep. You should be able to just pour on top of the rubble, which should be filled to maybe halfway up the block below the top course. The rebar should tie it all together. I'd use a piece of steel reinforcing mesh in that top 4" piece as well.

The concrete should be poured into the block cavities around the sides. If there are cavities that you have not filled all the way, you'll need to devise some kind of plug so the wet concrete doesn't just fall to the bottom. if the next part of the pier is intended to be concrete as well, you'll need to add some rebar sticking up from the middle of this cap so you can tie in the next pour. If it's going to be steel, then you'll want to put some carefully placed bolts in the cap to attach the steep pier.

Again, I don't have any experience capping a block section like this so others may have better ideas to offer.

-Dan


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corpusse
scholastic sledgehammer


Reged: 04/11/10

Loc: Mississauga, Ontario, Canada
Re: Brainstorming dream obs which will become real! new [Re: Gardner]
      #5856041 - 05/12/13 06:16 PM

Hey Gardner it is indeed getting close just want to solve this pier issue so I can get onto other parts of construction. I kinda thought I'd be able to do this quicker so in a way I am taking a step back but as long as it's built right I don't mind.

I ended up getting about halfway done smashing up the floor. Once I finally hit the ground I found it much easier. The first several hours I could not even get one piece the size of a goofball to come out in one shot. By the end I was pulling out several pound pieces with just a few hits and a pry bar.

I am so surprised it is sand underneath. I can almost dig with my bare hands. An auger or worse is not going to be needed! I was expecting bedrock. There are quite a few rocks but again with a pry bar they are easy to pull out. I guess I should be saving this stuff as filler for the pier vs dumping it at the side of the building

I noticed the pier you made is only 24x24. Do you think 40x40 is overkill? Or crazy overkill I should say. I don't mind overkill so that one day it could handle the heaviest sized mount and scope the dome would support.

I can use either the 6" 8" or 12" wide blocks. If I do the 40x40 I will have to make the hole in the floor about 45x45 so I can put foam around it to isolate it and to give myself a little space around..

I want to order the blocks as soon as I figure this out incase they have to order them. I know they had the 6" ones there.

The little hardware store on the island is like going back in time. The guy infront of me paid with a check! I haven't seen someone pay with a check since I was a little kid. They like the other small shops on the island close on Sundays again something I haven't seen since I was a kid. They still use CRT monitors too. The good news is they will deliver the blocks to the house for about 25$ and it can be any amount they will break down skids ect.


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corpusse
scholastic sledgehammer


Reged: 04/11/10

Loc: Mississauga, Ontario, Canada
Re: Brainstorming dream obs which will become real! new [Re: corpusse]
      #5856678 - 05/13/13 12:38 AM

Here are some pics. When I got there it was beautiful. A little cool, but down by the water I saw several turtles.



I opened up the dome but could not reach the lock on the bottom part of the shutter to fully open it up.

It was also neat to see the dome reflection on the house







I bought a spray gun to paint the outside of the building but tried it on the stairs first (not finished at this point)



It works okay but does create some splatter. Also a pain to clean.. For outside it will be good since it won't have to be perfect and will be very hard work with a roller but I don't really recommend these products.

I had a real hard time getting to the the bottom of the floor which was 6" thick. Once I did it became much easier to break up but still a very challenging job I could not complete.





I will be able to finish it next weekend. Getting to this point was hard and if my hands and arms weren't sore I probably could have finished today.

The weather took a drastic turn






at least i know the dome is snow proof!



I just gotta figure out what way to do the pier. I'll do another search and look at everyones tall / concrete block piers and come up with something. I want to order the blocks ASAP since I will be there for 3 days next weekend and then won't be back up for a couple of weeks.

This was the original plan, which now that I actually look at it didn't make much sense at all.



More to come. Thanks again to everyone for their help.

For the rest of the pictures please check out the gallery http://andrewastro.smugmug.com/Other/Island-Observatory/28704158_nc6MKQ#!i=24...

I'm spending way too much time trying to figure out which images are under 200k. I originally had linked a few other images but had to delete them.


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Midnight Dan
Postmaster
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Reged: 01/23/08

Loc: Hilton, NY, Yellow Zone (Bortl...
Re: Brainstorming dream obs which will become real! new [Re: corpusse]
      #5856804 - 05/13/13 03:09 AM

Nice photos! That floor doesn't look like anything a little dynamite couldn't handle.

-Dan


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Gardner
scholastic sledgehammer
*****

Reged: 01/19/04

Loc: New Hampshire
Re: Brainstorming dream obs which will become real! [Re: Midnight Dan]
      #5856896 - 05/13/13 07:03 AM

Andrew,
We chose the one piece blocks to keep it simple and faster to construct. After the base was poured and cured for a couple days we did 5 blocks tall and let the mortar cure for a day so not to squeeze it out at the bottom. Then we filled the column from the top with hand mixed concrete and topped it off with the sonotube and placed the pier top plate on it. The pier was really sturdy and didn't vibrate unless a really large truck went by on the street, but I don't think you'll have that issue.


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