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Gina

Concrete Pier Preparation and Construction

159 posts in this topic

I've pretty much decided on the design of my pier and started the work for it. I've dug the hole ready for the concrete foundation. I've taken photos showing the location, mould or moulds for the pier and the hole.

I'm going to use an old swing bin container upside down with the bottom removed for the main part and probably an old paint container (also less bottom) for the top part to give more height. The bin is 23" high and the paint bucket another 9" giving 31" altogether. I might decide to go a bit higher by adding another plastic container on top. Still thinking about that. No decision needed until I start pouring.

1. The location looking South - bit of wood marks the approximate pier position.

2. The bin upside down on the lawn.

3. Added plastic paint pot on top.

4. Another view of the above looking SW

5. Digging the hole.

6. Hole dug down to a very firm layer of clay, which I think will do.

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Forgot to say... Hole is about 3' by 2'6" and a bit over a foot deep where I hit solid clay. I might increase the width to 3' as it's not as deep as I'd planned.

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looks great, I love to see observatories going up from the pier to the floor and then the obsy itself,

id love to have one, but cant at the moment

going by the scenery it looks like your in the country side, if so you must have brilliant skies,, is that field beside you for sale by any chance:D

keep the pictures coming as it progresse

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Gina - that does look a lovely area for viewing !

Nice to get started.

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We wanted to buy some of the field next door but our neighbour farmer won't part with any land! But apart from that he's extremely helpful :eek:

We have virtually clear views to the far hills south and east, in fact covering well over 180 degrees :icon_salut: I've just copied an aerial view form Google Maps of this immediate area and marked where my obs is going with a red blob. I'll post some more views from the obs position later. The skies are very good at night (unless our neighbour to the west have their security light on) with just a faint glow from Honiton roughly SW and something like 5 miles away.

BTW Our location is no secret as I have a weather station with associated website and details are on that. We do have plenty of security though with PIR lights, alarm and CCTV cameras. Plus a dog with very sensitive ears :) We have a smallholding and farm machinery and equipment has a tendency to "walk"!

Here's the obs location from the air :-

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There are some suggestions regarding pier height in the book on building your own observatory that I'm reading at the moment. I'll try to find them later.

James

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There are some suggestions regarding pier height in the book on building your own observatory that I'm reading at the moment. I'll try to find them later.

James

Thank you James :)

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I'd go deeper if possible

Steve

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I would recomend going at least a foot deeper with that pier base!! You will find that it pays - too shallow a base and you will get movement caused by water/drying out and ice in the winter. You may not notice for a while until your mount continually "goes out of polar alignment" for no apparent reason. You only put a pier base down once so - dig deeper!!

Have fun!!!

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Whenever possible I drive re-bar or angle iron "piles" into the hole at angles and then pour the concrete around them...

All my piers are on 10 feet of "made" up ground so digging untill I hit clay or rock isnt an option.. I also undercut the sides so the bottom is quite a bit bigger than the top...

Each to their own...

Billy...

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This free e-book has some guidance about pier height on page 84 (or 74 if you go by the page numbers on the actual pages).

Setting-up a Small Observatory

That's the one I'm reading. To cut to the chase, he suggests that you want a pier no taller than 1m above floor level for a newt, or between 1.2m and 1.8m for refractors, SCTs and so on. He goes on to say that the correct height should be one that puts the eyepiece at a comfortable viewing height when seated with the scope on the meridian and pointed at between 50 and 60 degrees altitude.

James

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Thanks :) Thought I might want it a bit higher. I'll sort something out. I could go down to a bit smaller diameter at the top - easier to get the scope pointing straight up if wanted. I'm thinking of using threaded rod for the dual purpose of fixing the mount and reinforcing the top of the column.

It is necessary to pour all the concrete in one go or will it join up OK if I wet the dried part? I know this is generally OK for walls and floors but this is more critical. I plan to use plenty of scrap iron for reinforcing.

As for digging deeper, it is possible using an iron bar to loosen the clay and stones and then using a hand trowel to remove the clay and hands for the stones. The latter seem to get bigger as I go lower. At least getting the topsoil out was relatively easy - nice and dry following all the dry weather we've had :eek:

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I think it should be ok if you pour the pier foundations in more than one go -- that's more about mass than structural integrity. I think I'd want to pour, say, at least the top 6" of foundation and pier all in one hit though, and use a spare bit of rebar or something similar to agitate the concrete after pouring it to try to get rid of any large bubbles.

James

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I am NOT a concrete engineer but I believe that you must pour your concrete in one "go". However this causes a problem when trying to create a pier as, unless your shuttering (plastic bins in your case) is very well made and weighted down the concrete in the pier will try to escape under the influence of gravity!

I think you may "get away" with allowing the base concrete to "start to set" and then pour the pier on top - concrete sets by a chemical reaction, it does not "dry out", if you see what I mean.

Hope this makes some sense!!

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Good to see your getting going Gina! :)

Good luck,

Michael

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Got any rocks or old bricks or concerte blocks handy (not breeze blocks).. you can always work heavy rubble into the concrete as you go especially towards the bottom of the hole...

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Yep, use loads of rubble in the hole, will save on concrete costs.

If using a plastic bin for shuttering certainly do secure it otherwise the weight of the concreate WILL force its way out. Also consider a few rounds of chicken wire in your pier for reinforcement.

Cheers

Ian

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Thanks for the advice :) The bin has a rim at (what was) the top - I think I shall sandwich that in shuttering, probably held together by coach bolts and wing nuts for ease of dismantling.

Our neighbour is partly rebuilding a stone barn and has plenty of spare rubble - he's promised me some :eek: We've also got lots of old chicken and pig netting which I can incorporate. And odds and ends of scrap iron.

I've been digging the hole for the pier foundations deeper. The clay is not quite as hard as I thought and I think I may have it dug out in a couple of days. Then Tuesday or Wednesday I shall go into town and pick up some cement etc. from a builders merchant. Also, threaded rods, nuts, bolts, etc.

Had a (weird) thought about a pier adapter... If I have to have a tripod with the mount, I could cut off the top part of the legs and embed them in the concrete of the pier. Sounds horrible to destroy a good tripod... OTOH maybe the top might come off to be bolted onto a plate at the top of the pier.

Edited by Gina

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Hole a bit deeper - nearly 2ft now. Harder going, wet clay and stones! Still... getting there :)

Have an EQ6 mount on order (FLO) so will be able to see what I need on the pier when it arrives.

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Thinking I may want a higher pier than the bin plus paint bucket, I've been looking at what else I have around. One thing is a thick cardboard mailing tube, 7" ID and nearly 1/4" thick. I could cut off a section of this and wedge it in a round hole in the bin end, maybe glue it in. I think the cardboard will be thick enough to withstand wet concrete until it sets - or I could put some polythene sheet inside.

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Been out this afternoon and bought cement, ballast (gravel mix) and 4m rebar plus 4 lengths of M14 threaded rod with nuts and washers. Hole very nearly ready. Need to find a few more bits of scrap iron for reinforcement then just about ready to go.

Having received my EQ6 mount with the most massive tripod I think I've ever seen, I'm about to set that up near where the pier is going, with telescope, to see what height I shall want the pier.

I also received David Arditti's book "Setting-up a Small Observatory" so I shall be reading that for more ideas on the "shed".

Edited by Gina

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On the pier itself, is there any reason for using the bucket, (other then you have it)...what I mean is why not use a length of something like 8 or 10 dp (underground pipe) - i'm assuming they still make it, they did when I worked for Geberit, and then fill it...

I've never made a pier, so there might be a good reason not to use it, but food for thought anyway...

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Yes, this was what I first thought of but so far I've not been able to locate any. I tried one builders' merchants but the biggest pipe they had was 6". There is another builders' merchants in town I can try another time. Obviously someone sells sewer pipe but I don't want to buy something like a 5m length or more. I just want an off-cut. I also looked at household rubbish bins as a mould. I could add one on top of my rounded corner square one. Could be worth the £15 I guess.

Anyway, while I'm deciding what to do for the pier, I'll set up the EQ6 mount/tripod and use the mount on it's tripod for the time being. Plenty to sort out there :)

Edited by Gina

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