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Help Please, Pier length/Diameter ratio's


Mick UK
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I am contemplating removing half of my concrete garage roof (gulp) and replacing it with a roll off wooden roof, but due to the roof been 7 1/2 feet from the floor of the garage, im wondering what diameter pier i will require.

Is there a formula to work out the correct diameter for a 7 foot pier anywhere for the weight it will have on top of it?

Also what length of pier would need to be buried into the concrete?

My mount is the neq6 pro and on this i will have my skywatcher 250 pds and my skywatcher 80ed pro along with the obvious weights camera etc.

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I wouldn't imagine a formula exits for such things m8. But, I am thinking that you would need 8" minimum, possably 10". As for the depth, my 4' pier is 3' into the ground as per recomendations on here and elsewhere, so I would imagine you would want to be further into the ground than that.

But, hats off to you m8, its a heck of a project........ ;)

Keep us informed.

Gary

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Hi. Mick,

If that was my project, I would not use a metal pier for the mount.

Have a look around your local Water utilities yard, and see if you can find any high pressure water pipe. It will be coloured blue, and it will have an external diameter of 30 centimetres.

The wall thickness will be about 3 centimetres, and will drill and tap to allow you to attach things if you so desire.

Go down to a depth of about 3 feet, or one metre if the ground will allow. If you hit solid clay, and the depth is at least 2 feet, don't knock yourself out going any deeper. Make it 2/3 metre square too.

Once you have that depth established, you can work out the height you need for the pier to stand in the hole, and reach the level of the garage wall. Don't forget the EQ6 will add to the height, so you need to do some measuring to allow for any levelling mechanism you will employ on which to afix the mount itself.

Once you have the pier length worked out, Drill some large holes into the pipe from the bottom, to a few inches from the level of the hole.., which means all the holes will be below ground.

Stand the pipe in the hole, and find a way to hold it in a perpendicular position, using a spirit level .

Once it is held steady, you can begin to fill the hole with concrete.

To the level of the top holes you drilled in the pipe at the base. Make sure the concrete is seen to penetrate those holes to the inside of the pipe. Once the concrete is level with the hole you dug out, start to put concrete into the pipe itself, to the same level.

The holes you put in the pipe, will allow the concrete to key together, and when it has fully cured, the pipe will never move.

And will be as numb as you can possibly get. No vibration at all will bother it. You can fill the pipe also, to a level below the point where your mount plates will reside.

This is the method I used in my Obs. and it is rock solid.

If you wish, you can put some waste pipe of 2" diameter inside the pipe, to carry any data cables. The diameter will make it easy to draw the cable through afterwards. I used a separate conduit for the mains cable I ran through the pipe. A 13 Amp socket was fixed to the pipe itself.

Here is a picture which shows partially what I did.

Hope this helps you in someway.

Ron.;)

post-13213-133877461327_thumb.jpg

Edited by barkis
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Thanks Gary, appreciate your reply:)

Ron, your pier looks the business!

One question about it tho, how come your pier stops short and you have built an extention table above it ? with the mount and mount extention above that, why didnt you make the pier upto the height of the mount or the mount extention tube, was thier a specific reason for this?

Thank you for replying, you've given me a lot of ideas from your picture for my pier.

As for the pipe, a few months back the water board were doing some work near to where i live and there was lots of what looked like 10" and 12" Diameter plastic pipe (the yellow stuff, thick walled) off cuts laid about, i had at the time considered get a few pieces incase i ever wanted to build my own Newt...i wish i had now! ;)

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you have been slightly mis-informed. All the mechanical analysis for steel piers has been done by a fellow in the USA. You may be able to find it on Google.

Dennis

ps; my pier is five foot and eight inch dia.

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Thanks Gary, appreciate your reply:)

Ron, your pier looks the business!

One question about it tho, how come your pier stops short and you have built an extention table above it ? with the mount and mount extention above that, why didnt you make the pier upto the height of the mount or the mount extention tube, was thier a specific reason for this?

Thank you for replying, you've given me a lot of ideas from your picture for my pier.

As for the pipe, a few months back the water board were doing some work near to where i live and there was lots of what looked like 10" and 12" Diameter plastic pipe (the yellow stuff, thick walled) off cuts laid about, i had at the time considered get a few pieces incase i ever wanted to build my own Newt...i wish i had now! :)

The reason it is shorter, is because I actually have two mounts in two different Obs. One behind the other. One houses a 12" SCT, which has the same pipe as a pier. That one is the full height.

The one you see in the pic, is the remainder of the pipe from the first one, unfortunately, too small as you observed. However, it does make a solid foundation for the Epsilon Extension which raised the mount to the height I required. I could have bought another length, but it meant a long trip, and I was happy that the alternative would suffice.

Ron.;)

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Dennis, i'm not quite sure what you mean by "slightly mis-informed"?

Ive tried googling for mechanical analysis for steel piers etc but i cant find anything to what you are referring.

Do you have any more information on the subject that could help me find it on Googling. Cheers.

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Har har, i knew there was something "fishey" about your pier Ron!:)...you have made an excellent job of bringing it up to the required height mind, you've also giver me some excellent ideas to play around with, due to the Epsilon Extension you've used.

One of the reasons i was thinking of using my garage as an obsy was although i have a 10ft x 12ft shed whic would make an excellent obsy, unfortunately, my main sewer pipe runs buried right through the middle of it!

I am now toying with the idea of using 3 or 4 steel concrete filled legs to span the sewer pipe, and weld a center tube onto them straight up to the height i require.

As i will be installing a false floor of around 2 ft high around my pier, the legs could branch off Under the floor into separate poured concrete blocks to help keep the pier vibration free!;)

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you have been slightly mis-informed. All the mechanical analysis for steel piers has been done by a fellow in the USA. You may be able to find it on Google.

Dennis

ps; my pier is five foot and eight inch dia.

Dennis,

I really was not suggesting Metal piers were inferior, in fact as you know, you were there at Kelling when Arthur brought several he had made, for their owners to collect. All were more than satisfied with the quality.

My suggestion was simply one of economy. I would think a pier of the dimesions the OP required, would be very expensive.

In hindsight, perhaps I should have stated my reason.

Ron.

Edited by barkis
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Mick,

the second post above suggests that a formula for such things would not exist althought the reference to M8 is about right for the size of bolt to hold it into it's concrete base. Hence my reference to your being slightly mis-informed.

You can find the analysis here, and probably a link back to the original work done by Dennis Persyk.

Pier Design Fundamentals - How To

Dennis

ps; Ron, not sure what you meant about me being at Kelling, have not been for years and never had a conversation with anyone about piers when I have been there.

Edited by roundycat
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As for the pipe, a few months back the water board were doing some work near to where i live and there was lots of what looked like 10" and 12" Diameter plastic pipe (the yellow stuff, thick walled) off cuts laid about

I hope not, yellow MDPE pipe is for gas supplies, blue for water and black for sewage.

Peter

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"I hope not, yellow MDPE pipe is for gas supplies, blue for water and black for sewage."

Good job i didnt take up a mates offer to dig it up and cut a length off it for me then for a tenner!!...floods i can handle, explosions are another matter!;):)

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Mick,

the second post above suggests that a formula for such things would not exist althought the reference to M8 is about right for the size of bolt to hold it into it's concrete base. Hence my reference to your being slightly mis-informed.

You can find the analysis here, and probably a link back to the original work done by Dennis Persyk.

Pier Design Fundamentals - How To

Dennis

ps; Ron, not sure what you meant about me being at Kelling, have not been for years and never had a conversation with anyone about piers when I have been there.

Well, I offer my apologies If I'm wrong Dennis, But I was certain you were there, and I saw you having a conversation with Martin Bradley.

I have never met you personally, so there could be mistaken Identity going on here.

I shall attempt to clear the matter up, for the sake of my own sanity ;):D.

Ron.

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Ron, the last time I was there I did indeed have a conversation with Martin but your original comment seemed to mention Arthur and some piers he had made, I don't recall seeing them, or talking to Arthur or anyone else about them.

Dennis

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Ron, the last time I was there I did indeed have a conversation with Martin but your original comment seemed to mention Arthur and some piers he had made, I don't recall seeing them, or talking to Arthur or anyone else about them.

Dennis

Perhaps you didn't see Arthur. or the piers he brought with him, and lined up at the fence not far from where Steve Flo. had their tent erected. The only connection the piers have in this matter, is that I was agreeing that very good steel constructed piers exist, and Arthurs products were good examples of them.

Ron.

Edited by barkis
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