Steel Pier Construction

[souls33k3r]

Hi All,

I will soon be embarking on journey toward my steel pier construction. It will not be housed in an observatory but in the open garden.

The plan is to dig a hole in the ground, put a template with bolts in the wet concrete and let it set and then put the pier on the top and bolt the pier down. This is so that when i move house, i can take the pier away and not leave a nasty surprise for the next owner in the middle of the garden.

I do however have a few questions:

1) How deep and wide should the hole be?

2) I'm open to suggestions but am not thinking of the rats nest design because i don't think that top two plates being separated by 4 x M10 or M12 bolts design is rigid enough to hold the weight, it might flex. I think that the pier which is solid enough should be holding the weight of both the mount and the scope rather than the 4 bolts. But the positive thing about such design is the ease of levelling the mount even when the pier isn't. I've heard so much that the mount does not have to be levelled but it will be a peace of mind for me if it is.

3) If i choose not to have the rats nest design, that bring me to another problem, how can i have the pier levelled? I've seen people put a leveller at the top of the template cardboard and make sure that is level, but is that going to stay level once the concrete sets?

4) Does the base plate of the pier have to be in contact with the concrete?

@angryowl will be helping me through this project which is very kind of him so he might chip in and ask some questions. 

Thanks in advance.

[JamesF]

This is for a steel tube pier?

James

[souls33k3r]

11 minutes ago, JamesF said:

This is for a steel tube pier?

James

Correct. Sorry i should've mentioned that. Will amend the post to reflect this

[JamesF]

Given a steel tube pier I think I'd be tempted to go with a hole in the side to get a hand in to tighten up the bolt holding the mount and not worry too much about it being level.

If you really must have it level, then some fiddling around with the concrete around the bolts using a template the same size as the base of the pier (or perhaps an inch larger in diameter) may do the job -- drop it over the bolts and squish it about in the concrete checking it's level in both directions and leave it until the concrete goes off.  If that's not perfect enough then perhaps add metal shims around the bolts under the pier before bolting it down.

As regards the size of the concrete block, I'd suggest that a two foot cube would be ample, but it depends a bit on the ground.

James

[Davey-T]

I have levelling bolts in mine but only because " sky modelling " mounts apparently need a level playing field to start with even then it obviously only needs to be level in the east / west direction.

Dave

[souls33k3r]

6 minutes ago, JamesF said:

Given a steel tube pier I think I'd be tempted to go with a hole in the side to get a hand in to tighten up the bolt holding the mount and not worry too much about it being level.

If you really must have it level, then some fiddling around with the concrete around the bolts using a template the same size as the base of the pier (or perhaps an inch larger in diameter) may do the job -- drop it over the bolts and squish it about in the concrete checking it's level in both directions and leave it until the concrete goes off.  If that's not perfect enough then perhaps add metal shims around the bolts under the pier before bolting it down.

As regards the size of the concrete block, I'd suggest that a two foot cube would be ample, but it depends a bit on the ground.

James

Cheers James. The rats nest was never to serve any other purpose than the levelling of the mount and like you said, if i go away from that design then a hole in the pipe was the plan all along.

Very good suggestions on levelling the pier. I was also thinking of something like this that i put the template in the wet concrete, let it set, then take off the template cardboard and put the nuts on the bolts and then back off slightly. Then put the pier on the top and put the next set of bolts to tighten the pier which will now be sandwiched in between the two nuts. If i have to level the pier, i can always loosen the nuts below the pier base plate and then do this but @angryowl did pose a very good question as to whether the pier base plate definitely needs to be in contact with the concrete? My concern with this was that i'm not sure if the nuts would strip the threads in the long run making the pier unstable in the future.

7 minutes ago, Davey-T said:

I have levelling bolts in mine but only because " sky modelling " mounts apparently need a level playing field to start with even then it obviously only needs to be level in the east / west direction.

Dave

I remember your design Dave, gave me lots of ideas to be honest. I know what people say that the mount doesn't need to be levelled but i really can't wrap my head around the fact that if it's not going to be levelled, then it won't be parallel to the earth rotation.  

[Davey-T]

32 minutes ago, souls33k3r said:

I remember your design Dave, gave me lots of ideas to be honest. I know what people say that the mount doesn't need to be levelled but i really can't wrap my head around the fact that if it's not going to be levelled, then it won't be parallel to the earth rotation.  

North / south is never going to be level as soon as you adjust the PA, I did need to level my wedge east /west for maximum performance.

Dave

[old_eyes]

Altair Astro recommend 15” square, by 36” deep for their skyshed pier. A number of people have said that we go overboard on concrete block size, perhaps driven by US builds where frost heave and ground movement can be a much bigger problem.

[fwm891]

1 hour ago, souls33k3r said:

i can take the pier away and not leave a nasty surprise for the next owner in the middle of the garden.

When we moved house taking the pier was the easy part but breaking up the block the pier rested on was another matter. Why did I break it up? because if the new owners broke a wrist because their spade struck a block of concrete who's liable? If you tell them there's a meter cube of concrete under their lawn they're likely to make it a condition of sale it's removed or walk away...

Just a thought...

[bottletopburly]

Here is  mine 

 

Hole 600x600 x900 deep  basically half a sq meter of concrete 

[souls33k3r]

1 hour ago, Davey-T said:

North / south is never going to be level as soon as you adjust the PA, I did need to level my wedge east /west for maximum performance.

Dave

I can also understand that north/south will always be off because the the altitude adjustment but east/west has to be levelled. That's how I see it. 

1 hour ago, fwm891 said:

When we moved house taking the pier was the easy part but breaking up the block the pier rested on was another matter. Why did I break it up? because if the new owners broke a wrist because their spade struck a block of concrete who's liable? If you tell them there's a meter cube of concrete under their lawn they're likely to make it a condition of sale it's removed or walk away...

Just a thought...

You're quite right there. What I was thinking is that I'll cover the concrete bit back with the grass carpet it took out in the first place. Nonetheless, good shout and one which I'll keep in mind. 

24 minutes ago, bottletopburly said:

Here is  mine 

 

Hole 600x600 x900 deep  basically half a sq meter of concrete 

Cheers for the idea. Mind if I ask if you levelled the concrete first? Was your pier levelled when it went on or did you have to make any adjustments to make it level? Also your pier is exactly the sort of design I'll be looking to do

[souls33k3r]

1 hour ago, old_eyes said:

Altair Astro recommend 15” square, by 36” deep for their skyshed pier. A number of people have said that we go overboard on concrete block size, perhaps driven by US builds where frost heave and ground movement can be a much bigger problem.

That's very valuable information. I agree, I'm sure I've seen people do around 24" Square to 36" deep which is around what @bottletopburly has done.

Trying to find all the right information here so that when I start digging, I don't dig anything less. 

[Davey-T]

All depends on your local soil conditions, have you got any neighbours who've had extensions built recently, the footings would have been specced accordingly, dirt is good, sand or shingle is bad 

Dave

[JamesF]

I reckon you leave the concrete in place if you decide to sell.  Just whip the pier off and stick a cheap concrete bird bath or other ornament in its place

James

[bottletopburly]

46 minutes ago, souls33k3r said:

I can also understand that north/south will always be off because the the altitude adjustment but east/west has to be levelled. That's how I see it. 

You're quite right there. What I was thinking is that I'll cover the concrete bit back with the grass carpet it took out in the first place. Nonetheless, good shout and one which I'll keep in mind. 

Cheers for the idea. Mind if I ask if you levelled the concrete first? Was your pier levelled when it went on or did you have to make any adjustments to make it level? Also your pier is exactly the sort of design I'll be looking to do

 

35 minutes ago, souls33k3r said:

That's very valuable information. I agree, I'm sure I've seen people do around 24" Square to 36" deep which is around what @bottletopburly has done.

Trying to find all the right information here so that when I start digging, I don't dig anything less. 

Yes concrete levelled within a thou ?? I put nyloc nuts under pier and levelled that way ,  I put rebar into hole as well , I cut 100mm owl hole in pier  I would advise an oval hole to make it easier for your hand I also ran pipe into centre for electrical, I would advise using rigid 4” pipe makes life easier I used 2” 

[bottletopburly]

Found my old thread here 

 

[Craney]

49 minutes ago, Davey-T said:

dirt is good, sand or shingle is bad ....

What about  clay ??      Beautiful but at the same time .... hard work....!!!

[Davey-T]

4 minutes ago, Craney said:

What about  clay ??      Beautiful but at the same time .... hard work....!!!

Mines in clay that's why it's not in a very deep hole 

Dave

[souls33k3r]

2 hours ago, Davey-T said:

All depends on your local soil conditions, have you got any neighbours who've had extensions built recently, the footings would have been specced accordingly, dirt is good, sand or shingle is bad 

Dave

Got two who have done extensions. I can easily approach either of ttem to find out

1 hour ago, JamesF said:

I reckon you leave the concrete in place if you decide to sell.  Just whip the pier off and stick a cheap concrete bird bath or other ornament in its place

James

Good shout. That's that sorted

1 hour ago, bottletopburly said:

Found my old thread here 

 

Top man, I'll have a read

[Jkulin]

Ahmed, did you not get the design drawings of my pier, it is exactly what you are describing that you want?

My concrete block is 75cm x 75cm.

if you can’t find the drawings then when I get home can resend them to you.

[fwm891]

15 hours ago, souls33k3r said:

You're quite right there. What I was thinking is that I'll cover the concrete bit back with the grass carpet it took out in the first place. Nonetheless, good shout and one which I'll keep in mind. 

I broke the main block up but the obsy wall foundations I simply constructed a square raised bed garden with a few brick courses and filled it with dirt top soil and a few plants...

[Astrokev]

I have no intention of removing my pier if I ever move, or the observatory for that matter. In my view, regarding any future sale, it’s a case of “buy as seen”, as was the case when I bought my property. 

I’ve never heard of any situation where a seller has ever been liable for any injury to a buyer, and can’t believe this is a risk. 

Regarding mount levelling, which you seem unsure about, it is 100% correct that the pier does not need to be level. Providing you can adjust the mount / polar axis in both altitude and azimuth then you can point the PA to any point on the sky (obviously constrained by the limits of the adjustment!) and can achieve polar alignment. A non-level pier top makes absolutely no difference and is unimportant. 

[Davey-T]

36 minutes ago, Astrokev said:

A non-level pier top makes absolutely no difference and is unimportant. 

Still makes no sense to me not to be level East / West 

Something like this must play merry hell with meridian flips 

Dave

 

[Gina]

The pier top would have to be really very noticeably off level to affect PA setting.

[adyj1]

57 minutes ago, Gina said:

The pier top would have to be really very noticeably off level to affect PA setting.

And I'd go so far as to say I can't see why theoretically even a leaning pier of Pisa would have any affect on PA - I would expect it to only limit  the maximum travel in one direction, not adjustment travel for PA. 

However from SGL discussions I have observed so far,  I understand there to be  four EQ pier levelling Belief Systems; 1. Pier levelling is critical in both axes,  2. Pier levelling East/West is critical, 3. Pier levelling is not critical in either axes, and 4. "I don't think belief 1 (or 2) should matter, but I'm going to do it anyway just in case they turn out to be right" ?

IMHO, each of these beliefs is respectful of the other (in the main ? ), but none can be easily convinced otherwise by theoretical argument. In other words, we all agree to differ. 

(Which is surprising, given we all believe in the scientific method, but nevertheless this has been my observation) 

For what it's worth... 

Ady