Steel Pier

[Adaaam75]

Guys,

Just been advised by my local fabricators that a square pier is going to be significantly cheaper than a circular one. The reason is they have all sizes of square lengths in stock but would have to order a circular one in. Additionally they don't have a laser cutter so it would be much cheaper again to have square plates to mount the mount!

Thoughts on the advantages between the two types of pier please.....

Adaaam75

[pete_l]

Idle thoughts:

1.) Any pier is better than no pier.

2.) You won't be operating the metalwork to anything close to its structural limits

3.) Think what you could buy with the savings of a square cross-section. Why would you turn down a free <whatever>

4.) If pipework was rectangular we would all have square piers

[Juicy6]

Like this one?

 

[Davey-T]

My pier is 200 mm square steel, gives you nice flat surfaces to mount stuff on.

Dave

[RayD]

Structurally round is much stronger, but as noted above, with the lateral loads you're likely to apply I wouldn't think it will be a deal breaker.  My advice would be to get it made in as big a section they can manage, and make sure it's at least 5mm thick wall.

[RayD]

4 minutes ago, Davey-T said:

My pier is 200 mm square steel, gives you nice flat surfaces to mount stuff on.

Dave

That's a definite positive for square section Dave 

[Alan White]

What sort of cost are you being quoted out of interest Adaaam75?

[Adaaam75]

Thanks guys, not sure about the quote yet as my mate works next door in a wood burner shop and is trying to get mates rates for me but he reckons he has a gut feeling it's going to be around the £200 mark which would be a deal breaker because I could make a cement one cheaper.

The other question is how do I factor in the latitude locking screw so it doesn't hit the mounting plate? Im reluctant to cut a shape out of the plate as it will weaken it and cost more. See pic....

I like juicy6's picture very much and may get a quote on that!

 

[RayD]

16 hours ago, Adaaam75 said:

Thanks guys, not sure about the quote yet as my mate works next door in a wood burner shop and is trying to get mates rates for me but he reckons he has a gut feeling it's going to be around the £200 mark which would be a deal breaker because I could make a cement one cheaper.

The other question is how do I factor in the latitude locking screw so it doesn't hit the mounting plate? Im reluctant to cut a shape out of the plate as it will weaken it and cost more. See pic....

I like juicy6's picture very much and may get a quote on that!

 

 

Most have a pier top adaptor that raises the mount high enough for this to clear as they are the same diameter as the mount base, but otherwise it is cutting a recess out.  It depends how big your top plate is.

If he can do it for £200 that's a really good price mate. By way of example I am having a pier made to my specifications, which is due for delivery Monday, and that is costing just under £500.  This is substantial tube section, but even in square £200 all in is very good.

[spillage]

Have you considered changing the bolt for a shorter one. I have used a length of threaded bar for my neq6 and just locked off two nuts at the end.

As polar alignment only needs to be done once in a blue moon I dont mind having to use a spanner to make my adjustments.

[Adaaam75]

4 hours ago, spillage said:

Have you considered changing the bolt for a shorter one. I have used a length of threaded bar for my neq6 and just locked off two nuts at the end.

As polar alignment only needs to be done once in a blue moon I dont mind having to use a spanner to make my adjustments.

Are the bolts just the same as a normal m10/12/14 (whatever size) that can be adjusted with a spanner? I thought the thread would be different just to be awkward. I guess there's only one way of checking! If that is the case then I will definately replace the bolt with a shorter one for stability. Like you say, it will only be one initial adjustment and then not required again.

[Adaaam75]

4 hours ago, RayD said:

Most have a pier top adaptor that raises the mount high enough for this to clear as they are the same diameter as the mount base, but otherwise it is cutting a recess out.  It depends how big your top plate is.

If he can do it for £200 that's a really good price mate. By way of example I am having a pier made to my specifications, which is due for delivery Monday, and that is costing just under £500.  This is substantial tube section, but even in square £200 all in is very good.

I'm hoping to avoid a pier adaptor as that adds an extra £80+ that I can avoid just by installing two plates made up by the fabricator. I'm thinking a smaller bolt as suggested and going ahead with the pier now I've been given a good idea of what I'd be expected to pay. I'll keep you all posted.

[spillage]

My neq6 took a standard thread from toolstaion M10 I think.

[Adaaam75]

Cool I'll remove the bolt and take it to Screwfix, they will help match it up before buying.

[Starflyer]

If it helps at all I shared my pier journey here, it's been nearly two years and it's transformed my imaging.

It's made from 6 inch tube and is rock solid, I designed it so I could fill it with sand if needed, but it performs so well I've never bothered.

It regularly holds a 10" f/4.8 newt with camera, filter wheel etc with excellent guiding.

This cost me around £120 for the pier (galvanised and powder coated), £40 for the EQ6 adapter plate, £25 for bolts and anchors and around £80 for the spotmix concrete, so it's doable for your sort of budget.

[Adaaam75]

Wish I had a friend!

What diameter pier do you think would be sufficient bearing in mind I'm having a square pier with 5mm thick walls?

[Davey-T]

£200 sounds reasonable, I made this one a few years ago, I was still working at the time and got the steel trade price from the guys we were getting a lot of steel from for buildings.

2 meters of 200mm square steel tube, 600mm square 5mm steel plate, 4 X 2 meters 75 X 75 mm steel angle plus a few other bits cost around £100 and prices have gone up a lot since then.

This was a bit elaborate as I made it telescopic to raise 300mm to see over the side of the obsy, raised with a car jack in the pic' but I have replaced that with an electric ram now.

Dave

 

 

 

[Peter Drew]

I've given up on metal piers these days, far too expensive for what they have to do. All my recent piers are made from hollow concrete building blocks 200mm square and bolted together for whatever height is needed and based on a 600x600x50mm paving slab. No need for a pier top, less than £50 and less than an hours work if you have all the bits to hand.

[Adaaam75]

2 hours ago, Peter Drew said:

I've given up on metal piers these days, far too expensive for what they have to do. All my recent piers are made from hollow concrete building blocks 200mm square and bolted together for whatever height is needed and based on a 600x600x50mm paving slab. No need for a pier top, less than £50 and less than an hours work if you have all the bits to hand.

I'd very much like to see an example of this Peter! I'm all for cheap and effective!

[speach]

I've gone for a square as it was the easy to get and make. Was told afterwards by an engineer the the square section is more stable than round, so a win win aways.

[RayD]

8 hours ago, speach said:

I've gone for a square as it was the easy to get and make. Was told afterwards by an engineer the the square section is more stable than round, so a win win aways.

He's kind of right and kind of wrong.  If you were to stand equal lengths of square section and round tube on their ends, then push the tops laterally at the same point with the same force, the square would fall later for the same size across flats as per diameter of tube.  However, in the application of piers, and the reason most are made from tube is that it is stronger laterally for the same section and thickness than square section, and, importantly, this strength is uniform, and is therefore the same in every direction.  A square section has strong and weak axes (it is stronger across the corners laterally than across the sides).

As I've said on posts before, it really shouldn't make any difference at all at the loads and forces we are using, so square or round is a choice probably decided on cost alone as square in large sections is much easier to get and much cheaper, but there is a difference, and it does favour the round pier in pure engineering terms, and where you really want to see as little movement as possible for a given section.  As Dave notes square has a benefit that it is easy to drill and fix bits to.

If you look at many structures you will often see square main beams, which then have round braces or strengtheners.  The reason for this is as design engineers we can use the square to reduce costs knowing the amount it will flex in opposing axes, but strengthen with the more costly round, knowing that strength is applied through 360 degrees.

If using square or round, it is more important that the diameter of the section is sufficient.  If you imagine a pier of 100mm diameter and 5mm thick at 2m tall.  Now apply a given force laterally at the top and measure the deflection.  Now double the thickness of the section to 10mm and do the same.  Now do exactly the same test but doubling only the diameter, and you will see there is a huge reduction in the deflection over the increased thickness.  This is of course just a simple example, but it is to emphasise that provided you have sufficient diameter, you don't really need to go silly with thickness as the stability comes mostly from the diameter, the strength is in the thickness.

[Adaaam75]

Received and understood! "Pillars" of creation. Round pillars are used feom new build towers to ancient roman structures so there is much in that. As you state the loads from a scope set up will have a negligible difference between a tube pillar and a square pillar, as long as the diameter and wall thickness are proportionate.

So RayD, if I am looking at a 130cm square pier would you say a 5mm thickness and 20cm diameter pier would be sufficient?

[Adaaam75]

Although I must admit I am going to look at Peters suggestion of hollow blocks when I'm ready to start as they are £5 each and offer so many options!

[RayD]

5 minutes ago, Adaaam75 said:

Received and understood! "Pillars" of creation. Round pillars are used feom new build towers to ancient roman structures so there is much in that. As you state the loads from a scope set up will have a negligible difference between a tube pillar and a square pillar, as long as the diameter and wall thickness are proportionate.

So RayD, if I am looking at a 130cm square pier would you say a 5mm thickness and 20cm diameter pier would be sufficient?

With all of it, it's only relative to what you are putting on top of it.  If you have a light and very balanced set-up, then you can have smaller than if you were intending to put the Hubble space telescope on top. 

I would think with an average set-up you will be fine with either, and Peter's idea is also very valid and will no doubt work well, but the longer and heavier you go in terms of telescope, the more you will need to look at the detail of what is holding it steady.

[1parsec]

Using square or round section doesn't make appreciable difference in pier design. As RayD says, its the outside dimensions of the pier that's important.

For example comparing a 6" diameter tube with 1/4" wall section  vs    8" diameter tube with 1/4" wall section.
The 8" tube will be 2.44 times more rigid than the 6"

Often you'll see a nice sized tube mounted on a thin base plate without any braces. This un-does all the good work selecting a suitable tube.
Make sure the base plate is well braced and put the bolt positions close up against the braces. A thick plate with a smaller foot print is much better than a larger thin base.