good price for my pier

[nightfisher]

I was at one of the local firms that do jobs for the people i work for, when i realised, they do fabrication work so i asked for a rough price to make me a pier mount, he has steel tube 90mm od 86mm id and would do the two top plates to drawing, plus weld one plate to steel tube................for about £30.........think i should take him up on that, will only have EQ5 head with ota`s up to 6kg:D

[spaceboy]

Will that be the dimension of the pier? 3 1/2" isn't much.

[FairviewSteve]

The tube is only 2mm thick on the wall, depending on the length even taking into account that it's a cylinder you may have some issues with vibration and if there's too much weight you may find that you have a cantelever effect. Most piers I've seen are at least 5mm thick and tapered to spread the load over a wider area.

[nightfisher]

right will have to see if he can make it from heavier metal

[malc-c]

Hummm - Like most I opted for the plastic pipe and concrete approach. The pipe was 160mm diameter and has a wall thickness of around 4mm. Personally a 2mm thick wall and 90mm diameter won't be sturdy enough, especially if it's not going to be filled with something, and whilst the OTA may only weigh 6KG there is the mount and CW to factor in

[malc-c]

right will have to see if he can make it from heavier metal

If you have a look at other fabricated piers the steel is often a lot larger diameter, and often made from 1/4" plate, with braces and a tube of similar wall thickness. - my guess £80 - £100 is more realistic

[spaceboy]

Steel is reasonably expensive and fabricators usually drop a percentage into the cost. It may pay to pop to your local tat yard and see if you can pick up a thick wall box section and some steel plate. It wouldn't cost much for someone to drop a bit of weld on it to get it looking more like a pier for you.

[opticalpath]

Diameter of the pier is much more important than wall thickness when it comes to stiffness/rigidity, so go for bigger diameter if you can. It's well explained here:

Pier Design Fundamentals - How To

Adrian

[AndyH]

I'd recommend 5 or 6mm thick wall thickness.

Andy.

[nightfisher]

cheers guys, better to make it to heavy than to light

[nightfisher]

just a silly idea, as i know very little about pier design, i have a piece of very strong rsj , if i had an Lshape bracket welded to top section, with a hole to bolt mount to, would this worked provided it was concreted in with the L facing north

[AndyH]

As long as it's nice n thick n heavy, most anything could work well. I'm a great believer in adapting what you have.

I once made a small but tall pedestal, fully welded with feet out of stuff that was in a scrap bin ! Works perfectly for one of my mounts.

Andy.

[spaceboy]

If you could pick up a nice sized piece of 12mm plate you could weld this to the base of the RSJ and bolt it down to a block of concrete in the ground. The advantage is if you move house you can unbolt it and take it with you.

[nightfisher]

think i must have described poorly!

what i had in mind is using RSJ, concreted in but with a very heavy L shape (say 5mm steel) welded to top section of RSJ facing north and bracket having a suitable hole and alignment peg to mount the EQ5 head to, so in theory the eq5 would be offset by about 120mm from stem of RSJ..............if all that makes sense

[spaceboy]

This is what I was thinking. For some reason I thought you planned on moving house at some point so thought the idea of bolt fixing would offer more flexibility over a fixed post. If this isn't the case then doing as you say should work fine. It will pay to add a couple of triangle braces to help support the flat running of the top of the RSJ. The only problem if any may be the risk of catching the RSJ with the OTA due to the off set.

[nightfisher]

nice one nick, that little diagram really gets the idea, and highlights the possible ota to RSJ clearance!

i have the RSJ, its actually a long piece of [ section, but about 8mm thick and will need cutting down as its near 9ft long.

I will be saving this project till i move house, as just no point in putting a pier in my own garden, to much light pollution and very little horizon, it will be nice to go house shopping and first priority will be rear garden from an astronomers eye

[Peter Drew]

Why not have two pieces of your section welded together to make a box section, it would only need to be tack welded at intervals as the end plates would do the rest.

[spaceboy]

It's a shame you don't live closer as I could have sorted it out for you.

[nightfisher]

been to fabricators again today, and mentioned the need for heavy steel, he has 5mm wall 90mm od tube maybe this project is a goer after all

[malc-c]

Personally I would suggest that it has some form of bracing as 90mm is very small. IMO minimum would be 120mm diameter, preferably 160 or 200mm

[AndyH]

Whilst wider is always better, 90mm o/d + 5mm thk should be fine, especially if it's your eq-5 that's going on top. After all, the smaller diameter Tal pier is 3" I/D and it's solid as a rock. Mind you it's only approx 3ft high. What are you going for? 5ft?

If I were you I'm make sure the top-plate has a hole, to let you fill it with sand.

I'd also have 3 or 4 triangular pieces of steel(same thickness as the base), welded from the base-plate to tube, for extra rigidity.

Cheers,

Andy.

[nightfisher]

i mentioned that the top plate would need a hole as i plan to fill the tube with sand or cement, i think the biggest scope it will have is my 100rs or maybe a skymax 150

[Gina]

Are you really really sure you won't want to go for a bigger scope later?

[ollypenrice]

As for the filling, I'm told that sand and oil is the tasty mix to use. The idea is to damp vibration so I wouldn't use concrete which is extremely rigid. I just used sand in mine and it's fine but I can see that dropping in some old engine oil as well would be better.

I think it's a good idea to trianglate with tripod like legs but make sure they won't tangle with a long OTA because going past the meridian is one of the big plusses of a pier.

Just a thought, but you can buy MIG welders from Machine Mart or second hand from about £150 and I have found mine incredibly useful. It isn't hard to get the hang of it. In hindsight I'd have gone for a slightly bigger one because it would have handled thicker metal. Of course, if you want it to look good maybe use a professional because, as you'll see below, a professional look was rather beyond me!! But it all works and the pier is not the limiting factor when it is windy.

Olly

[nightfisher]

Are you really really sure you won't want to go for a bigger scope later?

No plans for a bigger scope, in fact i have sold my 200 as it was not right on my eq5! if i go bigger it will be a dob.................unless i win the lotto then a different story

Olly, thats a novel idea for a sturdy mount, looks very solid