Urgent pier height help

[Anthonyexmouth]

Ok, hole dug, ballast and cement on site, weather warmer. 

I've done a few measurements on my tripod and made a sketch. Current tripod is a little low for visual so thinking of coming up 300mm with the saddle height. 

I'm trying to keep it as low as possible for imaging but still ok for visual. I'm keeping the concrete at what I think is a sensible height and then adjust as needed later with plates and extensions. Here's a few pics. Advice and others experience greatly appreciated as I really want to start the pour today while the weather is ok. But this concrete is a one shot and done. No going back. 

[JamesF]

I don't think anything looks hideously out of place to me.  Are you planning on standing or sitting at the OTA?

James

[Anthonyexmouth]

Me standing mainly but maybe sitting on a high stool for shorter people if needed. Main use is for imaging so want stability but not so low that I can't do visual for visitors. 

So you think that height is a good compromise.

[JamesF]

I think it's probably fair, yes.

Without the extension I think it would work out much the same as I have decided on for my observatory, but I'm not planning on using it much for direct observing other than from a low chair, so it feels about right to me.

It's a bit variable anyhow depending on what OTA you're using, so there's rarely one definite answer.

James

[Anthonyexmouth]

Yeah, my thought is the 950/800mm high * 300mm wide concrete pier is a nice solid base and then I can make up the difference in variable steel work as needed. Just don't wanna f-up the concrete as I can't adjust that later. The studs are 4* 16mm and 150mm to the plate for leveling so that should be stiff enough I think. 

[bottletopburly]

I made mine same height as Eq6 tripod at its lowest height I used with a Newtonian approx 950mm ish .

[Anthonyexmouth]

If I do this at the same height as my tripod I think it'll be too high with the plate, studs and adapter. As the concrete is 300mm wide I'm thinking the steel work will reduce that down a little too give more movement. 

I can't imagine using a newt. I think it's more likely refractors and maybe a nice 8" edgeHD or 9.25 somewhere down the line so always viewing from the bottom. This gives me a maximum eye piece height of 1600mm when horizontal for visual and with the use of a diagonal should be fairly comfortable. Sat here looking at the hole and hoping a few more chime in before I start mixing and then there's no going back

[Dr_Ju_ju]

The lower you can sink the ducting, the more stable it will be.

I used the same type, but have added a smaller diameter (150mm) to lift the mount and ensure there is no clash between equipment & pier(s). Also I'd suggest drilling some holes lower down & pushing some re-bar through to produce more anchorage.

 

[Anthonyexmouth]

 

35 minutes ago, Dr_Ju_ju said:

The lower you can sink the ducting, the more stable it will be.

I used the same type, but have added a smaller diameter (150mm) to lift the mount and ensure there is no clash between equipment & pier(s). Also I'd suggest drilling some holes lower down & pushing some re-bar through to produce more anchorage.

 

I'll be coming off the concrete 400mm with a 100-150mm steel pipe extension, thick walled steel that'll be clamped between the bottom plate and pier adapter. That gives me a saddle height of @1600mm and the ability to swap out the pipe section to give different heights

Rebar is already in the hole and a cage will come up where the tube will be. Only sinking the tube in 100mm is only got to contain the concrete while it cures. 

this is a mock up of top of the pier. The middle MDF disc is 300mm. The top MDF disc is 250mm, the same as the metal plate. The plate will be 150mm(ish) off the concrete to allow for sockets, cat 6 and usb hub to be mounted later. 

Edited February 11, 2019 by Anthonyexmouth

[Anthonyexmouth]

Well the base is poured, no going back now. Just the pier to fill now. Hope I've got my heights right

 

[JamesF]

Good start

James

[Anthonyexmouth]

Yeah, glad I'm putting the cabling inside the pier. Got 2 laser cut MDF discs, one 297mm and one 350mm screwed together. The smaller one sits inside the tube to perfectly center the hockey stick. Probably picky overkill but better that it looks like there's some effort put into making it look good, gonna be stuck in the middle of the garden and if something is not centered or level it'll drive me nuts looking at it in the daylight

[Anthonyexmouth]

What kinda depth have other people set their studs into the concrete? I don't want to waste too much stainless steel.

[bottletopburly]

Screwfix sell SS Threaded Bar in 1m lengths so 500mm overall and bend last 150mm inward  so it can’t unscrew out concrete.

[Anthonyexmouth]

Oh I've got the 16mm stainless. Just wondering how much to sink in. Was thinking 250-300mm in the concrete

[Astrokev]

That would be plenty I think. I used 12mm stainless. I think I got 1m lengths and cut them in 2, so probably sunk about 400 into the concrete but I think this was excessive. It's absolutely solid. 

[Anthonyexmouth]

I'm out of gas so struggling to put any bend in 16mm stainless. Might just have to rely on the square washers bolted on the ends. There won't be any rotational strain as the plate and adapter are fixed with nuts tightening against each other and not turning the rod itself. 

[Anthonyexmouth]

Here's the approx finished height. Wasted a sunny day sorting cables in the workshop. Should have found my true north but that'll have to wait for the next bit of sunshine. Going to be so nice having all the cable internally routed. 

[symmetal]

I set my studs into the concrete after the concrete had set. I had an Astro Engineering pier top kit from years ago. There were three 300mm M20 rods to fit the pier top plate. Like you there were nuts to fit above and below the pier top so there was no great rotational force on the studs themselves. I drilled 25 mm holes about 200mm deep in the set concrete and used Anchorset two part styrene based resin to glue the studs in place. I cut the bottom of the studs at a 45 degree angle to give some rotational resistance and they've been rock solid to date. 

Alan  

Edited February 14, 2019 by symmetal

[Anthonyexmouth]

Cool, I've got 4* 16mmx500mm studs so I'll probably set them in 250mm and then I've got plenty to play with above the concrete. 

[Anthonyexmouth]

Well, got the alignment done last night on a totally clear sky before the final pour this morning and now it's done. Pier plate drilled and maybe I'll paint it but I'm planning on splurging on a stainless one as soon as everything is finished and this steel one will be a pattern for any changes. Also going to get a white plastic disc cut to cover the concrete top.

 

[Astrokev]

Looking good. I presume the white pipe is a cable conduit. What cables d'you plan to route through this?

[Anthonyexmouth]

1 minute ago, Astrokev said:

Looking good. I presume the white pipe is a cable conduit. What cables d'you plan to route through this?

Cat6, usb, 12v and 240v

[Astrokev]

I had the same plan to run data and power through a single conduit for my pier (similar pier to yours). I was recommended not to run power through the same conduit as data as this could risk signal interference. Please don't think I'm preaching here, as I'm no expert, but several folks said the same thing so maybe this is something to consider before you're too committed? 

Following the advice I installed a second conduit for data.

Edited February 16, 2019 by Astrokev

[Anthonyexmouth]

I'll be using shielded cat6 and usb cable and the 240v is 2.5mm SWA so plenty of separation. 12v shouldn't be an issue but if it does cause any problems I'll change that for 1.5mm SWA too