Well the 1st step to a permenant obs...a Pier and as they say..."what a pier".
Not cheap, but damn solid. 1.1m high, 500mm (sq) x 22mm bottom plate, top plate 15mm, gussets 10mm, Pier 220mm x 12mm pipe and lots of welding. All done by a local welding fab house all powder coated "astro black".
Yep... got it from the wharf, they used to tie up the QE2 to it...well not really but the damn things is as solids as.
Has a top hole to allow sand backfill and I have some top adapter plates: a Losmandy MA and 300mm round 1" alloy top plate to cap off the pier. I didn't see the sense in an adjustable top plate for levelling.
This pier should be able to hold much larger mounts...you never know!
Now the real works for the rest of the obs begins.
Well if it won't work as a pier you could always put a rocket motor on it and fly it :-)
Looks like it should do the job nicely, that should hold a good tonne with little to no movement, those gussets are huge, I love it. Made a couple of piers myself and never thought of using full length gussets.
Well if it won't work as a pier you could always put a rocket motor on it and fly it :-)
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I don't think NASA has big enough solid boosters...around 200kgs mass at a guess.
I debated about the gusset lengths and decided what the hell...they will help reduce flex by holding the pipe under tension on each corner and caterpillar welding along these should help reduce harmonics nodes. Thus placed the gussets to base apex's.
Well that's the theory.
I was going to concrete in studs to the base but was recommended to ChemWeld the base bolts to the concrete pad. Sounds interesting...better start researching about this.
edit:
Hi Rodger. Of course all structures have a natural harmonic freq. At a guess, along a pipe this will be a node half the pipe length ~1/4 wave of the natural freq. The sand is to help dampen & absorb oscillations. Just like a dead blow hammer I guess. The theory was that the gussets welds would change the nodes points along the pipe by creating hard points.
Well, as for mechanical engineering, what I know you could write it all on the back of a postage stamp! Just stuff I picked up researching piers and deflections. In reality vibrations are probably the least of my problems.
And I thought mine was a beast (http://www.iceinspace.com.au/forum/s...ad.php?t=81601)!
Your not going to have to worry about vibrations Brendon it's either the chiropractor or the hernia operation costs that'll get you!!
Have fun.
And I thought mine was a beast (http://www.iceinspace.com.au/forum/s...ad.php?t=81601)!
Your not going to have to worry about vibrations Brendon it's either the chiropractor or the hernia operation costs that'll get you!!
Have fun.
Cheers
Stephen
Stephen...yours is definitely sexier in red....mine was like ...as Henry ford would say they can have any colour as long as it's black!
I debated about a level adjusting plate. Don't know if I made the right choice but I figured I can shim the top plate that bolts to the pier if worst case. But there again...once drift aligned I'll not be needing to adjust it again.
Last edited by wasyoungonce; 15-06-2013 at 04:01 PM.
I like what you have had done. Very solid and very little deflection if any present. I did something similar myself and it carries a huge amount of gear on it. Nothing wrong with making this very sturdy.
Your probably spot on Paul...I just asked for a top hole in-case I decided to back fill it. Too late if I wanted and had no hole.
I want to try measure the natural resonance of the damn thing just for interests sake. Guess I'll be browsing the web for some time on this.
I was advised to "chembolt" the thing down. I know zilch on this atm. The pier is way over built but I wanted that. You never know what you will want to put on it in the future. I went for steel...it can be moved if really necessary.
In theory I can bolt sturdy wheels to the base holes and wheel it around to move, like a miss-formed Daleck, cannot do stairs though! Where's Davros when you need him?
In its temporary location on my front verandah I just used expanding Dyna bolts and haven't had any problems, but I was looking at the Chem Bolts the other day and they do look better.
Load on theses anchors is generally low since the telescope with counterweights is sort of balanced on the pier - relatively speaking. Therefore, mechanical anchors like Dynabolts will easily do the job for you (one M12 mechanical anchor has a pull out force equivalent to a 750kg load!). However, most mechanical anchors don't have many contact points and so if you have a poorly drilled hole you won't get the full load capacity of the anchor.
Chemical anchors have two advantages. Firstly, you get full contact with the concrete for the length of the anchor and, secondly, you don't induce a stress into the concrete as you do with mechanical anchors as you try and flare out the bottom to grip the concrete. If you couple this with a good grade steel you could reach pull-out strengths 50%-100% more than a mechanical anchor.
But in saying that, you have this super pier now and you want to compliment it with the best anchors you can get. My existing pier has four M12 drop-in anchors (these sit flush with the concrete and have a bolt going down)and they're holding my 10" newtonian without a problem. Though, when I get a new pier I'll be using chemical anchors.
I was thinking dynabolts would induce splitting force in the concrete if they were all tat the same depth and if the bolts was too close the pad edge.
I also thought about in bedding bolts in the wet concrete pad using a template. But doing this means if I have a slight misalignment, it all goes to pot. I had the base holes (Qty 12, 2 either side near gussets, one in centre between gusset quarters) oversized drilled to 20mm for this. So I can use smaller threaded rod, lets say M16...which allows for some bolt misalignment errors.
But Chem bolts certainly have an attraction I'd like to try and I really don't need to use all the bolt holes.
Brendan, having twelve M16 rods chemically bonded is ample and should give you a rock-solid platform - roadside bollards don't have this! However, I think the hardest part for you now is drilling the holes where you want in the concrete. Drill bits tend to wander as soon as they hit aggregate and this can easily put you off 5mm if you're not careful. It should be OK if you drill into the concrete using the holes of the pier as a guide (i.e., the pier is in position while you drill). Ideal case would be to use a diamond core bit if you can get hands on one.
If you haven't set you pad yet then I would recommend making a template and setting the rods that way. It will be a better bond and will be more accurate than drilling.
I haven't done the pad yet I waited for the Pier, next the Pad but I didn't want to jump the gun. I was tossing up to either concrete in rods using a base template or to Chem bond.
Concreting in the rods has an appeal, I can weld them on mesh to hold shape.
But as you said Chem bond is appealing indeed. Looking at around 1m^3 concrete and having a base pad step up to fit the base plate buy around 300mm or so so I can adj the pier to the right height. If I have a 300mm setp up then obviously dynabolts are out but also isolates the floor from the base.
Probably going to order pre-mixed concrete, much quicker that way. or...a hire a mixer and get some cold ones on ice! Should be interesting if I do that!
Why the sand fill ? is harmonic vibration a problem?
