Anti-vibration observatory piers (Part 2: The foundation and fastening of the pier)

[@kippyjohnson]

What a difference between the ring, and the thud! Incredible!

[@jamesdixon2085]

You talk about drilling holes in the cured concrete and using epoxy. If you've decided on the pier ahead of time why not use a template and insert the bolts into the wet concrete? Seems like that would be easier and better.

[@ColeRees]

A bit late bit for anyone else who clicks on this, both ways work. I do remodeling and whenever we have to drill new bolts into foundations we use epoxy and go at least 8 inches down. It'll hold.

[@Kyle_Hubbard]

@@ColeRees 8 inches is always enough.

[@ScoutCrafter]

Outstanding tutorial!!!

[@fredmercury1314]

4:40 What if I'm operating it remotely from my sofa?

[@mike150160]

What torque were you saying the bolts had to be at? It sounds like kilograms but did you mean kg.m (160 seems very high) or kg.cm (seems a bit low)

[@FyreMunky69]

Excellent video

[@tyrelli001]

Why don't you just fill the pier up with concrete to stem vibration?

[@RocketPlanet]

Hi - actually the number 160knm is what is known to many high precision industries as a WAG (Wild A**e Guess)! The wrench I used, with difficulty as I had to put a pipe on it to get leverage, clicked over at about 140 before the nuts locked off. I just boosted this number for ‘safety’. I actually regret mentioning any numbers here at all as it has led to confusion. I should have said simply, the nuts need to be done up as hard as you can without wrecking the thread on the studs. KR RJD

[@dave4gee]

Just to be pedantic chaps, a block of concrete 1m x 1m x 1m (1m^3) is about 2.3 metric tonnes, substantially more than the often quoted "metric tonne" that is quoted in the video. Otherwise an excellent video. DaveGee Australia

[@RocketPlanet]

Hi Dave, no you go ahead, I'm partial to pedantry. Dry or wet? I'd be surprised (not shocked) if the dry weight was over 2 tonnes. In practical terms you start out aiming for a 1m^3 hole but because of tapering (fatigue!) it ends up less anyway. The key is that 1 tonne should be a minimum to aim for. I've only got one real experience with this (n=1!). I once had an experimental container of sand that was a whisker over a cubic metre and it weighed in at under 2 tonnes - wet. KR RJD

[@yasnac7576]

Why Glue in the studs? Why not a steel frame inserted into the wet concrete at the time of the pour?

[@RocketPlanet]

Hi Scott. Well it's mostly down to what kind of procedure you can safely recommend in a video. The 'glue' method can be done poorly and still get a good result. If a hole goes wrong, say on the slant (remember: I'm talking to DIYers, not construction professionals), you can always shift the pier a couple of inches or rotate it a degree or so and re-drill. The whole procedure is in small safe steps - with minimum performance jeopardy. If the studs set in concrete 'fail' for any reason, you need a diamond cutter, and there's aggro a-go-go! The frame concept is a safer embedding method - probably the best solution when perfectly executed (deep enough to resist corrosion and consequent expansion spalling, etc). But it's hard to recommend to a broad viewer-base with average construction skills. I think if we say 'glue the studs', anyone with practical experience, and is familiar with the issues, will go their own way. That said, glueing is still the safest method in terms of the staged approach. Step one, you cast the concrete block and wait for it to cure. And then you fix the pier as a completely separate step. Combining both steps puts the lone installer under considerable pressure contending with two critical foci rather than one. Just my opinion. Thanks for the helpful message letting me clarify this point. KR RJD A&NTV

[@yasnac7576]

@@RocketPlanet now the issue is finding a concrete contractor that will leave just a little bit more on his truck to satisfy you. Because they won't come out for just one yard of concrete. They have to have a major pour. My son is in construction and he said they'll probably offer you a small site mixer that'll do 60 lb at a time so you'll be doing it yourself. Ugh I'm too old for that!

[@robertjdalby96]

Hi Scott Yes I'm too old for that too. Don't take my recommendations too literally. You only need about a ton (say 200lbs) under the pier for maximum benefit- and that's only about half a cubic yard. I'd be surprised if you can't find someone to bring it for a small premium. If you have enough (easily pleased) friends/neighbours you might try the old 'concrete party' rouse. You'll need the site mixer, sand etc, as well a quantity of beers and barbeque fodder. Tip: don't skimp on the beers - a pier is forever. KR RJD A&NTV

[@yasnac7576]

@@RocketPlanet well I already have a whole dog as big as yours and it's not going back now.

[@yasnac7576]

@@RocketPlanet Just as a follow-up Yes I did the 200-lb pier. It doesn't work.... You need to weight! 👍

[@Rarius]

1 cubic metre of concrete weighs 2.4 metric tons, not 1 metric ton.

[@forrestroche2909]

I had that immediate reaction, that's a pretty big mistake from someone who presents himself as a fact-based purveyor of high tech pier installations. And he says it twice.

[@RossSkilton-hl8bf]

A cubic meter of concrete and reo has a mass of about 2.5 metric tonnes

[@barlow2976]

Very interesting, you obviously know your stuff. I happened across this because I am thinking of building a pier for my 20x80 bins on a p-mount, as I only have a camera tripod that can support 5kg, which is pushing it. I had planned on drilling into the shale 2ft+ and sinking either a section of railway line or an Acrow prop, with appropriate plate welded on top.I can't afford a tripod that's man enough, and have those materials on the farm. I'm just worried that having,say, 5ft of steel sticking up will allow flexing, and vibration. Or will it suffice for 20x bins ?- I'm just trying to improve upon my over-loaded tripod.

[@8Zeitgeist]

We're not worthy!

[@mar504]

My god... so much overkill, you aren't anchoring a bridge.

[@RocketPlanet]

Well spotted; as you so rightly say, we're not anchoring a bridge. Or a power tool. Or a garden shed - or any host of things that folk are generally, and successfully, experienced in providing a foundation for. But we are mounting a 14" telescope, and this is, in principle, a very sensitive seismometer capable of detecting variations of 100th of an arc-second in a 1000th of a second time interval. Indeed, the instrument can detect a human being walking 30m to 40m (130ft) distant simply from small deviations in the moment to moment position of a star. Decades ago now, I thought like you and placed too much trust in my general experience of conventional building principles. It took many years and much practical experience (sadly, building and advising on 50+ or so pier installations - incorrectly!) before finally gaining some grasp of what was actually happening on a small but vital scale on telescope and pier installations and getting it, if not perfectly right, at least right to a standard I now feel safe in recommending. The problems with telescope piers flow from the very simple, but little-recognised observation that steller wander derived from instrumental vibrations (and the oscillatory motions typical of a dynamic mechanical system like a telescope and its mounting in particular) look identical (at the film-plane or on an imaging chip) to seeing induced steller wander. Go on to any amateur astronomy internet forum and you will find literally thousands of posts from people (often quite experienced sensible people) bemoaning their poor 3+ arc-second seeing conditions. Unless they have completed tests to properly discriminate between vibration and seeing they are, to put it bluntly, just guessing. Which is a shame because their actual seeing/instrumental imposed resolution limit may be much better - indeed, almost certainly is better. I realise you didn't know any of the above - you wouldn't have sent that post if you did. But my reply is aimed more at those who imagine their experience of the black-smithery required to mount a power tool on a steel support equips them to understand the mounting needs of scientifiuc instruments. It's important to 'know' when you don't know something and act acordingly - usually by maintaining a modest silence and keeping those restless fingers away from the keyboard. Thanks for posting and allowing me to challenge those assumptions. KR RJD A&NC TV

[@Handles-R-Lame]

Damn. Talk about a burn to nth degree.

[@woody5109]

40 years as an engineer and I can tell you, you are 100% over built. It’s just a little telescope, what 40, 50 lbs…so over built. A cubic meter of concrete weights 2.4 tons, that would easily secure a 40 foot flag pole. You guys are completely out to lunch with this build.

[@nighttrain1236]

The concrete isn't acting like a traditional foundation, it's there simply as mass, which makes vibration less noticeable by reducing the frequency...or at least that's my take on it. Perhaps the same could be achieved with a more modest concrete pile or block and a couple of tons of ballast?

[@silicononsapphire5102]

Rubbish. Thats one way to put people off. Use high tech talk for a simple job and over engineer things so you need to spend more cash. Makes me wonder how the Victorians and the rest before them managed. Thats a small observatory so I guess you won't be spending much time in there. More likely sitting at a desk in the warm with the computer taking pictures. If you're taking pictures that makes you a photographer, not an astronomer.

[@jcinaz]

I suppose you think that gazing into an eyepiece and drawing images of what you see is what today's professional astronomers do all night? If Victorians had access to CCD cameras, they would have used them.

[@mrsqueaksqueak8686]

+SiliconOnSapphire "If you're taking pictures that makes you a photographer, not an astronomer." - I see, by your logic, Edwin Hubble was a photographer. Most professional astronomers do not spend their time looking through eyepieces. Where is the eyepiece on the Hubble telescope? Your logic falls-down when one realises that the naked-eye cannot see much of the wavelengths that an optical telescope can capture. Then there is x-ray and radio astronomy. Furthermore, there is a thing called the internet, so modern professional astronomers never need to visit the telescopes they use. Your comment was quite simply: Simplistic rubbish.