Removable Pier Idea.

[perkil8r]

Just pondering an idea at the minute. I won't be able to get planning permision off the SWMBO to build an obsy, so I'm thinking next best thing here. I was going to build a very strong and sturdy non bouncy deck at the top end of the garden so I could set up with the mount etc. I'm in the fortunate position that I have an outdoor socket at the end of the garden, so power on demand too.

Then I got to thinking. What if I were to build the deck with a trapdoor in it. Then I could have a pier which is bolted to a few tonnes of concrete (slight exageration perhaps) but so I could remove it when not in use, meaning that SWMBO would be able to use the deck as, well, a deck. Does the idea sound at all plausable? How would one go about making it removable yet solid as a rock?

I was thinking a number of holes in a thick plate on the bottom so that it could slide over some studs sticking out of the concrete (a bit more technical, but you get the drift) then just bolt it down and away we go. Thinking 8 or so M10 or M12 in a ring with a slight difference in spacing so that it only fits one way around meaning less work to align. As I say, only pondering at the minute, it's dull and cloudy so plenty of time for thinking about such things.....

Another method I thought of was using some clamps, not sure exactly what they are called, but they are like a lever that you push into place, they use them a lot in fastening pressure chamber lids down etc so I'm sure you could get a good solid fix with them if you had enough of them. That would mean no messing about with nuts, washers, spanners etc....

Like these?

[carpman]

Sounds plausable will follow as i would also be interested and have contemplated some thing similar

[perkil8r]

The clamps I linked to have a clamping force of 1 tonne or 0.5 tonnes for the smaller version. Whilst I realise that a M12 bolt will carry more than this the actual requirement is far less. The issue with bolts really is the tensile strength and the amount they will stretch. If using M10 or M12 I intend using around 8 of them, and probably in Stainless, not only for weather issues but also tensile strength. With the clamps I feel they will be strong enough in theory, but would still go with 8 or so.

We need to bare in mind that if it's blowing a gale I won't be out there anyway and whilst tracking with motors the forces are going to be smooth so I doubt it will wobble enough to be noticable.

I think (if using nut n bolt method) 2 x discs of say 1/2 inch thick and say 12 inches dia would be the starting point. On both drill the 8 off holes. On 1 of the plates add 4 or 5 off holes threaded for M20 and thread the 8 off @ M12. In the M20 holes countersink from the top a little, prob 2 or 3mm. Then wind in lengths of M20 bar say 1m long each so they are just bellow the top face, "just" proud of the bottom of the countersink and weld filling the countersink. Then grind flush.

It the M12 holes wind in M12 x 40ish from the underside and tack the heads with weld. The 1m lengths of M20 would then go into the ground / concrete and the concrete would come just shy of the top face of the plate with the bolts through. The other 12" plate would then obviously go on the bottom of the pier column and get bolted down. Flat washers only would be needed as there won't be enough vibration to undo the nuts from use of the scope, or at least not enough to matter before the pier is removed to make way for SWMBO to get the table up and enjoy a glass of Pimms...

[steelfixer]

Hi there

The idea is perfectly feesable.

The 8 bolt fixing is way over the top though.

Why not just use 3 number 20mm chemfix anchours.

They will have more than enough tenstile strength for what you need.

Set them into a triangle pattern so orientation of the pillar is simple.

When you set up the pier cover the underside of the pier base with clingfilm.

Place a 30mm tall piece of steel in the center under the pier to allow for leveling.

Level the pier using the 3 studs untill perfect and then grout under the pier with a strong mortar mix or industrial non shrink building grout.

The cling film will stop the pier sticking to the grout. When it is dry it remove the pier, it will leave a perfectly level surface for when you replace it.

graham

[Zakalwe]

Dig a big hole and fill it with concrete. Float the top surface so it is smooth, and cast 3 pins into the surface (or bond them with chemical fixers. Space them so they line up with a Skywatcher pillar mount.

Then you can just drop the pillar mount over the pins, and job jobbed.

Or you could use three stainless threaded rods, and fabricate some "wing nuts" (stainless nuts with some short sections of 6mm bard welded to them to allow tightening by hand). This would allow you to bolt the pier down.

Have a look here for an idea for a another pie design

http://stargazerslounge.com/astro-lounge/69687-pier-mount-skywatcher-180-pro.html

[perkil8r]

Food for thought there, thanks.

I plumped for the idea of 2 x big plates as they are less likely to alter or get damaged by frost, dropping stuff on them etc. It would be easy to brush the plate to make sure there wasn't anything foreign on it, meaning that the pier would always be (in theory) in the same vertical plane (hopefully perpendicular!) I always believe in the wisdom of my old man who says "if in doubt, build it stout"