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  #21  
Old 26-02-2020, 05:59 PM
appiice (Ed)
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3 or 4

Hello Paul

Good luck with your build, some comments if not to late,

3 or 4 bolts, 4 is no harder to plumb the pier with than three, just think of adjusting the bolts on a diagonal pattern. Bottom right, top left as one adjustment pair, bottom left top right as the other pair.

Mpa, not really an issue, you are going to mount, what, a mount and scope weighing, say 100Kg's and your mass base will be about 2.5 tons, the bolts won't pull out of poorly batched 15Mpa concrete. if you are worried 35Mpa in theory is water proof.

I am a licensed builder and built a dome and Obs 2 years ago, your mass base will be fine, don't over think it.
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  #22  
Old 27-02-2020, 07:27 AM
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The_bluester (Paul)
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Actually, the block was poured on Saturday, I went with 25Mpa in the end and a light reo box to help avoid cracking. I have decided to use four bolts as the pier base I have is square and that allows me to spread the bolts as far apart as possible. This will be an AP pier so precise level won't matter that much.

I am waiting another two weeks for close to final cure then drilling holes to chemset the bolts in. I could probably do them this weekend given it is not really stressed much, the nuts more or less only need to be snugged up rather than torqued down to hold the Sydney Harbour bridge, but the last thing I want to do after digging that hole by hand is pull chunks out of it by being impatient!

Last edited by The_bluester; 27-02-2020 at 07:45 AM.
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  #23  
Old 08-03-2020, 01:35 PM
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muletopia (Chris)
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Smile digging

Paul,
Somewhat late but I just found an old print kicking around in our implement shed so the pic is a scan complete with grot. It shows that all is not hard labour digging the hole for the concrete.


Chris
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  #24  
Old 08-03-2020, 07:51 PM
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The_bluester (Paul)
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Ha, I never had a cup of tea down there!

The concrete is curing away, I am going to drill and chemistry set some bolts and mount the pier next weekend. It will be a week or so away from final strength, but it is not like this has to hold up a bridge or anything.

Then Andy01 will be keen for me to start digging his!
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  #25  
Old 19-03-2020, 01:40 PM
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So. First light for the pier was on the weekend. Setup is so much easier than before without needing to mess around with getting a tripod aligned close enough to the pole.
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  #26  
Old 19-03-2020, 01:50 PM
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Outcast (Carlton)
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Nice one...

When are you putting the 'building' around it...?

You know you want to...
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  #27  
Old 19-03-2020, 02:23 PM
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The_bluester (Paul)
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In Current circumstances, who knows. But if we see a lockdown coming a quick trip for some RHS, some quickset for footings and Tracks for the roof and I am set. I have everything else including plenty of corrugated iron to clad it as a temporary building.

Last edited by The_bluester; 20-03-2020 at 07:27 AM.
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  #28  
Old 20-03-2020, 12:00 AM
Sunfish (Ray)
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Excellent work of concrete and steel. A pier is a great thing.
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  #29  
Old 20-03-2020, 07:31 AM
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It is funny, I never really though that the concrete would feel different to a regular slab (Due to the depth and mass) but it does. If you jump on it it actually feels more solid and "dead"

That will be an experiment for the next night I suppose, get it set up and the guider running then jump up and down on the concrete to see if it shows up in the guiding.
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  #30  
Old 20-03-2020, 10:26 PM
Sunfish (Ray)
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I have administered construction of 3m concrete cantilevers and one surely does feel vibration from a heel drop. Bridges can be the same with traffic. You could dance around on your pier block and not notice a thing in the imaging.

Quote:
Originally Posted by The_bluester View Post
It is funny, I never really though that the concrete would feel different to a regular slab (Due to the depth and mass) but it does. If you jump on it it actually feels more solid and "dead"

That will be an experiment for the next night I suppose, get it set up and the guider running then jump up and down on the concrete to see if it shows up in the guiding.
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  #31  
Old 21-03-2020, 10:09 AM
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People don't realise how flexible concrete is. There is a substantial bridge I cross regfularly and when you get stopped on it you soon realise that it is gently bouncing up and down. By the feel of the way it moves I reckon has a gentle sine wave of movement bouncing from end to end.

Last edited by The_bluester; 22-03-2020 at 09:41 AM.
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  #32  
Old 21-03-2020, 11:07 PM
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Not to forget the seasonal thermal expansion of concrete arch dams. The centre may move up and down stream a metre or so during the course of a year.
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  #33  
Old 22-03-2020, 02:27 PM
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The_bluester (Paul)
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That much?

How does concrete compare with steel regards thermal expansion? I assume it would have to be similar or the reo inside would lead to some crazy stresses.

Last edited by The_bluester; 23-03-2020 at 08:11 PM.
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  #34  
Old 23-03-2020, 01:34 PM
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Sorry Paul,
A bad head moment here, the documented thermal effects on concrete dams are cracks in the down stream face. When I can contact my dam engineering friends I will find the actual excursions.
It is large clay core earth filled arch dams the have large excursions, as surveyed here in WA.
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  #35  
Old 25-03-2020, 01:04 PM
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Still, regardless of what is inside the shell, that is an amazing amount of movement. I suppose though that the actual expansion ratio though is probably expressed as a fraction of a percent?


All the things that go into engineering things. Like people not liking the old noise on trains as they go over the gaps in the rais for expansion (ANd them not being suited to high speed use) so now they weld them, and in the summer the risk is of railse expanding and going too far out of alignment (I have to use the term buckling)


Or just getting the cant of a bend wrong so that trains do not go through it at the natural speed of the bend and they either ride up or fall down the cant as they go around and wear out the wheel flanges on one side or the other. Which happened in Melbourne where both high speed commuter and slow freight trains use the same line, if you recall the wheel wear issue on the Ballarat trains.
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  #36  
Old 02-04-2020, 12:55 PM
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Well, zero progress toweards putting a shed over this, but I have found that even though I need to break everything down to carry it out 25M away where I was cheating before and simply brute force hauling the whole kit (Scope, cam, mount, tripod etc) out in front of my garage, it is taking less time to set up as the polar alignment is so much quicker. Octans is ALWAYS visible via the Polemaster software as soon as it is dark enough instead of trying to get the tripod aligned the same and spending time hunting around for Octans.
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  #37  
Old 03-04-2020, 09:32 AM
Sunfish (Ray)
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A pier is great thing. I have two of differing heights now made out of leftover 6mm 102 pipe on my slab looking North and I am thinking a third in the garden looking South could be good.
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  #38  
Old 03-04-2020, 04:22 PM
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The_bluester (Paul)
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While it will be really nice to have some sort of shed over it, but I am loving having a pier there.
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