Another pier design to critique

Here's a quick picture of the steel cage for the pier going together.

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Ahhh.... 20 ounces of Ireland's finest. When a lager just won't do -- when a long, hard day's work is done -- when you're in need of a bit of replenishment -- Guinness is for strength.


[SIZE="Small"]Oh, and that thing in the background? That's just an 1800 lb pipe sitting on some blocks in a hole in the ground.[/SIZE]


-- Jeff 8)

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Today I hung the steel cage inside the pipe (suspended from the wooden collar that also holds the pipe upright). I then wired in a square cage around the pipe in the hole, and tied it into the round cage coming out the bottom. The square cage is also hung (the hangers are a bit hard to make out, but the red arrows point to them).

The perspective (and lighting) isn't very good in the picture, the all the steel is suspended off the pit bottom by about 3".

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Today was the big pour. The cement truck arrived at 11am with 1.5m³ of concrete for the base. In this picture, the driver has just started the pour. The gentleman in the blue sweatshirt is a mate; I'm in the blue plaid. (My girls are the ones in pink. Gotta love the Wellies on the youngest!)

-- Jeff.

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I threw together a quick drawing for the steel pier that goes on top of the concrete one. I'm doing the top bit in steel for two reasons: more room around the scope for my Kendrick Ultimate III observing chair (a great chair!), and more flexibility to switch out piers for altaz fork, polar fork, or GE mounts.

I'm going to get quotes for both stainless and for powder-coated steel. Stainless would be really nice (especially here in humid Ireland), but it may be significantly more money. We'll see....

You'll note that some of the dimensions allow quite a bit of range. I find things tend to be cheaper if the machine shop can use stuff at hand, rather than having to machine down larger bits. So where the final dimension isn't really important, it's good to give plenty of flexibility.

BTW: I've posted a jpg of one of the drawings. I have the original (w/ top, side and bottom views as well) in a PDF -- if anyone wants the full Monty, give a shout.

-- Jeff.

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Back out at the site, I've been doing a bit of digging. The post foundation will get 1/2" of styrofoam, followed by 6" of hardcore across the whole circle, followed by sand blinding, a bit of polythene, and then 4 - 5" concrete.

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The wet concrete which went into the base did shrink. There's about a 1/2 to 1mm crack around the bottom of the pipe. The more important area (inside the pipe), which was filled with a drier mix, didn't shrink nearly as much. There are barely perceptable cracks around the edge of it (highlighted in red in the bottom picture), but there's an order of magnitude less separation than at the base.

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The digging complete, and the epoxy starting to harden, it was time to isolate the pier from the pad. I used 3/4" styrofoam, with a protective layer of torch-on felt over it (to keep the hardcore or concrete finishing tools from chewing up the styrofoam).

I also had to knock some of the edges off the base with a lump hammer. Since the base concrete was poured into a hole, it lapped up the sides a bit in places. These, once hardened, might have poked through the styrofoam, transmitting vibrations from the pad to the pier.

I'm hoping to get the hardcore tomorrow, but I forgot to call and order it today.

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Well, I did manage to get same-day service on the rocks. They arrived just after lunch.

Despite assurances that 1.2 meters was 3 tons, I've got serious doubts that all that mass fits in that there hole.... :S

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I hired a nice little petrol wacker to compact the hardcore.

(I used to think "wacker" was slang for "compactor" or something, but dang if it didn't say "Wacker" right on the front of it. )

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