Genesis
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It all started with a circle in a field... |
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| ... and a "back of the napkin" sketch. |
Foundations
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Sonotube, that remarkably good friend of the observatory pier builder, turns out to be hard to find in Ireland. With the Celtic Tiger-inspired building boom, though, sewer pipes are a dime-a-dozen.
(They're also socketed -- which doesn't matter to us -- but tell a site manager that you'd be happy enough with one with a busted seal and you'll get it even cheaper.) |
The sewer pipe would be set about 1 foot deep in a 4 foot cube, with a steel reinforcement cage extending from the cube up to the top of the pipe. J-bolts would then be set in the top for anchoring of a steel pier for the final mounting.
Since I didn't feel like digging a 4 foot cube, now seemed like a good time to get a digger man out and have a cable trench dug as well. I installed 2.5mm² three-core armoured cable, which in retrospect was too small for a 150m run.
(I get a fairly significant voltage drop, particularly with a kettle plugged in. The current solution is to use a low-wattage "caravan" kettle.) |
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I couldn't find anyone to supply me with rebar hoops, so I bent my own around a log. This is a lot harder than it sounds -- even 1/2" rebar is pretty stiff stuff. (Springy too; note how much larger the hoops are than the log.)
I also fabricated some stainless steel J-bolts out of threaded rod. |
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The finished cage.
This section goes up the middle of the sewer pipe and down into the 4-foot cubic foundation.
Blockwork was added to the hole to hold the pipe at the right height. Additional reinforcement bars will be tied to the central cage extending out into the cube. |
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Did I mention that dang pipe weighs about 1800 pounds?
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I ended up spending half a day erecting some scaffolding pipes to allow me to winch up the pipe. While I bent the crossbar fairly severly, it did work, and no one died in the process. |
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| Just rewards. |
The Big Pour
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On the day of the big pour, we spent the morning getting ready for the concrete delivery. I ordered enough to do the 4-foot cube, after which we'd give it a few hours to firm up and then pour the pipe filling by hand. This was meant to ensure that we didn't have a cold-joint between the two, but also that the wet concrete in the pipe wouldn't just run out the bottom.
The two guys with the tamping sticks are myself and my buddy Gerry; my back is to the camera. The two lassies are my girls, out for a look-see. |
| After lunch, the race was on. We mixed and bucketed 1m³ of concrete up the scaffolding and into the pipe in the span of about 3 hours. After that, the J-bolts were forced into the wet concrete with a plywood template on top for spacing. |
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