| Roger51 |
| (member) |
| 07/03/09 10:50 AM |
Concrete pad for 16 Lightbridge
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I have a couple of questions. I’m getting close to pouring a 3 foot square concrete pad for my 16 “ Lightbridge in a 11.6 x 11.6 observatory. At first, I planned on just bringing the pad level with the floor but after thinking about it for a while I’m contemplating whether or not this is a good idea.
The concrete pad will be 18 inches thick if level with the floor. My thoughts are if somewhere down the road I decide to add a tracking system is there anything I should do now to ensure I won’t run into problems. Also, would a leveling system such as four J bolts placed into the cement with a plate of some sort for the scope to sit on be a good idea for making up any difference from small ground movement? If I took this approach I would leave the concrete pad below the floor by two inches to compensate for the thickness of the plate.
Lastly, what is a good filler to use between the concrete pad and the floor? I think I remember someone in the past mentioning expansion foam.
Much appreciated,
| Kaizu |
| (sage) |
| 07/03/09 02:04 PM |
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Re: Concrete pad for 16 Lightbridge
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Why four bolts? Three are easier to adjust.
Closed cell type, soft polyethylen foam is quite good between the pad and floor.
Kaizu
| Roger51 |
| (member) |
| 07/03/09 06:12 PM |
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Re: Concrete pad for 16 Lightbridge
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Kaizu,
I have four 1/2 x 6 stainless steel bolts. They are not a J-Bolts. Is there any trick I can employ so I can use them in the cement pad. That is, how can I make sure they won't eventually slip inside the concrete?
| Kaizu |
| (sage) |
| 07/05/09 03:39 PM |
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Re: Concrete pad for 16 Lightbridge
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If they are full threaded, you can tighten one holed square plate against the screw-head by a nut and put that in the concrete. If there are not screw-heads, then use two nuts and tighten the plate between them. Also the plate can be welded there.
By the way, reinforcing steels are not stainles. Black steel holds tighter in concrete.
Kaizu
| Roger51 |
| (member) |
| 07/05/09 08:09 PM |
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Re: Concrete pad for 16 Lightbridge
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Thanks! What I ended up doing was similar to your suggestion. First, I put on a nut and screwed it all the way down, then added an extra-large washer with another nut tightened against the washer. Once everything was snug, I put the bolt in a vise with just the washer sitting on top of the jaws. A few smacks with a hammer starting bending the washer on both sides. I finished the bend on an anvil. So essentially I bent the washer sides up 90 degrees. Hopefully this protects against slipping.