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Equipment Discussions >> Observatories

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dhaval
professor emeritus
*****

Reged: 07/21/08

Loc: Round Rock, TX
Anchor bolts for Skyshed POD
      #5533093 - 11/21/12 10:55 PM

I am looking to put a concrete slab in place for a future Skyshed POD XL3 and as I plan for the slab I am wondering where should I place the anchor bolts in the slab in order to easily anchor the POD when it arrives? At this point, I am thinking of putting in a 12'x12' slab with a concrete pier for the mount right at the center of the slab and the POD radiating from the center as well - I might need some guidance around that design as well given the fact that there is an obvious issue with the zenith. If I do have to move the center of the pier away from the center of the slab, then I am thinking of having a 12'x14' patio done and maybe off-centering the pier by 2 feet. Regardless though, how should I space the anchor bolts for the POD? I believe there are 12 anchor bolts and maybe I won't need all, but if I am going to put the slab in, I might as well put in all 12 right now.

Thanks,
Dhaval


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harpnfool
journeyman


Reged: 08/16/11

Re: Anchor bolts for Skyshed POD new [Re: dhaval]
      #5533310 - 11/22/12 02:30 AM

Cant comment on spacing, but as a rock climber of 25 years use stainless steel anchors. Preferably 5 piece Rawl 3/8". You wont believe how fast zinc bolts will degrade. Especially at ground level exposed to water.

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mclewis1
Thread Killer
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Reged: 02/25/06

Loc: New Brunswick, Canada
Re: Anchor bolts for Skyshed POD new [Re: harpnfool]
      #5533842 - 11/22/12 12:10 PM

Dhaval,

Don't place any anchors in the concrete before you finish your POD installation. As you do your POD installation you'll need to move the base around a little bit (to get the top of the walls circular so the dome rotates really smoothly) but sometimes the base of the walls won't be exactly circular and the bolt holes may not line up with what you've already installed in the concrete.

You will be much better off to use a common hammer/drill and a concrete bit to drill a few holes where the POD mounting points finally end up. No you won't need to do all 12 ... 6 will be very sufficient.

1/2" x 3-4" long lag bolts work very well when attaching to a wooden deck surface but for concrete you can get away with smaller diameter bolts. Once you drill a suitable hole you can add metal insert and then use something like 1/4" diameter bolts to hold the POD down. The size (diameter) of the holes will depend on what type of concrete inserts you can get locally.

Using some drilled holes with soft metal concrete inserts will also allow you to move the POD's position in the future once you figure out what type of pier offset will be most appropriate for your setup.

Yes an offset position for the pier is usually a good idea. It appears that the most popular amount of offset is around 16" (this is from some research and my questions to a number of POD owners a few years ago as I was planning my POD installation). Much more than 16" and you will seriously reduce your ability to move between the mount/pier and the wall on the side of the offset. The final amount is dependent on the type of mount/scope you have, how much room you need to have inside the POD, and to some extent your local viewing conditions (latitude, any obstructions, etc.).

I offset my pier a small amount (about 6") and used it for about a year like that before I then added a PZT to remove any zenith access issues.


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Startraffic
professor emeritus
*****

Reged: 02/12/06

Loc: Lat. 39.143345, Long. -77.1748...
Re: Anchor bolts for Skyshed POD new [Re: dhaval]
      #5534279 - 11/22/12 06:02 PM

Dhaval,
I have an XL3 & have moved it around a fair amount to get the "perfect" spot. I still haven't quite found it & it's been 2 yrs.

Clear Dark Skies
Startraffic
39.138274 -77.168898
518ft ASL


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