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To the ones that built a concrete pier... question

Started by IGastaldo, 06/10/2005 03:18PM
Posted 06/10/2005 03:18PM Opening Post
I'm finally finishing up with the paperwork/permits to start building my own roll-off roof observatory in my backyard... (light polluted, but I guess "something" is better than "nothing"!) wink

Question:

How did you secure the Sonotube in place, in order to fill it up with concrete?
I'm planning on using an 8" diameter tube for the pier, in order to support the 10" LX-200GPS. (comments/advise always welcome) 8)


Thank you for your attention, and clear skies!

Ivan Gastaldo 8)
Coconut Creek, FL

Ivan's Observatory
Lat 26N 16' 48" Long 80W 10' 48"
[COLOR="Red"]Personal Website:[/COLOR] http://www.ivangastaldo.com

CCD Imaging and Processing/Deep Sky - Moderator
I like to complain about everything - Moderator
Posted 06/10/2005 04:14PM #1
Hi Ivan,
I would recommend pouring a concrete pier base with embedded bolts and using a metal pier on top of that. The advantages are a narrower metal pier and more flexability down the line should you change mounts or want to lower your mount. The disadvantage is the increased cost.
If you decide to go with the concrete pier, I would recommend increasing the diameter to at least 12". Not only would it give you much more lateral stability, but remember that you will need to embed bolts for your mounting plate on top and those have to be spaced in from the edge of the concrete to work properly.
The bottom of the Sonotube can be stabilized by temporary backfill or a frame of boards that are anchored to stakes in the ground. A frame of wood around the top of the tube is stabilized by angled boards attached to outlying stakes.
The most important rule in forming for concrete is to overbuild. Almost everyone underestimates the weight and power of wet concrete.
I hope this helps.

dan kowall
Posted 06/12/2005 01:06PM #2
Ivan,

For my C11 I also used a 12" concrete filled sonotube. 35 bags of hand mixed concrete in the hole and tube with a 4" prefilled steel basketball pole down the middle, found by the side of the road. I had everything perfectly lined up and nothing seemed to be shifting, so I made the mistake of NOT supporting the sonotube while it was drying. The pier was poured last summer and I thought it was pretty good. Until I put the dome walls up. A took a shot just before I painted it flat black this morning to show you how much an unsupported pier will shift. Anyway, once its black and Dan's top plate is leveled it should be ok.

Look forward to seeing future shots of your observatory. Good luck!

Regards,
Steve

Attached Image:

fugardi's attachment for post 92996
Posted 06/12/2005 01:10PM #3
Ivan, 1 more thing. Take the extra time to pack the concrete down with a 2x4 as you fill the tube. I noticed a lot of air bubbles at the lower edges on mine. I did not start packing until it was almost full which was too late. Good luck!

Steve
Posted 06/15/2005 10:47AM #4
Ivan. Looks like you are getting a lot a good, free advice! Last night I connected my base plate to my pier and found almost no room to get to the bolts underneath. Also, the bolts sticking out of the concrete were not all exactly at the same height. To optimize the setup, 1 bolt had to be flush with the top, to give another barely enough thread to tighten. It's ok but could have been a disaster.

Having gone through that, I've attached a shot of my base plate setup right before I mounted my telescope base. There is only 2-3/4" clearance from the top of the concrete pier to the top of the j-bolt. Ideally, I was going to "double-nut" the base but I did not have enough space. Based on this, I would recommend minimum 4" from concrete pier to bolt top. You can use your top plate as a template when filling the sonotube. I only used 1 2x4 spacer, you should try for 2.

According to weather.com, Saturday night may be clear so I am shooting for first light then...

Good luck!
Steve

Attached Image:

fugardi's attachment for post 93083