Pier Construction


Tim Khan
 

--- Mark Jenkins <markj@pcsincnet.com> wrote:

The sonotube/concrete only solution has me worried
about cracks in the
concrete where the bolts protrude. Are these fears
unfounded?

Just a note on sonotube/concrete:

Concrete cracking around the bolts are due to, a
couple of items. First cracking is ussually due to too
much water in the mixture (shrinkage during curing),
use between .25 to .35 water to cement ratio.
Secondly, be sure that you use horiz. reinforcing like
#3 ties at 8" and where the anchor bolts are use #3
ties at 4" to increase the confinment.


--- Mark Jenkins <markj@pcsincnet.com> wrote:

I posted this to alt.binaries.pictures.astro but
have yet to get a response.

Looking for any and all advice for constructing my
permanent pier.

Is a solid concrete pier better than a steel tube
set in concrete?

Initial thoughts are:

Dig a 4' x 4' hole 7' deep.

Pour 1' thick of reinforced concrete with 4 "J"
bolts set in the concrete.

Fabricate a steel pier that is constructed using a
8" - 10" mild steel tube
5/16" to 1/2" wall thickness with a 3/4" x 2'
square plate on the bottom.
Paint with industrial grade epoxy both inside an
out. Use the bolts at the
bottom of the now 6' deep hole to secure and level
the pier to the footer.
Fill the hole with reinforced concrete and let cure
for about a week. Fill
the steel tube with concrete and let cure. Weld a
3/4" steel plate on top to
be used to fine adjust the level of the Meade
SuperWedge or AP 400GTO that's
due in July, or future AP mounts like a 600 or 900.

Or...

would it be better just to pour concrete in a
sonotube with bolts at the
top?

Looking for a proven design and willing to go to
extremes to assure complete
stability.

The sonotube/concrete only solution has me worried
about cracks in the
concrete where the bolts protrude. Are these fears
unfounded?

Thanks.

--
Mark Jenkins
markj@pcsincnet.com
http://www.pcsincnet.com/astronomy/



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John J. Kasianowicz <surpher@...>
 

Hi Mark,

I don't know the specific answers to your questions, but you might want to
contact John McCubbin (mccubbin@usit.net). His Halfmoon Observatory
(http://www.usit.com/mccubbin/astronomy.html) looks great and has some nice
design ideas. John is very helpful.

His metal pier/concrete deadman design has several neat features. First,
different hollow metal tube piers can be interchanged easily (with some
grunting). Second, it looks really massive (Le Seur's AstroPiers suggests
using much less concrete, which is probably unwise for an observatory,
particularly if you ever want to do imaging). I'd tend to err on the side of
using too much concrete placed too deeply. Third, the base of the tube that
mates with the ring (that bolts to the metal atop the concrete deadman) is
reinforced w/metal ribs (gussets?).

If you go this route, and if you use a wood floor instead of a concrete
slab, John's design makes it easy to remove the pier and cover the deadman
with wood flooring (you have to make sure that the bolts coming out of the
deadman are below the level of the bottom of the wood floor). If your
observatory is designed with flexibility in mind, it can be used as a garden
tool storage shed or a kid's playhouse by whoever buys your house (i.e. the
structure will ADD to the value of your home).

I'm in the next to final design stage for my own backyard observatory. I'd
love to toss some ideas around, if you like.


Best,
John Kasianowicz

Looking for any and all advice for constructing my permanent pier.


Mark Jenkins <markj@...>
 

I posted this to alt.binaries.pictures.astro but have yet to get a response.

Looking for any and all advice for constructing my permanent pier.

Is a solid concrete pier better than a steel tube set in concrete?

Initial thoughts are:

Dig a 4' x 4' hole 7' deep.

Pour 1' thick of reinforced concrete with 4 "J" bolts set in the concrete.

Fabricate a steel pier that is constructed using a 8" - 10" mild steel tube
5/16" to 1/2" wall thickness with a 3/4" x 2' square plate on the bottom.
Paint with industrial grade epoxy both inside an out. Use the bolts at the
bottom of the now 6' deep hole to secure and level the pier to the footer.
Fill the hole with reinforced concrete and let cure for about a week. Fill
the steel tube with concrete and let cure. Weld a 3/4" steel plate on top to
be used to fine adjust the level of the Meade SuperWedge or AP 400GTO that's
due in July, or future AP mounts like a 600 or 900.

Or...

would it be better just to pour concrete in a sonotube with bolts at the
top?

Looking for a proven design and willing to go to extremes to assure complete
stability.

The sonotube/concrete only solution has me worried about cracks in the
concrete where the bolts protrude. Are these fears unfounded?

Thanks.

--
Mark Jenkins
markj@pcsincnet.com
http://www.pcsincnet.com/astronomy/