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Equipment Discussions >> Observatories

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Midnight Dan
Postmaster
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Reged: 01/23/08

Loc: Hilton, NY, Yellow Zone (Bortl...
Re: Pier diameter? new [Re: HunterofPhotons]
      #6045381 - 08/25/13 03:06 PM

Quote:

Just out of curiosity, how many mount piers have you seen pulled apart by frost heaves?

dan k.




None. The few piers I've seen have all had rebar in them and have not been pulled apart by frost heaves or any other reason.

-Dan


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roscoe
curmudgeon
*****

Reged: 02/04/09

Loc: NW Mass, inches from VT
Re: Pier diameter? new [Re: Midnight Dan]
      #6046157 - 08/25/13 11:01 PM

Quote:

Quote:

Just out of curiosity, how many mount piers have you seen pulled apart by frost heaves?

dan k.





I'm a small-town contractor/carpenter, and I've seen quite a few that have pulled apart from frost action - mostly foundation piers under porches and decks. They normally seem to break about 6" below the ground surface, or near the bottom of a j-bolt or short piece of rebar put in to attach a post anchor to.

On the other hand, an 8" pier with a single 1/2" re-bar in it can be cracked, but cannot be broken fully or pulled apart, even if slammed with the bucket of a backhoe in an attempt to break it into pieces for removal. With 2 re-bars, they're hard to even crack, and must be in both cases dug up whole.

While they're not quite as rust-resistant or strong, I often use lengths of threaded rod for re-enforcement, because they serve both strength and anchor purposes at once.
Russ


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dawziecat
Carpal Tunnel
*****

Reged: 10/20/10

Loc: Rural Nova Scotia
Re: Pier diameter? new [Re: roscoe]
      #6046540 - 08/26/13 08:35 AM

I have ordered the top plate from Dan's Piers but I can not wait for delivery of the stainless steel L bolts. They are not available locally either. Dan suggested SS threaded rod with a couple of nuts on the end instead. My contractor suggested bending them but how can I bend 3/4" rod?

Another possibility are galvanized L bolts.

So, options are:

1/ SS threaded rod with nuts.
2/ SS rod "home bent" into an L shape (if possible!)
3/ Galvanized L bolts

Opinions?


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Midnight Dan
Postmaster
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Reged: 01/23/08

Loc: Hilton, NY, Yellow Zone (Bortl...
Re: Pier diameter? new [Re: dawziecat]
      #6046566 - 08/26/13 08:56 AM

Hi Terry:

You can get the stainless L-bolts at McMaster-Carr here:
http://www.mcmaster.com/#l-bolts/=o8ciz1
BUT ... they are more expensive than the kit from Dan's. You might get away cheaper by asking Dan to overnight his kit to you. He includes the thin-profile jam nuts, stainless washers, and fiber washers that work well for attaching a mount.

Keep in mind that a normal L-bolt is designed to hold something, like a house foundation, tightly to the concrete. The force of the nut tightened against the foundation attempts to pull the bolt out of the concrete, so the "L" part is necessary to resist that pull.

However, your mount is a totally different situation. Most people suspend the mount above the concrete between two nuts on the threads. There is ZERO force trying to pull the bolt out of the concrete. In fact, just the opposite is true - the weight of the mount and optical gear are trying to push the bolts INTO the concrete. An "L" at the end can help a little by spreading out that weight, but it isn't really needed. Concrete is so strong in compression that a simple piece of threaded rod should work fine.

If you want to bend the end yourself, it should be easy to do. Just clamp the rod in a vice and beat on the end with a hammer, or use a pipe wrench to grab and bend the end. It doesn't have to be a 90° bend and it doesn't have to be pretty.

Personally, I'd stick with stainless instead of galvanized. The thread will be smoother which makes it easier to adjust the mount to level. Not sure about other brands, like the McMaster-Carr ones, but in the kit I got from Dan's Pier Plates, the bolts were amazing well made - more like fine machining than the normal crude bolts I'm used to seeing for foundation work.

-Dan


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Midnight Dan
Postmaster
*****

Reged: 01/23/08

Loc: Hilton, NY, Yellow Zone (Bortl...
Re: Pier diameter? new [Re: Midnight Dan]
      #6046580 - 08/26/13 09:05 AM

Just a reference regarding frost heaves and rebar in piers:

http://www.structuretech1.com/2013/06/frost-heave-and-deck-footings/

The whole thing is pretty short and can be read quickly. But to get to the pertinent information, scroll down to the bottom and read the two paragraphs between the image of the sonotube with the concrete bell-bottom, and the drawing of the pier with rebar in it.

-Dan


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rimcrazy
sage


Reged: 03/03/12

Loc: Overgaard, AZ
Re: Pier diameter? new [Re: Midnight Dan]
      #6046593 - 08/26/13 09:14 AM

Just a quick note. If you use SS bolts, be sure you don't use SS nuts, or if you do remember to put anti-seize on the threads.

You can get locking threaded inserts that you simply put into a drilled hole in concrete. This is what I did on my pier. I had lots of bolts to put in (20) and there is no way you can locate that many bolts accurately to holes in the steel. We simply put the pier down, drilled the holes with an industrial drill, put in the threaded inserts and screwed bolts into the inserts. In our case, to be sure, we put a special concrete epoxy into the holes to be sure nothing came out. Probably unnecessary but there is no way the bolts are coming out.


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dawziecat
Carpal Tunnel
*****

Reged: 10/20/10

Loc: Rural Nova Scotia
Re: Pier diameter? new [Re: rimcrazy]
      #6046653 - 08/26/13 09:59 AM

Please don't forget that I am in a third world country! Sometimes that's how I feel about Canada! Getting things shipped here from the US is slow and prohibitively costly. And that's when the merchants agree to ship to Canada at all, and they often don't!

The industrial supplier here informs me I have virtually no chance of obtaining SS L bolts here! And I can't wait for all the delays of having them shipped to Canada from the US. If I could, I'd just order 'em from Dan's.

Now, what's this about not using SS bolts on SS rod lest they seize? Please tell me more about that. I've heard of Loctite, but never an "anti-seize" compound. Teflon tape? Plumber's joint compound?

PS: I have ordered the SS L bolts from McMaster-Carr. We'll see what happens.
Thanks for that link, Dan.

Edited by dawziecat (08/26/13 10:22 AM)


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rimcrazy
sage


Reged: 03/03/12

Loc: Overgaard, AZ
Re: Pier diameter? new [Re: dawziecat]
      #6046833 - 08/26/13 11:40 AM

If you put a SS bolt with a SS nut and you do not use an anti-seize compound you get what acts like welding of the nut to the bolt. It's not really a weld per se but the metal is soft enough that the heat generated by screwing a nut on to a bolt will cause spalling at the surface which, for all intent and purpose, is a weld.



I neglected to do this or rather did not realize the nut I was using (came from the proverbial collection of random nuts in a jar in the shop) was SS and I did not use anti-seize. You can see how far the nut got on to the bolt before it totally seized up. I needed an 18" breaker bar with a pipe to get it off... or rather snap the bolt in this case. I keep this on the mount to remind me of my stupidity.

The simplest way around this is just use anodized or zinc coated nuts if you use SS bolts. The same goes for vice-versa. If you have SS nuts just be sure to use anodized or zinc coated bolts and you won't have a problem. This also happens with aluminum to aluminum bolts and nuts, etc.


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dawziecat
Carpal Tunnel
*****

Reged: 10/20/10

Loc: Rural Nova Scotia
Re: Pier diameter? new [Re: rimcrazy]
      #6046967 - 08/26/13 12:57 PM

Thanks for that Rimcrazy. I'll be sure it doesn't happen.

McMaster-Carr cancelled my order to Canada.
What I don't understand is why they offer drop-down menus to select other countries in the first place when they won't accept orders from anything but the US?

I think I'll move to Botswana!

Edited by dawziecat (08/26/13 12:59 PM)


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roscoe
curmudgeon
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Reged: 02/04/09

Loc: NW Mass, inches from VT
Re: Pier diameter? new [Re: Midnight Dan]
      #6046978 - 08/26/13 01:03 PM

Quote:

Just a reference regarding frost heaves and rebar in piers:

http://www.structuretech1.com/2013/06/frost-heave-and-deck-footings/

The whole thing is pretty short and can be read quickly. But to get to the pertinent information, scroll down to the bottom and read the two paragraphs between the image of the sonotube with the concrete bell-bottom, and the drawing of the pier with rebar in it.

-Dan




An excellent description of the situation!

And....frozen ground will lift EVERYTHING! .....like my Buddy's large bulldozer parked on a concrete slab for the winter, for instance.....

This is something to consider for those who build observatories on foundation blocks on the ground, and piers below frost line.... the building will move while the pier stays in place.

Russ


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tomcody
Carpal Tunnel
*****

Reged: 07/06/08

Loc: Titusville, Florida
Re: Pier diameter? new [Re: dawziecat]
      #6047063 - 08/26/13 02:10 PM

Terry.
ATS uses 3/4" SS all thread rod for their J bolts, they use a straight length of rod and weld a section of the same rod about 2" long at the bottom to form an L shape. (if you have a welder available? may be faster?)
Rex


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Midnight Dan
Postmaster
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Reged: 01/23/08

Loc: Hilton, NY, Yellow Zone (Bortl...
Re: Pier diameter? new [Re: roscoe]
      #6047066 - 08/26/13 02:11 PM

Quote:

McMaster-Carr cancelled my order to Canada.




Yeesh! You can't catch a break.

Here's a good article on the potential of galling when using stainless on stainless:
http://www.estainlesssteel.com/gallingofstainless.html

I use "Never-Sieze" brand anti-sieze lubricant in situations like this, but according to the article, there are lots of good greases that will work just as well.

-Dan


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dawziecat
Carpal Tunnel
*****

Reged: 10/20/10

Loc: Rural Nova Scotia
Re: Pier diameter? new [Re: Midnight Dan]
      #6047137 - 08/26/13 02:45 PM

"Never-Sieze" is probably something else I can't get in Canada!

I'll use non SS bolts.

Now I need a welder!

Good grief. This whole pier thing is turning into a nightmare! Between international border complications and metallurgical spalling catastrophes, not to mention proper rebar technique, it's enough to make me "rend my garments!"


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Christopher EricksonModerator
Carpal Tunnel
*****

Reged: 05/08/06

Loc: Waikoloa Village, Hawaii
Re: Pier diameter? new [Re: dawziecat]
      #6047156 - 08/26/13 02:54 PM

Skyshed is in Canada and has lots of the things you might need.

http://www.skyshed.com/


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tomcody
Carpal Tunnel
*****

Reged: 07/06/08

Loc: Titusville, Florida
Re: Pier diameter? new [Re: dawziecat]
      #6047298 - 08/26/13 04:31 PM

Never seize or a simular anti- seize compound is sold at all hardware and
auto parts stores. its used for preventing bolts on car engines from seizing.
Rex


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dawziecat
Carpal Tunnel
*****

Reged: 10/20/10

Loc: Rural Nova Scotia
Re: Pier diameter? new [Re: tomcody]
      #6047366 - 08/26/13 05:19 PM

Quote:

Never seize or a simular anti- seize compound is sold at all hardware and
auto parts stores. its used for preventing bolts on car engines from seizing.
Rex




Thanks, Rex. I'll try the local NAPA.


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Midnight Dan
Postmaster
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Reged: 01/23/08

Loc: Hilton, NY, Yellow Zone (Bortl...
Re: Pier diameter? new [Re: dawziecat]
      #6047373 - 08/26/13 05:24 PM

They should have something. Again, the article says any decent Moly grease will work too. If you can't find Moly grease ... well, then you're in a 4th world country!

-Dan


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Raginar
Postmaster
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Reged: 10/19/10

Loc: Rapid CIty, SD
Re: Pier diameter? new [Re: Midnight Dan]
      #6047386 - 08/26/13 05:29 PM

Dan, you get the top of your pier done yet?

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Midnight Dan
Postmaster
*****

Reged: 01/23/08

Loc: Hilton, NY, Yellow Zone (Bortl...
Re: Pier diameter? new [Re: Raginar]
      #6047395 - 08/26/13 05:38 PM

Hi Chris:

If by the "top of the pier" you mean the observatory, then no. I'm still waiting for the POD to ship. Did you mean something else? The pier has been done for quite a while now.

-Dan


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Christopher EricksonModerator
Carpal Tunnel
*****

Reged: 05/08/06

Loc: Waikoloa Village, Hawaii
Re: Pier diameter? new [Re: Midnight Dan]
      #6047538 - 08/26/13 07:07 PM

Quote:

Hi Chris:

If by the "top of the pier" you mean the observatory, then no. I'm still waiting for the POD to ship. Did you mean something else? The pier has been done for quite a while now.

-Dan




I was simply referring to pier parts.

Also, Break-Free CLP is a great anti-seizing lubricant.


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