Pier Base

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mcolbert
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Pier Base

#1

Post by mcolbert »


I'm not too sure if this is the best sub-forum to post this in, so if it is better in the DIY section, mods please transfer.

Copy from another forum;


most threads on different fora describe steel piers (or wood etc) atop a concrete base. So I wonder which would reduce vibrations better, the steel pier on a concrete base or a steel pier bolted to a square yard of steel, say about 6-8 inches thick?

I was wondering more if there would be similar benefits in dampening time if a metal base were to be used and the vibrations travelled horizontally rather than vertically.


Thanks
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Re: Pier Base

#2

Post by JayTee »


Typically the pier is disassociated from everything else, the obsy floor especially. So, where are these vibrations you are mentioning come from?

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Re: Pier Base

#3

Post by mcolbert »


JayTee wrote: Sat Jul 13, 2019 12:07 am Typically the pier is disassociated from everything else, the obsy floor especially. So, where are these vibrations you are mentioning come from?

Cheers,
JT
thanks JayTee,

wind, if outside of an obsy, accidental knocking of the ota or attached equipment, if I were to use a film camera with a manual shutter, the (very) odd animal or two - events like that. ;). I was under the impression that some piers have a concrete footer which is placed at varying depths.

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Re: Pier Base

#4

Post by KathyNS »


I have never heard of anyone trying a base like that. A flat plate of typical 1/2" steel stock would, I think, be very vibration-prone. But, since you specified 6-8" thick, that might be enough to stop any flexing.

It would have the advantage of being moveable (if not exactly portable) in the event you move, more so than leaving a bunch of concrete in the ground.

Why not try it?

My first pier installation was a plywood pier standing on firm-packed ground, anchored by four steel rods driven 4' into the ground. I was surprised at how vibration-free it was. I now use the same pier bolted to a concrete foundation, and it is not as vibration-resistant as the original. Still good enough, though.
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Re: Pier Base

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Post by mcolbert »


KathyNS wrote: Sat Jul 13, 2019 11:31 am I have never heard of anyone trying a base like that. A flat plate of typical 1/2" steel stock would, I think, be very vibration-prone. But, since you specified 6-8" thick, that might be enough to stop any flexing.

It would have the advantage of being moveable (if not exactly portable) in the event you move, more so than leaving a bunch of concrete in the ground.

Why not try it?

My first pier installation was a plywood pier standing on firm-packed ground, anchored by four steel rods driven 4' into the ground. I was surprised at how vibration-free it was. I now use the same pier bolted to a concrete foundation, and it is not as vibration-resistant as the original. Still good enough, though.
Thanks KathyNS, my initial query has been to ascertain if there is something that I've not considered, a reason why people use footers of concrete and not metal. Transportability is certainly one other consideration, but I also am thinking of placing several 'slabs' down, one for each dedicated OTA - eg solar, IR imagery etc. My next question is whether there is any significant difference between using steel or aluminium as rust is another factor to consider with steel - not that aluminium doesn't corrode, it is apparently develops a protective coating through oxidation - a plus then for Al.

As there have been few other opinions from other sources, the only practical thing is, as you say, try it. This may lead to another thread in the DIY sub-forum though.
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Re: Pier Base

#6

Post by Gulf Coast Guy »


mcolbert wrote: Fri Jul 12, 2019 11:09 pm I'm not too sure if this is the best sub-forum to post this in, so if it is better in the DIY section, mods please transfer.

Copy from another forum;


most threads on different fora describe steel piers (or wood etc) atop a concrete base. So I wonder which would reduce vibrations better, the steel pier on a concrete base or a steel pier bolted to a square yard of steel, say about 6-8 inches thick?

I was wondering more if there would be similar benefits in dampening time if a metal base were to be used and the vibrations travelled horizontally rather than vertically.


Thanks
I don't know the answer but I hope to be exploring the conventional wisdom soon. I'm currently drawing up a finalization of a pier design I began years ago. Parts of which that were completed and have been following me around since. Just to be clear my design involves a concrete post on a steel plate with a steel top plate designed for my current mount (LXD75). Te base plate will be bolted to ~ 1 yard of concrete below grade with an extention above grade to the level of a surrounding deck. And Yes, I know how much 1 yard of concrete is.
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Re: Pier Base

#7

Post by OhNo »


I am coming up on the one year anniversary of putting my pier in. I have only used a tripod a handful of times since I installed the pier (and I attempt astronomy about 300 days of he year). One of the real benefits is I've only had to polar align a couple time since it's installation. My pier diameter and depth below ground could have been wider and deeper....

That said, you're asking all the right questions, and received good answers. You have to consider the soil type and your environment. Soil like my pier is in (clay) and is well drained is fairly stable. However I live in an environment that has months of freezing that can drive frost deep into the ground. The the thaw cycle kicks in. This yearly cycle has been known to jack things out of the ground.

IMO stability and resistance to vibration (oscillation) is the goal, especially if your thinking astro-photography. There are lots of great ideas on the net for pier designs, and some that woulda/coulda/shouda been thought through some more. If your no going to be in a location for the long haul, you're wise to consider the portability, I don't regret drilling a hole, using a scrap grain auger tube and pouring some cement. But I had the hole auger, form, and a wheel barrow, little money and a dream. The in ground pier will outlast me.... And as I'm on a farm a pier isn't likely going to devalue my property when the time come to sell.

Hope this helps!
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Re: Pier Base

#8

Post by mcolbert »


OhNo wrote: Sun Jul 14, 2019 3:57 am I am coming up on the one year anniversary of putting my pier in. I have only used a tripod a handful of times since I installed the pier (and I attempt astronomy about 300 days of he year). One of the real benefits is I've only had to polar align a couple time since it's installation. My pier diameter and depth below ground could have been wider and deeper....

That said, you're asking all the right questions, and received good answers. You have to consider the soil type and your environment. Soil like my pier is in (clay) and is well drained is fairly stable. However I live in an environment that has months of freezing that can drive frost deep into the ground. The the thaw cycle kicks in. This yearly cycle has been known to jack things out of the ground.

IMO stability and resistance to vibration (oscillation) is the goal, especially if your thinking astro-photography. There are lots of great ideas on the net for pier designs, and some that woulda/coulda/shouda been thought through some more. If your no going to be in a location for the long haul, you're wise to consider the portability, I don't regret drilling a hole, using a scrap grain auger tube and pouring some cement. But I had the hole auger, form, and a wheel barrow, little money and a dream. The in ground pier will outlast me.... And as I'm on a farm a pier isn't likely going to devalue my property when the time come to sell.

Hope this helps!

every bit helps in this game! ;)

re the soil type, clay as we are in the foothills of the Great Dividing Range (Snowy Mountains), temperature does get below 0 rarely usually hovers between 1-5 in winter.... so far at least. ;). Thanks. ;)
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