[RE-wrenches] helical screw piers

[Glenn Burt]

As they are driven, they were constantly checking for plumb along 2 axes.
This can be adjusted with their hydraulic driving tool by changing the angle
of drive into the earth. They also had a string line between the 2 outermost
posts (which they set first) to maintain alignment of the row.

 

Not perfect, but what is? We had no troubles with minor deflections from the
true line when installing the 2" top and bottom tubes of the U-LA through
the clamps. Also the racking system has a great deal of tolerance for
mounting points.

 

The drive machine was a tracked vehicle with an articulated arm, don't know
its weight but it came in an enclosed trailer, pulled by a pickup truck.

 

BTW, they work through the winter up here in the North East - propane
torches to heat the ground I think they said.

 

-Glenn

 

From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of John Raynes
Sent: Monday, January 26, 2009 11:37 AM
To: RE-wrenches
Subject: Re: [RE-wrenches] helical screw piers

 

What kind of post-post horizontal tolerancing can you hold with those
things, and how is it adjusted or compensated for while driving in?  Usually
at least one of the two horizontal surface coordinates has a reasonably
tight alignment tolerance in my experience.

They look like a great idea, although one advantage of concrete is you have
lots of time to tweak the post alignments if necessary while the concrete
sets.  I would think a helical screw would be prone to walking just a
little, unless the drive apparatus is extremely well-anchored.  

John Raynes
RE Solar
Torrey, UT


At 08:45 AM 1/26/2009, you wrote:




We have also used the local franchisee of TechnoMetal Posts for many jobs
that are ground mounts.
Around $250 per post is what we paid also.
They were in and out on our last job in 2 days, but their machine did break
down for a while. They placed 32 posts in 2 arrays for a 12.6 kWp array (60
modules).
We marked the 4 corners of each array & told them how far apart to place the
posts & off they went. Marked, drove, cut off those too high & welded on
extensions to those too short, then ground the welds & painted.
 
We also topped them with Unirac U-LA racking and it lined up well.
 
-Glenn
 
From: re-wrenches-bounces at lists.re-wrenches.org [
<mailto:re-wrenches-bounces at lists.re-wrenches.org>
mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Larry Brown
Sent: Monday, January 26, 2009 7:24 AM
To: info at asappower.com; RE-wrenches
Subject: Re: [RE-wrenches] helical screw piers
 
Wrenches,
We used a company called techno Metal Post  ( www.technometalpost.com ) I
believe it is a franchise arrangement with the main company in Canada. Here
is a business opportunity if a franchise does not exist in your community.
They are screwed into the ground while hydraulic pressure is applied. We
received a stamped engineering report after completion that identified how
many posts were set,  to what depth and how much hydraulic pressure had been
applied for load bearing capacity
It requires a special unit designed for this purpose
We set 8 posts in 2 rows of 4 and then attached a UniRac U-LA Ground Mount
racking system for 28 Sanyo 200's
The posts in this case were 2" schedule 40 galvanized steel pipe ready for
the UniRac mounting system
They also shot the elevation and cut each pipe to the proper height so that
the relationship between the front row of pipes and the back row of pipes
was set to receive the racking system and then the mounting rails would be
at latitude for this site.  We supplied the heights that were required.
Many other uses for these screw piers.  Pictures on their website
 
Larry
 

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