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: [email protected] [mailto:[email protected]] 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: [email protected] [ <mailto:[email protected]> mailto:[email protected]] On Behalf Of Larry Brown Sent: Monday, January 26, 2009 7:24 AM To: [email protected]; 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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