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Re: [TowerTalk] Be Careful With the Tolerance in Laser Levels (Tower bas

Subject: Re: [TowerTalk] Be Careful With the Tolerance in Laser Levels (Tower base leveling.
From: Grant Saviers <grants2@pacbell.net>
Date: Sun, 23 Jul 2017 10:07:12 -0700
List-post: <mailto:towertalk@contesting.com>
IMO, straight is more important than plumb (assuming reasonable) for guyed towers. Otherwise the tower is being bent and has stresses not in the load calcs. Pro tower installers use a level-transit at each anchor (two is enough) for tall towers to insure the guys are keeping it plumb and straight when guys are being tensioned. A decent one is better than +/- 3/16" at 150'. Easy to rent. Pretty hard to eyeball that or keep a plumb bob unaffected by wind or thermals.

I think a 6' carpenters level properly used is good enough to get the bottom section plumb and they are certainly cheap and easy to check, even if made in China. (Stanley 6' spec 0.036" over 6', $43) It's easy to see 0.1" error. At 100' that is 1.7". I think I measured my R65 bottom section 4 times all around before pouring and at least 2 times afterwards. One trick is to use offsets at both ends of the level so interference from galvanizing imperfections can be minimized. For towers <80' a level and eyeball check of straight are probably good enough. Laser levels - nice for drop ceilings, setting forms, and grading. (the coolest is the dozer blade that follows the laser).

For fun, one could use a 3D mems accelerometer to measure tilt, even cheap ones (new cars have lots of them) have sub 1 milliG resolution for +/- 1G range. 1 deg of tilt is 0.983G Z axis output, so dynamically measuring your tower's sway in strong winds is not so hard. Use X & Y to measure direction of tilt. 1 deg tilt at 150' is 2.6'

Now that is REALLY gilding the lily.

..snip..

Grant KZ1W

https://www.digikey.com/en/articles/techzone/2011/may/using-an-accelerometer-for-inclination-sensing
http://www.analog.com/media/en/technical-documentation/data-sheets/ADXL313.pdf
lots of Arduino and other boards available
http://www.littlebird.systems/products/adxl313-breakout/?gclid=Cj0KCQjwktHLBRDsARIsAFBSb6zX0xmEobuQKJnIMuxZDAoiTp6pd487_6-cqYjKR3lBCu0Holh3ARoaAvROEALw_wcB
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