Agreed Grant.
I have two 6 ft. Aluminum bubble levels... I use cheap black electrical tape (
not Scotch 33 or 88 ) to attach them to the first section @ 90 degree angles
on one leg.... this method has served me well on quite a few tower install .
I then walk back a far distance and use a 3 ft aluminum level held vertically
by the shank of a round screw driver as a SITE-BOB @ 90 degree sightings.
guy tensioning and a Loose gage and your in business .
Wayne W3EA
________________________________
From: TowerTalk <towertalk-bounces@contesting.com> on behalf of Grant Saviers
<grants2@pacbell.net>
Sent: Sunday, July 23, 2017 1:07 PM
Cc: towertalk@contesting.com
Subject: Re: [TowerTalk] Be Careful With the Tolerance in Laser Levels (Tower
base leveling.
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
Using An Accelerometer for Inclination Sensing |
DigiKey<https://www.digikey.com/en/articles/techzone/2011/may/using-an-accelerometer-for-inclination-sensing>
www.digikey.com
Cell phones now commonly change screen orientation as the user rotates the
phone.
http://www.analog.com/media/en/technical-documentation/data-sheets/ADXL313.pdf
3-Axis, ±0.5 g/±1 g/±2 g/±4 g - Analog
Devices<http://www.analog.com/media/en/technical-documentation/data-sheets/ADXL313.pdf>
www.analog.com
3-Axis, ±0.5 g/±1 g/±2 g/±4 g Digital Accelerometer Data Sheet ADXL313 Rev. B
Document Feedback Information furnished by Analog Devices is believed to be
accurate ...
lots of Arduino and other boards available
http://www.littlebird.systems/products/adxl313-breakout/?gclid=Cj0KCQjwktHLBRDsARIsAFBSb6zX0xmEobuQKJnIMuxZDAoiTp6pd487_6-cqYjKR3lBCu0Holh3ARoaAvROEALw_wcB
ADXL313 Breakout - Little Bird
Store<http://www.littlebird.systems/products/adxl313-breakout/?gclid=Cj0KCQjwktHLBRDsARIsAFBSb6zX0xmEobuQKJnIMuxZDAoiTp6pd487_6-cqYjKR3lBCu0Holh3ARoaAvROEALw_wcB>
www.littlebird.systems
The ADXL313 Accelerometer measures up to +/- 4g with SPI or I2C digital output
of 1024 LSB/g. This breakout board allows for rapid prototyping and testing
with the ...
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