[TowerTalk] Be Careful With the Tolerance in Laser Levels (Tower base leveling

[Patrick]

A good transit would be an excellent choice for checking tower plum 
after the tower was up.  A water level could be used to check level of 
the steel in the concrete prior to tower erection (and prior to the 
concrete pour too.

What you want to do is increase the "baseline" for a more accurate 
reading.  Lets say the tower base has the legs 2 ft apart.  We can pull 
a string tightly across the 2 ft apart steel mounts securing the far end 
to a stake driven securely into the ground.  If the string is 10 ft end 
to end it is 5 times the width of the tower leg connectors set in concrete.

This multiplies the error by a factor of 5 making it easier and more 
accurate to read the error with a water level.  This approach will 
measure level as good as you can read a digital level or spirit level 
and likely better.  Use a good strong string and pull it very tight and 
you could move the stake out to 20 ft and magnify the error by a factor 
of 10.  This would be (in my opinion) getting into diminishing returns, 
beyond good enough.

The above water level approach would also work on the first section of 
tower but would get difficult above that. A plumb bob in a no or low 
wind condition would be better (suspended from the top of the tower.)  
Of course a transit would also be excellent for checking plumb of the 
erect tower but not everyone has a good transit.  A plumb bob can be 
jerry rigged very inexpensively but a transit can't.

Patrick        NJ5G


On 7/23/2017 9:06 AM, john at kk9a.com wrote:
> How do you use a water level to plumb a tower?  I have been using a transit
> level for decades and it works in any WX.
>
> John KK9A
>
>
> To:	towertalk at contesting.com
> Subject:	Re: [TowerTalk] Be Careful With the Tolerance in Laser
> Levels (Tower base leveling.
> From:	Patrick Greenlee <patrick_g at windstream.net>
> Date:	Sun, 23 Jul 2017 06:02:32 -0500
> List-post:	<mailto:towertalk at contesting.com>
> Roger, What did you use to measure the error in the water level. My
> experience with water levels vs 4 ft and even 8 ft spirit levels shows the
> water level to be as close as I could read it, essentially zero instrument
> error.
>
> I second the disparaging comment posted here regarding cheap Chinese laser
> levels.  I have a transit and find it no better than the water level.
>
> For a water level I use garden hoses with clear plastic extensions.  The
> extensions are sold to use for filling RV water tanks.  A small tipped
> marker pen can scribe a narrow line on each when the water is not disturbed.
> Some of the plastic extensions have 90 degree ball valves incorporated which
> makes it easier to move the hoses around without spilling water.
>
> Patrick        NJ5G
>
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