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

Patrick Greenlee patrick_g at windstream.net
Sun Jul 23 09:13:19 EDT 2017

I once asked Karl Tashjian (Engineer and owner of Tashjian Towers, ex 
Triex) how vertical was vertical enough and his reply was that +/- 
1degree was the tolerance.

Digital or spirit (bubble) level, you should read the instrument, turn 
it around, and read it again. If the readings differ, the truth is close 
to half way between the readings.  This is most likely not applicable to 
your  laser level.

I have never seen a "water level" that had an error great enough to 
read.  Further I believe a properly constructed/used water level is 
incapable of having an error.  The only error is in reading it.  I 
suppose theoretically a long enough water level could have a different 
extant barometric pressure at the two ends but I have never used a water 
level longer than 300 feet and haven't encountered that or any "spatial 
anomalies" or ruptures in subspace. A strong wind blowing over the open 
end of a water level could, by means of the Bernoulli principal, cause 
an error in the reading. Placing scraps of cloth over the open ends of 
the water level (Secure with tape or???) would eliminate the error at 
moderate wind speeds.  It is easy to check to see if wind matters.  Just 
place your hand next to the open end of the water level and move it 
around.  If there is no change in the level reading you can ignore the wind.

Not everyone has faith and confidence in gravity and therefore some 
avoid using a water level.  I had a neighbor offer to assist me in 
leveling a pad for a house I was building for my mom.  I had a water 
level set up but the neighbor and his friend/helper couldn't be 
persuaded that it could work and they insisted on using a small bubble 
level to which I added a straight board for a better "average" reading.  
Of course out here in our very rural setting anything more complicated 
to understand than slip-joint pliers is considered high tech.

You can lead a horse to water and you can hold his head under but 
whether or not he drinks is another matter.

Patrick        NJ5G

On 7/23/2017 6:49 AM, Dave Sublette wrote:
> OH DEAR…. Now you have me thinking.  What bad things do you have to say about the digital levels available in the big box stores?  I am using one to check the plumb of a Rohn 55 tower I am putting up.  It is on a rotating joint and the guys can be used to adjust the plumb.  When I put it up the first time I used a bubble level and it operated flawlessly for 28 years.  So now do I have to be worried about the new digital level I just bought?
> Really, guys, aren’t we gilding the lily just a bit?  Even on a self supporting base, which has less adjustment that a rotating bearing, I would think that you can get it  “straight enough”.  We have been putting these things up for years and I haven’t seen any news reports of “leaning towers”.
> Just a bit of tongue in cheek here — 73,
> Dave, K4TO
> ps— my Rohn 55 is already at 55 feet, including the rotating base.  It is on its way to 153 +/- feet and is looking “straight as an arrow”.  The extra odd footage is due to the short base section with the rotary joint and rotator on it, plus the top section is only 7 or 8 feet.  I forget which..  At my age (75), the doctors (and my wife) would like me to quit climbing, so I reconfigured my 200 ft Rohn 55 with the rotary joint at 50 to this configuration with the rotary down where I can stand on the ground and service it.  I figure it will be easier to get volunteers to climb to 150 than it would be to 200 feet.  I still climb to 60 feet or so. I’m feeling great.
>> On Jul 23, 2017, at 7:02 AM, Patrick Greenlee <patrick_g at windstream.net> wrote:
>> 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
>> On 7/23/2017 1:25 AM, Roger (K8RI) on TT wrote:
>>> I've never been able to successfully use a plumb bob for more than about 10 ft vertical outdoors.  The repeat ability just isn't there for here, at least not enough to trust it enough to make adjustments. It may be absolutely still on the ground, but above 30 or 40 feet a breeze so light you can hardly detect it can produce a substantial deflection of several inches at ground level.
>>> Be careful with water levels. I've seen as much as an inch or more in 3 feet and when the ends were paralled, there was still the same deflection.  This as in 1/4/, 3/8ths, and 1/2 inch Tygon. It was worse when antifreeze was mixed in the water (used in some unheated garages and sheds). Water levels are commonly used in building home built aircraft.  The big box store laser transits and levels for home construction were close enough for 18 to 20' fuselage construction, but on an 18 to 24" tower base?
>>> 73, Roger (K8RI)
>>> On 7/23/2017 Sunday 1:40 AM, Clay Autery wrote:
>>>> I'll use a combination of plumb bobs and water tubes....  gravity is
>>>> remarkably more consistent than laser levels made in China.  ;)
>>>> ______________________
>>>> Clay Autery, KY5G
>>>> MONTAC Enterprises
>>>> (318) 518-1389
>>>> On 7/23/2017 12:00 AM, Roger (K8RI) on TT wrote:
>>>>> When using laser levels there is a tolerance of +/- Something per ft,
>>>>> yard, 10 feet, etc.  It's often a lot more than acceptable for
>>>>> leveling a tower base.
>>>>> I have two, a transit and a level.  Setup and calibration are
>>>>> critical.  I have a plain old combination bubble and 3 digit, digital
>>>>> level. Two digits to the right of the decimal is more than enough.
>>>>> Calibration is easy. Find something close to level (level is not
>>>>> necessary, but convenient) The two points should be about the same
>>>>> distance apart as the bolts. You can even use those bolts, getting
>>>>> them close with the bubble. Then you simply turn on the digital mode,
>>>>> set the level on the nuts and push a button, swap ends with the level
>>>>> and push a button.  The digital level is now zeroed.
>>>>> NOTE: The calibration points must be STABLE!  The nuts can not be
>>>>> loose. The digital level properly zeroed is more accurate than the
>>>>> laser transit or level you can purchase at the big box stores that
>>>>> require much more care in calibrating.  A surveying laser transit (A
>>>>> lot more money) is accurate, but still takes care in calibrating.
>>>>> Were I to go that route, I'd rent a surveying transit, but being
>>>>> frugal (some would say cheap) and a bit lazy, I'd use my digital
>>>>> level. I have it, know how to use it, and with a fresh 9V battery in
>>>>> it being the only cost.
>>>>> I've seen manufacturer's suggestions to use a plumb bob. Now depending
>>>>> on where you live, dead calm days may be rare. We might have 3 or 4
>>>>> days a year where it's dead calm long enough to use a plumb bob on a
>>>>> 60 - 100 ft tower and a plumb bob is far more work than these other
>>>>> methods
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