How to make a lot level

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I would fathom a guess that hot water is "lighter" than cold water, therefore if you had a 100' of hose, and one end of it is in 25' of direct sunlite (and had been for a period of time) about 20 degrees hotter, the colder water would push the hot water a little higher in the tube... dunno ... never experimented ... If you initially held the sight tubes side-by-side and leveled the water and marked the tubes... then stretched out the 100' of hose (some in sunlight, some not) and staked the sight tubed into the ground to measure from the sight tube marks down to the dirt, I would imagine, after a period of time, that it would be possible for the "hot" end to be higher than the sight tube marking, while the other end may be a little below the sight tube marking. Ken.

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Ken Sterling <Ken Sterling> wrote:

At temp T (F), it weighs about 62.46-0.01(T-68) lb/ft^3.

Imagine filling a 110 foot x 1 ft^2 hose filled with 100' of 68 F water. The water weighs 100x62.46 = 6246 pounds. Now heat half of the water (3123 pounds of it) to 88 F. A cubic foot of the warmer water weighs about 62.26 pounds, so the warmer water now occupies 3123/62.26 = 50.1606 feet of hose, ie the hose now contains 100.1606 feet of water.
Imagine hanging one end from the shady side of a 50 foot tall building at 68 F and hanging the other end from the sunny side around a corner. We might see water column heights Hc and Hw, where Hc + Hw = 100.1606 feet, and 62.46Hc = 62.26Hw, which makes Hc = 0.9968Hw, so 1.9968Hw = 100.1606, and Hw = 50.1606', and Hc = 50', and Hw - Hc = 0.1606 feet, or 1.927 inches.
If all the hose were on level ground, we wouldn't see any height difference, although both heights would rise by 0.9636 inches, or more, if air bubbles undissolved from the warmer water.
Nick
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Harry K wrote:

about the merits of a water lever! - damn Engineers! I recently bought a Porter Cable self-leveling laser for $100. It is great for projects like this. I use it mostly, however, when investigating settlement and sags in houses. Best $100 I ever spent. I may go for one that continuously spins next time.
Rob Munach, PE
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vaguely proposed a theory ......and in reply I say!: remove ns from my header address to reply via email
Gee! When I had my settlement investigated, the lawyer only read the first _page_ for $100! ..........oh.....sorry. <G>
A question if I may. How good are these things in sunlight over distance? Are there staffs that have sensors, or is this not needed? As usual we are way behind you guys in pricing, so until very recently these have been way out of range. They are starting to get there, and I am certainly looking at one, but I am worried that economics and laws about lazers may cause weak visual behaviour.
Thanks

**************************************************** I went on a guided tour not long ago.The guide got us lost. He was a non-compass mentor.........sorry ........no I'm not.
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Old Nick wrote:

I have not used it in bright sunlight yet - but I have heard that it can affect it. Also, the beam isn't likely to be powerful enough to be seen at a distance in bright sunlight. Hey, what do you want for $100?

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vaguely proposed a theory ......and in reply I say!: remove ns from my header address to reply via email
Not much for $100. But then I didn't think we had stuff for $100! <G> I see we do.
But I would hate something that simply did not work, or restricted me badly. I would pay more to avoid that. I may not need to.

**************************************************** I went on a guided tour not long ago.The guide got us lost. He was a non-compass mentor.........sorry ........no I'm not.
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Hi Nick, I bought one of these, http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item#95819744&categoryc2 no connection, just happy with mine. I can see it maybe 25 meters in sunlight using the red tinted glasses that come with it. I just turn it on and walk about with a staff I made from a tomato stake witn the blade out of a $2.50 tape measure nailed to it, it works very well.
Just to prove the point Rob made about damn engineers, I don't trust water levels because they level to a curve about the the same as the radius of the earth, where a laser is flat. LOL
regards,
John

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On Wed, 21 Apr 2004 22:37:10 +1000, "john johnson"
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hmm. $Aud95!
Ok. I would still rather spend $300 and get a reasonable piece of gear than $100 and get something that disappointsme.
Ok if I ask a few questions?
More to the point. Will you answer them? <G>
I have also just been out and fiddled about with my Class II pointer <G> and may have some ideas. (1) If you can make a shade for the staff, with both top and side shields, you can significantly increase the visibility. You would need to turn the staff so that the side shileds kept the sun off. There are a couple of spots where this would not work, of course.
(2) 3M make reflective film. I have some red stuff. That really makes the lazer point stand out. May even be a safety issue for a static lazer.

I hate ebay....however, it certainly seems to be reasonable and if it's OK up to 25m that's not bad!
So you are close to the staff, and can see the laser stripe on it, I guess. I can see where that would work. I have a laser pointer, and in sunlight I can't see the point if I am _at the laser_ and the beam is more than 10 metres away. At night, I can see it against a wall 250 m away!
I was assuming I was going to need to point, locate and mark. Of course with a rotating bizzo, you can walk around and see the beam.
What rotation speed do you use? I am interested because I would assume that the faster it turns, the quicker it wears.
Does it take rechargeables? What capacity and whow long does a set last?
How do you set the thing level? Bubble? Auto?
Have you done an "back checking" on its levels to see how accurate it is? By this I mean actually marking a level that it gives, then marking its own level, placing it at the new level and seeing it sends back to itself.
How big is the spot?

.....with a "thin spot" in the middle of the "run"? <G> **************************************************** I went on a guided tour not long ago.The guide got us lost. He was a non-compass mentor.........sorry ........no I'm not.
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Hi Nick, Reply below each question. regards,
John
vaguely proposed a theory

I'll try!

leading you astray.

to use it, this thing is easy by yourself.

Rotation speed is adjustable, the faster you make it the duller it gets, smaller range. You can slow it down to less than a rotation per second, but it still wizzes past pretty quick at 20M
As far as wear goes, the rotating bit is very light (no pun intended) and lightly loaded (and again) , I think it will out last me with the occasional use I will give it. If you wanted to use one every day I'd be spending a lot more on a professional model. I just bought it to map my sloping yard, so I can work out where is the best spot and shape for my new shed, then level the site and form work etc.

It takes three AAA cells, I'm still using the set that came with it about two months ago but I haven't used it that much. You could put rechargeables in it, but it comes with alakaline batteries. The book says it will run for three hours on set of batteries. That would do a lot of leveling, because you can turn it off without disturbing it.

It has two vials, you adjust the screws underneath to get the bubbles centered. I found it a bit difficult to get the bubbles centered, the vials are very sensitive, the screws are a little coarse.

level on few things across the yard, then set it up on the opposite side of the yard and did it again. The error was around 2.5mm across 20M of yard, I was impressed! It's rated accuracy is +- 5mm over 10 M, so it was better than I thought it would be.
While I had it there, I went back and readjusted the bubbles in the vials to try and get some idea of the sensitivity, and convinved myself that it would be repeatable to get this sort of accuracy.
One thing that worried me, and I haven't fully tested yet, was that the laser has to be at 90 deg to the axis of rotation, or it will project a shallow cone rather than a flat disc. The test I did above came at the same marks from different angles, not a straight line through them, so it did test this a bit?
It's at least as accurate as letting my wife read the stall with the cowley level! LOL

Close up it's about 2.5 mm, across the yard it grew to about 3.5 mm. Its not really a problem though as the edges are clearly defined and it's easy to judge the centre of the dot.
Another thing, it has a bracket at 90 deg to it's base mounting, so you can clamp it to things and use it to set up flat planes that aren't level. I've used it to 'draw' some straight lines down a model A chassis I'm working on. It's better than a string line because it projects a plane rather than the single line of the string.

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On Thu, 22 Apr 2004 19:57:10 +1000, "john johnson"
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Thanks for all of that! I will chew this one over. I may check out more expensive models, and see what I am getting, or if there is a "middle road" )some of them are a couple of grand!)
Talking of accuracy. When I have help my FIl lay out pads a couple of times, using a dumpy, I used to get really pissed off. I would tap in a peg, and p8ut the staff on top and he'd say "down a tap" and we'd go again..."up" (pull) "down" (tap) etc etc. We would have been talking 0.5 mm ? I have to suppose he worked to edges of the markings on the staff! <G>
Mind you, I have never seen more level pads thatn that guy did. Scary. When you wet them down after laying, and kept them wet, there was _never_ a pool anywhere.

**************************************************** I went on a guided tour not long ago.The guide got us lost. He was a non-compass mentor.........sorry ........no I'm not.
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On Wed, 21 Apr 2004 22:37:10 +1000, "john johnson"

Perhaps John would be happier with damn physicists, who will tell you that a laser beam follows a geodesic, so that it curves in the vicinity of a massive surface - like the Earth?
Brian W
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As I recall, "line of sight" radio and light waves bend around the earth as if it had a 25% larger diameter. We might be able to see the backs of our heads on a very clear day on Jupiter.
Nick
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In the early days of radar it was common to calculate the effective "radar horizon" by using an effective earth's radius of 4/3 of the actual radius. This factor accounted for the refractive effect on the radar beam through the atmosphere. For optical systems the same approach was used but the factor was only 1.06.
RB
snipped-for-privacy@ece.villanova.edu wrote:

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On 22 Apr 2004 10:20:48 -0400, snipped-for-privacy@ece.villanova.edu wrote:

True AND misleading! That's a refraction effect in a graded medium (air)
Fessing up: the deflection from a "straight line" due to relativistic effects is very, very much smaller than that .
Brian W
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On 19 Apr 2004 10:59:08 -0700, snipped-for-privacy@yahoo.com (Don) vaguely proposed a theory ......and in reply I say!: remove ns from my header address to reply via email
A warning with all water levels. You must not have any air bubbles in the line. It can stuff everything up. The same goes for any rises and falls in the line, as these will probably create air bubbles.
Such is my experience. I had wrong readings because of air bubbles.
I _believe that if the air bubble occurs _and the water levels are already exactly equal, and you don't alter anything_ then you are OK. Any change with an air bubble and you will get wrong readings.
IME.
As far as the actual levelling goes, depends what you have. I have done them with shovels and string lines, working in smaller squares to keep the scale down to size. I also use a scrape stick once I am close to get larger areas of flat.
But I would use a compactor very thorougly, then re-level, then recompact, expecially if you are going to cement/brick/pave afterward. Also remember that string lines stretch and sag. They need to be _tight_..did I say _tight_? The better the job, the less cement you need.
My FIL was a commercial grano worker, and used shovels, but had a dumpy level and used to place a perimeter of oregon planks , with spikes in the ground every 2 metres' square or so, and work around those. The spikes were very accurate (woe betide any poor bastard that kicked one! DAMHIKT) and stuck up the expected depth of the cement, say 100mm. When they laid the cement, they would simply work to the top of the grid of spikes.
The box grader is a good idea, but takes some skill to get really nice. I would still be finishing with a shovel.
And compact compact compact. This will increase your workload, but you will not regret it.
My dream is to have a layout that allows a really heavy bar or some such to be dragged across the top of levelled rails either side, simply levelling, then comnpacting and filling any missed bits, then again, and again, maybe working in strips. I have about 4 big pads to do at least, where I am, so it may be worth my while. **************************************************** I went on a guided tour not long ago.The guide got us lost. He was a non-compass mentor.........sorry ........no I'm not.
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"Old Nick" wrote: (clip)I _believe that if the air bubble occurs _and the water levels are already exactly equal, and you don't alter anything_ then you are OK. Any change with an air bubble and you will get wrong readings. ^^^^^^^^^^^^^ The water hose is essentially a U-tube, in which the water levels are PRESUMED to be at the same level in both legs. Obviously, if there is air on one side, the weight of water required to match the other leg will stand higher in that leg, introducing an error. The best way to make sure this doesn't happen is to bring both legs together and see that the levels match. To be doubly sure, raise the ends of the hose, so any air rises and escapes. Once this is done, there is no way for air to get in, and the system should be accurate, no matter how you drag the hose, or whether it goes over bumps or low spots.
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On Tue, 20 Apr 2004 06:35:02 GMT, "Leo Lichtman"
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Point taken. I was being cautious. It's hard to get sure that there is no air in 15 metres of hose, though, by raising the ends up till there are no folds <G>
Clear tubing is the safest. I saw a couple of mentions of garden hose.

**************************************************** I went on a guided tour not long ago.The guide got us lost. He was a non-compass mentor.........sorry ........no I'm not.
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On 19 Apr 2004 10:59:08 -0700, snipped-for-privacy@yahoo.com (Don) vaguely proposed a theory ......and in reply I say!: remove ns from my header address to reply via email
Wot you workin it for? Just let them car tyres dig it up as they slide across! <G>
Hope I got the same Don....

**************************************************** I went on a guided tour not long ago.The guide got us lost. He was a non-compass mentor.........sorry ........no I'm not.
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Others have suggested the best cheap solution, a water level. I'll add one more tip. If you need to take the level along a line, say, to check the level of the pad out in the center, do it with a cheap laser. Any laser can work, even a cheap laser pointer, as long as you can affix it securely.
The method is to aim the laser across the worksite at a convenient height. A cheap laser level is handy because it has a tripod socket. The level the beam using the water level. One end at the laser and the other end on the far side of the worksite. Once the beam is level you can shoot vertical distances at any point along the beam using a simple steel rule. Or even a string with a mark at the laser impact point. Just touch the ground with the rule and observe where the laser grazes it.
Most cheap lasers have too much beam spread to use the spot so use a grazing contact, say, on the bottom of the beam. My rule is magnetic and I have a cylindrical magnet that I can roll along the rule until the laser just barely illuminates the edge.
John
On 19 Apr 2004 10:59:08 -0700, snipped-for-privacy@yahoo.com (Don) wrote:

--
John De Armond
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As you can see a water level is the most popular low price solution. A few years ago I showed guy that was putting new siding on his house how to use a water level. He thought I was a genius for coming up with such a good method but I had to confess that it's an old trick probably a hundred years or more old. In old books I have seen them made by putting glass tubes in the end of an old rubber hose. The only real advantage of using a laser or transit is ease of use A pole barn or most residential building don't need any more accuracy than you can get from a water level
A good technique to actually do the leveling is to get an old bed spring and drag it back and forth.
Scp
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