water level

[dennford]

trick question - some finer point that we can't think of ?

[dennford]

example a plumb bob suspended from a 100 ft tower in London would be 163 degees to a plumb bob suspended from a hundred foot tower in Tokyo.

Denn

[joe greiner]

Works at shorter distances, too. For example, suspension bridge towers can be far enough apart to justify accounting, when fabricating the deck truss and estimating the amount of wire needed for the job.

Joe

[Barry Hicks]

Using water to find a level is not really a new concept. The ancient Egyptians used the idea when building the pyramids and probably borrowed the idea from an older civilization.

Barry Hicks

[pawnhead]

That's an interesting subject. Do you know how they did it specifically? Any links to read?
I suppose they could dig a long trench for water (or use clay pipes, or half-pipes), or just dig a short one and drive two sticks in it for a line of sight to use sort of like a dumpy level.

I suppose you could make a crude dumpy level using a short piece of water level as your sighting reference. It's amazing how accurate your eye can be over quite long distances, even when your reference distance is comparatively short.

[Barry Hicks]

PH, I'm not sure how the pyramid builders did it but I seem to recall (from some TV documentary) they cut a channel in the stone and achieved accuracy to within 5-6mm overall.
Some of our smarter forumites may have more accurate info.

Barry Hicks

[HappyHammer]

As a non-smart forumite can I just confirm the following....

If I am building a freestanding deck roughly 10m x 10m and I want to mark a point on the corner posts, I can use a 15m clear tube with water in it to ensure marks on both posts are level to enable me to cut the posts to the same height for instance?

No smart answers about irrelevant tollerances required

HH.

[Barry Hicks]

Yes HH, it is simple and accurate. I once re-stumped (and raised) a high blocked house using water to get levels. I was too mean to buy a great length of clear plastic tube but settled for the garden hose with a metre of clear stuff at each end.

I don't know how accurate it was but all the doors and windows worked OK afterwards so it can't have been too bad.

Barry Hicks

[dennford]

that's exactly it mark your line on the first post and fasten your tube to the second at the approximate hieght. take the other end of the tube to your first mark and raise or lower the tube untill the water level coicides exactly with the mark - if you have no one to hld it then tape it at this level, where the level is at the other end is your second level (I always recheck the first end again (akin to measure twice).

Denn

[rat52]

Barry,
the only problem with using garden hose is that you can't have any air bubbles in the tube and clear hose makes it easier to see them.

I think the air can compress or a bubble escape without you noticing and you get wrong readings.

These are the reasons I was given but I do know that bubbles do make a difference in the accuracy.

[dennford]

Barry,
the only problem with using garden hose is that you can't have any air bubbles in the tube and clear hose makes it easier to see them.

I think the air can compress or a bubble escape without you noticing and you get wrong readings.

These are the reasons I was given but I do know that bubbles do make a difference in the accuracy.

Sorrry, I hadn't taken notice of the garden hose bit. Rat is very much right on that. Thanks Rat

Denn

[pawnhead]

As a non-smart forumite can I just confirm the following....

If I am building a freestanding deck roughly 10m x 10m and I want to mark a point on the corner posts, I can use a 15m clear tube with water in it to ensure marks on both posts are level to enable me to cut the posts to the same height for instance?

No smart answers about irrelevant tollerances required

HH.

This thread may be of interest:
http://www.woodworkforums.ubeaut.com...ad.php?t=44361

[Barry Hicks]

You are right about the bubbles. The only difference with using garden hose is that you can't see them so 'de-bubbling' become an automatic thing every time the level was used.
And yes, bubbles in the line certainly do give wild readings. I was fortunate in that I had an old chippie mate look in regularly to keep me pointed in the right direction.

Barry Hicks

[pharmaboy2]

hi guys - getting a big enough bubble into the line is no mean feat. The only way it can be a problem if you succeed isif the line is coiled and you allow the buuble (has to be a decent size) to get to the highest point in the pipe ie above datum, then that will be the new height reading given.

I have used clear pipe always, and really cant remember making a mistake, but i always use a bucket at one end - the extra volume of water in a bucket makes sure that a small spillage out the end, essentialy makes no difference as it doesnt change the level in a bucket - much better than the small amount of water in a hose where 10mls might have reasonable catastrophic consequences to your heights.

I was using one once, and young carpenter came up, and said "mate, get yourself a dumpy - water bubbles can stuff you up in a moment!" - I asked him politely to empty the line, then refill it quickly with some bubbles in it - he declined the offer and took my word for it.
So, unless you think getting the whole coiled up hose, and pushing it into a bucket and trying top fill it that way is sensible, then you'll never have a partly filled hose. via tap or suction with siphon, never going to be a problem.

[BobL]

Some things are constants:
a) - Water is always level,
b) - a suspended weight is always vertical,
c) - a 3,4,5 triangle always creates a rightangle.

Things are not as constant as they might seem
None of the above are correct
a) if the water is rotating
b) if a suspended weight is being accelerated
c) the triangle is not on a flat surface.

Cheers