Spirit level broken ?

[marsaday]

How do you know when a level needs replacing?

I have been doing some work on the house and have used the 2 vertical levels on my spirit. The top one is slightly out of level, while the lower indicator is level. does this mean the level now needs replacing?

it is a stabila one.

 

[RonnyRaygun]

Surely if you rotate the level through 180 degrees the lower indicator becomes the upper indicator?

Just cover the one which is out of line with some tape or similar, then you can't use it accidentally.

Even then it might be worth checking it against a surface that you know to be plumb...

 

[marsaday]

yes i could do that. but i just wondered if one bit goes, what does this mean for the rest of the levels?

do levels have a life span. this is 10 yrs old.

 

[RonnyRaygun]

Can't see why they would have a specified lifespan.

The most important thing would be to calibrate them regularly to ensure they are still accurate I would think.

I used to use my Grandad's 12" J. Rabone "Boat" level to level my snooker table. Don't know how old it is exactly but quite possibly pre war.

 

[joinerjohn]

All depends what's happened to the levels. Have you dropped them at some point? Maybe years ago and didn't think anything of it?
Lots of factors can make spirit levels go out .
Easiest way to check them is

Checking horizontally :- Hold level on wall and mark a pencil line under each end. Turn the spirit level end for end. line one end up with mark, hold level and mark the other end. If the spirit level is out then you'll see 2 marks at this end.

Checking vertically : hold spirit level vertically. Make a mark at either end (on the straight edge) Turn the spirit level right to left hold vertically (To bottom mark, Make another mark at the top and check. If there are 2 marks at the top then it's out. The distance between the 2 marks at the top will give you an idea of how far out it is.

If the marks (both horizontally and vertically) are only a few mm apart then I wouldn't worry too much.

 

[ColJack]

nothing in this world can ever be truly "level".. since the earth is round then everything is on a curve..

if you extended your "level" 5 miles in each direction and took another "level" at that point, it would be out compared to the first one..

wouldn't the spinning of the earth also cause the bubble to be pushed to the west slightly? ( or would it push the liquid to the west and hence the bubble would move to the east? )

anyway those technicalities asside, to check a level, level something with it then rotate the level through 180° and see if the bubble is still between the lines.. if not either adjust the bubble if you can, or using a fine marker, average out the bubble location and redraw the lines....

 

[Norcon]

nothing in this world can ever be truly "level".. since the earth is round then everything is on a curve

Our Leica Geosystems dual grading laser level has a working diameter of 700 meters.
Are you saying the laser bends with the earths curvature?

 

[ColJack]

that would be idea if you could set 2 up 1350m apart and see how much th 2 lines differ where they meet..

 

[gregers]

nothing in this world can ever be truly "level".. since the earth is round then everything is on a curve

Our Leica Geosystems dual grading laser level has a working diameter of 700 meters.
Are you saying the laser bends with the earths curvature?

bet it isnt as accurate as a water level,

 

[ColJack]

bet it isnt as accurate as a water level,

but a water level isn't acurate at all over a long distance, if you had a long enough pipe to take it to the other side of the world then the "level" beween the 2 points would go through the center of the earth..

on a smaler scale, if you had a 10 mile long pipe then the "level" would dip towards the horizon and "back up" again as it reached the other end..

on an only slightly related tangent, if I had a piece of string tied tight round the equator and then raised it so that it "floated" 1m above the ground all the way round the earth, how much longer would it be?

 

[gregers]

how can you raise it if its tight against the earth?

 

[RonnyRaygun]

This is why the towers of suspension bridges aren't parallel.
The Humber bridge towers are 36mm further apart at the top than the bottom (just had to look that up ). But if you put a spirit level on them each tower would be plumb.

The other question: The circumference of the earth at the equator is 40,075.16 km or 40075160 metres, so assuming the earth is perfectly smooth (which obviously it isn't), it has a radius of 40075160 / 2 pi = 6378160 metres.
Now increase that radius by a metre to 6378161 and multiply by 2 pi and that gives you 40075166 metres.

So it's increased by approximately 6 metres. Not very much at all; was expecting a lot more than that!

 

[ColJack]

it's a lot simpler than that..

if we use D as the diameter of the earth, then to raise it 1m would increase D by 2m ( one each end )..
the increase is only 2 x Pi.. = 6.284m extra...

 

[joinerjohn]

nothing in this world can ever be truly "level".. since the earth is round then everything is on a curve

Our Leica Geosystems dual grading laser level has a working diameter of 700 meters.
Are you saying the laser bends with the earths curvature?

It's a well known scientific factiod that light can be bent by gravitational fields.
I would assume that even a laser light would be bent ever so slightly by the gravitational pull of the earth. Might be only a few microns but , bent it will be.

 

[RonnyRaygun]

it's a lot simpler than that..

if we use D as the diameter of the earth, then to raise it 1m would increase D by 2m ( one each end )..
the increase is only 2 x Pi.. = 6.284m extra...

Yeah, worked that out in my head after I went to bed...was hoping I'd got back here before you to give the right answer!