laser beam splitter for setting out a right angle

Setting out a right angle triangle: both sides are about 3m. I would like to make it right angled as accurately as possible. The obvious way of doing this is to split a laser beam into 2 beams 90 deg apart by firing it into an accurately ground internally reflecting prism. Is there any such device on the market?

There's no requirement for levelling in this: just need a 'perfect' right angle. I've looked at a variety of laser levels and line drawers but none appear to do this, or at least fail to proclaim the facility on the packaging. Or any other suggestion?

TIA

Reply to
jim_in_sussex
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jim_in_sussex presented the following explanation :

How perfect is 'perfect'?

Most people manage to make an accurate enough right angle out of three good straight pieces of wood forming a triangle.

One of the prisms in an old pair of binoculars might just be a 45 deg(?).

Reply to
Harry Bloomfield

Two lasers?

Shouldn't be hard to bond to an engineer's square and fabricate a micro-adjust?, should be a lot cheaper, too.

Just a thought... DIY and all

Reply to
Mike Dodd

Use trigonometry. The hypotenuse will be the square root of the sum of the squares of the other two sides. If yours were both 3m, then the hypotenuse is sqrt(3² + 3²) = 4.243m. The easy one to remember is a 3-4-5 triangle... sqrt(3² + 4²) = 5 Make up a loop of string (preferably as non-elastic as possible), which is 3+4+5=12m long, and mark it at the 0m, 3m, and 7m positions. when pulled taught (but not stretched), the angle between the 3 and

4 metre sections will be a right angle. Scale the units if this makes a triangle which is too big or too small for the given application.
Reply to
Andrew Gabriel

Yep. 3 straight pieces of in the ratio 3:4:5 guarantees a right angle as accurate as you can make the ratio.

The corners of an 8x4 sheet of reasonably thick MDF or ply are also very good right angles (unless bashed!)

Reply to
PC Paul

2 days ago there was a post about laser levels describing a tool that gives you horizontal or vertical or both

Regards Jeff

Reply to
Jeff

You could use something like this and direct the beam at a prism as you suggested.

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Benjamin Middlethwaite

Reply to
The3rd Earl Of Derby

Pricey though.

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Benjamin Middlethwaite

Reply to
The3rd Earl Of Derby

Dead right. Worked OK for the pyramids in Egypt didn't it?

Dave

Reply to
david lang

"The3rd Earl Of Derby" wrote

£19.95 actually

Regards Jeff

Reply to
Jeff

Bad catch 22 situation. The laser beam cross needs to be aligned vertical to the surface on which the line are shown, or else the lines won't be at right angles. How do you get this right angle in the first place without using a set square, or possibly a plumb line if the laser is pointed down to a flat floor.

john

Reply to
john

Spirit level?

Reply to
dave

In article , jim_in_sussex Sun, 1 Jan 2006 14:49:46 writes

I have one I bought when building my loft. It has two lasers at right angles.

I don't have the details to hand but I think it cost about £150

Reply to
Les Desser

QVC (UK) sell a tripod mounted laser device that projects a vertical line and a horizontal line. Each line is separately switcheable. The Vertical and horizontal lines are pendulously self correcting [within reason] and the tripod arrangement allows the projection head to be adjustable in height (heave axis) via a rack-and-pinion winding gear; rotation (yaw axis) is achieved by manually swivelling the laser head. The 'right angle' projected is "close enough for government work" and more that suitable for D-I-Y.

Reply to
Brian Sharrock

is there something wrong with using a spirit level?

NT

Reply to
meow2222

If he doesn't care about levelling, all he needs is a tape measure.

Reply to
Chris Bacon

The Egyptians didn't have trigonometry. They had some geometry (including 3:4:5 triangles), but not that much.

Reply to
Andy Dingley

Then buy a Cowley level or similar off eBay. Full-blown theodolites are cheap (tripods are harder to get hold of) and there are plenty of simple-to-use builders' levels and similar gadgets that can accurately lay out a level or a plan right-angle with minimal complexity.

Lasers are of negligible use here. it's easier to do it with eyeballs and a telescope than a projected spot. For 3m ranges outdoors you'd have to spend serious money to get a laser that was remotely easy to use or accurate.

Reply to
Andy Dingley

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