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

jim_in_sussex presented the following explanation :
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?

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(?).

--

Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

jim_in_sussex wrote:
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


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

In article .com,
"jim_in_sussex" writes:
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

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.

--
Andrew Gabriel

Harry Bloomfield wrote:
jim_in_sussex presented the following explanation :
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?

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.

Yep. 3 straight pieces of whatever 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!)

"jim_in_sussex" wrote in message
oups.com...
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?

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

Regards Jeff

jim_in_sussex wrote:
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

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

http://tinyurl.com/7cuvj
--
Sir Benjamin Middlethwaite

Jeff wrote:
"jim_in_sussex" wrote in message
oups.com...
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?

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

Regards Jeff

Pricey though.
http://tinyurl.com/dykt4
--
Sir Benjamin Middlethwaite

Andrew Gabriel wrote:
Use trigonometry.

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

Dave

"The3rd Earl Of Derby" wrote

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

Regards Jeff


Pricey though.
http://tinyurl.com/dykt4
--

£19.95 actually

Regards Jeff

jim_in_sussex wrote:
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?


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

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

I've looked at a variety of laser levels

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
--
Les Desser
(The Reply-to address IS valid)

"jim_in_sussex" wrote in message
oups.com...
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

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.

--

Brian

jim_in_sussex wrote:
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

is there something wrong with using a spirit level?

NT

wrote:
jim_in_sussex wrote:
Setting out a right angle triangle: both sides are about 3m. I would
like to make it right angled as accurately as possible. [ snip ]
There's no requirement for levelling in this: just need a 'perfect'
right angle.

is there something wrong with using a spirit level?

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

On Sun, 01 Jan 2006 23:39:35 GMT, "david lang"
wrote:

Use trigonometry.

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

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

On 1 Jan 2006 14:49:46 -0800, "jim_in_sussex"
wrote:

Setting out a right angle triangle: both sides are about 3m. I would
like to make it right angled as accurately as possible.

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.