Good evening
A customer has an oblong shaped kitchen and would like me to arrange the downlights in an oval shape.
Is there a mathematical solution to this, or any tips ?
I have a laser, but not sure it will help ?

Regards
Ady

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Resistance is futile.

Two fixed points on the centre line and a loop of string wrapped around them- pencil in the loop and pulled outwards then moved around the fixed pins keeping the string taut, this will scribe an ellipse, may be worthwhile experimenting on the floor- distance between pins and length of loop will all influence the shape/size of the ellipse- obviously any joists will need to be accounted for!.
Not simple-but looks good, done it a few times now, carefully measurement is the key to a good outcome.

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Those who make no mistakes do very little work!!......

'The Gardeners Ellipse' use two screws, a bit of string and a piece of coloured chalk if a white ceiling.

regards

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"Take nothing but a picture,
leave nothing but footprints!"
-------------------------
"Oh! The drama of it all."
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"You can throw all the philosophy you like at the problem, but at the end of the day it's just basic electrical theory!"
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Edited: 15 January 2013 at 11:46 PM by rocknroll

i have laid them out on the floor as well, it gives a good idea of what you are trying to achieve. Then all you have to hope for is that the ceiling joists aren't in the way.

Gary

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Specialised Subject. The Bleedin Obvious. John Cleese

you'd better not show your client the oval down lighters that are on the market. He's bound to like them.

Hey thanks guy's
I had no idea that's how you do it.
I'm much obliged to you all.
Ady

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Resistance is futile.

Talk them out of it, had to wire a living room in a diagonal strips, nightmare, 2 of us spent about hours marking these 16 spot lights out in the living room so we didn't hit joists

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Dougie
Power Plus Electrical.co.uk

My mission is to live as long as possible......so far so good!

lol
to be fair, the ceiling is getting repaired and replastered, its a bungalow and I can alter ceiling joists - otherwise, I would agree

Ady

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Resistance is futile.

Oval or segment of a curve?

I think I would be trying to mark it out on the floor using three wooden lathes tacked together and two nails to slide them against with a third nail giving a temporary reference before it is removed. This is a traditional method for marking out boat hulls, useful for setting out bricklayers arch forms as you can make them the correct rise to work brick courses.

Two nails at the end of the curve, the temporary one setting the depth of the curve, three lathes tacked together to form a triangle with the nails on the external intersection, pull out the centre one and hold a pencil in its place, then slide the assembly around the other two nails, it won't give a full oval though.

Clear as mud! I can't find a diagram with Google.

Andy

Ellipitic Arch


I can't find the three lath method of lofting on a Google search.

Andy

Hmmmmm
Fortunately - I'm quite 'arty' so would consider 'freehand' - but I've also just drawn on a piece of paper as follows.
12 dots in a 0 shape. top, bottom and sides on a cross axis and the others accordingly. Then 'it appears' that my spacings down could be 500, 1000, 1000, 1000, 1000, 500 and my spacings across could be 2000, 4000, 4400, 4000, 2000 so, i was wondering if there is a mathematical way like this of doing it.
Maybe I could find a small shape to fit just above my torch and draw its enlarged shadow ???
The mind boggles

Regards
Ady

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Resistance is futile.

Incidentally, I bought a USB snake camera from Maplin in the New Year sale to see where existing joists are before drilling:

Maplin snake camera

The quality isn't brilliant, however it does come with integral LEDs for illumination and the brightness is adjustable.

The camera is on the end of a flexible gooseneck which can be passed through an existing downlighter hole or a small pilot hole to survey.

It could also be used for detecting pipe leaks in hard to reach places too.

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M.I.E.T - Forfeited this due to The I.E.T's ridiculous membership rules!

Well you could always calculate the perimeter (P) of the ellipse and divide by the number of downlights you are fitting, the perimeter calculation is not perfect but if a (major axis) is not greater than three times the length of b (minor axis|) then it is accurate to around +- 3 to 4%.

Look left for Axis;

P ≈ 2 Pi √ (a² + b² / 2)

For a ceiling use the 'Gardners Ellipse' method which involves tying each end of the string to two screw points, to make it easier drill a hole in the pencil about 1 inch from the point and pass the string through the hole.

Regards

-------------------------
"Take nothing but a picture,
leave nothing but footprints!"
-------------------------
"Oh! The drama of it all."
-------------------------
"You can throw all the philosophy you like at the problem, but at the end of the day it's just basic electrical theory!"
-------------------------

Edited: 21 January 2013 at 03:53 PM by rocknroll

Elipse

Wow R&R !!!!
That's a fabulous answer - and very kind of you to spend the time you have.
I will enjoy working that one out - so will my dad (he's an accountant and loves number crunching !).

Will let you know how i get on as i'm doing them over the next couple of weeks.

Kind regards
Ady

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Resistance is futile.