Design question

I've got a project on and need to be able to do something I can't quite work out and hope someone more talented can help me out. Hard to explain in situ but will try to extrapolate it to a lampshade, sounds daft but will work when transferred to project I think.

So, I have a lampshade (coolie?), basically a cylindrical A shape, say it is 12" high, not that it matters, but for sake of explanation - I'm going to practice on an A shaped lampshade I think. I want to be able to cut out shapes that make various 'rings' around it, an equator-looking strip that is 1" wide and goes all around the cone at various heights, say 2" from the base, a 1/2" wide 5 inches from the base. I also want strips that go only a half or third the way around the cone. I want to be able to cut the shapes out in tracing paper or similar.

Is there a simple way to do this so that any number of variations of equators are easy to produce?

Any help appreciated.

p.s. just thought while writing this, that a dunces hat would have been more appropriate to use

GG

 

Cut out a copy of the shape needed to cover the lampshade as exactly correct as possible. It will be a segment of a circle so a compass will be an asset. In fact, don't cut it out, just draw it on a very large sheet of paper.

Then, using the little pinhole that the compass made when you made this drawing, you can draw as many concentric circles with the compass as you like giving you lots of equators.

In fact, I'm not sure if you even need to draw out the lampshade cover replica at all, you just need the concentric strips.

Easy if you are using paper, a lot less easy if you using fabric.

 

Thanks Madahhlia. I thought of that also, but didn't have a compass, haven't used one since I was a kid! I tried using a bit of thread between a nail at the centre with a pencil tied to the end. It didn't work for some reason, was wonky and the vertical shape was a bit off also and would not hug the flat surface on my trial. Maybe I did something wrong.
Perhaps I'll have to buy a compass to get it super accurate. Back to school for me

ps I think you need to outline the largest possible circle (in this case the bottom of the lampshade) and work inwards from there....

Cheers GG

 

Is this any help GC ?

http://craig-russell.co.uk/demos/cone_calculator/

If I understand you are trying to mark out large radii , the tool for this is called a trammel ( many different configurations ) . I thought that a drawing pin , string and pencil would manage this with a little practice though .

http://www.axminster.co.uk/trammel-cutter-set?gclid=COb1wvz30LsCFSKWtAodtnAAcw

 

Hi Harry,

Sorry for late reply, but have been away for a couple of days.
That is part of the answer, but have found something that goes on further from that which seems to answer the conundrum. It is a lot more complicated than I thought and involves Pythagorases Theorum, gosh haven't thought of that since I couldn't understand it at school

It seems a bit faff for something that looks on the surface quite simple!

Cheers
GG

 

GC is it not easier to nip into Next , and see what they have

 

Maybe if we knew what you were trying to make it would be more understandable.
Are you looking to make sections of the surface area of a cone?