Hi,

 

Met a gal who likes Douglas fir and I happen to have a nice old piece which I'll sacrifice into slats. Want to *wow* her with a test of skill. Figured I'd use a similar shape jewelers use, the hollow pyramid.

 

If I take four identically-sized equilateral triangles and cut all of the edges at 60˚, will these assemble into a three-sided equilateral pyramid with an identical equilateral base? So it is uniform no matter which side is down?

 

 Thank you! 

Are you talking about a tetrahedron?

http://tamivox.org/redbear/tetra_calc/index.html

https://rechneronline.de/pi/tetrahedron.php

Ahhh … my brain just sneezed, after inputting data. Maybe I’ll just bring her a box of chocolates. 
 

And keep making scrap wood as I try trial and error. 

Do it with cereal box cardboard and tape. Cheaper and faster. 

Using your shape terminology I found this:

 

A tetrahedron is a polyhedron with 4 faces, 6 edges, and 4 vertices, in which all the faces are triangles. It is also known as a triangular pyramid whose base is also a triangle. A regular tetrahedron has equilateral triangles, therefore, all its interior angles measure 60°.

 

So that means 30° on all edges. I think. 

Except the bottom edges.

My goal is same any position. I’ll try cutting the parts on a scroll saw. Can tilt the deck. It’ll be safer freehand. 

5 hours ago, lew said:

Do it with cereal box cardboard and tape. Cheaper and faster. 

Wait, you mean give her a cardboard mock-up instead of a model in wood?

Get her the chocolates....they'll have a box.

9 hours ago, Gene Howe said:

Except the bottom edges.

 

I would think even the bottom, Gene.

20 minutes ago, Cal said:

 

I would think even the bottom, Gene.

I'm no chemist but, to sit flat,  wouldn't the bottom edges be a different angle?  

7 minutes ago, Gene Howe said:

I'm no chemist but, to sit flat,  wouldn't the bottom edges be a different angle?  

 

This is above my pay grade   I'm just thinking all four pieces are identical in order to get the results he wants.

 

10 hours ago, Woodman said:

My goal is same any position. I’ll try cutting the parts on a scroll saw. Can tilt the deck. It’ll be safer freehand. 

 

I would make a jig fixture to attach to a ts sled.  That would ensure you get each piece to match.

@Cal, our pay grades are similar.

Mine is probably lower. When it comes to math. I'm a total dunce.  I can figure angles....IN ONE PLANE ONLY. Beyond that. I'm lost. It's usually T&E and cut to fit, for me.

I liked math in school and was good at it then.  Now I like wood turning.

2 hours ago, Cal said:

ts sled

Can you believe I had to google that phrase?

First I'll sketch out four 4" triangles. Go from there.

 

19 minutes ago, HandyDan said:

I liked math in school and was good at it then.

I had a Polish GF who was mature and demanding of my time. Flunked calc.

8 hours ago, Woodman said:

Wait, you mean give her a cardboard mock-up instead of a model in wood?

 

Cardboard diamond, wooden diamond either would be OK at this point in the relationship!

I was told there would be no math when i signed up here.

 

Platonic solids - good fun!

21 hours ago, Woodman said:

Using your shape terminology I found this:

 

A tetrahedron is a polyhedron with 4 faces, 6 edges, and 4 vertices, in which all the faces are triangles. It is also known as a triangular pyramid whose base is also a triangle. A regular tetrahedron has equilateral triangles, therefore, all its interior angles measure 60°.

 

So that means 30° on all edges. I think. 

To make matters worse, when the saw setting is 0, you are really cutting 90. And when it says 30, you are cutting 60 on one edge and 30 on the other.  calculator

Edited May 15, 20224 yr by kmealy