[TheForge] lamp shade

[Janet Rivera Switzer]

If you cut a horizontal slice and look straight down, yes, that's a 90 degree
angle. But if you lay angle iron along the entire corner edge of the pyramid,
that's not straight down. 

I got to thinking of a squished-down pyramid with a real wide base and a very
low height. Even in my mind I can see that 90-degree angle iron isn't going to
fit very well along those corner edges because they will be splayed out too
much. An obtuse angle is needed in the angle iron, but I haven't a clue how to
figure out just how much obtuse.

Janet

> I have been waiting for someone to raise this question.  I can't see how you 
> need anything other than a 90 degree angle for the vertical side pieces.  If 
> you take a horizontal slice through a truncated pyramid it will be a square 
> and those angles must total 360 and be 90 each or it isn't a square.  Now 
> the included angle of the piece across the bottom will be something less 
> than 90 and the angle across the top will be something more than a 90.  I 
> would do the top and bottom out of flat stock with tabs welded on to hold my 
> filler material.  Take a piece of paper and fold it into a 4 sided payramid, 
> the angle of the fold is still a 90.  Or am I missing
something