# Tetrahedrons revisited

A while back I posted a question about calculating saw angles for making a tetrahedron from square stock. It took a while to solve the problem, but I was finally able to make what I was after:
http://www.flickr.com/photos/74619244@N00/3032662076 /
Fast forward a couple of months - we've been building a house using engineered TJI lumber, and had some 7' cutoffs that were headed for the demolition bin. On Wednesday it was snowing too hard to work outside, so...
http://www.flickr.com/photos/74619244@N00/sets/72157613120378769 /
I'm going to paint it white and sell it to some big corporation as art. Bidding starts at \$10,000 - anybody from Merrill Lynch on the rec want to spend a little of his 2008 performance bonus?
Scott
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I love it!
Just curious, why did you taper off the corners? Break too easily?
--

-MIKE-

"Playing is not something I do at night, it's my function in life"
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The corners aren't actually tapered, they form those angles when beveled to fit with the other two pieces. A line from one corner to any other corner lies on the surface of the 2x4 chord of the joist, so the corners aren't tapered or rounded off in any way.
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Elrond Hubbard wrote:

http://www.flickr.com/photos/74619244@N00 /
On the old ones, the pieces come to a point. On the new one, they are beveled.
Help me understand this. :-)
--

-MIKE-

"Playing is not something I do at night, it's my function in life"
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Those were both made with sticks that are square in cross section. The one with the sharp points has the sticks rotated 45 degrees from the where they are in the 'beveled' one.
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Would you care to share the calculations that you came up with?
Pretty interesting.
jc
p.s. "Merrill Lynch performance bonus" hahahaha

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The cuts were made at 35 1/4 degrees, with the saw tilted 30 degrees. I cut from both sides, which forms the point at each end of the joist. The interesting thing is that with those angles, a 90 degree angle is formed on the surface at each end. You can see the three 90's at each intersection.
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