topic Creating a 4-sided Pyramid (tetrahedron) in Fusion Support Forum

Creating a 4-sided Pyramid (tetrahedron)

Anonymous — Sun, 21 Apr 2019 18:27:24 GMT

I couldn't find a simple explanation of how to easily accomplish a 4-sided pyramid. I figured I wasn't the only one with this issue so I'm sharing. 🙂

Sketch a rectangle (square) then Stop Sketch
Extrude your rectangle and set this formula as your taper angle
- -(90 - (109.47/2))
Press enter and you're done!

https://gyazo.com/f32fd2384868061532f8be4f3ccb7066

Re: Creating a 4-sided Pyramid (tetrahedron)

JDMather — Sun, 21 Apr 2019 19:29:32 GMT

@Anonymous wrote:

I couldn't find a simple explanation of how to easily accomplish a 4-sided pyramid.

Sketch a rectangle (square) STOP HERE - THIS IS WRONG

You have posted the incorrect solution on two different forums.

1. Your result is a 5-sided pyramid (if you include the base in count of "sides"), not a 4-sided pyramid. (The requested a Tetrahedron.)

2. Your techniques required calculations.

3. The attached technique is the easiest for a tetrahedron. With just a bit more work a fully parametric pyramid of any number of sides can easily be created.

Re: Creating a 5-sided Pyramid (tetrahedron)

Anonymous — Sun, 21 Apr 2019 19:35:32 GMT

Heh, probably why my Google searches didn't find anything. Thank you for correcting my oversight. Do I need to post the calculations or the source of the calculation?

https://en.wikipedia.org/wiki/Table_of_polyhedron_dihedral_angles

I had noticed shortly after that it was the Inventor board, which is why I re-posted here. Apologies if that breaks any rules.

Do you mind explaining why drawing a square (or creating a box/cube) is the wrong technique here?

Re: Creating a 5-sided Pyramid (tetrahedron)

JDMather — Sun, 21 Apr 2019 20:15:16 GMT

1. The best solution would not require ANY calculations (other than those entered into User Parameters).

2. Try changing the number of sides in your first 2D sketch. What happens to your Pyramid.

3. You have posted this in the wrong forum. The correct forum is over here. But now what is done is done.

Create "pie" sketch.

Loft to point.

Pattern Loft.

Combine.

The original base size and number of sides can now be parametrically changed at will.

Re: Creating a 5-sided Pyramid (tetrahedron)

Anonymous — Sun, 21 Apr 2019 20:00:25 GMT

Thanks again for your help! To be fair, I never said this was the "best" solution. I just felt it was a quick and easy way to create the shape.

Re: Creating a 5-sided Pyramid (tetrahedron)

JDMather — Sun, 21 Apr 2019 20:25:51 GMT

But a four sided base will not generate a Tetrahedron.

Funny thing is - I thought I had a general solution for this problem and now I can't find it and can't recreate it (N number of sides of x length). I have to get some other work done but will try to revisit this problem when I have time.

Driving me crazy.

Re: Creating a 5-sided Pyramid (tetrahedron)

JDMather — Mon, 22 Apr 2019 11:08:17 GMT

A tetrahedron is a special pyramid in that all edges can be equal length.

Attached is a general pyramid "solution".

Edit the Parameters of Number of sides (not including the base as a side), Base edge length, and Apex height.

The geometry should update.

Let me know if you find an issue with the "solution".