Relief Comes

December 10, 2007

After spending the past two weeks just trying to figure out the initial reactions on a flat Howe truss, and trying umpteen different variations of method of sections and method of joints and all that jazz, I went to the engineering learning center.

The MTU engineering learning center, or Student Innovation Center as they call it, is a nice large quiet room. There are plenty of folks there who can help you. Unfortunately for me, none of them were good with Howe trusses. The coach who was helping me tried many different ways, but didn’t get anywhere. Surprisingly, he got different answers than I did using the same equations. He got confused enough he had to go grab two different structural engineering books. While he was poring over those, I made a breakthrough:

  1. My angles were flipped around. I had been finding the vertical components as horizontal components and vice versa
  2. I was starting at the wrong point, which had too many unknowns to solve for
  3. I was complicating this far too much in my mind

What I needed to do was start at the top leftmost joint and go from there. There, there were only two forces acting on only two members, which left a solvable equations (Sum of forces in X/Y direction = 0) By starting there I removed an unknown from my previous equations, which allowed for me to solve for the Y component in the diagonal member by summing forces in the Y direction. Once I found the forces in the diagonal member of the truss, I used simple trigonometry (cosine of the angle times force in the member equals the horizontal component) and summed forces to find my last force in the bay.

Funny enough, when I went to check (sum forces = 0) it did not check out right away. Silly calculator error.

So I’m relieved and in the mood to work on this once more.

I will post images of how to actually do a Howe truss later. I’m sure that there are gonna be people stumbling on to my blog looking for it at some point, might as well deliver.

We got our engagement proofs in. The first few don’t look that great since we were just getting into the hang of posing for photos [(10:15:16 PM) jillithpru: i look pregnant and bad expression on my face] , and there are a couple that are a bit odd, but for the most part they turned out amazing.

If you want to see them ask me and I’ll show you.