The next week of class was consumed by each student presenting and speaking to their design what their main tenets would be for the project. Part of the previous week’s assignment had been to pick your tenet or tenets and be prepared to stick with them. My main tenet was to see the design through and devise a way to pull off the cantilever. I knew it was going to be tough just by all the drawing work I had put into SketchUp. Seriously, there are only 6 90-deg corners (aside from all the joints in the torsion box) in the whole design. I was truly worried I would be told this was too aggressive.
When my turn came to present my concept I prefaced my comments with the fact that I intended to attempt a design with a cantilever in it. I discussed my inspiration piece. Our instructor liked the beam table (see the previous blog entry). This was a good sign… I unveiled my second design concept and Willie (the instructor) instantly commented it was a strong design but in the same breath noted the complexity. I jumped right in and spoke to the ideas I had about how I could strengthen the joint by bolting the top to the main support.
The gap in the torsion was intended as a slot for a flush-front drawer. He ultimately could see that I had put a lot of effort into accessing the problems I would face and supported my decision to build it as long as I 86’ed the drawer. I was ecstatic and surprised at the same time.
After everyone had talked about their proposed projects we each got to spend a little time in one on one !discussions with Willie. He reemphasized the challenge ahead of me but also told me he would like to see me succeed. We set about addressing the top and it’s weight. Rather than execute the design as it was, why not just make the whole top a torsion box? It would further cut down on the weight and since it was a torsion box, there would be plenty of strength even with a 5/16 skin of plywood on the top of the box. I agreed I would take the next week to modify the drawings. The only problem was, at the end of design presentations, our new assignment was to bring a model to class the following week…
Here are some views of the final design where the whole top would be a torsion box.
Now, all I had to do was build a model. Here is a sneak peak of the 1/6th scale model. In the next entry, I’ll discuss what the model helped reveal about the design.
-- Jeff, St. Paul, MN