Balsa Has Been Framed

Well, yesterday (for me - I'm writing this on Wednesday but this won't be published until Friday afternoon when everyone's had a chance to test and I don't have to risk influencing people for better or worse. Perhaps I should say Tuesday) we broke our balsa wood frame, the culmination of a process that had begun a few days earlier. Sunday afternoon, we met in that room high in the corner of the Engineering building - 317 - that room which, if our teachers are to be believed, we will be considering our home by the end of the semester. But for now, it still felt like a bit of a vacation into another world - a world full of excitement, but also a world of danger - where else (except maybe Australia, where they say you are never more than 6 feet from something that can kill you) can you glue your eye shut, inadvertently make a permanently attached accessory of a piece of balsa wood, and eliminate unneeded digits - all without walking more than a few paces (excluding trips to the hospital afterwards) . Fortunately for us, construction went relatively smoothly. As you can see in the photo below, our frame consisted of an outer triangle frame, and reinforcing pieces within. On Sunday, in about 1 1/2 hours, we constructed the outer frame and added the major structural triangles (the ones made of the fat balsa wood). Considering that a fair accomplishment for the day, and requiring time for the glue to cure before adding a second layer, we left the lab and the fumes of CA that never seem to completely vent even with the windows completely open. But the next day we were back for more. This time, we used the remainder of our thick balsa wood to create the triple-thick stiffening triangle which would transfer the majority of the force from the block in the center outward to the side supports of the Satec frame. We used the thin pieces of balsa wood to add additional reinforcement, and placed leftover scraps of balsa over critical butt joints as gussetts. Then we were done - with the construction. I might have wanted to take the frame down to the lab, test it, and end the suspense, but we had to wait at least an hour for the glue to cure, and if you're going to wait that long, you might as well wait the full 24 hours. So Tuesday, right after our classes ended, we took our frame down to the lab and prepared for the worst, hoping to get at least 50 lbs. Imagine our surprise when the numbers passed 50 and kept clicking upward into the triple digits. The experience itself is impossible to describe - the report says that it took almost 4 minutes but it felt like less than a minute - a minute of incredible tension, the beating of my heart fighting for attention with the sound of balsa wood straining and threatening to crack. We thought that it was over at around 140, when the glue joints holding our top beam popped and left the center bar in a v-configuration. But by that time the pressure was enough to keep the top from falling off, and the numbers kept clicking up - 150...200...300, at which point the top of our frame was starting to slant to the side. But it still kept holding until 319.9 lbs, at which point the top bent off to the side and the pressure dropped to the mid 100's and the test was declared finished with a final amount of 319.9 lbs - they tell us it's the highest the school has ever seen. I still can't believe it - none of us had any building experience before. We went into this completely blind, and about halfway through the building we stopped calculating the sizes things should be and started just measuring them by appearance, then cutting and sanding them to fit. All I can think of is that it was a combination of our triple-thick bracing (which kept the taller single-triangle design from folding to the side) and the fact that our butt joints were all done at 45-degree angles rather than the right-angles usually used. But overall, it was a fun project, and I guess now I feel a little more comfortable going into the rest of the design competition knowing that we were able to at least build one thing, however small and simple it may have been. The design project seems rather far off still, although we are pretty much down to our final design decision, with the only remaining decision being about the details of the steering. I'll try to write a more detailed post about that process soon, as I promised in my first post (but right now test tips were more interesting and more pressing to get out while it was still talk like a pirate day)
So, we're celebrating our success, but of course, there's the possibility that someone may come along and beat us yet. We're crossing our fingers, but if someone does manage to do that, I congratulate them as well. I also congratulate Section B as a whole, who so far is maintaining an average of over 100 - Great Job everyone! And seeing as I'll know the final results shortly after I publish this, I'll update with the final results when I know them.
Until next time...

The Initial Structure Before the Crunch


Starting to Feel The Squeeze

"You Look Like You've Been Through A Satec"

Note the main breakage point at top left. If you look closely you can see how the wood started to splinter as the top tipped sideways. The most obvious damage - the separated joint at the top left, was the one that occurred in the mid 100's - that portion seems to have been superflous to the structural integrity of the frame.
These images have been scaled down in consideration for people's download times. You can see them in full resolution in the Pilot's Ponderings Photo Gallery

UPDATE: I have been informed that the results are in, and our record stands. Congrats also to all of Section B on achieving the highest class average - 106.80 lbs, and to everyone else who participated. Now on to the design competition.