I remmeber doing something simliar to this in seventh grade in shop class, of course on a much less sophisticated scale. We had to cut the wood into pre-fabricated designs and then if we had extra time we could extra support stuff. I think mine did about 140 lbs. (not sure what that is in Kg.). Nice work on your bridge though, I like the trusses.

hehe reminds me of science competitions we used to do when I was about 10 years old. National competitions (small key things, not massive industry) held down in Cambridge (2 hours on bus), tons of schools took part - loads of lego/other such stuff on a table, and a problem to solve.

Had similiar things, construct bridges, or hold as many bricks as possible with 10 pieces of paper, move weights across spans with just a few implements etc. Ahh that brought back good memories, even if it is slightly off topic from your post - thanks

I don't think they do that type of thing anymore, which is a great shame - it was awesome fun and got to meet kids from all over the country.
*edit for the dire use of remembers me, when i meant reminds? dunno *

Edited by - Chips on 11/20/2006 12:49:39 AM

<memories>

I remember doing this in school, i made a right pigs ear of it. years later i had to do it again on my teacher training course, but out of straws! The guy who did the best one kind of cheated, he'd poured glue into each straw the night before so that they were completely rigid. But he got top marks for creative thinking (i still think it was cheating though)

these things are still done, my daughter and her fiends used to enter these inter-school competitions every year, always design and construction projects, They won one year, a robot competition.

These kind of projects are the best tools for hands on learning, which is, in my opinion the best kind (though it can't be used exclusively). However, this project isn't all fun and games... this being a college course we now get to conduct a full failure analysis of the structure, determining all internal forces, etc at the moment of collapse. Loads of fun.

I had an engineering project earlier this year except we had to design an air piston motor with a particular speed and power output at a particular air pressure. It took quite a lot of work designing the general configuration, figuring out the dimensioning of the various parts to get the desired effects and then material selection, machining methods etc. Finally after loads and loads of work we were ready to actually make it and we met our first problem: the guys at the workshop told us that a particular grub screw we were going to use to connect the cam to the driveshaft wouldn't work. So at the last minute we had to alter the design to make the shaft and cam all one piece (a hell of a lot harder to make).
After several hours of working in the workshop, machining the parts out of lumps of aluminium, we had the drive shaft machined and all the necessary sections at precise angles removed from it for the pressurised air to flow through. Now we needed to finish off the final part: the cam.
We shove the whole thing into the lathe and as soon as the tool touches onto our work, it bends the entire shaft!
We were running out of time so we managed to bend it back and used emory cloth to remove the ever so slight kinks in it but we'd lost a lot of our air tightness.
Regardless we carried on, built the damn thing and presented it to the profs to run it and measure it's power outputs.

It was AMAZING! It actually worked despite all our problems! It was the only motor out of all the groups that actually self-started. Although the power output was low, it turned out everyone had underestimated the air loss anyway and we were far from the only ones with an underpowered motor. The prof however got excited as he increased the air pressure and the motor put up with ever increasing speeds. It was now vibrating and zipping around the table! Eventually though, he overdid it, something stripped off or wore out and the whole thing jammed and died.
Months of work destroyed in a few minutes by the capable hands of a mechanical engineering professor

Wow, that turned into a stupidly long story!

I think the above would rather fall under the category of the professor wanting to test your design, the fact he got enthusiastic says alot about your groups effort and design.