Elevated Bridge B/C

[Pleiades]

oh thats too bad. my school would be dead if they didnt allow 9th graders

[koreangeek95]

This is my first time doing bridges and i was just wondering if i could find a pic or diagram ofr building a bridge. This will be my second year doing scio and last year I did towers so I've never built a bridge. I hope someone can help.

[sachleen]

our team, sadly, doesn't meet until like November and stuff. I'd like us to meet earlier but that wont happen. over the summer, I've posted updates on our school loop thingy but i don't know how many people check that during summer.

[Pleiades]

This is my first time doing bridges and i was just wondering if i could find a pic or diagram ofr building a bridge. This will be my second year doing scio and last year I did towers so I've never built a bridge. I hope someone can help.

These are the draft rules for next year: Division B Divison C
At the bottom of the first page for each of them there is a small diagram of an average elevated bridge. After the rules there is a few pages of info. After the draft rules came out i built a bridge for each set of rules out of chopsticks. I would upload a pic to share with all of you but my computer broke so i'm on my aunt's laptop and it is VERY old so i cant do anything like uploading pics on it. Hopefully my computer will get fixed and i can upload it.

[Aia]

I built another bridge today- this one was more like an A frame/tower.

I don't know if I can really rave about the style yet. I think an A frame has a lot of potential... but I don't think I captured its capacity in my design. If only we could run tension beams to connect the distal ends! That would just make everything so much simpler.

[Pleiades]

i used an A frame for both of my bridges [division B and C] of course the div B one was better since it was smaller. well atleast i think its better.. it feels stronger but i havent been able to test them since i dont have a testing thing [chain and loading block] besides the A frame what other designs did you use? my coach is going to that summer thing next monday so hopefully he'll learn more about this event and share the info with me.

[andrewwski]

Anyone have good tips on arching balsa, or another type of wood? It seems an arch would be ideal...but not very feasible.

[Aia]

I've thought about arching balsa... but it seems very difficult. To get a perfect arch, the balsa would have to be the same density throughout the stick, then multiply that by two for each side. When a friend of mine was competing in gliders, she told me that she baked the balsa somehow to get the arches.

What advantage would an arch give anyways? Would you be gaining strength or losing mass by using them?

Besides the A frame, I've also built a bridge that looks similar to the example on the rulesheet. However, I changed up the crossbeams and main supports to what I thought would be more efficient.

[sachleen]

my first boom was arched, it was really cool looking but sucked lol I don't know where I read this but if you soak it in water and then bake it it decreases the mass by a lot. Also, if you wanted to do that you should take one strip of balsa and cut it in half length wise. That's about the only way to get two really really similar pieces density wise imo. What we did was soak the wood and put it in a cheap 'frame' we made out of weights. It was basically 3 weights, one at each end and one in the middle. The wood would have to stay in that position over night and the next day it was curved.

[Pleiades]

what was the mass of your bridges?? have you tested them yet?