Elevated Bridge B/C

[croman74]

I agree with you. The highest score will be around 1800. Maybe a team hit 2000, who knows?

[baker]

JimY,
After Nationals do you think you can post a picture of the bridges you are speaking of? The design sounds exciting, hope your willing to share...thx

OK, time to put some real numbers in here. I coached elevated bridge for three schools this season: the two middle school teams in my town, plus the high school team. One of the three is going to nationals. I'll start with the two teams that aren't going to nats. Both won first place at state in elevated bridge (Indiana). The B division entry was between 7.1 and 7.2 grams and was loaded to 15 kg (it actually failled at 15.3 kg). The C division entry weighted 6.86 grams and was loaded to 15 kg without failing for a 2186 efficiency.

Second place in B division was the other middle school team that I coach. Their's weighted between 7.3 and 7.4 grams and broke somewhere in the 13 kg range. Second place in C division was about 1200 efficiency.

The winning state B and C division designs had two things in common. First, they both used 9 structural nodes per truss and second, the truss designs for both were completed back in October and not changed since. The second place B division bridge had 11 structural nodes and it was also designed back in October and not changed since. I didn't see the second place C division bridge, however, in general, the bridges that I've seen in competitions have been extremely complicated in comparison with ours. They have dozens of structural nodes per truss. Why are they so complicated?? I hope the readers out there at getting the picture that simpler may be significantly better.

So, the team that I'm working with for nats is taking the 9 node design and the build is about 1.5 hours from being completed. The total number of individual pieces of wood on the completed bridge will be 98. 88 of these are bass. Yes, bass. Note the almost complete lack of balsa. Since it isn't completed yet, I don't know the final mass; however, I expect it to be a shade under 6 grams. I also expect it to be able to do somewhere between 13 and 15 kg of load.

I have experimented with balsa this season, but am staying away from it for nats. One reason is Georgia humidity. Another is limited success. I've built 5 prototypes in balsa this season (4 in B and 1 in C). All 4 in B division broke somewhere between 10 and 12.2 kg of load (and were 4.78 to 5.65 g in mass). Three of these were the at the lower end of this mass range. Three (not the same three as the previous sentence) also used the stiff balsa that is discussed throughout this thread. Also, the designs had either 86 or 90 individual pieces of wood, and of this total, either 20 or 24 were balsa. The lone C prototype used 24 pieces of balsa and I stopped the loading at about 14 kg because it was about ready to fail. It weighted 6.1 to 6.2 grams.

So, I'm hoping that everyone that is going to nats and/or is reading this thread is getting the idea how good the best bridges may be. For B, expect top ones to be somewhere slightly over 2500 efficiency. In an earlier post on this thread, I predicted the best would push 3000. I'm backing off from this, mainly because I can't seem to get there. However, I'm holding out hope that one or two teams can still approach it. On C, I still expect the top ones to push close to 2500 efficiency.

[Bridges and Bots]

I got back from the state competition yesterday and my bridge placed second overall with an efficiency of 1072. It weighed 14 grams and held the whole load. It was made of bass wood legs to withstand compression, and balsa tension pieces.

[sr243]

I got back from the state competition yesterday and my bridge placed second overall with an efficiency of 1072. It weighed 14 grams and held the whole load. It was made of bass wood legs to withstand compression, and balsa tension pieces.

Nice job, i also just got back from states. I got 1090 and got 1st. My bridge was 5g holding 12 pounds. I got lucky because the bridge broke before it was loaded on the bus so i built one overnight. Which state did u get back from? I guess you are marshall from WI cuz u got 19th in mystery architecture. LOL i beat u guys barely, but my team sucked, waunakee. I did pretty well though getting 4 medals, ecology, bridge, stars, and meteorology.

[Dark Sabre]

Some pics from state...hopefully will have more coming.

Image Gallery

Either picture 3024 or 3027 won. Not sure what efficiency was.

[EastStroudsburg13]

At nationals the highest would probably be 3,000 from some beastly school

Has anyone ever gotten that high? The school I coach has a bridge in the 1000s, not sure exactly where.

[gyourkoshaven]

I heard that somebody in California got a 4000.

[fli754]

What the heck, 4000? you need a 3.75g bridge to hold all 15k to get 4000 efficiency. that's beyond amazing

[croman74]

I highly doubt that anybody has gotten 4000. The highest scores I've heard of are the low 2000s. Maybe next year scores will reach higher. But I don't think that at nats the winning score will be 3000. Maybe it will be 2500, but I doubt that it will be that high this year.

[fli754]

Some pics from state...hopefully will have more coming.

Image Gallery

Either picture 3024 or 3027 won. Not sure what efficiency was.

what state, may i ask?