Elevated Bridge B/C

[Balsa Man]

That was like 15 posts in one!
I just finished building my bridge. It's weight is 16 grams. I'll test it tomorrow.

yeah, and there will be a test on it Monday! (lol)

Well, one thing lead to another......

Good luck on your bridge test; 16gr is quite respectable, sir.

Len Joeris
Fort Collins, CO

[croman74]

That was like 15 posts in one!
I just finished building my bridge. It's weight is 16 grams. I'll test it tomorrow.

yeah, and there will be a test on it Monday! (lol)

Well, one thing lead to another......

Good luck on your bridge test; 16gr is quite respectable, sir.

Len Joeris
Fort Collins, CO

Thank you! I'm trying this completely new design using bass wood with balsa as the cross section. I'm going to guess that the bridge will probably fail at the joints. If it does, I'll make another one like it, only with gussets.

[sewforlife]

thanks for all your help Balsa Man, especially for putting in paragraphs that I haven't looked back to see.
croman, tell us how your bridge does.

[nejanimb]

Thank you very much, Balsa Man, for your care in replying!

I think you're definitely right - every competitive team for the structure events finds their own system. I have to confess our system is far less scientific than the one you've described, and I think much less scientific than the one that many competitive teams do actually use. I hope, that it is not too much to our detriment.

This is my fourth year doing a balsa event, and I've always far preferred bridges to any other. This is, however, my first year building seriously for C division. Last year, we were fortunate enough to have a veritable wizard on our team - he spent very little time on Booms (I think he put together a grand total of 4 all year) and took a medal at nationals anyways. In his absence, the team has significantly ramped up the pipeline for this event, since it takes a lot to match that level of success.

However, we've never spent too much time on the pre-construction work. We take, I think, something of an unorthodox approach. We've never used the bridge/truss simulator program, we've never tested individual pieces, there's very little math involved, we use balsa exclusively, and we don't laminate anything. Certainly, I don't think that these possibilities are a bad idea - done right, I'm sure they are beneficial. We've just never done it that way.

Instead, we as a team have built I think more than 30 bridges this year. For the first several months, everyone was all over the place - designs were all totally different, and we experimented with a variety of options. You can see one of my experimental bridges in the image gallery, and I'll just say that it's entirely different from anything we're doing now. However, in every test, we could see some things that worked, and some things that didn't.

Eventually, we hit on one method that worked much better than everything else had. Then, we applied some of the positive that we had found with our other tests, and, for the first time, we broke the critical 1,000 barrier. Since then, we've been working with that general design, and making just one small change on any given bridge. These are the minute changes I was talking about: changing the angle in one place, or changing the member construction in another, or changing the number of trusses in one area, or adding an additional bracing elsewhere. Some changes have worked, and others have not, but every bridge has been helpful for us to tweak things and figure out how to improve.

Your comments about angled sides are definitely interesting, and having seen so many people using that it's something we'll have to consider. We've experimented with it, and found that it wasn't always helpful, especially factoring in the added difficulty in construction. May be something to pull out and try again, however.

Thanks so much, again, for the insight into your process. Like you said - there are many good ways to do anything, and whatever works for them is what people should do.

[croman74]

Thank you very much, Balsa Man, for your care in replying!

I think you're definitely right - every competitive team for the structure events finds their own system. I have to confess our system is far less scientific than the one you've described, and I think much less scientific than the one that many competitive teams do actually use. I hope, that it is not too much to our detriment.

This is my fourth year doing a balsa event, and I've always far preferred bridges to any other. This is, however, my first year building seriously for C division. Last year, we were fortunate enough to have a veritable wizard on our team - he spent very little time on Booms (I think he put together a grand total of 4 all year) and took a medal at nationals anyways. In his absence, the team has significantly ramped up the pipeline for this event, since it takes a lot to match that level of success.

However, we've never spent too much time on the pre-construction work. We take, I think, something of an unorthodox approach. We've never used the bridge/truss simulator program, we've never tested individual pieces, there's very little math involved, we use balsa exclusively, and we don't laminate anything. Certainly, I don't think that these possibilities are a bad idea - done right, I'm sure they are beneficial. We've just never done it that way.

Instead, we as a team have built I think more than 30 bridges this year. For the first several months, everyone was all over the place - designs were all totally different, and we experimented with a variety of options. You can see one of my experimental bridges in the image gallery, and I'll just say that it's entirely different from anything we're doing now. However, in every test, we could see some things that worked, and some things that didn't.

Eventually, we hit on one method that worked much better than everything else had. Then, we applied some of the positive that we had found with our other tests, and, for the first time, we broke the critical 1,000 barrier. Since then, we've been working with that general design, and making just one small change on any given bridge. These are the minute changes I was talking about: changing the angle in one place, or changing the member construction in another, or changing the number of trusses in one area, or adding an additional bracing elsewhere. Some changes have worked, and others have not, but every bridge has been helpful for us to tweak things and figure out how to improve.

Your comments about angled sides are definitely interesting, and having seen so many people using that it's something we'll have to consider. We've experimented with it, and found that it wasn't always helpful, especially factoring in the added difficulty in construction. May be something to pull out and try again, however.

Thanks so much, again, for the insight into your process. Like you said - there are many good ways to do anything, and whatever works for them is what people should do.

The first part is true about my work as well. I didn't do much of the stuff that most competitive people do. I've only done the bridge simulator. Over the summer, I hope to get more work done in this area.
Referring to your comment about the boomilever guy, I think that some people just find one really good design their first try. Others take a different path. However, I believe that with enough work everybody will eventually get to a really good design that they feel comfortable with. On the other hand, even if the boomilever guy found a really good design his first couple bridges, he probably should've tried to further improve his scores. When you get a really high score, it seems harder to do better. But I think that with a little change here, a little there, that you should be able to bring weight down without really affecting strength. What place did the boomilever guy get at nats?

[Allirog24]

I am so excited. We have had our bridges weighing in from 20 grams all the way up to 34ish grams. The most it held was 12 kg, and we could not figure out what was wrong with it. This is going to be our third completely different design, we have done little tweaks here and there, but, nothing this big. It weighs only...7.35 grams! I am so excited to test tomorrow! It only has to hold like 4 kg to match what we have been getting, but it feels strong, and I am positive it will hold more. We have two bridges to test tomorrow, the 7.35 gram one and the 30 gram one!

[croman74]

That is incredible! I wish I could get a bridge down to 7 grams. I think soon that I might be able to get close, but it'll be after a couple of bridges.

[nejanimb]

Without a doubt, more work will almost certainly lead to better results. But... he medalled at nationals last year. Not top 3, but still excellent.

The lightest bridge we've built this year was in the 6 gram range. It didn't hold everything, but making them that light is definitely difficult in the first place.

[croman74]

I think that for me, the hardest part is getting it lighter while being just as strong.

I also just want to point out that what nejanimb and his teammates are doing is really incredible. It's just shows how if everybody pulls their weight and does their job, you can get great scores. I hate to say it, but on my team the belief that everybody follows is that it's your bridge/device against the other one. There's not much teamwork. I would like to try to fix this though. The only problem is that the other people that are working have scores that aren't as good as mine, yet they still seem to focus on the same design. I'm going to try to talk them into working on a different design. I'll probably ask them to build one design that I would like to try, but don't have time to.

[nejanimb]

Thanks for the compliment, Croman!

I think with B division it's harder. Unfortunately, you're by necessity dealing with students that have less experience and, usually, less maturity.

(no offense meant whatsoever - it's obvious that you've got a pretty good idea of how things ought to work.)

Having teammates who are less experienced prototype new ideas is extremely useful. This allows the more experienced builder to focus on making competition bridges, but everyone still gets to contribute to the team's final product.