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I'm in the middle of building another bridge. I think that it'll weigh 7 grams. But I don't think that it'll hold more than 5kg. I'm just experimenting with it.

With a little help from DarkSabre, some photos are up in the Image Gallery, with notes explaining. I'll try to get one of the safety tower rig up in the next few days.

Image Gallery

Wow, that's all very impressive. Everything is done with care, and the rigs are a good idea. That bridge is also beautifully made. It must've taken a while to build it. I can tell that bridge building is taken very seriously in your household. Thanks for submitting the pics.

I just finished my bridge. It's 10 grams. I'll test it tomorrow and see how it does. If it holds over 6.2 kg, then that'll be my top efficiency.

croman74 wrote:Wow, that's all very impressive. Everything is done with care, and the rigs are a good idea. That bridge is also beautifully made. It must've taken a while to build it. I can tell that bridge building is taken very seriously in your household. Thanks for submitting the pics.

Thanks; Peter has gotten to be a very careful, skilled builder. The build time was, oh 6, no more than 7 hours. As I mentioned earlier, his partner built most of one side of it.

Now you can see what I'm talking about when I talk about precision. It takes time, but it pays off.

croman74 wrote:I just finished my bridge. It's 10 grams. I'll test it tomorrow and see how it does. If it holds over 6.2 kg, then that'll be my top efficiency.

Hope the testing goes well

nejanimb wrote:I'd bet that for upcoming PA states, the winning efficiency for B division will be upwards of 1500. What won at regionals was only just above 1000.

You're talking about division B right? What region was it that had a winning efficiency of 1000?

Balsa Man wrote:

croman74 wrote:Wow, that's all very impressive. Everything is done with care, and the rigs are a good idea. That bridge is also beautifully made. It must've taken a while to build it. I can tell that bridge building is taken very seriously in your household. Thanks for submitting the pics.

Thanks; Peter has gotten to be a very careful, skilled builder. The build time was, oh 6, no more than 7 hours. As I mentioned earlier, his partner built most of one side of it.

Now you can see what I'm talking about when I talk about precision. It takes time, but it pays off.

croman74 wrote:I just finished my bridge. It's 10 grams. I'll test it tomorrow and see how it does. If it holds over 6.2 kg, then that'll be my top efficiency.

Hope the testing goes well

It's good that his partner puts forth as much effort as him. That way they both work well.
For the testing, I don't expect it to be too good. I could probably guess where it's going to break. After this test, I'm going to change the design a little. It's a bummer I don't have more time before states. I have so many different ideas. But even after comp, I'll still be building. Not as much, but every once in a while. I might try to make a safety tower so that next year I have that to work with.

That tower is an ingenious idea, to say the least. It allows you to see where the initial point of failure is. Loading normally will result in the first failure leading to others, and often it's a guess as to where it initially broke.

I've used a Structural Stress Analyzer to do the same thing. It basically pulls a plate downward, and measures the force and displacement. You can stop the machine after the first break and observe how and where it broke, as well as see the mark in the force-displacement curve.

Is the structural stress analyzer something you buy as a whole, or did you make it yourself? I also think that the tower idea is ingenious. It's really annoying to have to guess where it broke first. That's why I try to video tape it, but it's still hard to see.

eyeball138 wrote:

nejanimb wrote:I'd bet that for upcoming PA states, the winning efficiency for B division will be upwards of 1500. What won at regionals was only just above 1000.

You're talking about division B right? What region was it that had a winning efficiency of 1000?

SE region. Welsh Valley was the only school to get anywhere near 1,000, continuing their now 5 year streak at the balsa events. I'm betting they won't win states, however. What is Strath Haven's new score? Did you guys get into the 1200 plus range?