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Re: Bridge Building Supplies

Posted: January 16th, 2015, 3:38 pm
by JonB
i am one of dr cubbins students so i really want to attend at this station because of previous experience with bridge building so i juts wanted to know if most of the bridges will they arch bridges or will they truss bridges or is it a possible to have a combination of the types of bridges because i was wondering if there is a restriction of how much would use depending of weight also the type of substance to attach the wooden pieces would it a be a problem of what type of glue to use
:geek:

Start here:

http://scioly.org/wiki/index.php/Bridge_Building

That addresses most of your questions.

Re: Bridge Building Supplies

Posted: January 27th, 2015, 2:28 pm
by drcubbin
Tanjil - How about this? Pretty cool, but I am not sure why we don't see more of this design in competition. Anyone?

https://www.youtube.com/watch?v=RRzqnvA ... J2&index=3

Re: Bridge Building Supplies

Posted: January 27th, 2015, 5:05 pm
by chinesesushi
Tanjil - How about this? Pretty cool, but I am not sure why we don't see more of this design in competition. Anyone?

https://www.youtube.com/watch?v=RRzqnvA ... J2&index=3
I have likewise seen that video on Youtube. Thing is, the record really isn't that high, as the "score" I believe it would get in a normal competition would only be 1650. And that 's if you were allowed to hold up to 419 pounds. You can try a design like that, but with the load limit of 15 kilograms, you would have to lighten down some of the pieces which would in turn decrease the strength of the bridge.

Re: Bridge Building Supplies

Posted: January 27th, 2015, 5:39 pm
by DoctaDave
Tanjil - How about this? Pretty cool, but I am not sure why we don't see more of this design in competition. Anyone?

https://www.youtube.com/watch?v=RRzqnvA ... J2&index=3
Although the bridge's score isn't too impressive, I have seen a few arch bridges do very well whose designs were somewhat similar to the one in the video. I don't think the design of the bridge in the video was very well optimized, because the builder braced the tension members, which only adds weight without giving any more strength to the structure.

If you're a beginner at building with balsa wood, I would just stick to a "normal" truss bridge as those are much easier to build. Both types of designs can get you great scores, but the extra time and experience needed to build and experiment with arch bridges would probably outweigh any advantages to using an arch.

Re: Bridge Building Supplies

Posted: January 28th, 2015, 6:20 am
by dholdgreve
Agreed Dr. Dave... Last week at Magsig there were a couple of tall arched bridges... From an engineering standpoint (efficiency), they didn't score exceptionally well, but from an architectural standpoint, they were off the chart! (Very unique, symmetrical, and real pleasure to look at!)

Re: Bridge Building Supplies

Posted: February 9th, 2015, 3:15 pm
by drcubbin
Also, I saw on one of the Launched Glider videos that an "accelerant" is used to dry the CA glue much more quickly. Does anyone know where I can buy that (without having to order and wait since we are in a bit of a rush? I thought they said it is sold at Walmart, but I couldn't find it there.

Re: Bridge Building Supplies

Posted: February 9th, 2015, 3:51 pm
by chalker
Also, I saw on one of the Launched Glider videos that an "accelerant" is used to dry the CA glue much more quickly. Does anyone know where I can buy that (without having to order and wait since we are in a bit of a rush? I thought they said it is sold at Walmart, but I couldn't find it there.
Most hobby shops will carry it.

Re: Bridge Building Supplies

Posted: February 9th, 2015, 4:06 pm
by drcubbin
Much appreciated. We are pushed for time as we a new, taking two teams into B competition, and only started (technically) last week. Thank goodness I have some really bright young people!

Re: Bridge Building Supplies

Posted: February 10th, 2015, 8:18 am
by chinesesushi
Much appreciated. We are pushed for time as we a new, taking two teams into B competition, and only started (technically) last week. Thank goodness I have some really bright young people!
What types of CA glue are you using? Most CA glue should be able to dry quickly. E.g. I can finish a bridge and have it ready for competition in like 2 days (i'm sorry to say it has come to that at least once).

Re: Bridge Building Supplies

Posted: February 10th, 2015, 10:37 am
by iwonder
Much appreciated. We are pushed for time as we a new, taking two teams into B competition, and only started (technically) last week. Thank goodness I have some really bright young people!
What types of CA glue are you using? Most CA glue should be able to dry quickly. E.g. I can finish a bridge and have it ready for competition in like 2 days (i'm sorry to say it has come to that at least once).
Yup, I think we've all been there. You shouldn't need the accelerant if you're using CA glue 'right', just put very very small amounts on the joints and it'll dry in seconds. The accelerator, when I've seen it used, was used on large joints (which is why is comes in a spray) and it took a 15 second drying time and turned it into 3 seconds.

In other words, unless you're building something at the contest and have minutes, it shouldn't make a big deal.

Also, the spray can get those chemicals everywhere on the structure, which weighs it down at best and effects the wood badly at worst, not to mention the fact that it makes for weaker glue joints.