Bridge Designs

bernard
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Re: Bridge Designs

Postby bernard » October 23rd, 2015, 4:16 pm

I've heard of people getting insulin syringes, washing them out well, and loading them with CA to inject it neatly onto the balsa. Seems like it would solidify too quickly in the syringe, though...

Ask your biology teacher for micropipette tips and put them on your glue. Cheap, disposable.
Or take a disposable pipette, stretch the tip with pliers and you'll have a narrower tip. Cut the pipette at a wider section, attach to the top of your glue nozzle.
Here's the pipette tip, minus the cutting.
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Re: Bridge Designs

Postby jander14indoor » October 27th, 2015, 11:13 am

Since you are talking about minimizing glue weight, let me point you to this paper I wrote almost 10 years ago. (scary...) Its posted on the WS event page, but is applicable to any of the light weight structures events.
https://www.soinc.org/sites/default/fil ... weight.pdf

It discusses various glues and joint execution to maximize strength. It misses Gorilla style polyurethane glues as they hadn't become a big player yet. Not sure how I'd update it to cover those as I haven't seen much use in SO. My puzzle would be how to use SMALL amounts needed for SO structures.

On pipettes, there is an alternative discussed in that article. See http://www.gryffinaero.com/models/ffpag ... yaapp.html My implementation of this is real sophisticated. Two pins stuck through a scrap stick that come to a point. I can build a WS wing with CA and weight add under what I can measure with my scale good to 0.01 gm...

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Re: Bridge Designs

Postby Shummers » January 23rd, 2016, 6:21 am

I am new to bride building designs. Does anyone know any techniques I could use? Also, i'm looking for a software I could use to design bridges. Thanks!

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Re: Bridge Designs

Postby brayden box » February 18th, 2016, 5:51 am

Triangles. Always use triangles as your designs, not squares or some other shape, triangles are the strongest.
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Re: Bridge Designs

Postby brayden box » February 18th, 2016, 5:52 am

Also try to keep the bridges light. (i.e. less glue, light wood, less wood) for more points. Ours weighed about 9.6 grams, but the winning one at NY state last year weighed like only 5 grams. (Or that may have been regionals?) :?:
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Re: Bridge Designs

Postby retired1 » February 18th, 2016, 8:00 am

For software, take a look at pre-engineering.com model smart 3-D. Download is $49.95
It takes a while to get used to it as it has so many options. I have found it to be quite accurate when I use it correctly. The best part of this is that you can use it on towers next year. Both our B and C teams did extremely well in the state of FL the last time the towers event was run.
A function that I use a lot is the "save as" where I can keep the basic bridge and make changes to it.

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Re: Bridge Designs

Postby Bazinga+ » February 18th, 2016, 6:46 pm

For software, take a look at pre-engineering.com model smart 3-D. Download is $49.95
It takes a while to get used to it as it has so many options. I have found it to be quite accurate when I use it correctly. The best part of this is that you can use it on towers next year. Both our B and C teams did extremely well in the state of FL the last time the towers event was run.
A function that I use a lot is the "save as" where I can keep the basic bridge and make changes to it.
At the very high levels the simulator isn't as helpful since there are a lot of things that it cannot account for. Also just some general advice, if you're planning on going all out on bridges I really recommend getting a good scale (milligram accuracy) since many of the top bridges are practically the same design, and it really comes out to how they pick out the wood densities.
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Re: Bridge Designs

Postby embokim » February 19th, 2016, 8:19 am

hello, i have been recently trying out a new design, a triangle topped bridge but on the bottom instead of a straight line to connect the two legs of the triangle it is a curve. It has been working like magic, any thoughts?
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Re: Bridge Designs

Postby Bazinga+ » February 19th, 2016, 9:03 am

hello, i have been recently trying out a new design, a triangle topped bridge but on the bottom instead of a straight line to connect the two legs of the triangle it is a curve. It has been working like magic, any thoughts?
In theory bridges with arcs are optimal, but the problem that many people have is that making the wood curved requires steaming it which can weaken it and its not a very precise process. If you have the resources to have pieces laser cut or something like that, then curves are a great idea, but if not I would avoid it since steaming wood often has unpredictable effects on the wood strength. But I think curvy bridges are fine ;)
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Re: Bridge Designs

Postby JonB » February 19th, 2016, 9:45 am

hello, i have been recently trying out a new design, a triangle topped bridge but on the bottom instead of a straight line to connect the two legs of the triangle it is a curve. It has been working like magic, any thoughts?

I cannot visualize this... picture? creative drawing in Paint?

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Re: Bridge Designs

Postby embokim » February 20th, 2016, 5:56 am

Attached is a paint file, Just imagine the bottom leg to be an arc.It buckles a lot during testing, but always manages to stay in tact until about 14kg. The way I make it, it is around 9-10 g.
I cannot visualize this... picture? creative drawing in Paint?
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Re: Bridge Designs

Postby Bazinga+ » February 20th, 2016, 7:39 am

Attached is a paint file, Just imagine the bottom leg to be an arc.It buckles a lot during testing, but always manages to stay in tact until about 14kg. The way I make it, it is around 9-10 g.
I cannot visualize this... picture? creative drawing in Paint?
I dont think an arc on the bottom is a good idea. This is because ideally you want to make your bridge top loaded, which means the bottom beam is under tension. Since the bottom beam is under tension you want to make it straight not curved. It seems odd to me that it worked better for you, maybe it had something to do with the cross beams connected to the bottom.
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Re: Bridge Designs

Postby embokim » February 20th, 2016, 12:33 pm

I made a slot in the bridge to allow for the loading block assembly to fit. The entire bridge is an elongated pyramid and the curve when pressure is applied to the top, naturally tries to revert back into a straight angle. The top of the triangle holds the arc back and thus allows for a load to be placed onto the bridge.
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Re: Bridge Designs

Postby XplodingCesium » February 20th, 2016, 7:31 pm

Use
a triangle
because it is
the strongest design
out of all of the designs
that I and my partner have tried.

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Re: Bridge Designs

Postby samlan16 » February 21st, 2016, 11:24 am

Use
a triangle
because it is
the strongest design
out of all of the designs
that I and my partner have tried.
Lovely poem! We need to have a forum for all the SciOly poets.
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