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Chuck Patterson
01-12-2010, 1:00 AM
Hello, once again I am out here to ask for assistance. My daughter has a physics project that is requiring her to build a bridge from only spaghetti and glue. I am asking if anyone else has any experience with this sort of project? This is a learning project and I intend for her (and me) to learn from it. If I can get some guidance or answers to help her (and me) to learn it would be appreciated.

What does this have to do with this forum you ask? I am looking to gain knowledge, to pass on to her and assist her with using either Signlab 7 or CorelDraw X3 to design the bridge and use the laser to do the precise cutting. I want her to experience the power of the software, the capabilities of the laser, and how to think through the problem using the tools available to her.

If anyone has any experience with a project of this nature and willing to share their experience, knowledge, or designs it would be greatly appreciated. (we are currently working with a truss design http://upload.wikimedia.org/wikipedia/commons/thumb/3/33/Parts_of_a_truss_bridge.svg/400px-Parts_of_a_truss_bridge.svg.png )

Please note, I am not looking for an answer that I can just give her. There a ton of rules, weight restrictions, length restrictions, etc. If you are interested, I can upload them. But at this time, I am just looking for guidance, knowledge, and assistance so that I can teach her to think through the problem and hopefully we can take it from there.

Somebody has a quote on their profile that says, "I have a creative mind, but it is not attached to the rest of my body." (or something like that). I seem to resemble that quote.

Roy Nicholson
01-12-2010, 4:32 AM
http://www.bridgebuilder-game.com/links.php

Give this site a try


Regards


Roy N.

Mike Null
01-12-2010, 5:30 AM
Why would you use the laser when you can break the spaghetti by hand? Or put a drop of water where you want to cut and use a knife.

Dan Hintz
01-12-2010, 7:33 AM
Support everything with temporary structures that can be easily removed. Glue all of the spaghetti and let it dry. Remove supports. If you try to make large structures a few spaghetti links at a time, you stress the original pieces more and more as you add to the structure, which leads to breakage sooner than necessary.

All of this assume they'll be testing for strength as part of the project. If it's just for looks, ignore my advice.

Daniel Muller
01-12-2010, 9:40 AM
Chuck,
Its funny that you ask this. I teach Engineering Design at a HS level and we do a major structures activity. There is a program that can be downloaded for free call West PointBridge http://bridgecontest.usma.edu/
It is a contest but don't need to participate. It allows you to design and test bridges on the computer and the color changes on the members will indicate if the sturcture is under tension, compression or shearing. It is very easy to use and will take only a few minutes to design a bridge. As for the bridge make sure that any jointery is cut to the proper angles and not just filled with glue. this will take away from the structural intergrity of the bridge. Also not sure it the teacher gave any constraints but laminating pieces together will strengthen it tremendously. Hope this helps

David Fairfield
01-12-2010, 10:05 AM
I recall there was an article about this in Model Railroader Magazine years ago, the author built an HO scale (1/87) steel truss bridge from pasta. The premise is, the structural properties of dry spaghetti are a close match to steel, scaled down by a factor of 87. I can't tell you which issue it was in, but they do have a website you can check www.kalmbach.com (http://www.kalmbach.com)

Neat project, wish my teachers gave me practical stuff like that instead of tormenting me with meaningless theory.

Dave

David Fairfield
01-12-2010, 10:09 AM
PS you can probably make some really nice curved parts by cooking the pasta, forming it, then letting it dry. You could make the formers in the laser cutter.

Dave

Dan Hintz
01-12-2010, 10:25 AM
PS you can probably make some really nice curved parts by cooking the pasta, forming it, then letting it dry.
<chuckle> I like it...

Dave Johnson29
01-12-2010, 8:23 PM
Hi Chuck,

Good luck with the project. I would suggest trying to consider the following design criteria.

Opt for the maximum components in tension, next in shear and finally compression. Minimize shear and compression the best you can.

Skip any curved parts as they will have built in deflection just waiting to fail.

The object of spaghetti bridges generally is load carrying so have as many items in tension as is possible. It is highly unlikely you can skip having shear entirely but try to minimize it. If possible, try and omit all compression with your final design.

David Fairfield
01-13-2010, 6:37 AM
Chuck, when its done, please remember to post a photo of the completed bridge, and let us know how it went. Such a cool project, I'd really enjoy seeing how it turned out! :)

Dave

Dave Johnson29
01-13-2010, 11:32 AM
I like it...

Hey Dan,

Recall some time back we were discussing bending a walking cane and breaking it. I mentioned 5-degrees of deflection and up to 40% loss of strength. :)

Here's what I was talking about.

http://www.youtube.com/watch?v=hqC2URQstz4

The shelves are very safe as long as they are stable and straight. The same will apply to the spaghetti bridge with curved structural members.

The forklift bends the first leg more than 5-deg but the other shelves just fold with the minimal amount of deflection.

Chuck Patterson
01-13-2010, 1:01 PM
Thank you everyone for the information, links, and ideas.

Yes this project is about how much load it can handle. 10% of the grade is on looks. Looks like, at this point, we have at least a 90%. LOL

Everyone might want to purchase stock in Spaghetti, we are sure using a lot of it trying to figure this out.

Mark Ross
01-13-2010, 2:18 PM
Check all the rules carefully. Did this with my kids back in the day. One year, someone dipped their entire completed bridge in the glue. Rules didn't say you couldn't do it...argument went to the national level of the orginization and the ruling came back, it wasn't in the rules therefore it is allowed.

Another year, someone "accidentally" used the wrong glue. Yeah right...since the contest did not have a portable mass spec on site, how are you able to determine that grey line between cheating and an honest mistake?

Depending on the type of adhesive you have to use and the rule list you have...you might be able to soften the pasta and dissolve the glue into the water and when the pasta cools and absorbs all the "water"...well the pasta might be stronger...

George Brown
01-13-2010, 2:28 PM
Here's what I was talking about.

http://www.youtube.com/watch?v=hqC2URQstz4




Wonder if they fired him??:(

Dan Hintz
01-13-2010, 3:03 PM
Wonder if they fired him??:(
It's in Russia (I think it was a vodka distributor), so they probably took him out back and gave him a pair of concrete boots.

Chuck Patterson
01-13-2010, 3:30 PM
The rules do state that we can NOT use "Spaghetticrete". It is defined as: Spaghetti chopped up in to small strands and mixed with glue.

Hmmmm, I wonder if your suggestion would be considered Spaghetticrete? After all the rules specifies "...chopped up small pieces..".

David Fairfield
02-26-2010, 1:40 PM
Well, how did it go? Did you win anything? Got any pictures of your entry? :)

Dave

Lee DeRaud
02-26-2010, 3:22 PM
I recall there was an article about this in Model Railroader Magazine years ago, the author built an HO scale (1/87) steel truss bridge from pasta. The premise is, the structural properties of dry spaghetti are a close match to steel, scaled down by a factor of 87.Arrrgggh...I just hurt my head by visualizing various types of pasta, scaled up in size by 87X and made out of steel. :eek:
Rigatoni turns into pipe 3' in diameter with 2"-3" wall thickness. Lasagna? Don't ask.

Speaking of "things (possibly) not in the rules": probably wouldn't be that big a deal to laser-cut custom dies for a pasta-maker so you can extrude I-beams or similar structural shapes.

David Fairfield
02-26-2010, 3:27 PM
Hey Lee, I like the extrusion form idea! That is genius!

Dave

Jack Burton
02-26-2010, 5:50 PM
maybe you could use some carbon fiber to sleeve the spaghetti or coat the bridge in fiberglass.....

Chuck Patterson
03-04-2010, 3:24 PM
It is not pretty, but it got the job done and an earned grade. Others in the class did not do as well. Many of them breaking in the 2 - 15 pound load tests. Others broke on the way to school and never saw the testing table. Ours did not break till 35 pounds. One kid in the class built one that held over 175 pounds. When asked what he used, all he would tell us was that his secret was the glue.

Thank you to everyone who contributed their knowledge and advise.

Dan Hintz
03-04-2010, 5:10 PM
I'm guessing a water-based glue so it would soak into and throughout the pasta...

David Fairfield
03-04-2010, 6:54 PM
35 lbs is pretty respectable for dry spaghetti, good job.


I'm guessing a water-based glue so it would soak into and throughout the pasta...

Sounds like the pasta my sister cooks. :(

Dave