I'm taking an Engineering Class and so I need to build a bridge out of two 8.5x11 pieces of cardboard without using any adhesives. It needs to span 16 inches and carry 2lbs =( Any tips?

I actually did something similar to this for my 7th grade science fair project. But I used craft sticks. Give me a second to come up with some designs and i'll post something useful.

Clarify:
You can cut the cardboard into pieces, correct?
Does the bridge need a top face? (that is, does it need a surface, or does it just be say two connected beams running parallel to each other.
By cardboard do you mean like, the stuff shoeboxes are made from or post cards?

Yes, I can cut the cardboard however I want.

A top face would be preferable, so that it can hold the block that bears the bucket which contains all the weight. Making that surface area smaller would put more load on the pieces, as far as I understand

http://www.flickr.com/photos/10703755@N04/3749496259/

You did not clarify the type of cardboard.

its typical, non-corrugated cardboard. Its basically the type of cardboard that make up the back of notebooks

How about a top and bottom deck, connected by strips cut and folded to be like \/\/\/\/? Of course, each point would need to be glued to the respective deck. Are you permitted to do that?

no, but we're planning on using slots to attach those parts

Wait, what if you just take a single sheet and accordion-fold it? if you lay it such that the folds go from one side of the abyss to the other, that arrangement can hold a lot more weight than a flat sheet. Try it with a piece of normal 8.5x11, you'll be surprised.

Are you permitted to use staples (or anything other than cardboard for that matter?)



Haha I won that competition in 6th grade during "Engineer's Week Challenge". Our bridge held up 210 lbs (it could've held more, but we ran out of weights.) To my knowledge my science teacher still has my group's popsicle stick bridge on her desk

nope, nothing but cardboard =/

@Kerm
We decided to break the cardboard into 5 8.5X2 inch strips (works better with the grain) and build a trapezoidal bridge with a somewhat strong base with lots of trusses.

Why not just fold 1 inch on the left and right sides down, then attach the two pieces together? Super simple, and it'll definitely hold a few pounds.

I remember a similar project in middle school, it used balso wood and my team didn't do very well but it was combined with a project to build a tower which my group won, the tower was build of 250 inches of 1/8 inch square balsa wood and glue. My group used my design and I think it could have held more if we had build it better but it still held over 200 pounds if memory serves. The tower had to be 6-8 inches tall and I don't remember how long a side but they were tested in a more advanced way, we used a pneumatic stress tester (at least that is what I would call it) it had a load plate that was pulled down by air pressure generated with a hand pump and it recorded the peak force pulling the load plate down.

We did something like this with popsicle sticks back in the day, I don't remember what all we did, but we had the best design. *shrug*

Whatever you manage, care to share pics or a diagram of it?

Thanks guys! Sure, I'll post up some pics of the CAD/real life model once I finish =D

I know, I should edit, but lets all just ignore that for now.

It does hold several pounds, and is by far the most complex bridge; most people just rolled up the cardboard or tied several pieces together. I didn't bother to actually "design" it using CAD software, so here are just some pictures of the monstrosity =D

http://www.flickr.com/photos/10703755@N04/sets/72157621812533040
[img]http://farm3.static.flickr.com/2592/3752746221_ba6291a26f.jpg?v=0[/img]
[img]http://farm4.static.flickr.com/3478/3752746253_2fc5e39623.jpg?v=0[/img]
[img]http://farm4.static.flickr.com/3485/3753540698_aa5dcf6082.jpg?v=0[/img]
[img]http://farm4.static.flickr.com/3203/3752746187_6d0151ed21.jpg?v=0[/img]