Saturday, August 21, 2010

Advice about building a popsicle stick bridge?

hey, for an assignment i've been told for me and my group to construct a bridge out of popsicle sticks and a white wood glue. it has to be over 15 in. and less than 18 in. long. and a like 3-5 in wide. From what i understand there has to be a roadbed with a gap wide enough to accomidate the thing the load will be hung with. Any advice will be greatly appreciated.Advice about building a popsicle stick bridge?
I'm really not sure...but we have the same hair!!Advice about building a popsicle stick bridge?
The most strongest structural element is a triangle. So combined triangles one pointed up, next to one pointed down, next to one pointed up will give you the best bridge. That is why steel bridges are always constructed that way. You may also want to use the same thing for the road bed base and then build up straight sticks on top for the road bed.





Remember there is glue and there is glue. When companies make glue laminated wood (a sheet of plywood like material filled with wood chips) the glue is stronger than the wood material itself. Try something like Gorilla Glue or Borden's Ultimate Glue. Those glues are stronger and should be at least as strong as the sticks themselves. If you use Elmer's White Glue then expect failure. Unless your instructions specifically say you have to use Elmer’s glue I would use something else, and avoid using super glue. The glue I am thinking of is stronger and cheaper by volume. You can find that glue at your local home center.





The key to a strong structure is to distribute the weight and control how it goes down into the ground. The Middle Ages say the invention of the flying buttress which allowed thinner walls and more glass, but transferring the force to thick outer columns. You will want to control the load in a similar fashion. For example use a triangle to pull the load from the sides of the bridge to the columns. A good column would be to have one vertical stick with two bracing sticks on each side at a 45 degree angle or so. You don't want to make a long stick by combining two sticks in a straight pattern; try a triangle instead and use those as your basic unit of design.





If you use the triangle base for under the roadway then that will help you tie both sides of the structure together. Don't be afraid to use cross bracing under the bridge, real bridges do. How many columns are you limited to? Will you have to span a certain distance? That will be the critical factor. If you can make your spans as short as possible and for stability don’t just have the bridge end in points. You can use a flat stick that attaches to the base to transfer the load from the column into the ground; that’s the job of a foundation. Your “bedrock” base will be the floor and you can’t dig into it but you can distribute the weight across it.
Do several practice glue joints before you start it. Get the rules in writing and use them. If they say you can only use sticks and glue, you could drill holes in the sticks and make wood pins to tightly fit in them and greatly strengthen the joints for example..
Somethings to take into consideration: On the bottom and the top of the road, lay your sticks in a X about every 2-3 inches. If you do layers - you can do a X then a strait layer another X layer a strait layer and a final X layer. That way if it starts to buckle,the X's hold it together a little bit more because the X creates stability. If there is a limit on the number of sticks you can use then I would say an X on the middle would be the best. Middle being between two layers.





Remember - Angles are you friend. What you want to do it support the bottom and top with angles or arches, they dont look like much but it really helps. Your going to want to use extra glue, and make sure that you have enough time to let it solidly dry. Make it in pieces - suck as the left side of the bridge - the right side of the bridge, and the road. The left and the right should be held togther by lot of support beams.





If you can use any more things, then I would say twine would help if you can make arches. If you can use twine - then twist two pieces together (like the cables on suspension bridges) and secure them below the road, not to the road. If its attaches to the road it will break - even with glue holding it. If you go below it or even through it, then it supports it even more.





I hope this helps, I used this rig and one a building fair type of thing. Science club or whatever you call it. WE called it Young Engineers.
maybe a mansion with 16 bathrooms
Triangles, lots of them.
Triangles are the strongest shape you can use to support weight. Squares and rectangles (vertically) will collapse.
trusses! check out real bridges! this is what engineers do all day. :P
Just use triangles and ask your teacher of other strategies that can be used to help you!

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