Creating shapes with gumdrops and toothpicks is a lot of fun, but the challenge comes in when you try to build a structure using them. Still easy, right? The goal is to make a load-bearing bridge crossing a 10 inch span, using only 20 gumdrops and 40 toothpicks. The gumdrop bridge challenge was going to be super simple. This time, instead of having the kids take the challenge, my husband and I sat down to design our own bridges. Within about a minute, we knew this wasn't going to be so simple. Don't let the gumdrops fool you.
What you need:
20 gumdrops per person
40 toothpicks per person
Get ready, get set...
First, think design. Sketch, tinker, whatever you need to get into a creative mode. Once you have a design, it's time to build.
Bridges work by distributing compression and tension forces - compression is pushing, while tension is pulling. We know that there are different types of bridges: beam, arch, suspension, and truss. Truss bridges reply on triangles, and triangles are extremely strong, which is what I set out to make. Halfway through, my materials were running out. I was not going to be able to bridge the 10 inch span. Back to the drawing board.
My husband quickly worked out his more complicated shape before putting his bridge together. We both sat and stared at our materials. I reconfigured some of my triangles into cubes to help lengthen my bridge. I made it to 10 inches with toothpicks to spare, but as I held my bridge up, it sagged. More reinforcement was added. It was ready for testing.
It looked good...for about three seconds. Then it flopped over. My last four toothpicks were added. I tested it again. This time it sagged, but held it's shape there. I placed gumdrops on it as additional weight, and it collapsed. My focus has been so much on getting the bridge to work across the span, that not enough consideration was given for how it would distribute additional weight. It needed different towers.
My husband went with a more creative design. It sagged, but overall, held up over the span better than my bridge, which was the first success. Once we added weight, it couldn't take on much before it failed, too. The middle of his bridge clearly needed more support.
The challenge was fun, though, thankfully neither of us are bridge designers.