Okay, this weekend was as low key as it gets, almost to the point of ridiculous. My wife worked twelve hour days all weekend and my son was grounded. I had no one to play with. So, I decided we should spend Saturday getting a jump on a science project my son has that is due on November 23rd.
He brought home a piece of paper that said “Engineering Project” at the top. I just so happen to know an engineer. My wife, who is a chemist, is usually the self-designated helper with all things science related, but this one clearly fell into my realm.
Friday evening we sat down and discussed the parameters of the project. The gist of which was, build a ping pong ball launcher to launch a ping pong twelve and have it land inside an empty 3lb coffee cup. We put together a Hypothesis and a list of steps needed to carry the launcher from idea to completion.
We developed a rough materials list and though I led him with gentle nudges here and there, he came up with the items needed on his own.
A mousetrap to be the launch mechanism.
A spoon to hold the ball
Duct tape to hold the spoon to the arm of the trap
An angle bracket to keep the trap from closing all the way.
A piece of wire to be able to trigger the trap without having his hands in the way.
A block of wood to stabilize the trap when it is triggered.
Screws and wood glue to hold the trap to the block of wood.
A means to “sight in” the trap for accurate launches into the can.
Paint to decorate it.
Saturday morning, I got up early and worked up a series of parabolic equations to calculate the angle of launch necessary to give the ball the proper trajectory. You see it is not enough that the ball goes twelve feet, but the arc of its path has to be such that it is coming almost straight down when it lands so that when it is used on test day, the height of both tables and the height of the coffee can would not be a factor.
By the time my son was ready to begin construction, I knew what he needed to be done, I just had to figure out how to help him without giving him the answers. It is HIS project after all. You would be surprised (I know I was) at how easy it turned out to be.
I calculated the force exerted by the arm of the trap, the weight of trap and used it to determine the best means of stabilizing the launcher was to attach it to a block of wood. Using a two by four, I determined that we needed about ten inches of the two by four to keep the trap from moving when it was triggered.
I asked my son how big he thought the base should be. He promptly placed a large chunk of wood on our work bench, placed the mousetrap on it and rested the spoon up against the spring. He grabbed a tape measure and looked up at me and said, “We should probably leave an inch up front to put the sights on. He moved the trap back and measured from the end of the wood to the end of the spoon. Guess what… it was just shy of ten inches, so he decided to round up for good measure.
We continued on in this fashion until the entire thing was constructed. My only interference came when I asked if I could set the angle of the restraint used to keep the trap from closing all the way. I set it at “X” angle (I’m not revealing that one in case someone else googles this to do their project).
We prepared to launch and though the trap was vertically stable, it moved from side to side on the table as he tried to pull the trigger. I suggested putting Velcro on the bottom, but my son had a better idea. He grabbed the tip of a broken skateboard deck, used a hacksaw to shorten it to the right length and attached it to the bottom. Worked like a charm.
He was read for his first test launch. We measured out twelve feet, put a coffee cup on one end and the trap at the other. He pulled the trigger and it went right into the center of the coffee can and stayed…
I think he may just get an “A” on this thing and I was shocked at just how little I actually had to help. I wonder if this means my boy is a chip off the ol’ block. I guess time will tell.
So, how was your weekend?
Labels: Weekend Recap