Christmas Crunch Time!

We are making Christmas presents again this year. Once again, despite an early start, we are still working on them. We limit our gift giving to grand kids which makes our productions smaller and easier. Yet, here we are, on the Eve of Christmas Eve, putting things together. The truth is it is hard to get anything to the top of the "to do" the list around here until it is urgent. Well, Christmas gifts became urgent a couple of days ago, and we are now at the point where they have reached our highest level of critical, life threatening urgency, which means we will finally work on them today.

This years gifts for the Grand kids are trebuchets. If you are not up to date on your medieval war craft, this is a catapult-like siege machine. They were used to hurl large stones at town walls until the walls became rubble. We have down sized these to toy stature, to keep the surrounding houses safe. This is a simple mechanical device. It works on the principle of leverage, angular acceleration, and using a very heavy weight to transfer energy to a much smaller weight which is flung out with a lobbing trajectory that is perfect for destroying stone walls. This toy can be used as an instructional device to introduce physics at a level young children can appeciate. It is wonderfully destructive in an instructive sort of way making it a great gift for grand kids.

As it turns out, it is great for grandparents too. Grandma and I have had a great time perfecting our prototype trebuchet. We launch a few rocks, make adjustments in the sling, and then launch a few more to test the results. Hours slip away as targets are set up and fired upon. So far, we haven't actually hit anything we were aiming at. I think this is pretty good news for the parents although we have had rocks thrown 180 degrees in the wrong direction and straight up in the air. Also, one of the houses these will be going to has a very tiny dog and we wanted to test to make certain with this size trebuchet, a dog launch wasn't possible or that an errant projectile would not be lethal to small pets, children or grandparents.

I believe adult supervision is probably going to be necessary. However, I am not sure male adult supervision is going to be adequate. Even at my age, I have an almost irresistible urge to launch small rocks at the chickens despite the sure knowledge that Grandma would kill me if she caught me. The wooosh of the launch, rocks being flung into the sky, the anticipation of impact, ahhh.... well it is just too tempting.

I am also concerned the toy sized trebuchet could be used as a model to create bigger units. The physics of a trebuchet being what they are, a doubling of size way more than doubles the launch capabilities. If you have been to one of the farms that launches pumpkins, you have seen the results of super sizing. It would be easy to do and again, almost irresistble. Grandma and I have already discussed something large enough to throw water balloons and small pumpkins across the pasture.

For young (and old) siegers alike, the fun is in making minor adjustments to the sling for a good launch trajectory, trying to achieve maximum distance and accuracy, seeing how big of rock you can launch and dodging launches that have gone awry. In the interest of making these look safe, we should go buy harmless balls to be launched, but they would be lost in a day and rocks will end up being the ammunition readily available. I suspect, after seeing a few launches, the parents will wish to send these gifts back with Grandma and Grandpa to be used at the farm where there are open spaces and the educationl nature of our gift can be stressed. That way, when the kids and I have finally succumbed to temptation and send one in the general direction of the chickens, I can point out the perfect logrithmic curve the rope to the sling traced during the launch---just before Grandma starts chasing us around.