Snowball Trebuchet

For the last few weeks the UK has been deluged by snow and apart from making everyone feel like stocking up on food and messing up public transport, it makes most people feel like staying in and doing nothing but watching the television or sleeping.

Well, if I am not doing anything important that takes a lot of my attention then I can get bored fairly easily, and so with no money, too far away to visit friends for half an hour and too cold to do much outside I was going a little stir crazy.

I have no idea why, but in an effort to alleviate the boredom my friend and current landlord suggested a scrapheap challenge to make a snowball Trebuchet. Now anyone who has been to his house, knows that in almost every corner of his place there lurks some sort of mechanical part of gizmo, but in the efforts to keep things relatively tidy he suggested his old Fischer Technik building set.

Technik is a bit like a plastic cross between technical lego and meccano, in that it comes in strips, blocks, wheels and spindles and you can clip some of it together while other bits needs to be bolted together with tiny rivets.

It was good fun trying to learn how to use it, as when I was younger I did love my lego and meccano ( and even baco, though admittedly not as much ) and pretty soon we got ourselves a very basic version of a Trebuchet.

Although to the eye a Catapult and a Trebuchet may appear similar or do the same job, there is one distinct difference that separates them, and that is their workings. A standard catapult uses elastic / similar tension holding material to propel its munition through the sudden release of its built up tension.

A standard Trebuchet uses a heavy mass as a counter balance to a much lighter throwing arm via a central pivot, then after being raised into position the weight is drops and thus flings the throwing arm. Many Trebuchets also featured the addition of a slingshot at the end of its throwing arm, which gave greater speed and distance but required slightly technical more work to effect a successful release.

Sadly, with the materials at hand and in the quantities that I had available, I was unable to build a model of any great scale or to include and perfect the slingshot mechanism, but after a few hours or learning and working I was able to fashion a very basic version. However on release it only chucked a fairly small snowball about 2 feet, hardly even worth the effort.

After looking at it, and going back to the drawing board ( plus using standard AA batteries as extra weight ) a couple of hours later I was able to build a device that would hurl a snowball around 4 feet.

A Few more tinkerings and I tried it out in the back garded, and filmed it with mixed results. On the down side as that the first time I released it outside it' collapsed upon itself, but on the upside not after we captured the full throwing motion and upon viewing the tape was able to see a glaring technical fault.

Without the slingshot release mechanism built in I was relying on the sudden stopping of the weight as it hit the supports to launch the snowball, but the angle of release was far too forward and instead of it throwing the snowball up and forward it threw it almost directly down into the ground, hence the short distance.

As it was now already 3am, I packed it up as a job half done and went to bed, however it must have been buzzing through my mind all morning as I slept, as I woke at 8am filled with a desire to do better.

As the plans had already burned themselves into my mind, it took barely an hour to construct a much more streamline and tall machine with a counter balance of almost a kilogram in weight and looked quite beefy and serious looking. In trial runs it could throw a snowball at least 6 feet, but with so much weight it was still prone to smashing itself up during / after each release.

However, I feel that the main problem of the device was just that on a scale model the counter weight just never got a chance to build up any serious speed as no sooner had it started to fall than it had reached its bottom position, thus doubling the balance weight was having precious little to the speed.

I noticed that changing the angle of release, the angle of pivot, the position of pivot, the amount of swing of the counter balance weight, the overall weight of the counter balance, the height of release and the aerodynamics of the throwing arm and the projectile of the design all affected the performance - but not having a proper slingshot release was its biggest downfall.