This video has been around for a few months, but I just came across it and it's astounding. Check out this Brazilian teen's scratch-built model backhoe. Using plastic syringes and silicon tubing, he's created a miniature hydraulic system that functions the same exact way as the mechanism inside a real excavator. This kid is sharp.
I especially like watching this junior engineer's finesse at the controls. There are no jerky movements -- every manoeuvre is fluid and smooth. If you watch closely, you can see him overlap the four control pistons, ensuring a smooth, seamless transition between vertical and horizontal motions.
There are a bunch of great instructions out there that show you how you can build a syringe-based hydraulic system to power creations of your own. Toys are way more interesting when you make them yourself. [Catalin Sogor via BoingBoing]