I'm pretty beat, so I'm going to slide by falling back on the "post a video" gambit. A website about building complex machines with LEGO® building blocks has instructions for building a Babbage difference engine. Here's a video of the LEGO® difference engine in action:
Of course, the William Gibson, Bruce Sterling collaborative novel The Difference Engine, which depicts an alternate history timeline in which steam-driven Babbage engines have allowed a 19th century computing revolution to occur, was one of the landmark works of fiction in the "steampunk" literary subgenre. While there are some whimsical Lego steampunk creations out there, it's much, much more impressive to see an actual, working mechanism. I wonder if Gibson and Sterling will come out with a Legopunk novel any time soon.