There is nothing more rewarding than imagining a machine and building it. Below are a few of my creations. My views on pragmatism in mechanics have been strongly influenced by Dorian Clair, who is the most excellent teacher of machines I could have hoped to apprentice under.
Stirling Engine #2
At left is a stirling engine I made from scrap material over Christmas a few years back. Planning and construction took two weeks. The engine runs at approximately 100rpm when placed over a mug of (very) hot water. Engines of this sort have been made that run on the heat generated by a human hand; mine is not this functional primarily because it has a latex diaphragm rather than a conventional piston and cylinder. The diaphragm is surprisingly difficult to deform and with each engine cycle, a lot of energy is lost in flexing it. The upside is that diaphragms are much easier to make than pistons and cylinders. The engine takes advantage of many unconventional machine materials, such as styrofoam, acrylic, and silicon caulking, which is an excellent sealant and adhesive. Assembly is by no means "permanent", as the silicon can very easily be sliced through and removed with a razor.
Stirling Engine #1
At right is a stirling engine I made a few years ago which I could never get to work. It was designed to be a hand held demonstration piece (view the handle in back). It was meant to function by passing air back and forth between a hot and a cold cylinder. Simultaneously, the air volume was to change, causing expansion when the air was hot and contraction when the air was cold (and hence a net amount of work done on what ever is acting on the air to contract and expand it, in this case the flywheel). I think that a small net volume of air was its major problem. Also having aluminum pistons in brass cylinders wasn't too bright. I've avoided an extensive error analysis because it would be depressing. What's important is the push this engine gave me in constructing the one above.
At left is a tourbillion device I made from an old Westclox Big-Ben alarm clock movement while in high school. Tourbillons use a planetary system of gears to rotate an escapement and oscillator. The escapement and oscillator are at the heart of the timekeeper, and are generally sensitive to changes in their position. The idea behind the tourbillion is that continual rotation of the escapement and oscillator will subject them to all positions equally. This way, the timekeeper keeps the same average rate regardless of its position. This line of thinking isn't strictly correct, and I believe that in practice tourbillions proved more trouble than they were worth. Nevertheless they are fascinating and beautiful.
At right is a perpetual calendar device I made while in high school. It needs to be toggled once a day, but with that input alone it will correctly display the date and month, even keeping track of short months and leap year. Most parts (including all the gears) are hand filed out of copper stock taken from an old restaurant door handle.
The Second Generation
At left is generation two of my perpetual calendar device. This model is made from plexiglass, steel, and brass, and features fewer levers than the previous model. Also, the levers it does have are spring driven, so it even works upside down!
This is a mouse I caught. It was endearing enough that I gave it a rice cake with peanut butter. Unfortunately it escaped shortly after this photo was taken.
J'aime beaucoup les casse-tetes!
Here's a puzzle-sculpture I carved out of plastic sections of tube. The pieces fit together in more than one way, but once I got them to fit together as shown I never had the courage to take them apart again. The tube cross sections are a quarter inch square, and the entire puzzle is about three inches cubed. It can be tossed in the air without falling apart.
Darwin's Revolving Wall
Darwin needed to spice up his apartment so he tore out some dilapidated accordion doors and built this cool revolving wall. Like most practical things architects are involved with it didn't work. I mounted it on a race of bearings and now it rotates even in the wind.