Cool party trick: Van Arsdell's coffee cup stirling engine kit.
With the potential to achieve much higher efficiencies and run cleaner than internal combustion engines, Stirling engines—which use an external heat source to perform work—have long been a source of fascination for engineers. In fact, when Aeronautical Engineer Brent Van Arsdell first saw a friend of his running a Stirling engine on a bowlful of ice cubes, his first thought was, "I've got to build one myself." Since then, he has come up with ten different engine designs and "probably assembled a couple thousand engines by hand." And, he has made it his mission to educate the world about this unique engine design. Plus, he gets to show people the Ideal Gas Law in action! His company, American Stirling ( www.stirlingengine.com), develops Stirling engines for the educational market as well as demonstration kits. His most popular item: The MM-5 Coffee Cup Engine Kit, which includes all the components needed to build an engine that operates at 250 rpm on a Starbucks' espresso or 100 rpm on a bowl of Cherry Garcia ice cream. It's a great party trick, he says. As far as practical use, Van Arsdell says that his engines put out only a tiny amount of power—anywhere from 2 to 30 mW. The problem, says Van Arsdell: It's difficult to build a Stirling engine that puts out a high power density, and the cost would be prohibitive for many mainstream applications. In fact, if you know of a small Stirling engine that is cost-competitive with gas or diesel engines on a per kW-basis, Van Arsdell would like to hear from you at firstname.lastname@example.org.
Two different shape-shifting polymers have been announced from two different universities: Wyss Institute at Harvard University and Zhejiang University in eastern China. Both of them change their shapes when immersed in water, and the one from Wyss Institute was made with 3D-printing techniques.
When you think of the DARPA Robotics Challenge, you may imagine complex humanoid contraptions made of metal and wires that move like a Terminator Series T-90. But what actually happened at the much-vaunted event was something just a bit different.
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