Maybe everyone knows about this engine but me, but if not, this is a very
cool little piece of machinery worth looking into. It's the rotary-valve
4-stroke used in the Honeywell hovering drone that's being prepared for
field use by the US Army:

http://www.nytimes.com/2009/08/12/bu...l?ref=business

It's built by a British company, RCV Engines Ltd., and it's amazingly
simple. They've made available a 7-year-old SAE paper about it, with lots of
detail about the seals (for anyone who's followed rotary-valve engines over
the years, that's where most of the action is):

http://www.rcvengines.com/pdf_files/saepaper.pdf

It must be pretty darned reliable to be used in the drone, so this is more
than just another weird engine curiosity.

Here's RCV's home page. They make model engines, too:

http://www.rcvengines.com/index.htm

--
Ed Huntress