An engine simalar in layout to two inline engines joined at the heads, most likely arranged horizontally to create a flat and wide engine.
The pistons would reciprocate on a common cylinder, in sync so they travel towards and away from each other, nearly meeting in the center. A variety of valve systems may work. Perhaps a combination of slide valves and/or ports simalar to a 2-stroke.
Benefits include a very low center of gravity and a large possible displacement. Because it's not very tall, you can pack lots of goodies up top, like turbochargers and other fun things. It would also be easier to change the shape of the flame front because piston design is not limited by a typical combustion chamber.-- KLRico, Jan 28 2004 Doxford Opposed-Piston Main Propulsion Marine Engines http://www.oldengin.../Marine/doxford.htmVery thoroughly baked in Sunderland UK from 1890 to 1970s [phlogiston, Oct 04 2004, last modified Oct 05 2004] Deltic http://www.fact-ind.../napier_deltic.html [Fussass, Oct 04 2004, last modified Oct 05 2004] Fairbanks-Morse http://gelwood.rail...anual/fm-index.html [Fussass, Oct 04 2004, last modified Oct 05 2004] Dyna-Cam Engines http://www.dynacam....esign_overview.html"Cylinders of both blocks line up so that six double-ended pistons can fire back and forth between the aligned cylinders of each block " [Klaatu, Oct 04 2004, last modified Oct 05 2004] As UB points out Commer also baked this http://www.oldengin...l/Technical/TS3.htmGo to the bottom of the page for cutaway drawings [Gordon Comstock, Oct 04 2004, last modified Oct 05 2004] Dair aero engine http://www.dair.co.uk/Just what [KLRico] ordered [squigbobble, Aug 28 2005] You mean this idea has nothing to do with cat-dog mutations or conjoined fighting opponents?-- phundug, Jan 28 2004 //nearly meeting in the center// that's where your third chamber is. You have a single cylinder with two pistons sliding in it dividing it into three separate volumes. Power is coupled to the outside magnetically; permanent magnets in the pistons and coils in the cylinder walls to make a generator. Could work for modern hybrid cars.-- kbecker, Jan 28 2004 Actually, it should be "Thai Boxer."-- spacecadet, Jan 28 2004 Why Thai?-- KLRico, Jan 29 2004 I thought this was going to be about Muy Thai-- monkeywidget, Jan 30 2004 So this isn't underwear for two?-- Worldgineer, Jan 30 2004 I changed the title to something more descriptive. I shall cease my pitiful attempts at being witty. ;-)-- KLRico, Feb 01 2004 What was it before? Siamese Pistons? Siamese Briefs (??) Akh, now I can't sleep..-- dryman, Feb 01 2004 I've always loved the idea of harnessing the pistons' power magnetically, kbecker. Only problem is, permanent magnets demagnetize when they get hot (at the Curie temperature). Which rather unfortunately unbakes that elegant croissant.-- TerranFury, Feb 01 2004 i think Subaru made these too, their was enuf room to put the spare tire on top of the engine-- WhiteWiz, Mar 01 2004 Engines built this way have been widely used for railway locomotives: Fairbanks-Morse in the States, and the Napier Deltic in UK. The same engines are still used in submarines, other ships, and electrical generation.-- Fussass, Mar 01 2004 Sounds like the Dyna-Cam engine. <link>-- Klaatu, Mar 01 2004 This is baked right this very second :D Even in the 2 cylinder configuration that [KLRico] envisaged (see link) although he/she probably wasn't thinking of a diesel.-- squigbobble, Aug 28 2005 But surely all this would mean is that the power would be halved for each set of cylinders, so in affect it's just identical to one engine? Which would be even smaller, and even lighter.-- quaero curvus, Sep 09 2005 random, halfbakery