"Rob Turk"
sednews:xmXie.4098$184.3491@amstwist00:

"Matt Whiting" wrote in message
...
Sport Pilot wrote:
Most flat fours are not a boxer, and many twins are not. A boxer
engine will weigh and cost more. It's not really needed on a flat
four anyway, as on a non boxer the pistons on the front and rear
pair will be going opposite directions


True, but this doesn introduce a "rocking couple" vibration mode.
There's no free lunch WRT to engine design. :-)

Although some configurations come close (I-6, V-8, etc.)


Matt

A very interesting design is the Diesel Air engine (www.dair.co.uk).
They have two pistons per cylinder, moving in opposite directions. The
ignition happens in the center of the cylinder, which is also the
center of the engine. All forces that can cause vibration are supposed
to cancel eachother out, so there's a minimum of vibration. The engine
has two cranks which are mechanically coupled on the outside to bundle
the power to the prop. Pictures are on their site.

A fairly old idea, but it was quite successful for the Germans in WW2, the
engine giving a good SFC and allowing long range maritime patrols.
I've seen a sectioned example of this engine up close and it's fairly
complicated, not to mention absolutely huge!
http://www.billzilla.org/ideas4.htm
But it goes back even further than that, at least to 1898 when the Arrol
Johnston company made that same design into this contraption.
http://www.britishmm.co.uk/history.asp?id=65