Split off from another thread: what is the history of the opposed cylinder aircraft engine?
Some rumour that I heard, but never found confirmed:
The father of all opposed cylinder engines is the VW Beetle engine, designed by Ferdinand Porsche in the 1930’s.
But did I hear that the Beetle had been meant to use the 3-cylinder 2-stroke engine that originated at DKW, and (after the war) became the DDR standard in the Trabant, Wartburg and Barkas vehicles? Whereas Porsche’s boxer had been originally conceived for aviation?
The opposed cylinder engine was invented by Carl Benz in 1896 and he called it “contra motor”. The later term used by Porsche is “Boxermotor” which is still the term used in German for an opposed cylinder engine. So it’s much older than the VW Beetle or any aircraft engine.
Actually the father of all boxers is the Benz engine :)
OK, fellows, Mr. Benz may well have been the first to think of the principle, and he may even have produced a working sample – but I do not find a continued story from there on, into Mr. Porsche’s design or into any other? It seems to have been a nice idea at that time, and credit to Carl’s genius, but not a giant step forward in history.
BTW let us all beware of the minefield of terminology, the really generic name seems to be “flat engine” which then splits up into “boxer” and “V-180” … I will not go into that. Consult en.wikipedia if interested.
There is a story. Wilson cars early 1900’s, BMW bikes as of the 20es, then the VW E-motor. Porsche didn’t come with the idea out of thin air. Other than pushrod attachment on crankshaft there are no differences between boxer and V180.
There are a zillion of different engine construction principles and almost all of them were discovered very early on. Only time showed which principles were best for different applications. Same with airplane construction, it didn’t take long after the first powered flight to develop all important principles.
I believe the Lycoming 65 was the earliest production volume four cylinder flat aircraft engine, I think the Aeronca BMW-style opposed twin was before that. The Lycoming was revved a bit too high for propeller efficiency and as a result when the larger displacement Continental A-50 and subsequent A-65 came out in the mid to late-30s, they dominated for a while. Zillions of A-65s were made during the WW II, although they weren’t designed for military applications.
Gossipy answer: the layout of the flat twin, shaft drive motorcycle was pioneered by the English ABC Motorcycle. Sadly ABC were in the throes of bankruptcy just as BMW were starting motorcycle production. Plus ça change … At the end of the 60’s BMW turned their engine upside down so that the camshaft was below the crank. This was to improve ground clearance when cornering. It also means the cam is smothered in oil. If only Lycoming would do the same!
Technical answer: I recall studying the theory of primary and secondary balance of engines, and the flat four being the best-balanced layout of any four cylinder engine
Technical answer: I recall studying the theory of primary and secondary balance of engines, and the flat four being the best-balanced layout of any four cylinder engine.
Yes, and I believe the advantage over a flat twin is that the rocking couple due to offset con-rods is cancelled. Franklin none-the-less introduced and produced an opposed twin as late as 1971 or so.
Of course the significant benefit of a flat engine for aircraft is that it doesn’t block the pilots view when the prop is positioned where it needs to be for other reasons. Nor does oil drain into the cylinders.
