Throwback Thursday: A V8 Engine With Only Two Connecting Rods

Recently, we posted this engine on our Facebook page for Weird Engine Wednesday. While our plan was to use that as a teaser for this Throwback Thursday article, several of our more adept fans found the article on their own and posted it in the comments. This engine is so interesting, it’s definitely worth the repost.

Starting with a Honda based four-cylinder engine, Dieter Hartmann-Wirthwein patented a system in which four cylinders operate using only one single connecting rod.

Essentially, the two center pistons are connected via a “Y” shaped connecting rod. Also attached to those center pistons is a pivoting mechanism that is attached to the two outer pistons. This unique arrangement allows all four pistons to work as a single mechanical assembly, which transmits power to the crankshaft via a single connecting rod on a single crankpin.

Illustration Figure 1 from German Patent DE102008047719B4, “Crank drive for four-cylinder internal combustion engines” by Dieter Hartmann-Wirthwein. As you can see the outer pistons are connected to the inner pistons via a pivot linkage, and the inner pistons are connected to the crankpin via a Y-shaped connecting rod.

From there, Hartmann-Wirthwein made the next logical advancement — doubling the assembly and making a V8. Using a Ducati V-Twin engine as the basis upon which to build, the V8 assembly displaces 868cc (or 52.9 cubic inches) thanks to the 56mm (2.204 in) bore and 44mm (1.732 in) stroke.

While in the original EngineLabs article published by Mike Magda, the V8 variant — dubbed the “Elenore V8” — hadn’t fired yet, We are happy to be able to include the video below from 2019, where Hartmann-Wirthwein is running the engine in his apartment.

While we have seen the engine mocked up in a motorcycle frame, we haven’t found any videos of anyone actually riding the bike. Still, this is an incredible feat of engineering, even if it only proves to just be for engineering’s sake.

About the author

Greg Acosta

Greg has spent fifteen years and counting in automotive publishing, with most of his work having a very technical focus. Always interested in how things work, he enjoys sharing his passion for automotive technology with the reader.
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