Otto Langen Free Piston Engine Registry





Early engraving of original design as shown on patent


Designed and produced by Nicolaus Otto and Eugene Langen between 1864 and 1877, it was an important stepping stone for the introduction of the 4 stroke cycle engine. Several unique mechanisms appeared in this engine . Most famous was the overriding, or roller-wedge clutch that engaged only the downward movement of the piston and rack assembly which resulted with the spinning of the main shaft and flywheel. Secondly, the free piston concept: where the piston movement was independent of the main shaft. As the engine fired, the piston was allowed to travel as far as the explosion carried it. The rack, connected to the piston in conjunction with a gear, housing the directional clutch, made this mechanical movement possible-similar to a rack and pinion gearing system engaging in only one direction. Use of a crankshaft was unnecessary with this system. Another mechanism was the noncontinuous rotating cam. Even though the camshaft itself spun continuously with the main shaft, the cam and follower only cycled at one revolution intervals, at such time the piston returned to its lowest point. As this happened, a spring loaded pawl engaged a ratchet, thus spinning the shaft. Nearing one complete revolution, a tail on the pawl caught a lever, disengaging it and ending the cycle. Slide valve operation and piston/rack lifting (for the intake stroke) were both controlled by this momentary operation.


As the design of this engine was refined over the years several mechanical and cosmetic iterations appeared.  They were produced by Otto & Langen, Crossley and Langen and Wolf.


The purpose of this page is to catalog all known free piston Otto & Langen style engines



This is a work in progress.  I welcome any corrections or engines that may have been missed.  I am especially looking for missing serial numbers, photos or history that can be documented here

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