Free-piston compressor with opposed pistons and rack and pinion gear synchronization. Basis for the air compressors built from the mid thirties, especially in the use in German WW2 submarines.
The trials of Hugo Junkers to simplify the piston synchronization. Ultimately, on this issue all manufacturers of free-piston engines failed - with the exception of Pescara - Sigma.
In the early thirties, the Junkers free-piston engine was calculated by Pescara engineer Robert Huber, in order to come up with money for commissioned work.
Single piston-cylinder compressor of Raul Pateras Pescara. Pescara had the idea to propel his helicopter with this engine. The engine, however, could not be realized in this version.
The famous Pescara helicopters (first flight 1922) had a very heavy propulsion. The idea was to drive the rotor by means of compressed air through a system of a hollow shaft and nozzles at the blade tips. Pescara expected remarkable weight savings. This idea, however, was never realized.
That spring (1924), a French inventor (Pescara) came to Stodola (ETH Zurich) looking for a "bright young man" to engineer some of his revolutionary ideas on a light propelling plant for a helicopter.
It was fortunate that Pescara, the dreamer and glib-tongued persuader, chose Huber the engineer, who was young and capable and devoid of any inhibitions on the constructional details to be used in developing the new free piston machinery. Under his supervision, over twenty-five different sizes and types of free piston machinery were designed and seventeen were built and tested -
AMERICAN SOCIETY OF NAVAL ENGINEERS, 1950
1927: This historic photograph shows the first experimental engine AC-2 from Pescara, on the test bench near Paris in Meudon-Val-Fleury, France.
The experiments performed by Robert Huber correspond to the work of Rudolf Diesel, Nicolaus Otto and Felix Wankel.
This engine, however, bears the name of its inventor, Pescara, whereas it was designed and built by Swiss engineer Robert Huber.
Birth of the fourth motor system in addition to Otto (gasoline), Diesel, and Wankel
This engine was operated on gasoline. That time Bosch launched diesel injection pumps and injectors on the market, and soon Robert Huber designed the second prototype - similar to the AC-2, but with direct diesel injection.
Free-piston compressor with opposed pistons. Synchronization through connecting rods and a rocker. Built from the early thirties as air compressors for various applications. Compared with Junkers, the design was much more elegant and simplified.
This early opposed piston compressor AC-6 already had a Bosch direct diesel injection. It was started by means of a spring system. Even today, the restored engine starts at once at minus 5 degrees Celsius, without any preheating.
Example S26 with technical data
To reduce the risk of explosion, a mine locomotive was equipped with a free piston compressor. The locomotive ran with compressed air instead of steam and had therefore no longer an open fireplace.
Among the built compressors there were several vertical types of an enormous size.
Miniature free-piston engine compressor research at the University of Minnesota.