Special cases: Harold Kosoff, Frank Stelzer, Jack Horton
As early as 1964 he had a vision of a linear generator, which powered cars and supplied houses with electricity and heat. The engine was not developed further.
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Special cases: Frank Stelzer
Frank Stelzer (1934 - 2007) worked on this engine nearly his entire life, without any commercial success. A first patent was filed in 1963. There is no such first working model known .
Automotive News 1981
The starter usually consist of a hydraulic chuck, moving the piston back and forth until combustion begins. Then the pressure is released from the chuck and the piston can oscillate freely.
Stelzer built the engines much over square. On the one hand, to keep the vibrations within limits, on the other hand because the stroke was severely limited by reason of this hydraulic starting system.
Special cases: Jack Horton
Probably the most dangerous free-piston engine ever built. According to an MIT study of 1974 (see below), the information about 80 pounds of thrust at 20 lbs weight is not exaggerated. The generated noise, however, is about 145 decibels and the engine is extremely dangerous in operation.
Acetylen-oil-air mixture is compressed in pump cylinder on right side. On left side, pump cylinder is drawing in acetylen-oil-air mixture. Acetylen-oil-air mixture in power cylinder left is being compressed, as shown right in above figure.