Article · Wikipedia archive · Last revised May 30, 2026

Manson engine

The Manson engine is a hot air engine that was first described by A. D. Manson in the March 1952 issue of Newnes Practical Mechanics-Magazines. Manson engines can be started in either direction. It has a stepped piston. The front part acts as a displacer and the back part acts as a work piston. The engine only requires three moving parts: piston, piston rod, and crank.

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May 30, 2026
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The Manson engine is a hot air engine that was first described by A. D. Manson in the March 1952 issue of Newnes Practical Mechanics-Magazines.1 Manson engines can be started in either direction (clockwise or anti-clockwise).2 It has a stepped piston. The front part acts as a displacer and the back part acts as a work piston (the displacer and the work piston move as a single component).31 The engine only requires three moving parts: piston,3 piston rod, and crank.

The engine is double acting,1 using both the expansion of the warmed air and atmospheric pressure overcoming the reducing pressure of the cooling air to do work.345

The engine currently has no commercial or practical applications. The engines are built mainly as desk toys, physics demonstrations, and novelties.2

Functioning mechanism

Drawing based on the original design1 source ↗
ideal PV-Diagramm67 source ↗
  • Phase 1 (cooling down the work medium, suction stroke)
    • when the Piston is moved toward the heat source, the hot gas inside the engine is moved to the cool side of the cylinder.
    • the gas is cooled there, resulting in pressure dropping below atmospheric, further moving the piston toward the heat source.
  • Phase 2 (top dead centre)
    • When the piston reaches top dead centre, the inlet valve is open, releasing the vacuum.
    • the flywheel keeps the piston moving
  • Phase 3 (heating up the work medium, expansion stroke)
    • when the piston is moving away from the heat source, the air is pushed toward the heat source.
    • the air is then heating up, resulting in the air expanding and the piston being further pushed away from the heat source
  • Phase 4 (bottom dead centre)
    • when the piston reaches bottom dead centre, the exhaust valve is open, releasing the build up pressure and hot air.
    • the flywheel keeps the piston moving

Differences from Stirling engines

Stirling engines are typically closed systems, while Manson engines are open systems.3582 The displacer and work piston of the Manson engine have zero phase angle.4 Unlike many Stirling engines, Manson engines generally do not get very hot during operation as a result of the intrinsic cooling effect of taking in cold air and releasing hot air in every cyle.

Variations

Manson-Ruppel-Engine9 source ↗

The valves and gas paths are considered by some to be complicated to manufacture, so various variants exist with improved, modified, or simplified valves and gas paths.910

Sources

Sources

  1. "The Manson experimental double acting engine". stirlingengines.org.uk.
  2. "Nano Disc Manson-Guise Engine". stirlingengine.co.uk.
  3. "Manson". techref.massmind.org.
  4. "New generation of hot air engines: Manson engine". Archived from the original on 2019-09-13. Retrieved 2021-06-18. (gone)
  5. "Manson". geocities.ws.
  6. "Principes de fonctionnement du moteur Manson". December 22, 2018. Archived from the original on 2018-12-22.
  7. "Manson-Motor". w-haag.de.
  8. "A Novel Hot-air Engine" (PDF). Archived from the original (PDF) on 2021-06-24.
  9. C2 DE 19904269 C2, Michael Ruppel, "Heißluftmotor - Heat engine has a simplified design with combined piston and valve and with alternate sides of the piston vented in either limits of the piston movement", published 2000-11-9, issued 2001-6-5 
  10. GB application 2554458A, Christopher Guise, "Improvement to Manson engine", published 2000-11-09