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.[1] Manson Engines can be started both ways (clockwise and anti-clockwise).[2] It has a stepped piston. The front part is acting as a displacer and the back part as work piston (displacer and piston move as a single component).[3][1] The engine only requires three moving parts (piston,[3] piston rod and crank).


The engine is double acting,[1] as it is using both the expansion of the warmed air and the contraction of cooling air to exploit work.[3][4][5]

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

Functioning mechanismEdit

Drawing based on the original design[1]
ideal PV-Diagramm[6][7]
  • Phase 1 (cooling down the work medium, suction stroke)
    • when the Piston is moved towards 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 a drop in pressure, further moving the piston towards the heat source.
  • Phase 2 (top dead center)
    • When the piston reaches top dead center, the 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 towards 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 center)
    • when the piston reaches bottom dead center, the valve is open, releasing the build up pressure and hot air.
    • the flywheel keeps the piston moving

Differences to Stirling enginesEdit

Stirling engines are typically closed systems, while the Manson Engines are open system.[3][5][8][2] The displacer and work piston of the Manson Engine have zero phase angle.[4]



The valve/gas paths are considered by some to be complicated to manufacture, so various variants exists with improved/modified simplified vales/gas paths.[9][10]


  1. ^ a b c d "The Manson experimental double acting engine".
  2. ^ a b c "Nano Disc - Horizontal - From".
  3. ^ a b c d "Manson".
  4. ^ a b "New generation of hot air engines: Manson engine".
  5. ^ a b "Manson".
  6. ^ "Principes de fonctionnement du moteur Manson". December 22, 2018. Archived from the original on 2018-12-22.
  7. ^ "Manson-Motor".
  8. ^[bare URL PDF]
  9. ^ a b 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