M4 Köller
Type
National origin Germany
Manufacturer Dr. Kroeber & Sohn G.m.b.H.
First run 1930s
Major applications Möller Stomo 3, ITS-8

The Kroeber M4 Köller was a 2-stroke air-cooled horizontally-opposed piston engine designed and built by Dr. Kroeber & Sohn G.m.b.H. in Germany in the late 1930s. The M4 proved relatively popular, for powering the ultra-light aircraft and motor-gliders in vogue during the 1920s and 1930s.

Variants

Kroeber M3 Köller
either a typo or a variant of the M4, (only reference is Cynk's Polish aircraft 1893-1939)[1]
Kroeber M4 Köller
Main production variant

Applications

Data from:AEHS : HOAE Kroeber[2]

Engines on display

There are several M4 engines on display, but one of the best preserved and presented is at the Polish Aviation Museum in Kraków.[3]

Specifications (M4)

Data from Flugzeug-Typenbuch. Handbuch der deutschen Luftfahrt- und Zubehör-Industrie 1944,[4][5]

General characteristics

  • Type: 2-cylinder 2-stroke air-cooled horizontally-opposed
  • Bore: 75 mm (2.95 in)
  • Stroke: 72 mm (2.83 in)
  • Displacement: 0.634 L (38.69 cu in)
  • Length: 550 mm (21.7 in)
  • Width: 550 mm (21.7 in)
  • Height: 646 mm (25.4 in)
  • Dry weight: 27.8 kg (61 lb)

Components

  • Fuel system: 2x Meco S1/f carburetor
  • Fuel type: 1:25 SAE 50 oil / gasoline blend
  • Oil system: blended with fuel
  • Cooling system: air-cooled

Performance

  • Power output:
  • 18 PS (18 hp; 13 kW) at 2,700 rpm (30 minutes) at sea level
  • 16.6 PS (16 hp; 12 kW) at 2,650 rpm (max. continuous / cruise) at sea level
  • Specific power: 28.4 PS/L (0.46 hp/cu in; 20.89 kW/L)
  • Compression ratio: 6.2:1
  • Specific fuel consumption: 0.228 kg/PSh (0.510 lb/(hp⋅h); 0.310 kg/kWh) at max continuous
  • Oil consumption: 0.002–0.003 kg/PSh (0.004–0.007 lb/(hp⋅h); 0.003–0.004 kg/kWh) at max continuous
  • Power-to-weight ratio: 0.645 PS/kg (0.289 hp/lb; 0.474 kW/kg)
  • B.M.E.P.: 2.55 atm (2.58 bar; 37.5 psi)

References

  1. Cynk, Jerzy B (1971). Polish aircraft 1893-1939. Putnam. p. 652. ISBN 0-370-00085-4.
  2. "Kroeber". www.enginehistory.org. AEHS. Retrieved 5 February 2020.
  3. "Aircraft engine: Köller Kroeber M4". Polish Aviation Museum Kraków. Retrieved 25 December 2023.
  4. Schneider, Helmut (Dipl.Ing.) (1944). Flugzeug-Typenbuch. Handbuch der deutschen Luftfahrt- und Zubehör-Industrie 1944 (in German) (Facsimile reprint 1986 ed.). Leipzig: Herm. Beyer Verlag. p. 417. ISBN 381120484X.
  5. Grey, C.G.; Bridgman, Leonard, eds. (1938). Jane's All the World's Aircraft 1938. London: Sampson Low, Marston & company, ltd. p. 64d.
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