Kroeber M4 Explained

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]

• Grunau Motor-Baby – German motor-glider conversion of a Grunau Baby
• Kocjan Bąk I – Polish motorglider
• Dittmar Condor 'La Falda' (a removable power-egg with M4 and pusher propeller)
• Möller Stomo 3 – German high-speed ultralight aircraft
• Akaflieg München Mü13M Motormerlin
• ITS-8 – Polish motorglider sic Kroeber M3 Köller (only reference to M3)

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]

Notes and References

1. Book: Cynk . Jerzy B . Polish aircraft 1893-1939 . registration . Putnam . 1971 . 0-370-00085-4 . 652.
2. Web site: Kroeber . www.enginehistory.org . AEHS . 5 February 2020.
3. Web site: Aircraft engine: Köller Kroeber M4. Polish Aviation Museum Kraków. 25 December 2023.