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 Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwe ...

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) ;Kroeber M4 Köller:Main production variant

Applications

''Data from:''AEHS : HOAE Kroeber * Grunau Motor-Baby - German motor-glider conversion of a

Grunau Baby The Schneider Grunau Baby was a single-seat sailplane first built in Germany in 1931, with some 6,000 examples constructed in some 20 countries. It was relatively easy to build from plans, it flew well, and the aircraft was strong enough to han ...

* 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 The Polish Aviation Museum ( pl, Muzeum Lotnictwa Polskiego w Krakowie) is a large museum of historic aircraft and aircraft engines in Kraków, Poland. It is located at the site of the no-longer functional Kraków-Rakowice-Czyżyny Air ...

in Krakow.

Specifications (M4)

References

{{Reflist Boxer engines M4 1930s aircraft piston engines