The Mikro 5 cc racing engine from Copenhagen, Denmark, was manufactured by Kaj Nielsen in his small workshop at Kronprinsensgade 8 in Copenhagen. A summary of Nielsen's activities in the model engine field is included in my separate article on the early post-WW2 Danish model engines.
The Mikro 5 cc racing engine was introduced in 1951 in response to a demand from Danish tether car racers for a domestic engine that could compete with the foreign imports like the Dooling and ETA 29 models. It was a very well-made unit which drew some of its design inspiration from the Dooling 29.
Unfortunately, in standard trim the engine failed to match the perfomance of its imported rivals. However, some owners were evidently succesful in extracting more power through well-focused tuning, as a result of which the engine did achieve some competition success.
Unfortunately, the demand from the Danish tether car racing fraternity was quickly satisfied. The engine's considerable weight (320 gm / 11.29 ounces) and bulk militated against its use in model aircraft service. Moreover, Kaj Nielsen found that he could not compete in price terms with the various import models. Consequently, production of this excellent engine was terminated quite early on after only some 500 examples had been produced.
Kaj Nielsen continued in the precision engineering business for many years, working on a range of special projects. Up to 1984, new examples of the Mikro 5 cc racing engine could still be purchased from Nielsen's Copenhagen workshop at a bargain price of only 50 kroner! These engines represented New Old Stock left over from 1951. They are all long gone now.
An in-depth review and test of the Mikro 5 cc racing engine may be found elsewhere on this website.