U.S.A. Herkimer OK 075 Diesel
Manufactured and marketed by Herkimer Tool and Model company in the 1950's
This line of small model engines were designed by Charles Brebeck in the U.S.A. and featured ultra light construction with a high power to weight ratio which made them popular with the modelling community.
The OK Cub engines set the design standard for most small engines produced for decades to come: introducing a cylinder with integral cooling fins; radial exhaust and transfer porting; a steel cylinder threaded into the di-forged aluminium crankcase; cylinder head threaded into the top of the cylinder; backplate threaded into the crankcase and even the spray bar is press fit into the air intake. Infact there is not a single screw or nut used in the assembly of these engines, except for the two screws used to attach the propeller and the fuel tank. These features result in a remarkably light weight engine.
Other examples of this engine feature an aluminum tank mount
Test set up; better result were obtained when fuel supply was augmented with a larger external tank, because the integral tank was depleted too quickly
The visual material used in this page are reproduced here courtesy of YouTube channel Jose Maria Gonzalez-Calatayud Saiz of Spain
Propeller size used for the test run was 7X3.5 inches
In 1938, Charles Brebeck formed the Herkimer Tool and Model Company to manufacture his engines. A year later, he obtained a patent for improvements to engine design to minimize heat distortion and facilitate economical manufacture. Charles' engines were known as OK Engines. Charles applied for and received a patent for a method to fabricate a model engine crankshaft using a cooling jig to prevent welding heat from softening and distorting the assembly. In the summer of 1949, Herkimer came out with the OK Cub, the first real mass-produced .049.and by the end of 1949, there were OK Cubs in .049, .074, and .099 displacements. Charles introduced his diesels in .049 (0.803cc) and .075 (1.23cc) displacements. By 1952, Herkimer was making more than 1000 engines a day and their advertisements appeared in most of the popular magazines of the day such as; Air Trails, Model Airplane News, Flying Models, Boy’s Life, Popular Science, and Science & Mechanics. By the end of 1953, Herkimer had sold more than a million engines, had 700 distributors, and was carried by 4400 dealers.
Watch a short video showing a cold start and a hot start of this engine