Siemens-Halske Sh3

Siemens-Halske Sh3 (Randy Huff)

Siemens-Halske differential rotaries featured opposite cylinder and crankshaft rotation at a maximum speed of 900 rpm. This resulted in an effective engine speed of 1,800 rpm while the slower propeller speed resulted in greater efficiency, and the slower cylinder rotational speed reduced gyroscopic effects and power lost to air resistance.

A development of the 9-cylinder version, the 11-cylinder Sh3 had a 124 mm bore and a 140 mm stroke, for a displacement of 18.6 l. The propeller was attached to a crankcase extension, and the engine was mounted to the airframe via a stationary rear transmission housing. A one-piece master rod with 10 H-section articulating rods ran on a two-piece crankshaft, which was supported on ball bearings. Each steel cylinder, with integral cooling fins and a nearly flat combustion chamber, included an intake and exhaust valve, each operated by a push rod and rocker arm. The Sh3 initially produced 160 hp, and was eventually developed to produce 240 hp.
It weighed 194.5 kg.


Sh3 Animations by Sergio Pasquali


Sh3 Cross Sections Courtesy of Arizona Model Aircrafters