Overhead Cam Engines
This was a further development of the Amazon. The bore size was increased to 122mm, with a stroke of 160mm. This gave a capacity of 11.23 litres. The engine had twin overhead camshafts, operating four valves per cylinder. The engine developed 200h.p. at 2,000r.p.m. It was considered for military use by the National Advisory Committee for Aeronautics, but was rejected as being already obsolete. The engine never went into production.
The Spartan was Louis Coatalen's only attempt to produce an air-cooled aero engine. It was a V12, with 105mm bore and 135mm stroke, giving a capacity of 14.03 litres. It had four valves per cylinder, driven from an overhead camshaft, and two magnetos and a geared propeller. The engine delivered 200h.p., which was small for an engine of this capacity. This was presumably because the engine was air cooled. The engine was not successful and wasn't produced commercially.
The Matabele was the last development of the Cossack family of engines. It was basically a Cossack, with aluminium, instead of cast-iron blocks. The bore was increased to122mm and the stroke was 160mm, which gave a capacity of 22.45 litres.
After the tests the engine returned to Sunbeam. Although it was advertised in the aviation press until 1923, the only order received was from France. How many were ordered, and for what use is not known.
The engine was further developed into the Matabele II, which had two magnetos and a direct drive. It was intended for non-aviation use.