The first to be cirtificated was the NR642 , a heavy duty versionof a basic twin rotor type with helecal reduction gearbox .
Rateing is 90 hp, and weight, complete with water cooling for the housing and a large exhaust ejector to cool the rotor ,
is 64 kg (140lb).
The slightly smaller NR 622, of 588 cc ( 35.9cu in ), has a rateing of 82 hp at 7.500 rpm and with 0.5 or 0.33 geared drive weighs 52 kg (115 lb 0 .
The NR 602 is basically a 622 with direct drive , reduceing weight to 48kg (105 lb ).
The NR 801 is a direct- drive single - rotor engine with liquid cooled housings , rated at 52 hp at 7.500 rpm and weighing 22.7 kg ( 50 lb ) .
The remarkable NR 731 is claimed to be the lightest RC engine in the world and to have the higest ratio of power to weight .
A single rotor engine with air cooling throughout , it has a width of 236 mm (9.3 in ) lenght of 188 mm (7.4 in ) and weight in running order of only 10 kg (22 lb ) , yet output at 7.500 rpm is 38 hp . Chamber capacity is 208 cc ( 12.7 cu in )
By Golly , you have to put it in a motorcycle sideways though .
from " Development of piston aero engines ." Auth. Bill Gunston . yes well , whats a piston , between friends .
