Our first product is a radial, five cylinder petrol engine for models: H80 BOMBUS. Because for giant models, the radial engines are currently being produced, and the present trend shows that for financial and transport reasons, airfields dimensions requirements, and last but not least for global restraint of civil liberty by self pleased bloated bureaucracy, the construction of models with wing span to 3 meters is prevailing. So we have chosen such engine size to be applicable for models in scale 1:5 to 1:4. The company Falkon, which is a reputable distributor of ignition for worldwide producers of model engines, according to designer´s requirement has developed a microprocessor controlled ignition, specially for this engine. Development and testing of the engine lasted for more than two years.
H80 BOMBUS Technical description
H80 BOMBUS is a four-stroke five cylinder radial engine, intended for propulsion of radio controlled models, especially semimaquettes and maquettes. The engine has been designed with reference to small outlines, both the diameter (240 mm) and length (151 mm), keeping a similarity to engines of the “golden age of aviation”. As well the weight is low.
The fuel supply is provided, in conjunction with an efficient fuel pump of own design, by a well tried carburetter Walbro®. The crank and valve mechanism is lubricated by a mixture of fuel and oil.
The duralumin cylinder heads, made by precision casting, are permanently assembled with cylinders which are made of alloy-steel with special very hard surface treatment having excellent sliding characteristics and long working life. The pistons have two packing rings. The valves with excessive working life come from a prestigious producer of stationary engines. The valve head is made of stainless heat-resisting steel, the valve shank is made of hardening steel. The whole valve has a most progressive surface treatment with a high hardness and excellent sliding characteristics. The valve rockers are treated in the same way, which gives them a demand of very limited, eventually no lubrication. This technology has been applied for very stressed parts in automotive and armament industry.
The crankcase, its front and aft casing are duralumin castings. All threads at duralumin castings are rolled, not tapped, which ensures the maximum strength of them.
The master rod rotates on the crankshaft by means of a needle bearing and has been made of very strong aeronautical duralumin. Articulated rods, made of the same material, do not require any bearings due to used style of lubrication.
The crankshaft is supported on a pair of ball bearings. As well the cam disc, the part of valve actuating mechanism, is supported on a pair of ball bearings. The designer´s effort was to design a cam disc of the diameter as big as possible, so as innacurate setting of valve clearance has minimum impact to valve timing. The engine thus tolerates relatively inaccurate setting of valve clearance and does not require frequent checking of it.
Excellently designed is a microprocessor controlled ignition system Falkon®, completely embedded in aft casing of crankcase. Thus there is no need of heavy and big connector between engine and ignition. Therewithal tough cables of spark-plugs do not complicate an installation the engine onto a model. The ignition system measures crankshaft speed and sets up an optimal spark advance. As a component of its software is a speed limiter inhibiting engine overspeed. The ignition system maintains a constant spark energy across whole range of speed and whole range of supply voltage. This ensures a reliable engine running in all operating modes.