Bernard Hooper Engineering Ltd has over 45 years experience of contract design and development work for many customers, including; UK Ministry of Defence, DERA, QinetiQ and other World renowned Research organisations and manufacturers.

THE STEPPED PISTON ENGINE

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BHE holds patents on technology for stepped piston engines. This technology has been the subject of extensive engine testing aimed at Industrial, Automotive, Marine and Defence applications ranging from 80 cm³-1800 cm³ (using gasoline, kerosene, diesel and gaseous fuels). Engines under development for various clients with interests in the recognised benefits offered by two stroke engines, but with the essential attribute of durability. This is afforded by the crankcase isolation provided by the stepped piston (see operating principle). The key advantages are as follows:-

STEPPED PISTON ENGINE SPX OPERATING PRINCIPLE (schematic)

(Alternative 1,2,3,4 ....cylinder formats)

ADVANTAGES

WET SUMP - conventional 4 stroke lubrication

PLAIN BEARINGS

NO VALVE GEAR

LOW THERMAL LOADING OF PISTON

LOW EMISSIONS WITH DURABILITY

LOW MANUFACTURING COSTS

COMPACT LOW MASS DESIGN

EXTENDED OIL CHANGE PERIODS (Oil does not degrade)

FAST WARM UP (lower cold start emissions)

ABILITY TO OPERATE ON A WIDE RANGE OF FUELS (including GAS)

Piston mass is naturally higher for a stepped piston design. However our unique approach means that for identical power cylinder bores the stepped piston is only around 20% heavier than a conventional looped scavenged two stroke piston. The multi section or step of the piston provides a flange stiffening effect resulting in thinner skirt sections. If necessary the mass increase can be reduced to below 15% by composite methods. However the engine uses the two stroke cycle and therefore with the absence of load reversals piston mass is not as critical as it is for four stroke engines. The Hooper stepped piston also provides improved load bearing and guidance resulting in low ring wear and reduced piston noise.

SPV580 Unmanned Aircraft Engine

Designed and developed under MoD contract, this 580 cm³ four cylinder engine produces 35.4kW (47.5BHP) at 5250 RPM. The V4 configuration offers exceptional smoothness with NVH characteristics similar to a V8 four stroke engine. Gasoline and kerosene AVTUR / JET A-1 versions have been developed. The 30kW target performance was achieved with simple exhaust system and a very low engine mass of 18.2kg (air-cooled) or 18.5kg (liquid-cooled).

For further information on the stepped piston engine (sometimes also known as the stepped engine or step piston engine) or contract design and development of conventional 2 and 4 stroke engines and test rigs, see linked pages or contact BHE:-

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BERNARD HOOPER ENGINEERING LTD

For further information please enquire via the Contact us page of our website