The Pivotal™ Engine was conceived by Pivotal Engineering LTD to overcome some of the inherent problems associated with a conventional two-cycle engine, such as high wear rates and friction losses due to piston tilt and large port openings, reliability problems due to lack of control over piston temperatures and high oil consumption. The Pivotal engine is an Otto cycle two-stroke engine. The engine is assembled from 500cc modules utilizing a rectangular piston that pivots on a plain bearing at one end. The pivoting motion of the piston allows coolant to enter the piston through the centre of the pivot giving temperature control of the combustion chamber while restraining the piston so it has little or no contact with the chamber walls. Although friction loss, temperature control and oil consumption problems have thus been mitigated, prototype engines still experienced problems with high compression seal wear rates. Compression seals run in a reciprocating motion along a flat chamber wall, somewhat analogous to piston rings in a conventional engine, although velocity varies along the seal length. The goal of this research is therefore to select and test compression seals materials to obtain an adequate working life in the Pivotal engine. Based on the rotational tribometer results, the most promising chamber coating so far is plasma sprayed iron with molybdenum and the most promising seal material is reaction bonded silicon nitride.

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