Introducing a New Engine
The “Shepherd Engine,” created by Gray Shepherd, inverts the core motion of the combustion engine. It features fixed pistons and reciprocating cylinders converting linear motion into rotary motion without the use of a crank shaft.
In a conventional engine the majority of the power is harnessed from the combustion cylinder using inefficient techniques for pressure conversion and establising physical leverage. At the top of the piston stroke, where gas pressure is highest, force transfer efficiency is at its lowest, though it rises as the piston descends and the connecting rod’s leverage increases. Peak efficiency happens about 40% through the piston stroke, then drops at an exponential rate that mirrors its rise. In addition, the piston doesn’t travel a path that is strictly parallel to the bore, so an angular force is transferred to the cylinder wall. This increases friction, wear, and fuel consumption.
The size of the torque output in the Shepherd engine is not limited by the physical radius of the crank shaft journal where it is attached to the connecting rod, and the engine is able to extract power efficiently form the reciprocating sleeve over a greater range of the power stroke. The result is the production of more torque for a greater period of time. Thus greater more uniform torque is generated which dramatically improves the engines ability to harvess energy from the combustion event occurring inside the cylinder.
The Shepherd Engine
The Shepherd Engine is a new concept 2 cylinder, 2 stroke diesel engine designed and developed in New Zealand. It addresses the inherent inefficiencies in conventional crank shaft engines: the inability to efficiently convert combustion cylinder pressure into kinetic energy.
The basic principle of the Shepherd HTO Engine is to convert linear reciprocating motion of the combustion cylinder into rotary motion of the outer cam sleeve
This low-revving engine is roughly twice as fuel efficient as traditional diesels and produces four times the torque. It has 4 power strokes per 1 revolution of the cam sleeve, equivalent to the number of power strokes in a conventional 8 cylinder, 4 stroke crank shaft engine
The one-to-one [45 degree] slope of the cam lobes allows for the combustion cylinder pressures to be harnessed effectively throughout the duration of the power stroke. Cylinder pressure can be harnessed from the one o'clock position through to the five o'clock position which is almost double the duration of a crank shaft engine
A pair of liner transfer drive rollers follows a cam profile on each end of the rotating outer sleeve, converting the axial reciprocating motion of the combustion sleeve into the rotary motion of the outer sleeve. The outer sleeve can best be understood as a fly wheel whereby two reciprocations of the inner combustion cylinder are needed to complete one rotation of the outer sleeve.
The Shepherd High Torque Output (HTO) Engine is designed with 2 fixed pistons (with mounted diesel injectors), one at either end of the support sleeve which remains stationary. The support sleeve contains an internal sleeve with combustion cylinders at each end. An air pre-charge chamber is fixed in the center of the combustion cylinder sleeve. Also attached to this reciprocating combustion cylinder sleeve are two cam drivers, one set at each end, which drive the outer rotating cam sleeve.
The main support sleeve of the concept engine supports two fixed pistons, one at each end. Diesel is supplied through injectors in the piston, and the combustion drives the cylinder sleeve backward and forwards. The motion of the sleeve is controlled by slides running in axial slots in the stationary engine outer housing.