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Torsional vibrations of an engine-powered hydraulic system were analyzed. The system consisted of: a diesel engine, spline shaft with clearance, universal joints, propeller shaft, mechanical transmission with clutch engagement, hydraulic pump, and a load. Excessive torsional vibrations resulted in propeller, spline shaft, and U-joint failures. Although the system had been adequately designed for the steady-state horsepower requirements of the pump, field failures began to occur after several systems were built and delivered. A nonlinear dynamic analysis was performed, which included variations in system parameters. The analysis revealed that two design changes would reduce the dynamic stresses. These were to increase spline clearance and to add a torsional damper to the propeller shaft.

A Minimum Cooled Engine (MCE) has been successfully run for 250 hours at rated condition of 298 kW and 1900 rpm. This engine was all metallic without any coolant in the block and lower part of the heads. Ring/liner/lubricant system and thermal loading on the liner at top ring reversal (TRR) as well as on the piston are presented and discussed. Ring/liner wear is given as well as oil consumption and blow-by data during the endurance run. Another engine build with a different top ring coating and several lubricants suggested that a 1500 hours endurance run of MCE is achievable. Rig test data for screening ring materials and synthetic lubricants necessary for a successful operation of a so-called Adiabatic Engine with the ring/ceramic liner (SiN) interface temperature up to 650°C are presented and discussed.