S-RAM Engine is more efficient, less costly, more durable and significantly smaller than crankshaft engines. The S-RAM can be configured as a Variable Compression Ratio engine or Double Ended to deliver extreme power density.

The S-RAM can be configured as a Variable Displacement/Compression Ratio (VCR) engine or Double-Ended engine to deliver extreme power density.  The S-RAM technology dramatically reduces engine friction while enabling a unique, axial form factor that eliminates the need for a crankshaft.  The entire bottom works of an engine can be eliminated. The S-RAM engine works in an elegantly simple manner while providing an open-cylinder architecture that can accommodate any combustion and ignition technology. The engine can be viewed as an imaginative repackaging of typical engine components (i.e., pistons, cylinders, bearings, etc) in an axial configuration.

The S-RAM engine can also be configured as a variable compression ratio engine since the piston stroke can be adjusted while maintaining a fixed head clearance, which is not practical to do with a crankshaft engine. Finally, the S-RAM engine can be double-ended, which can dramatically increase the power density.

Key S-RAM benefits

  • 10-12% higher mechanical efficiency
  • 4x+ power density
  • Higher speed operation
  • 60% fewer parts…less costly to build
  • Open-cylinder architecture can handle any combustion/injection technology
  • Variable Compression Ratio by changing stoke while maintaining a fixed head clearance
  • Double-ended operation gives engine designer more opportunities to optimize
  • Superior durability


Axial Geometry

The axial geometry creates a compact cylindrical engine allowing for a wide range of applications that require limited space, fit and ease of installation and maintenance. The S-RAM engine can be designed in 3 - 9 cylinder configurations. Manufacturing costs can be optimized by designing an engine family designed around a 3-cylinder family with a range of piston bores and strokes or a series of 3 to 9 cylinders using identical piston bores and strokes.

Reduced friction

The unique S-RAM piston joint almost eliminates piston-cylinder friction, reduces required number of bearings and reduces bearing speed by at least 33%. The piston skirt and bearing friction of the S-RAM will be less than 25% of a typical crankshaft engine.

Sinusoidal motion/Near Perfect Balance

The motion of the S-RAM pistons is very nearly sinusoidal, and the harmonic components are unusually small. We have even balanced the third harmonics delivering near perfect balance. The S-RAM can balanced even when the stroke is changed. The sinusoidal piston motion also results in a 10-15% lower piston velocity over top-dead-center resulting in a longer piston dwell time. This may enhance combustion characteristics for certain combustion technologies.

Double-ended operation

The S-RAM can be easily configured with a double-ended piston that will operate 180 degrees out of phase with the first.  This takes up little space and can dramatically increase the performance and the power density of the machine.  The double-ended  S-RAM can also be configured as a supercharger, a compressor, a hydraulic pump or linear generator.  Our next generation preproduction prototype( see below) will be configured as a double ended engine operating in a Semi-Free Piston mode.

Variable Stroke Mechanism

By a simple mechanical means, the S-RAM can be made to change the stroke of the engine while maintaining a fixed head clearance. This is performed by simply moving the S-RAM joint in a prescribed relationship to the S-RAM nose pin angle.  The engine can effectively change displacement or compression ratio, on the fly, to optimize engine performance.

Are you interested in the S-RAM
Semi-Free Piston Engine test results?

Please insert email and we will keep you up to date with our progress.

{insert newsleter code here}

Current/Future Prototypes

S-RAM Semi-Free Piston engine prototype

We are currently designing a purpose-built engine with multi-fuel
capabilities and utmost power density for stationary and portable power applications.

We believe this engine will represent a low cost and high performance solution and will have an immediate market niche for both commercial and military applications. This state-of-the-art engine takes advantage of all of the unique advantages of the S-RAM mechanism.

The S-RAM technology substantially eliminates piston side loads, reduces bearing friction and substantially reduces the number of parts. In this double-ended configuration, the combustion/inertia loading of the common piston cancels over 50% of the mechanical loading on the S-RAM crank, thereby resulting in a "Semi-Free Piston" mode of operation. The S-RAM Semi-Free Piston axial engine will represent the highest form of mechanical efficiency, durability and power density. 

Please contact us if you are interested in using this exciting prototype.

© 2018 S-RAM Dynamics. All Rights Reserved