The S-RAM low-friction drive mechanism can be mechanically modulated, enabling more efficient compressors andexpanders.

The displacement of the S-RAM can be mechanically varied while keeping a constant head clearance, which is not possible with other drive mechanisms. The unswept volume can remain low over a wide range of displacements, significantly improving compressor/expander efficiency.

Key S-RAM benefits

Reduced drive-power and improved efficiency

The extremely low frictional losses of the S-RAM pay off in reduced input power and a reduced cooling requirement for compressors, over the wide range of displacements.

Variable stroke

The stroke of the S-RAM can be varied while keeping the head clearance constant, which is not possible with other drive mechanisms.

Near Perfect balance

The motion of the S-RAM pistons is near sinusoidal and the harmonic components are unusually small. There are no even harmonics since the piston motion is symmetrical about the midpoint of travel. Any number of pistons three or greater and evenly spaced can be near perfectly balanced.  The S-RAM with variable stroke can also be balanced.

Double-Ended operation

The S-RAM can be easily configured with double-ended pistons that will operate 180 degrees out of phase with the first. This takes up little space and can dramatically increase power density of a compressor/expander.

Open-Cylinder architecture

The S-RAM is a new way to drive pistons and no new requirements are placed above the piston. This open-cylinder architecture arrangement allows a designer to use the same valves, cylinders, manifolds, etc., and conversion from any current design can be fairly straightforward.

Fixed or Rotating Barrel designs

The S-RAM drive can be used in rotating or fixed-barrel configurations. We have built both.

Wear and Life expectancy

Tests on our prototype S-RAMs have shown very low wear, which one would expect as a result of low friction. Bearing surfaces on the S-RAM 500 hp pump showed no measurable wear after several hundred hours of operation under load.

Reduced parts count and weight

The S-RAM uses significantly fewer parts and less weight than crankshaft mechanisms and similar parts count as compared to swash plate and bent axis mechanisms.

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Current/Future Prototypes

Next Prototype

Previous testing of S-RAM compressors has been successful in demonstrating both high mechanical efficiency and low heat generation with near perfect balance. Our next prototype will include the next generation S-RAM mechanism that can vary compressor/expander displacement while maintaining a fixed head clearance, which is not possible with other mechanisms.

We have licensed the S-RAM to be used for an innovative Hybrid-Stirling waste heat engine. Both the compressor and expander have been designed for high-pressure, low-rpm requirements and, combined, will be the core for an exciting new Hybrid-Stirling engine that can operate with a wide range of low grade waste heat (100 to 400 degrees C).

The specifications of these prototypes are confidential. The two prototypes will be completed soon and will be tested by the end of 2012.

Past Prototypes

We have built and tested several compressors and hydraulic motors/pumps.  The results of the prototypes have been very positive and we have continued to improve the efficiency, balancing and variable stroke features of the S-RAM technology. A brief description of past compressor prototypes is included below.

Refrigeration Compressor

  • 2 Cylinder Opposed
  • Stroke, 1.50 in.
  • Bore, 2.188 in.
  • Displacement, 11.275 cid
  • Peak Pressure, 350 psi

Oil-less Air Compressor

  • 3 Cylinders
  • Stroke, .766 in
  • Bore, 1.75 in
  • Displacement, 5.53 cid.
  • Design P. 4.0 psi
  • Tested to, 30 psi

Air Compressor

  • 2 Stage, 2 Cylinder
  • Stroke, 2.973 in
  • Bore, 3.00 in
  • Displacement, 21.01 cid
  • Pressure 2nd Stage, 250 psi
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