The S-RAM is more efficient than crankshaft, swash plate, and bent axis motors and pumps
The extremely low frictional losses of the S-RAM result in increased torque and overall efficiency in hydraulic devices as well as low heat generation, higher starting torque and virtually zero slip stick. S-RAM motors and pumps can be built in variable stroke, double-ended, and fixed and rotating barrel configurations. The S-RAM has outstanding performance at reduced displacements. This is particularly desirable in energy recovery applications such as transportation, wind, geothermal, etc.
KEY S-RAM ADVANTAGES
Improved Torque and Overall Efficiency
The extremely low frictional losses of the S-RAM result in increased torque and overall efficiency in hydraulic pumps and motors. The S-RAM has high torque efficiency over a wide range of speed and partial displacements. The S-RAM also has excellent low rpm torque efficiency similar to a radial piston motor and matches or exceeds this efficiency at high speed when compared to a bent axis motor. These characteristics also provide an expanded bandwidth. Another remarkable feature is the performance at reduced displacement. Full, 3/4, and 1/2 displacements are all within a few percentage points of 90%. This is particularly important for energy recovery applications.
Stroke of the S-RAM can be varied while maintaining a constant head clearance, which is not possible with other drive mechanisms. Unswept volume remains close to zero as the capacity of a pump or motor is varied in a continuous fashion. This allows the efficiency to remain high at partial capacity (reduced displacements). Piston friction is also proportional to the stroke length so reduced stroke further reduces piston and bearing friction losses, improving mechanical efficiency.
Near Perfect balance
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 that are evenly spaced can be near perfectly balanced. A variable stroke S-RAM can also be balanced.
The S-RAM can be easily configured with a double-ended piston that will operate 180 degrees out of phase with the first. This can dramatically increase the performance and the power density of the machine, with little change in physical size and weight of unit.
Low heat generation
Low piston friction in the S-RAM leads results in minimal heat being generated within the body of the operating mechanism. Measurements taken from a working 20 HP hydraulic motor showed a temperature rise of only 40F (20C) at full load. All of our pump and compressor machines run this cool or cooler. Reduced heat generation can in some cases eliminate the need for an oil cooler, but in any case, reduce the size of the required cooler.
The S-RAM is a new mechanism to drive pistons. Architecture arrangement allows a designer to use the same valves, cylinders, manifolds, etc that complete the system 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 full 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.
Scaling to higher horsepower
Cool running of the S-RAM allows higher horsepower to be achieved. The 500 HP pump prototype ran with a low temperature rise such that a 3,000 HP pump was deemed feasible. At reduced power levels a fractional horsepower compressor with low friction allowed oil-less plastic bearings to run with little wear. Scalability is similar to that of a crankshaft mechanism in that no scaling problems arise as the square or higher power of linear dimensions.
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