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New Design for Fuel Efficient Piston Engines
Home » Technology Description 
Yoke Technology - Previous Attempts
There have been many previous attempts to utilize the “yoke” mechanism for piston engines. Most attempts have been met with limited success or no success at all. And all have failed to produce widespread application or develop worldwide interest. Russell Bourke's pioneering effort to incorporate the “scotch yoke” mechanism into the engine designs of the 1940’s & 1950s has been the most successful attempt to date. Bourke deserves much credit for Fisher's “yoke-arm” technology because the Fisher design was, in fact, inspired by Bourke's work and his promotion of the yoke concept for piston engines. Bourke’s R&D efforts provided Fisher a “bridge” to a superior design, which now includes additional features unknown to Bourke, and has significantly advanced engine performance beyond even what Fisher or Bourke was expecting. Many will recognize Russell Bourke, and also Collins Motor Corporation's (CMC Power Systems), Roger Richard and others, all Bourke’s modern day protégés, as determined pioneers who made significant contributions toward the advancement of piston engines. The eventual widespread success of the Fisher yoke-arm for piston engines and air compressors will promote increased recognition and appreciation for Bourke and others in their determined pioneering efforts. It will soon be obvious to many engine manufacturers and engine advocates that Russell Bourke and others understood the importance of continuing the evolution of technology within the Engine Industry, although Bourke could not quite bring about the final aspects of the needed breakthrough. Fisher has finally completed the equation for a superior piston engine design by discovering a new crankshaft linkage called the yoke-arm.

Yoke-Arm Advantages vs. Previous Attempts
Fisher has added a uniquely designed “yoke-arm” between the piston rod and crankshaft which is patent protected, both US & foreign (US patent no. 7,328,682). The yoke-arm is much different than previously tried yoke mechanisms such as, for example, the Bourke scotch yoke or “Bourke-Cycle” as previously discussed. The Fisher yoke-arm (shown below), an important and integral part of this breakthrough technology for piston engines, provides two main advantages over Bourke and conventional engine designs. (1) The increased piston dwell provided by Fisher is well beyond that possible with Bourke’s scotch yoke and associated "harmonic motion" for improving combustion efficiencies, and also well beyond all attempts by others. The Fisher yoke-arm can be designed for more or less dwell depending on the needs of particular applications, which is a severe constraint for the scotch yoke. (2) In addition to increased piston dwell, the added benefit of much less piston friction plus the increased mechanical advantage over conventional engines contribute to superior gains in mechanical efficiencies promoting even higher performance and added fuel economy. There is a 10% mechanical advantage over the conventional engine piston rod-crank relationship.

yoke-arm linking crankshaft to piston rod
a device to substantially increase piston dwell during combustion

Where are We Now?
Computer modeling and performance curves have demonstrated superior advantages when compared to conventional engines, and FEA testing has been completed for a very effective yoke-arm design. FEA testing shows that 3½" stroke engines will operate with ease above 6000 rpm. Based on the success of computer modeling and preliminary prototype testing, a second prototype is currently under construction with dyno testing scheduled for completion by early 2015. Our development team, has learned the benefits of piston dwell, and expects that dyno testing will validate the superior performance demonstrated by computer modeling, and also expects to reconfirm dyno test results for an earlier 2-stroke design that showed remarkable fuel economy and power increases.

Simplicity of Design - an Important Strength
Fisher's yoke-arm offers new, exciting and innovative "technological upgrades" for all conventional piston engines. Engines that are produced for the automotive, farming & construction, marine, aircraft, recreational, lawn & garden and motorcycle industries, both gasoline and diesel, will especially benefit to help protect our environment. Although performance benefits are substantial, it turns out that the conventional engine component parts are not appreciably affected. Performance curves derived from computer modeling plus our preliminary dyno tests have shown that the Fisher yoke-arm technology offers unprecedented operational and performance advantages never before achieved with a single modification that offers such simplicity and reduced cost for piston engines. An important strength for the Fisher Technology, is the relative ease of modifying existing engine arrangements at the factory. Retooling by engine manufacturers will be minimal, and the degree of simplicity that affords such big time performance benefits has never before been possible.

Advantages for Air Compressors Also
In addition to piston engines, efficiencies for piston driven air compressors are also substantially improved when using the yoke-arm mechanism. Some of the important benefits for compressors will be the noticeable reductions in energy required to operate air conditioning and refrigeration systems. Substantial increases in mechanical efficiencies, due to significant mechanical advantages and reduced piston friction, greatly reduce the power requirements for air compressor, refrigeration and heat pump systems. Home heating and air conditioning applications will experience noticeable reductions in power requirements which will reduce everyone's energy bills.


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