In Fall 2006, Maxwell Propulsion Systems made the decision to develop a new geared propeller speed reduction unit (PSRU). Our goal was to bring into the experimental aviation marketplace a professionally designed and scientifically tested system that would address the critical issue of fatigue and/or early failure resulting from torsional vibration. The design requirements included a projected TBO of at least 1500 hours.

To address the torsional vibration issue, the MPS engineer worked with the engineering staff at Lord Corporation to analyze vibration data. The proposed remedy was to use eight rubber bushings and run another series of vibration tests. This approach to handling torsional vibration ensures that the resonant frequency of the engine coupled to the propeller is not in the normal operating range. The elastomeric bushings between the engine and PSRU have a low enough spring rate to lower the resonant frequency significantly.

Ground testing was completed in January 2008 after 140+ hours run on the test stand. The results of the tests demonstrated that all the observed vibrations fell below or within the acceptable range. Since that time, SportCopter International has been flight testing the MX1 PSRU on their new SportCopter II. In addition, the Maxwell Dream Liner has logged approximately 90 flight hours.