TESTING OF THE GEARED DRIVES ^TM PSRU

The Geared Drive PSRU was tested under load for 50 hours on a stock Chevrolet 350 HP engine and then tested an additional 40 hours with our 400 cu inch 405 HP engine before being installed on the Wheeler Express 90 aircraft in early 2003.  The Geared Drive PSRU equipped, Chevy powered Wheeler  Express 90 has flown over 700 hours as of Oshkosh Airventure 2007, and is the only power plant and PSRU that this airplane has ever flown with. Just prior to the flight to Airventure 2007, Bud disassembled, inspected and mic'd the components of the Geared Drives redrive, and was delighted to find no evidence of wear of any of the components with the exception of the the clutch disc, which showed .003 wear. He was pleased to see how well the unit was holding up after that much use. Light wear to this extent after this much use with a 400 HP engine served to verify that there is no slippage of the clutch during use.

Using a fully automatic clutch and flywheel, Bud's original design, was also used during the test program with no perceptible wear. The automatic clutch became necessary after it was found that a flex plate was not sufficient to smooth out engine power pulses. Flex plates proved to be too light and tended to break due to sympathetic vibration during operation.  The clutch comes at no weight penalty and eliminates the possibility of harmful harmonics due to the clutch disc with heavy duty springs in the center.

The automatic clutch saves the starter by allowing the engine to start without having to pull the weight and inertia of the prop upon startup. Prop engages automatically at around 1000 RPM and engagement is imperceptible.  As engine RPM increases, the clutch grabs tighter and tighter. The clutch requires no attention or adjustment. When the engine is brought to idle in flight, the propeller becomes a speed brake as it will spin in proportion to engine RPM, a welcome feature when attempting to slow a high speed aircraft for approach or landing. There is no way that a pilot could cause the propeller to disengage during flight using this design as the wind will continue to cycle the prop and the engine at the same time and constant inertia will keep the propeller engaged until you land, taxi to a stop and reduce the engine speed to idle. Only then will the counter weights and springs in the automatic clutch disengage the clutch disc from between the pressure plate and the flywheel. The propeller will continue to spin down to a stop at that time due only to engine inertia.