sounds like one is out of synch at times. Hard to say more than that.
You definitely need a prop load for actual testing and you need the props for motor cooling, even though the motors won't make as much heat with no load as when loaded.
The minor variance in friction in the motors due to the bearings never (ever) being identical will amplify any imbalance when there is no prop load. Getting perfect synch through the full throttle range is virtually impossible. Even APC grey molded composite props from the same production run are not really identical. (very close... and those are the best at being matched that I know of)
Someone (many years ago) built a scale B-25 using a .35ci on one side and a .40ci on the other. Absolutely never in synch. It flew just fine.
Full scale multi-engine planes of the 1930's through 1950's they often flew with each engine at a different throttle setting to eliminate the need for rudder trim. (or eliminate the need for the pilot to keep pressure on one rudder pedal for several hours)
You definitely need a prop load for actual testing and you need the props for motor cooling, even though the motors won't make as much heat with no load as when loaded.
The minor variance in friction in the motors due to the bearings never (ever) being identical will amplify any imbalance when there is no prop load. Getting perfect synch through the full throttle range is virtually impossible. Even APC grey molded composite props from the same production run are not really identical. (very close... and those are the best at being matched that I know of)
Someone (many years ago) built a scale B-25 using a .35ci on one side and a .40ci on the other. Absolutely never in synch. It flew just fine.
Full scale multi-engine planes of the 1930's through 1950's they often flew with each engine at a different throttle setting to eliminate the need for rudder trim. (or eliminate the need for the pilot to keep pressure on one rudder pedal for several hours)
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