ORIGINAL: captain stowed
ORIGINAL: The Raven
My theorizing is that a single cylinder engine will never have a perfect balance. Adding a prop gives another plane of imbalance to the engine. It's better to have all those imbalances line up on a common plane or...theoretically...you now have two imbalances which could lead to vibration/harmonics that detract from engine performance.
Sorry mate, you've lost me. Statically and dymamically a balanced prop is a balanced prop and can be considered a disc as far as the dynamic forces go. There is no resulting ''imbalance'' in any plane in a balanced prop that can be used to offset the reciprocating imbalances in the engine. You need to look elsewhere for the reason for your 300 rpm increase.
michael.
I see your point but the prop is imparting a centrifugal force on the crank in one particular plane (along the prop centerline). Hence, I'd expect a minor but theoretically measurable sinusoidal load on the crank.
A single cylinder engine is inherently imbalanced due to the reciprocating and rotating forces. Placing the prop in-line with this imbalance, which I assume peaks around TDC/BDC, puts both the prop and engines forces on the same plane. Positioning the prop otherwise *may* (note I'm speculating) cause an additional imbalance which could magnify at various rpm ranges. By aligning the prop/crank you may minimize any effect the prop forces generate.
Yes, it's only a theory and perhaps a flawed one. However, I can't deny the empirical evidence that aligning the prop to TDC/BDC has yielded 300rpm improvements on every single cylinder I've tried.
Happy to hear anyone elses thoughts on this and/or an independent test to verify my findings.