| One thing to keep in mind is that the prop balancing on the ground is not as accurate as when the scimitar is loaded in flight. This comes directly from one of the SX300 guys testing one of the Scimitars for Hartzell on his Lyc 580. What he did was run the cables through the heat duct and perform the balance in flight conditions. He reported that balancing the scimitars was not easy. I had a hard time finding a good balance on the ground on the Legacy but it was passable. I may try the in-flight balance next time at the 2300 rpm mark. Our Legacy scimitars are simply cut shorter than the longer bladed scimitars for ground clearance.
Second, the engine and cowl moves a lot and the clearances are very tight in the Legacy. At 2700 RPM and low airspeed the cowl is different shape than at cruise and the engine is in a different position relative to the mounts that at 2300. The torque on the engine mounts is much different at 2300 versus 2700. I found a lot of interference showed up as the RPM came down from 2700 to 2300 and then the engine and cowling were slightly separated so that the banging was transmitted. I believe at other settings the engine was up against parts of the cowl and the actual vibration was transmitted. I had the nose gear interference as well plus the baffling hit the prop governor cable in cruise. Lots of areas where interference fits are really tight. My point is that there are many factors that can affect vibration with changing throttle and RPM and it isn't just the prop/crankshaft combo that can be at issue. I was seeing almost two inches of cowl movement between rest and flight at certain locations. Thats a lot.
Not to take anything away from the issue under discussion except to say that, in my Legacy, vibration amplitude did change with varying RPM as a result of mechanical interference.
Paul Legacy
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