I'll second the importance of keeping the prop dynamically balanced. A Dynavibe balancer, the one they call the "Classic" (rather than the higher priced model the name of I've forgotten, other than they want 4K for it) should be conidered an essential hangar tool. Mark has one and I've got both the classic and the X3 or whatever they call it. I've got both of them - the company just sent me the fancy one when it first came out. When I asked "why" they just said they'd appreciate an evaluation. In view of such generosity I didn't really give them an evaluation of the X3 since, to me, it's a complete waste of money. It will accept two cables providing info from two sensors, one in front and the other at the rear of the engine thus helping to diagnose some internal problem. You still have to take the engine apart to see what the issue is, so what good is a vibration diagnosis? At any rate, the features of the X3 may be of use to full-time engine professionals. For keeping a smooth prop that does just as good a job as its expensive brother, the $1500 Classic model is excellent. I found the X3 unusable actually. Supposedly it tells you exactly how much weight to use when balancing, but this is something you get a "feel" for after using the cheap one for any period of time. You still have to run the engine up one more time to check the accuracy of the weight placement, whichever one you're using, so the X3 turned out to just be a PITA. I should have sold it long ago. It's just another thing I've let pile up that needs doing.
Anyway, a dynamically balanced prop is a joy to operate. You'll get more RPM's for the same throttle/mixture setting. Instruments and control attachments will be less stressed, as will the pilot and passengers and the engine bearings. There's nothing like doing your balancing yourself. Take it to a shop and you can bet they won't do as fine a balance as you will. I've done a few balance jobs that had been recently balanced by a "shop" and in some (most) cases their margins were ridiculous compared to how perfectly you can do it using your own balance job. Since the intro of the Dynavibe back in 2006 or 7, one or two other companies have come out with low cost balancers so they're not hard to find. I can't imagine they'll be any better than the Dynavibe however. I've done dozens and dozens of balance jobs since I got mine in 2007 and I've never needed any maintenance with the sensors or the hand-held computer. Mount it on a pedestal shop fan for practice and to learn how it works and save a bunch of avgas. The "C" model Comanche and the Twin Comanches after a certain year had extensions and didn't have problems . . . but then they had Lycomings, not Revmasters. The cranks may be just as good on both, for all I know. They have to be forged of course. Cast cranks (and flywheels, etc.) were the death of HAPI. MikeKSEE
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