What's the Hold Up?

Updated - see below.

I know, I know. We haven’t flown yet. Sorry! So we have been doing a lot of engine runs and taxi testing. What is slowing us down from going is: we are getting a good amount of dynamic vibration in the engine and propeller. We borrowed a Dyna-Vibe propeller balancer setup from a local pilot and that unit is showing that we are getting from .8 to 1.6 inches per second of vibration from this engine and prop. We have run dozens of combinations and attempts at counter-balancing with no good results so far. Still working it! The worst vibrations as felt in the cockpit are between 950 and 1250 rpm and then it smooths-out by 1400 and feels good thru 1700. Starts to get a little bit at 1800 but nothing as bad as at 1150. The Dyno Vibe is saying that range is really bad too and that the 1600 is bad - tho I don’t feel it in the cockpit. We are statically balancing the propeller to eliminate that as a source. Then will test the compressions on the engine and see if a cylinder is causing the vibration. We can’t do too much if it is the internal engine parts (like the crankshaft counterweight) other than adding propeller flange counterweights. We are following the advice of a few experts on dynamic balancing and it really should not take this much time and effort. Steve Wolf, Brian Kelly and Mark Taylor all started their balancing at worse IPS’s than we are getting and all managed to get the vibrations down to .25 IPS or less with counter-weights. We can do it too. Wish us luck! The good news is that we have learned a lot about static and dynamic balancing. It is not as easy as should be! Will post some images over the next few days.

Update (6/22/2022): we had to statically balance the propeller. This caused us to create two kinds of propeller balancers. a horizontal one and a vertical suspended one. Interestingly, both told us that one blade was heavier and one was light, but not exactly the same weight. Im thinking it is small in-accuracies in the test rigs. We then invented a method of adding weight to the hub for the static balancing and then adding weight for dynamic balancing on a separate ring of the spinner base. Our latest runs show we are dialed-in at our 1800 rpm cruise setting. 0.016 IPS. We are still getting heavy vibrations at 1050 to 1300 rpm but that is even down to under 0.7 IPS. We can read the instruments in all throttle settings. Good enough to fly! Our compression testing has shown that all the heads are within 10 of each other, but wondering if that amount is enough to create some vibration and mess with us. This is a new engine and the rings still need to take a set which should stabilize the compressions and the blow-by in the oil breather system. Talking with Elliot about coming on out to fly her. She’s ready! STAY TUNED!