Hello, One question to ask would be are the cracked cranks caused in part by amplification of harmonics through the use of a prop extention? How does the data thus far compare? Aren't most Vair powered KR's using them to get a more stramlined cowl shape and wouldn't this be something unique to the KR which would differentiate from prior applications of the motor? This was one of the suspicions to the cause of Mark Langford's failure and probably something that deserves a closer look.
Still, even with little data it has been proven that nitriding parts increases their durability under stress in many other applications and even if there is only a 1% less chance of a failed crank is well worth the trouble. Unfortunately I've had enough motorcycle accidents where that 1% is the reason I'll hopefully live to operate a much safer craft above 150 mph, and well above 0 AGL where errors are at very least painful and much more common, catastophic, and deadly. Would you race a motorcycle without checking the tire pressure or the oil? Magnafluxing prior to and even after nitiding a crank would be cheap insurance. Could it offer a chance to keep the prop turning well enough to not become the best drag inducing device available? It's your decision but when it's time to build up a Vair, I'll be taking every precaution against engine failure available. Let's gather more data. Thanks to all the participating pilots for their contribution. Keep flying as safe a humanly possible, after all there is a Gathering to get to. B. Ferguson
