Dynamic propeller balancing

Neil wrote:

Not sure how it would be used in propeller balancing.

Me neither

We had the Yak in Straubing in August for the prop to be balanced by MT Mühlbauer. Yes, there is a optical reflex sensor mounted on the engine for the prop angular position plus of course the acceleration sensor to get data for the calculations in the balancing instrument. So you will get numbers from it for the weight and position to add screws or sheet metal to the prop hub or spinner base. On the display you can watch how effective the job will get. In 2009 we had the prop balanced by Peter Mühlbauer, not related to MT, as far as I know. He got his own instrument while he had the Hiller helicopter. The PDF graph in my document that I got from him looks a bit like the display of MT´s instrument. In between the wood blades had to be overhauled in Poland for the new German registration and were much better than before. I did the balancing on my manual tire balancer, see youtube link. That was better than MT expected to achieve themselves when they looked at their numbers in August, so only the blade setting was a bit tweaked. Anyway I´d recommend balancing any day if condition of your prop is unknown. MT charge € 300.- plus VAT fix price, time no factor. The same day a Cirrus was there with bad prop after filing one blade near the tip. That prop was far out of limits vibrationwise. Some grams missing at this radius are very noticable. Vic

Vic – That is too cool using the wheel dynamic balancer for your prop !

Looks like you had to fabricate a hub adaptor to make it work.

I’m not surprised that you got it fairly close with that, the only part missing was the engine.

Nice idea but if I were to consider having my prop balanced (and I’d like to hear people’s thoughts and results) I would want it done on the engine. When I build car engines I always have the whole rotating mass balanced to within 0.1g. It makes a noticeable difference but then the engines I usually build are from the 1960s and had a manufacturer tolerance of 5g.

Balancing on the engine has its limitation as the M 14 radial has a planetary reduction gear so you only really can balance the prop and hub itself. There remains a little rest of unbalance from the crank that you feel with fine senses in about 3-5 seconds intervals when there is resonance of prop and crank. But that is good enough for us anyway as it is. Yes, the splined adapter was a job but worth it for me. Vic

Peter, you just should purchase a PB-4 from smart avionics. It has all what you need. Acceptable cost and very good piece of equipment.