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Dynamic prop balance

bernsbm

Active Member
Friend
Hi All,
I'm looking for a shop in the southeast Wisconsin/northern Illinois area that can do quality dynamic prop balancing, preferably with Rotax experience. Any/all suggestions appreciated.
Barry
 
I'm curious... why do you feel the need to balance your prop? I set the pitch on my blades with Van's sheetmetal gage and I'm very pleased with the flight performance and engine/prop smoothness especially at cruise RPM.
 
I have balanced quite a few 12's and every one benefited significantly. It is also a recommended procedure by both Rotax and Sensenich.
 
Just finished balancing mine this weekend. Started out at 0.21 ips, was very happy with the final result after adding 11 grams of weight.
ot45rn.jpg


John Salak
RV-12 N896HS
 
Where and how did you attach the weight?

I started out by adding weights (washers) under the spinner attachment screws at the clocking angle indicated by the DynaVibe display. Took four runs to get the ips down to 0.01-0.02. I used a precision scale to weigh the washers and converted the inch/gram value based on the spinner screw hole location to the spinner plate location I drilled (radius decrease by 1/2" so weight value increased). I added a #8 screw with two nuts and a spacer weight at the new hole in the spinner backing plate. The total weight of the screw, nuts, washers, and spacer weight were 11g. I was fortunate that the clocking angle was almost exactly on a spinner attachment screw.

The factory listed weight difference between the two Sensenich blades is 6 grams (1204g and 1198g), so the weight location is actually near the root of the lighter blade. Not sure how that compares with other RV-12s, but it may be an indicator of the improvement you can expect from dynamic balancing.

John Salak
RV-12 N896HS
 
I spent Saturday morning trying to balance my RV6 / Superior IO360 / Sensinich setup with the same Dynavibe model shown in the photo above. However after 8 runs trying to dial in on the best balance, I discovered that none of the results were repeatable on subsequent runs! I removed all weights and headed home to ponder what could be going on.

Has anyone else found repeatability to be a problem? I was able to get down to about 0.12ips, but a 2nd trial with no change yielded 0.38ips!

Originally my setup was showing 0.42ips. The last run of the day was back to no weights, and I was getting 0.57ips. Not sure what is going on. We had similar results on a different engine and airframe earlier that week.

Don
 
Make sure the Dynavibe cables are well removed from any ignition wires. It's very susceptible to interference creating what you describe. We had this issue and the reading appeared random from average to average. Our soulution was to tape some empty oil bottles horizontally along the top of the engine & taping the wires on top. YMMV. This worked great for us. Bob
 
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