Looking for DynaVibe in Phoenix

[JetFox]

jrevens, sorry for the delayed response...
I am still working on the prop balancing, what I can say is that I had to add quite a bit of weight. You asked where I put the weight. In my case I have long prop bolt which are sticking out of the back of the Rotax prop flange. I just added smaller and larger washers under the prop bolt nut. It worked fine for temporary trials. I may replace the washers with a fabricated weights. What I can say is, I was actually surprised how bad the prop balance was. I may go back and do a prefect static balance and then a dynamic balance again. I will update here again once I have more details.

Regards
Peter Buehlmann
Kitfox4-1200 Rotax 80HP

[JetFox]

Here is an update from my balancing. I did remove all the added weights and measured again, just to prove that I am out of balance. All the numbers proofed it. Put the weights on again, the numbers came down again as before. I think I will stop now and fly for a while. Here are some stuff I learned:
-I needed to add approx 50 grams of weight to get a good dynamic balance.
- I did not do a static balance, will do it next time I remove prop
- There is no good balance trough the whole RPM range, I did the balance for my typical cruse RPM of 4800. I have higher vibration at around 3200 RPM compared to before I added the weights for a good balance at 4800.
- Changing in flight adjustable pitch changes balancing numbers too/
- Adding weights was easy on the back of the Rotax prop flange.

I came to the conclusion the the prop dynamic balance with Dyna Vibe help me to reduce the vibration, however I did not achieve a prefect numbers of 10 IPS or less through the whole RPM range. The lower the numbers you get, the harder it is to re-produce during the next test. I will do a balancing on a metal prop on a C145 next and see how Dyna Vibe works out there.

Regards
Peter Buehlmann
Kitfox4-1200 IVO prop inflight adjustable on Rotax 80HP

[jrevens]

...

I came to the conclusion the the prop dynamic balance with Dyna Vibe help me to reduce the vibration, however I did not achieve a prefect numbers of 10 IPS or less through the whole RPM range. The lower the numbers you get, the harder it is to re-produce during the next test. I will do a balancing on a metal prop on a C145 next and see how Dyna Vibe works out there.

Regards
Peter Buehlmann
Kitfox4-1200 IVO prop inflight adjustable on Rotax 80HP

Hey Peter,

I don't want to discourage you, but 10 ips would represent a lot of vibration. That would be a very high number. When I balance a prop, I aim for a velocity of less than .05 ips. If it's not just a simple out of balance propeller situation - for instance if you have something loose, or a gearbox or engine problem - it will be hard or impossible to balance the prop. It will be interesting to see what results you get with the C145.

[JetFox]

Hi John, after a hot summer in Arizona I am back in the hangar. Yes you are right, 10 ips is not a good number. This was a typo, I tried to achieve 0.10 ips. I did get 0.10 and below but not through the whole RPM range. I balanced for around 4800 RPM and I got it down there to 0.09 to 0.05 ips. I am still wondering why I do not have an equal result through the whole RPM range as the prob balance should stay the same in regards to weight distribution over the prop. I have to assume that engine vibration on different RPM influenced the prop balance result. Anyway, I have a much smoother ride around my cruising RPM of 4800. The vibration around 3200 just after pulling the power on a final has significantly increased. However this is just for a short time on final. I am happy the way it is now.
I have not done the C145 yet, will report back later.
Regards Peter

[n85ae]

Try clocking the prop differently. What I mean by that is rotate it one set of
bolt holes and try again. That can make a huge difference.

Jeff

Here is an update from my balancing. I did remove all the added weights and measured again, just to prove that I am out of balance...

[JetFox]

Jeff, I will give it a try next time I remove the prop.

[Delta Whisky]

Peter not that I've ever jumped in to a fun task without double checking the basics - but - did you check the prop track? That will create the condition you're describing.

[JetFox]

Delta Whisky, no I did not check the track of the prop blades. I did not consider it as important as these blades are very flexible (Ivo Prop). I did it on metal props on other planes. Well this is a good input and easy to do. Currently the prop is off, will check it once it is back on. Will report on the findings, thanks for the hint.
Regards
Peter Buehlmann