RV-12 Prop Balance Results

Walt · #1 04-05-2011, 04:32 PM

Did my first RV12 prop balance today on Petes very nice RV12. One thing I wasn't prepared for was I needed some metric hardware to attach my vibration pick-up to the engine so we had to go on a hardware hunt before we could even get started. But other than that the process went very well and we were able to reduce Pete's vibration from an intial of .563 IPS to a final of .039 IPS, a SIGNIFICANT reduction.

Keep in mind .2 IPS is considered the upper limit (the red circle in the polar plot below) so our intial reading of .563 IPS was almost 3 TIMES the upper limit. The final number of .039 IPS is less than half the "after balance" limit of .1 IPS and I was very pleased with how it went. We attached the weights (18 grams) to the spinner bulkhead as we usually do with certified aircraft at a single bolt location.

Thanks Pete for giving me an opportunity to work on your aircraft and I hope you enjoy the smoother ride

We also did an engine vibration survey (and all looks good there)...

Peterk · #2 04-05-2011, 05:53 PM

Yes indeed, Walt did a great job and the difference is noticeable as you would expect from reading Walt's documentation. Prior to the 12, I have always flown high performance aircraft with constant speed props. Both Hartzell and MacCauley encouraged flying with a balanced propeller for ride enhancement yes but as well for engine and propellor longevity. Both state in their operating manuals that dynamic balancing will prolong the life of the propeller, engine, airframe and avionics. To my knowledge, no such recommendation has been discussed concerning the RV12 yet the same reasoning should apply in spite of the gearbox.

Rotax with its extensive, well-written manuals makes repeated requests of owners to reduce anything that involves vibration. All engine specific maintenance isssues that influence vibration are highlighted repeatedly. Rotax doesn't sell propellers but propellers certainly influence vibration and are attached to the engine.

I now have a much smoother ride and hopefully have extended the life of my engine as well as everything else that doesn't like to vibrate, including my brain.

I do know that the balancing business can be much like the septic business...those who know what they're doing and those who just take your money. Make your selection carefully if you decide to go this route.

I think the decision to balance or not balance is a no-brainer. Walt made me a believer. He's also a very nice guy and very knowledgable concerning this topic. I couldn't be happier...thanks Walt.

Pete

Geico266 · #3 04-05-2011, 06:37 PM

Great job Walt. The Rotax 912 is no difference when it comes to balancing. Sure makes a difference. I balanced my -12 and the results were similar to what you achieved. Much smoother now.

I highly recommend dynamically balancing any aircraft.

BigJohn · #4 04-06-2011, 05:45 AM

My prop just came back from Sensenich with the new hub design. As soon as weather permits I will reinstall it and set the pitch, then test fly. Hoping for much less vibration than before, but the above posts suggest I wil probably want a dynamic balance as well. I'll report back.

John

rejnovca · #5 04-06-2011, 07:22 AM

Weights are added to balance when doing a dynamic propeller balance. For those who have completed a dynamic balance on the RV-12, where are you placing the weights?

Walt · #6 04-06-2011, 08:22 AM

Quote:

Originally Posted by rejnovca

Weights are added to balance when doing a dynamic propeller balance. For those who have completed a dynamic balance on the RV-12, where are you placing the weights?

We attached the weights to the RV12 spinner bulkhead the same way we do with many certified aircraft. We drilled a single hole for a 3/16 bolt and added washers for the exact amount of weight required.

On Lycoming powered aircraft we are able to use the flywheel holes for balance weights but there is no provision like that on the Rotax or Continental powered aircraft.

Peterk · #7 04-06-2011, 09:36 AM

Quote:

Originally Posted by BigJohn

My prop just came back from Sensenich with the new hub design. As soon as weather permits I will reinstall it and set the pitch, then test fly. Hoping for much less vibration than before, but the above posts suggest I wil probably want a dynamic balance as well. I'll report back.

John

John,

If you're not amazed, please call Larry and I immediately! By the way, I neglected to say that Larry did tell me to do it some time ago but you know how it takes awhile to get around to everything you want to do. Anyway, I do everything Larry tells me to do except cheer for Nebraska.

Pete

DHeal · #8 04-06-2011, 12:04 PM

I have been advised by a couple of professional prop balancers that one should wait awhile (@ 50 engine hours?) before balancing a prop. Supposedly this gives the engine a chance to "break-in" and get internally settled before you do the prop balance. Just a thought....

Geico266 · #9 04-06-2011, 03:11 PM

Quote:

Originally Posted by Peterk

John,

If you're not amazed, please call Larry and I immediately! By the way, I neglected to say that Larry did tell me to do it some time ago but you know how it takes awhile to get around to everything you want to do. Anyway, I do everything Larry tells me to do except cheer for Nebraska.

Pete

Now that Nebraska is not in the Big 12 I am a Texas fan big time.

Go Horns! Hook em!

David Paule · #10 04-06-2011, 04:18 PM

Quote:

Originally Posted by DHeal

I have been advised by a couple of professional prop balancers that one should wait awhile (@ 50 engine hours?) before balancing a prop. Supposedly this gives the engine a chance to "break-in" and get internally settled before you do the prop balance. Just a thought....

I had a freshly rebuilt engine and used prop balanced before the first flight. They did an excellent job. It lasted until the after-market camshaft pitted at about 350 hours, and we had to tear down the engine again.

From this, I'd say that there's no need to wait.

Dave