RV-12 Prop Balance & Vibration Survey

Balanced another RV12 today with great results, intial vibration was .425 IPS, final results .018 IPS! (red circle is upper limit)




I now have the machine files for the Rotax 912.
With this program I can identify the vibration levels of the following components:
Tach, Fuel pump, Oil pump, Water Pump and Alternator
Too Cool!

Walt,

If you have files like this for every engine, it sure sounds like another great way to monitor changes in your engine condition besides just oil samples. It is too cool, you're right.

Pete

Peterk said:

Walt,

If you have files like this for every engine, it sure sounds like another great way to monitor changes in your engine condition besides just oil samples. It is too cool, you're right.

Pete

Click to expand...

We do provide the vibration spectrum analysis on every prop balance. The Lycoming file labels are not as detailed as the 912 file but that is because they don't have as many different rotating speeds as the Rotax with it's reduction drive and gear driven accessories. Like the Rotax, we can pickup on potential problems and excessive vibrations and can spot potential problems.

Here's an example from a nicely running Lycoming IO390:

Adding my comments - -

Yesterday, Larry Geiger balanced Marty Santic & my props. I can certainly 'feel' the difference. I was used to putting my hand on the dash and feeling how much vibration there was. It reduced that a bunch. It is worth doing. AFTER you have your pitch set and matched well, and satisfied, I'd suggest getting the prop balanced. All components on the plane should be helped by this.

THANKS AGAIN LARRY ! ! !

John Bender

The B-17 to Lincoln, RV-10 Back to Davenport and Prop Balance

Will agree with all John has to say about prop balance.

Chapter 75 hosted the EAA B-17 Thursday-Sunday. On Monday flew the B-17 on its 2 hour flight from Davenport to Lincoln, Nebraska. Got 10 minutes of left seat time in "Aluminum Overcast". What a treat! My first multi time is NOW in my logbook.

Larry Geiger picked us up in Lincoln. Off to Crete for the 90 minute flight back to Davenport in his RV-10. 220 to 240 mph ground speed. A second treat.

Then Larry balanced both John Benders and my props. A third treat! After cleaning up for about an hour, checked the FBO parking lot. The guys that were driving back had not yet arrived back in Davenport. Larry was most likely back home before they finally got back home.

What a day! Thanks, Larry!

John's plane stated out at .43 IPS & Marty's was .23 IPS. Both came in at .04 IPS. I sure am glad they both came in the same, I would hate to have them think I worked harder on one than the other!

Great data points Walt. All aircraft can benifit from a dynamic balance. Less vibration means longer life on the airplane and engine.


Yesterday was a great day. Thanks Marty for putting it together!

Another prop balance report...

My motor always seemed pretty smooth to me but there definitely was vibration that could be felt by touching the instrument panel. I decided to get the prop balance done. Our Chapter has a Dyna-Vibe tool and I made arrangements for the two members who are trained in it's use to do the balance.
Here is the sensor bracket mounted on the gearbox and also showing how the washers are put on for trial runs. There is a light sensor and a vibration sensor. And there is a little piece of reflecting tape placed on the back of one blade on the prop so the sensor can see it turning.



The initial inches per second vibration level was 0.58. The desired value is 0.10 or less. After the first run they got it to 0.27, big difference that I could feel in the next run. The readout tells you where to put the weights by giving a phase angle referenced to the blade with the reflector tape. After each run the phase angle will change. We added more weights at different positions (washers under the spinner screws) and after a couple more runs it was down to 0.04. An excellent result.

After the needed weight and position is figured out we took the spinner off and drilled a hole in the spinner back plate and used an AN3 bolt and nut to hold the washers. There were a total of 6 washers used.

I flew the plane for 40 minutes after and it was really smooth . This is a highly recommended procedure.

Tony

Tony,
Just a suggestion for the balance crew, the vib sensor should be located as close as possible to the prop, there is an open bolt hole on the very front of the gearbox on the left side that works perfect. You could still mount the position sensor back there but move it over to the left side to help keep it inline with the vib pickup.
Just my 2c
Walt
PS: The RV12 can really benefit from balancing!

Thanks Walt,
Appreciate that feedback. There are usually ways to improve and this forum sure helps that happen.

Tony

Tony, the washers you added are over hanging the spinner a bunch. Be careful with that, I grind down one side to make sure they don't contact the bottom cowl. Obviously, they did not hit, but that would be a bad thing. Don't ask me how I know this.

Also, I have found doing 912s to use the back of the spinner instead of the prop. Like walt said the closer to the engine the sensor is the better the balance job. I don't think it makes a whole lot of difference, but I can leave the balancing tape on the spinner bulkhead for the next balance. The spinner back plate needs to be painted flat black in order for the pickup to "see" the tape.

Walt, I agree! .58 really needed to be corrected! If anyone is on the fence about dynamically balancing your airplane this should be a wake up call.

and furthermore...

if you make any changes up in that area you may well end up back where you started. Walt had mine perfect, then came the new hub SB and we had to re-do it. Now of course, it is perfectly smooth once again thanks to Walt.