I hope the scale is not wrong because it is the same one I use to weigh the carburetor floats and they came in at 6.7 grams for each pair.
Any thoughts?
Does anyone have an explanation for why vibration is expressed with units of velocity?
I agree that having locations (nut plates) on the backplate would simplify the process but that is a lot of up front work to save a little time once a year.
I have balanced several. Did one today. 21 grams to get it to .04 IPS with the weight mounted to the backplate.
Do yourself a favor. Don’t even bother to balance using weights under the spinner screws. The balance solution will change when you move the weight to the spinner backplate. You end up just doing it all over again. Take the time to drill holes and install #10 nut plates before hand. Put one at each screw location (10 total) leaving enough room to install an AN970 washer. The balance task will be fast and easy and you will end up using 2 or 3 of the holes.
I had balanced this prop earlier using weights under the spinner screws. The airplane owner decided to move the weight to the backplate. He did the calculations taking into account the difference in the arm and came up with the weight to make the same moment as the spinner mounted weights. We did a test run with the weights relocated. The recorded IPS was .26. This is more complicated than it seems. In the end, he ended up with holes in three locations.
You must have done something wrong with the calculation in the move or rotated the spinner etc. I have done many balances from Rotax to Lycoming. The move to the backplate or flywheel has never changed the ips more than .01.
I agree that having locations (nut plates) on the backplate would simplify the process but that is a lot of up front work to save a little time once a year.
I don't think I'd trust nut plates with fast spinning weight. Better to ream hole for correct AN bolt and then split weights (washers) front and back of spinner plate. The washers will trap the aluminum backing plate and distribute load evenly and bolt will not move in reamed hole...
I don't think I'd trust nut plates with fast spinning weight. Better to ream hole for correct AN bolt and then split weights (washers) front and back of spinner plate. The washers will trap the aluminum backing plate and distribute load evenly and bolt will not move in reamed hole...
Does it make sense to use two holes that bracket the initial location so small angular deviations can be handled with slightly different weights? (e.g., analyzer says 0.5 IPS @ 180°, drill holes at 150° and 210° and start with 10 gm?)
thanks in advance,
-dbh
Thanks for your explanation, BobbyLucas. I like that you said it was arbitrary--now I don't feel like I was missing something basic.
Time for another basic question, though. Does phase angle tend to change as you go though the trial solutions to arrive at a final balance? I can't think of why it would, but I've got enough grey hair to know that the world is more complicated than I think it is.
Does it make sense to use two holes that bracket the initial location so small angular deviations can be handled with slightly different weights? (e.g., analyzer says 0.5 IPS @ 180°, drill holes at 150° and 210° and start with 10 gm?)
thanks in advance,
-dbh
Man you guys are talking "martian"! I was hoping that the balance process would be somewhat understandable to a novice but I guess not!
#7 i have nailed!
- Mount accelerometer and phototachometer
- Run engine and record data
- Install test weight
- Run engine and record data
- Remove test weight and install recommended correction weight
- Run engine and record data one last time to verify that you nailed it the first time
- Have an adult beverage
Better?
Getting ready to balance prop, my mechanic uses Chadwick Helmuth equipment and has no RV-12 prop balance experience. Can anyone share photo of equipment mounting and Chadwick experience I can share with him prior to work?