Hi all,
I used our EAA chapter's Dynavibe Classic to balance my new Hartzell prop today. The readings were interesting, but I am not sure I quite understand what is going on.
The initial readings were:
2300 RPM .21 ips @317 degrees
2300 RPM .23 ips @313 degrees
2500 RPM .24 ips @316 degrees
2500 RPM .22 ips @313 degrees
All pretty consistent.
I added a bolt and nut, 11 gms at 120 degrees (my closest option) and got the following:
2300 RPM .12 ips @344
2300 RPM .14 ips @338
2500 RPM .14 ips @347
2500 RPM .11 ips @338
Still pretty consistent
I added a bolt and nut, 11 gms at 150 degrees and got:
2300 RPM .03 @81
2300 RPM .04@123
2300 RPM .05@198
2500 RPM .04@124
2500 RPM .07@115
A little less consistent
I used a smaller nut, removing 2 gms of weight at 150 degrees
2300 RPM .04@67
2300 RPM .04@61
2500 RPM .05@20
2500 RPM .03@39
The ips is pretty close, but the angle moves some.
I similarly removed 2 gms from 120 degrees and got:
2300 RPM .07@58
2300 RPM .01@95
2500 RPM .06@50
2500 RPM .03@39
Wider variations in both the ips and the angle
I did a second run with no changes:
2300 RPM .05@259
2300 RPM .05@211
2500 RPM .04@295
2500 RPM .05@250
Somewhat more consistent.
I puzzling through understanding the data. When the balance was relatively off, the numbers are consistent both in angle and ips. The closer I got to balanced, the more they seemed to scatter. I did notice some changes in the wind as we were doing the test and occasional slight fluctuations in the RPM, but mostly things were pretty steady.
Am I correct to assume that the closer you get to perfectly balanced, the more difficult it is to get that last couple of hundredths? 0.04 to 0.05 is not bad, but we obsessive/compulsive types are always looking for perfection....
Anyone have any insights on where to go next? Leave it and fly is probably the right answer.
I used our EAA chapter's Dynavibe Classic to balance my new Hartzell prop today. The readings were interesting, but I am not sure I quite understand what is going on.
The initial readings were:
2300 RPM .21 ips @317 degrees
2300 RPM .23 ips @313 degrees
2500 RPM .24 ips @316 degrees
2500 RPM .22 ips @313 degrees
All pretty consistent.
I added a bolt and nut, 11 gms at 120 degrees (my closest option) and got the following:
2300 RPM .12 ips @344
2300 RPM .14 ips @338
2500 RPM .14 ips @347
2500 RPM .11 ips @338
Still pretty consistent
I added a bolt and nut, 11 gms at 150 degrees and got:
2300 RPM .03 @81
2300 RPM .04@123
2300 RPM .05@198
2500 RPM .04@124
2500 RPM .07@115
A little less consistent
I used a smaller nut, removing 2 gms of weight at 150 degrees
2300 RPM .04@67
2300 RPM .04@61
2500 RPM .05@20
2500 RPM .03@39
The ips is pretty close, but the angle moves some.
I similarly removed 2 gms from 120 degrees and got:
2300 RPM .07@58
2300 RPM .01@95
2500 RPM .06@50
2500 RPM .03@39
Wider variations in both the ips and the angle
I did a second run with no changes:
2300 RPM .05@259
2300 RPM .05@211
2500 RPM .04@295
2500 RPM .05@250
Somewhat more consistent.
I puzzling through understanding the data. When the balance was relatively off, the numbers are consistent both in angle and ips. The closer I got to balanced, the more they seemed to scatter. I did notice some changes in the wind as we were doing the test and occasional slight fluctuations in the RPM, but mostly things were pretty steady.
Am I correct to assume that the closer you get to perfectly balanced, the more difficult it is to get that last couple of hundredths? 0.04 to 0.05 is not bad, but we obsessive/compulsive types are always looking for perfection....
Anyone have any insights on where to go next? Leave it and fly is probably the right answer.