hlangebro
Well Known Member
Just installed a Hartzell HC-C2YL on my RV-7A with a 160hp O-320. I previously had a WW GA200L prop.
I had it dynamically balanced to .15 IPS, which should be sufficient, however I noticed 2 types of vibrations for which I have some ideas, but I would like to hear your comments.
1. On the ground, while taxiing just above idle, there is some kind of resonance and when the sliding canopy is open it start to vibrate and shake and I need to close it.
2. During flight, there is a vibration that seems to be at the same frequency as the engine and the stick vibrates about +/- 0.060" or so. Vibrations can also be seen and felt on other items. When reducing rpm, the vibration seems to be more obvious.
I have the Sam James cowling and the transition from the plenum to the inlets have a different rubber than what came with the cowling. It is more of a rubber type, which provides smoother inflow, however it is less flexible. I have a feeling that with the heavier prop, this transfers more vibrations from the engine to the cowl, and thus transfers more vibrations to the airframe. I have ordered a different rubber foam material and will replace the transition pieces, which I think will make a difference.
The prop is a 0hr overhauled and built per Hartzell specs, and the assumption is that it is done properly. There doesn't seems to be any noteworthy difference between the blades in tracking and the spinner doesn't seem to vibrate either.
On the ground it could be a resonance problem, and not related to the cowl. I seem to remember while we were doing to dynamic balance that I had some vibrations, and this was with the cowl removed, so nothing to transfer engine vibrations through the cowl to the airframe.
Overall the new prop works great and improvement in takeoff and climb are fabulous and 1-2ktas on the cruise as well.
I am hoping that another go around with the dynamic balance will help. My goal is to have it below 0.1 IPS and hopefully around 0.05 IPS.
I had it dynamically balanced to .15 IPS, which should be sufficient, however I noticed 2 types of vibrations for which I have some ideas, but I would like to hear your comments.
1. On the ground, while taxiing just above idle, there is some kind of resonance and when the sliding canopy is open it start to vibrate and shake and I need to close it.
2. During flight, there is a vibration that seems to be at the same frequency as the engine and the stick vibrates about +/- 0.060" or so. Vibrations can also be seen and felt on other items. When reducing rpm, the vibration seems to be more obvious.
I have the Sam James cowling and the transition from the plenum to the inlets have a different rubber than what came with the cowling. It is more of a rubber type, which provides smoother inflow, however it is less flexible. I have a feeling that with the heavier prop, this transfers more vibrations from the engine to the cowl, and thus transfers more vibrations to the airframe. I have ordered a different rubber foam material and will replace the transition pieces, which I think will make a difference.
The prop is a 0hr overhauled and built per Hartzell specs, and the assumption is that it is done properly. There doesn't seems to be any noteworthy difference between the blades in tracking and the spinner doesn't seem to vibrate either.
On the ground it could be a resonance problem, and not related to the cowl. I seem to remember while we were doing to dynamic balance that I had some vibrations, and this was with the cowl removed, so nothing to transfer engine vibrations through the cowl to the airframe.
Overall the new prop works great and improvement in takeoff and climb are fabulous and 1-2ktas on the cruise as well.
I am hoping that another go around with the dynamic balance will help. My goal is to have it below 0.1 IPS and hopefully around 0.05 IPS.