Ed Anderson wrote:

 Subject: Loosening tip seals up

 > Yvon Cournoyer wrote:

Good afternoon Ed...
My understanding is that you are saying that your engine ran but shook
because the rear apex seals are still stuck in their slots....
I always thought that  defective apex seals deprived the engine of some

of

its compression but did not cause imbalance of the rotating masses

inside

the engine.
Why would stuck or defective apex seals cause the engine to shake?
Please elaborate,
Thanks,

Yvon Cournoyer

Hi Yvon,
    My understanding is that anytime one of the rotor faces is not firing
then the dynamic loads are different than when all are firing properly.
When one apex seal is stuck then the two adjacent rotor faces have no
compression therefore there is considerable less resistance to rotation
during that portion of the rotation cycle or 2/3s of that rotor's rotation.
In addition to the less resistance of those two faces, they also do not add
force to the rotating mass as there is no effective power developed during
combustion.  The end result is that contrary to what you may think ( that
the engine would develop less power but would not vibrate,) it does develop
less power but it also does vibrate quite noticeably. You would not want to
stay in the air with it vibrating that way.

I sure Paul and/or some of the others can explain the reason for vibration
better.

Ed Anderson

I think you did a good job Ed. I think it probably has something to
with torsional vibration. Missing torque pulses as you explained.

Paul Lamar
 
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