lml@lancaironline.net Mailing List Archive

Craig said;

Jim, I was really hoping someone would have had some input as I am building this exact same configuration. I can not think of a plausible reason for the engine to be creating this vibration and then going away after an hour, so I think it must be the prop. Did you get any input from MT Props?

Craig Berland

Hi all,

I just returned form 4 flights and 6.5 hrs total. The Vibration is still there and really doesn't go completely away. I still feel a steady shudder though out the airframe. Since it didn't sit long between flights it didn't seem as bad on full power as it seemed after sitting for 2 weeks. This is still not correct and was not there before the engine was overhauled. In discussing this and flying with other knowledgeable folks, we think that I need to try to have the Prop rotated 180* and rebalance it. Remember it was balanced twice in the first 12 hrs. by two difference shops with the same results. I was able to do somewhat of a visual check on the blade tracking, by running it up with the lighting reflecting just right off the back of the blades so that while I cycled the prop I though maybe I could see one blade showing something different from the others, but it looked all the same in all cycle speeds and pitch. I know this is not definitive but one more data point. The MT continues to show grease leak so I will be pulling the spinner and inspecting more closely. I haven't talked to MT yet.

Thanks for the help,

Jim Hergert
N6XE (An Sexy)
L4P 388 hrs.

Origanl post.

From: "Craig Berland" <cberland@systems3.net>

Sender: <marv@lancaironline.net>

Subject: [LML] Interesting Vibration problem

Date: Wed, 10 May 2006 16:09:13 -0400

To: lml@lancaironline.net

Jim Hergert wrote on 5/4/06: I say interesting Vibration problem because it goes away, after 30 min. it is almost gone and after 1 hr. it is completely smooth. I have a LlVP with a 550E and 4 blade MT prop. I had the engine completely overhauled 15 hrs ago and the prop sat on a pale for almost 4 months. The prop had new seals and grease installed over 200 hrs ago.

The problem is just after take off the panel glareshield vibrates up and down about 1 in. The engine installer balanced the prop before a test pilot flew it. He reported a vibration so I had the prop rebalanced after 5 hrs. Every take off since has done this and with RPM changes, power changes it is consistent. The only change in vibration is Time. It is perfectly smooth after 1 hr.

Possible causes;

Maybe a stuck valve or lifter not adjusting?? Not likely.

The MT prop still leaked grease after the seal replacement 200 hrs ago, however, a lot less then before. So one thought is that the remaining grease rests on one side of the hub when parked for 2 weeks and since it is in the cold end of the crankshaft, is heavy grease, and it doesn't get the warm oil for some time, it may take that long for it to even out around the HUB, causing out of balance?

Another is I'm told that the MT prop blades have a bearing preload that is set when being installed in the Hub, and that preload needs to be set the same for all 4 blades. This is done by hand and feel, I'm told. If one is loaded too much it lags in the Tracking and will cause this vibration which corrects itself after hub warms or given some time at the same setting. ???? Why would this start now after being off the engine and then reinstalled?