Vibration

[smccray]

My engine develops a pretty high vibration level whenever it runs at 2700 rpm. It's bad enough that the compass shakes pretty hard.  When I bring RPMs down the vibration subsides at 2600 and doesn't return at lower RPMs.

I've been reading and I'm thinking I might need a prop balance, but I'm not certain. Is there anything else I should think about?  I'm assuming the vibration isn't normal?

[jetdriven]

We had our prop balanced 2 weeks ago by Walt Aronow at 52F (Dallas).  It went from .5 IPS to .02 IPS.  A huge difference.  But the compass vibrates like yours does at 2600 RPM and over. Before and after.   I finally give up on that issue.  The solution is a 2" square piece of mattress foam between the compass mount and the glareshield.  

 

website is http://expaircraft.com/

It cost us 250$, but he lowered it to 200$ because our partner helped him.  Its worth it, the aircraft is much quieter now. And it doesnt buzz at 2500 RPM so thats a usable cruise RPM now. 

[Piloto]

Check at 2700 RPM but at a lower MP 20". If there is no vibration the problem may be due to a faulty injector or a spark plug. Check also engine mounts.

José

 

[jetdriven]

Great ideal Jose.  In our case the GAMI spread is .2 GPH and the compressions are equal. I would guess unbalanced pistons or tolerance stacking on the rotating assembly.  Mooneys are stiff airplanes and I think a lot more vibration gets transferred to the cabin. 

[smccray]

I'll try 20" and 2700 on my next flight.  I wouldn't guess the engine mounts would be a problem due to the recent maintanence history.  I don't have an engine monitor or I'd upload data here to scrutinize the injector/plug data. 

[smccray]

Vibration remained down at 2700 rpm below 20". Plane just came out of a prebuy/annual in August and was just at maxwell for an oil change a couple weeks ago. I wouldn't think the engine mounts would be an issue, but perhaps I'll pull the cowl and check it out. What am I looking for?

Any other possible culprits?

[bnicolette]

Well it's been well over a year now (17 months) since I purhcased my Mooney.  I did get some of the vibration out of it by replacing the Lord mounts.  My airplane has 600 or so hours SMOH, 2600 hours TT, compressions are all 75+ and other than an intake coming loose once, I have never had a problem with the engine.  I am just going to accept that the 4 banger Mooney's (well at least mine) get more vibration in the cabin than other airplanes I've flown.  It's not a bad vibration like the engine is coming apart, just more like a buzz that can be felt on the yoke, laying my head against the side window, etc..

The only thing I haven't done that I want to do is have the prop dynamically balanced again since I've had the Lord mounts changed out.

Do you guys with "J" models have this also?  I really need to ride in somebody else's "J" model so I can have something to compare it to.

[Vref]

Quote: JimR

Mine is pretty smooth, Brett. Not as smooth as the big bore Continental and Lycoming powered Cessnas that I used to fly, but noticably smoother than the non-counterbalanced Lycoming four bangers that I have flown. Definitely no vibration in the yoke.  

Jim

[bnicolette]

Wonder why mine is transferring into my yokes?  It's not like they're shaking or anything, kind of the same feeling as if I put my hand on the side window.  More like a "buzz".  Can you guys/gals feel any vibration in your side windows?  It's been like that since I bought the airplane.  The main guy at our local MSC flew it for about 3 hours while doing the rigging and never said anything about it?  Perhaps I'm just sensitive to it?  IDK????

Wonder if I get my prop dynamically balanced if that would help?  Or maybe it's just that it's a Lycoming up front instead of a Garrett, Pratt, or Rolls?

 

[jetdriven]

I would say if the yokes or windows are buzzing, it needs a dynamic balance. You could also try re-clocking the prop 180 degrees first.

here is our "compass buzz" story:

Compass vibration renders it unreadable above 2400 RPM.  Replaced ghetto homemade compass mount with factory mount. No change. Decided on dynamic balance but prop has 1100 hours and looks terrible. Repaint prop. Prop shop refuses to paint prop as it is beyond the 6 year TBO. Spend 100$ and two days removing prop, stripping, filing, and painting prop. New paint promptly has solvent pop; the paint is contaminated. (paint came from prop shop unwilling to paint prop).  Restrip and, re-etch, alodine, prime, and paint prop, now 3 days into the job. OK. Prop done. Call prop shop for balance work.. They say they will, but 3 weeks later, and 5 phone calls, give up. Ferry airplane to Dallas (200 NM each way), to balance prop.  Compass is still unreadable above 2400 RPM. Girlfriend of 3rd partner tears a piece of scrap foam off, and wedges under compass.        Problem solved.      Almost.      20 hours later the crank seal is leaking and needs to be changed......  Why didnt I buy a Beech again?

[Piloto]

Quote: smccray

Vibration remained down at 2700 rpm below 20". Plane just came out of a prebuy/annual in August and was just at maxwell for an oil change a couple weeks ago. I wouldn't think the engine mounts would be an issue, but perhaps I'll pull the cowl and check it out. What am I looking for?

Any other possible culprits?