Engine Mount Limits/Vibration

[bnicolette]

Hello all,

I was wondering if anybody had any intel or thoughts about the limits on engine mounts as far as when to replace them?  My plane has a bit of vibration and I am thinking of starting with the mounts and then moving forward.  My engine mounts are the "lord" brand and were replace at overhaul in 2000, 550 hours ago.  The engine shows a bit of sag, perhaps up to a 1/2 inch but no more than that.  I am assuming that it was shimmed properly when the engine was put on by the MSC who did the overhaul, so I don't just want to reshim it to bring it back up?? 

I was going to start with the mounts, then opt for the GAMI inectors (my spread is about .8 gallons between leanest and richest), then perhaps have my prop done.  The prop only has about 550 hours since new, but that was 11 years ago.  I have just started noticing it throwing a mist of grease on the window and front cowl (this was confirmed by removing the spinner and seeing the grease marks).  Then finish with a dynamic balancing.  I had the dynamic balancing done just the other day, but I didn't really notice a big difference even though at 2600 RPM it was a .01 (whatever the heck that means).  I have been accused of just not being used to single engine airplanes and the way they feel since I have been flying nothing but jets the last 14 years, but I still think that when I feel a vibration in the yoke, seat, etc. that something can be done about it???  (Thoughts on this??)  Or is it really just the way Mooney's are???

This was precipitated by having a bolt come out of one of the intakes the other day while flying at 7000' on my way from home to work and making a precautionary landing at KCXY to find out why my engine "farted".  I was running right around peak perhaps just a bit LOP when all of a sudden my engine lost power.  In a nano second I had the mixture full rich and boost pump on and everything seemed to be indicating properly on the JPI, but by then I also had the power back a bit and had started my descent for Capital City.

 

[Shadrach]

.01 IPS is actually quite good. It stands for "inches per second" and is a measure of amplitude. New lord mounts should last longer than 500hrs and 10 years IMHO depending on climate. Instead of replacing, you can also swapping them around. I would check to see if the engine was properly shimmed at OH. $hit happens and sometimes planes go out of the shop without all of the finer points being attended to.

4cyl Lycs are not the smoothest engines for sure, but vibes in the yoke and seat = bad juju. I don't see how it could be shaking so much and read .01 during a dyno...  I'm in KFDK and keep my F at KHGR.  I'm an easy 45min flight from Mt Pleasant if you want to compare/contrast... Let me know.

[bnicolette]

Ross,

Thank you so much for that offer and I might just take you up on that.  I'm not quite sure how I could make sure it was shimmed correctly when they first installed the motor/mounts?  I know the previous owner was pretty methodical with the airplane, but I don't know if he would have noticed that it was sitting low on the cowling or not?  I think at this point I have to assume that since it came out of a MSC that they would have made sure it was correct, but who really knows I guess?  There are the thin shims on the bottom mounts, so they attempted at some point to bring it up a bit?  I think that since I am going to try and make her as smooth as she can be I am going to replace the lord mounts and go from there.

The vibration is nothing I would call "bad", but rather a bit annoying.

[Shadrach]

Good luck, I have heard good things about Barry mounts as well, which will probably save you about $100 over the Lord mounts. Maybe someone else can ring in on that.

This is a good read, even if you're not participating, it's good to know the process.  

As I said before, I don't think it's good if you can feel vibration through the yoke an seat...

http://www.donmaxwell.com/publications/MAPA_TEXT/Alining%20Engine%20Using%20Shims/ALIGNING_YOUR_ENGINE.HTM 

[KSMooniac]

Don't assume the engine has sagged without thoroughly checking out the cowl.  Our fiberglass cowls wear and the camloc holes get sloppy, to the point that the cowl will ride-up under air load and make the leading edge sit a bit "proud" above the spinner.  Check out the gap between the cowl and the fuselage skin and see if it is even all the way around the perimeter.  You might notice that there is no gap on top in front of the windscreen and it gets progressively larger as you go towards the cowl flaps.  If that is the case, a good tug downward on the inlets might line it up, or taking it off and reinstalling (after an oil change, for example) will reset it and give you a better idea of the spinner-cowl alignment.

0.8 GPH GAMI spread is quite large for an IO-360, so I would check that second... Most IO-360s will be much better than that, even with stock injectors, so I would check thoroughly for induction leaks and clogged injectors, and then maybe try a set of GAMIjectors.  No sense spending the money first without checking the free items.    I have 0.0-0.1 GAMI spread with stock injectors.  I suspect some of your vibration is due to that spread, even flying at peak and not much LOP.

Good luck!

[bnicolette]

Hey Scott 

 

I have noticed that the cowling rides up a bit during the flight.  I am measuring the sag after pushing the cowl down as far as it will go.

Thank you for the suggestion on the injectors. I will definitely have him check those while we are doing the mounts. It would be nice if we could flush those out and have my spread be a bit closer!!!  Any money not spent is always a great thing.