bnt83
Final Approach
Anyone every swap the bottom & top engine vibration isolators around to eliminate sag? Favorable results?
These are less than 6 years old.
These are less than 6 years old.
Isolator sag on dynafocal mounts
- Thread starter bnt83
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Seems like it would be worth a try, all you have to lose is a couple of hours work, with the price of The Lord mounts, it may well be worthwhile to try.
Sleepingsquirrel
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I think I have read on Mooneyspace.com about loosening the bolts taking pressure off the rubber with an engine hoist then just rotating the rubber pucks in the mount. This puts the rubber that has been in tension in compression and the previously compressed rubber in tension with the desired result removing the sag.
bnt83
Final Approach
I need to locate an engine hoist... Maybe an extra pair of hands for a total of three plus a hook.
Dan Thomas
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Don't do that. Those rubbers are positioned the way they are because one side is a compression unit. It goes on the top aft and bottom front. It's the one with a line around it. Switching them is asking for trouble.
Cessna, in some airplanes, calls for a thick shim washer between the bottom rubbers and the engine mount. Sometimes they get left out.
Dan
Sleepingsquirrel
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http://www.donmaxwell.com/publications/MAPA_TEXT/Alining Engine Using Shims/ALIGNING_YOUR_ENGINE.HTM
This link may be helpful.
I agree that you should not change the rear rubber with the forward rubber. I was thinking as the sagging mount in the picture was just rotated around the axis of the bolt to put the sag up instead of down.
This link may be helpful.
I agree that you should not change the rear rubber with the forward rubber. I was thinking as the sagging mount in the picture was just rotated around the axis of the bolt to put the sag up instead of down.
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bnt83
Final Approach
As installed the shim washer conforms to the maintenance manual. I agree flipping the doughnuts around front to back ins't right.
bnt83
Final Approach
The installation you describe is exactly what the Service Manual for the airplane specifies. I started snooping in other models and found all are consistent with that. Pretty much the only thing that varies between them is the number and location of shim washers.
RotorAndWing
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kmead
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I wish I could help. I even have a hoist in the back of my truck right now but I'm in Ohio for the week and going back to MA. I've often wondered if rotating 180 degrees would work. I really can't believe how often I find the shock mounts installed in a reversed order, even from our dealers and service centers.
bnt83
Final Approach
Its interesting that the early serial numbers have a large spacer on the lower two and later ones have them in a different location.
I remember reading a Cessna SB for 210 sagging that amounted to adding shims. The sag was especially troublesome in those aircraft with air conditioning, but completely different mounting arrangement than dynfocal.
It seems to me the fit of everything is really trial & error. Especially when throwing cowling fit into the equation. Prior damage history with poor repair would likely explain some aircraft also.
Computerjim
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JimISC2452
Rubber engine mounts are normally good for 5-6 years, especially with the heavier 6 cylinder engines. On some high time airframes what looks like rubber engine mount sag can come from sag developing in the metal engine mount. I always send metal engine mounts out for inspection and "truing" at overhaul.
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bnt83
Final Approach
Another possibility, just installation variables themselves like how they were assembled and torqued.
There was an Embraer 505 here that after re-installation of the composite steps on the main cabin door, the door would hit the door frame of the fuselage. After much troubleshooting it was discovered that the fasteners attaching the steps where tightened in a manner that deformed the door enough to make it contact the frame. After removal of the steps a second time and careful torqueing the fasteners, the problem disappeared.
I've always wondered how effective engine mount "overhaul" is since they would need proprietary dimensions from the OEM to "true" a tubular engine mount. How did they get those dimensions?
Buy a new one and reverse engineer it.