REFLECTOR: Replacing rubber engine mounts

[Stockman, Bill]

The worst enemy to your engine mounts are the engine oil.   Don't ask  me how I know, but "I've heard" that if you have a major leak
that sprays oil everywhere its really difficult to get it off all parts.   The oil will soak into the mounts and they will slowly deteriorate
until you find what looks like  sand-sized  pieces of rubber debris in your bottom cowling--these are parts of your engine mount.   The damage
is normally under the washers so you can't normally see it when it starts.     As you might suspect, the engine will now move on the mounts.     

You can also change out the mounts one at a time without taking out the engine,
but it requires a lift and a lot of patience.
________________________________________
From: reflector-bounces at tvbf.org [reflector-bounces at tvbf.org] On Behalf Of Reiff Lorenz [Reiff at lorenz.com]
Sent: Friday, September 07, 2012 8:17 AM
To: Velocity Aircraft Owners and Builders list
Subject: REFLECTOR: Replacing rubber engine mounts

>> do the rubber engine mounts settle with age?  Is there a published service/replacement period for the mounts?<<





Fred,



This month's EAA Experimenter has an article on rubber engine mounts. Here's the link to the full issue:

http://experimenter.epubxp.com/i/81495



Here is an excerpt:

>>

In the certificated world, mounts are usually changed at

overhaul time. For our experimental aircraft the annual

condition inspection is a great time to check mounts . . . .



As a natural rubber mounting ages, its surface will

become covered with a waxy film. This protects against

ozone, UV, and some contaminants. Leave it on!

Old mounts may sag. You’ll notice this when the

spinner doesn’t line up with the cowl the way it used

to. Mounts also compress over time. When they do, the

original spring rate changes, and when the spring rate

changes, the performance of the mount changes. When

the mount’s performance changes, it’s usually not for

the better. . . .



If you notice your mounts getting hard or suddenly shiny, they

may be cooked. Replace them. Rubber parts on aircraft

that live in very hot, very dry, or very sunny areas tend

to deteriorate faster.

<<



Hope this helps!



Reiff Lorenz, Dayton, OH
Velocity XL-RG, 36% complete
Currently working on: Pressure testing fuel and oil hoses.


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-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On Behalf Of Fred Anderka
Sent: Thursday, September 06, 2012 11:26 AM
To: reflector at tvbf.org
Subject: Re: REFLECTOR: Oil cooler clearance (Don Johnston)



Hi Don:



I can't recall how much clearance I had initially, it may have been about 3/8".  What caught my attention was that the powder coating on the engine mount had been chipped and there was an abrasion mark on the corner of the oil cooler.  After adding the washers on the top of the right side rubber mounts there is about 5/8" clearance.



Tape a small piece of PlayDo on the engine mount tube that will show if the oil cooler is still contacting that tube.  As the engine turns counter clockwise (looking from the back) the torque reaction will tend to close the oil cooler/engine mount tube gap.  I have no idea how much the torque reaction twists the engine during maximum power T/O.  Another question; do the rubber engine mounts settle with age?  Is there a published service/replacement period for the mounts?



Fred

XL-RG (620 hrs.)



Date: Wed, 5 Sep 2012 17:05:54 -0500

From: Don Johnston <numa at comcast.net>

To: reflector at tvbf.org

Subject: REFLECTOR: Oil cooler clearance



Groan...



Fred,



How much clearance is needed to not hit the mount during startup and shutdown?



Don







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