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Date:  10-11-2014
Number of Hours:  2.50
Manual Reference:  
Brief Description:  New engine shock mounts

A few weeks ago I noticed the prop hub was lower (compared to the cowl) than usual. I Knew that meant the engine had shifted.

In the engine mounting instructions they called for fender washers on the FRONT of the shock mounts (the side facing the prop), and the washers sent with the AeroVee kit were sized for the engine mount bolts. There was nothing said about putting on fender washers against the engine mount BEFORE any shock mounts, and then the engine, are installed.

The welded face of the engine mount that backs up the rear shock mounts, are smaller in diameter than the shock mounts. So under gravity and aerobatic G-loads, the engine pushed on the rubber shock mounts, and they "oozed" out over the engine mount. This let the engine sag agains ALL the shock mounts, until they were crushed and elongated (photo 3).

So I needed to replace them.

1. I disconnected anything that would keep the engine from moving 3 inches forward.
2. I took the nuts off that were holding the engine to the engine mount.
3. I hung the engine by an overhead hoist and backed the airplane away about a foot.
4. The engine came free of the mount.
5. I added 2 fender washers to each engine mount bolt tube (the fender washers had to be up-drilled, since the bolt tubes are larger than the bolts that go through them.
6. I reinstalled the rear shock mounts (use soapy water to help slide them on).
7. Rolled the airplane forward again and went up and down with the hoist until I got alignment, then added the front shock mounts, and then 2 fender washers on the face of each.

When I went to put the cowl back on, I realized I had changed the geometry of the engine in relation to the cowl! It didn't fit! I had to tighten the upper bolts a bit more, and the lower bolts about double that. In all cases the washers are compressed more than I think they should be, but if I don't do that I can never get the cowl back on.
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Engine hoist holding the engine up and forward.

Engine hoist holding the engine up and forward.

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Engine mount to the left, engine off the mount, to the righg.

Engine mount to the left, engine off the mount, to the righg.

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Some of the old mounts that were removed.

Some of the old mounts that were removed.

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