I purchased the engine ring part of the mount from Aircraft Spruce (p/n 33521). I also purchased the rubber mount bushings (Aircraft Spruce p/n 08-03500). Again this is for the Lycoming O-360. If you are mounting an O-540 or other engine, you will need different ring mounts and bushings than I've shown here.
Since the mount bushings are rubber, you don't want to use them to bolt the
ring to the engine for welding. Instead, I'll substitute some washers
stacked up to the correct thickness to simulate the rubber bushings. To
determine the correct thickness, one of the rubber bushings was assembled
to the engine ring and torqued down to the correct torque value for a 7/16"
bolt (450 to 500 inch pounds or about 40 foot pounds). The thickness of the
bushing (where it will contact the engine lug) was then measured:
The same measurement was then duplicated using stacked washers:
To properly center the mount, I found some washers that exactly fit the inside of the hole in the mounting ring. The washers were stacked in such a way that the smaller diameter washers were in the hole keeping the bolt centered.
Here is the engine mount ring bolted to the aft end of the engine case using
the washers to maintain proper spacing:
Again, this is the set up for the Lycoming O-360 engine which is a little different than the O-540 mounts. OK, now we are ready to start fitting and welding in the tubes that go between the bushings bolted to the firewall and the engine mount ring.
The tubes are 4130N steel 5/8" x .049". I started with the 4 main tubes,
cutting and tack welding all four in place.
As you can see, the thrust line string is still in place and was checked
as each tube was fitted to assure that proper alignment of the engine was
maintained.
Since other tubes will be fitted and welded to the same bushings, I decided to go ahead and fully weld the 4 tubes before proceeding. That way, I know that they are completely welded to the bushings before another tube is fitted in place. Again, the thrust line and engine alignment was constantly checked for proper alignment during the entire process.
With the 4 main tubes welded in place, the next 4 tubes were fitted
and tacked in place as shown below.
These 4 tubes were then completely welded at both ends. As you can see, the thrust line string is still in place and centered through the crankshaft area of the engine crankcase.
The only thing remaining are a couple of diagonal tubes that go between the upper bushings at the fuselage and the lower motor mount attach points.
Here is the completed engine mount:
As you can see, the thrust line reference string is still in place and centered
through the engine crankcase.
Here are some close-ups of the various attachments:
Lower engine mount:
Upper engine mount
Upper firewall mount
Lower firewall mount
And finally . . . here is the completed engine mount awaiting the Bob Barrows
built Lycoming O-360 that I will take delivery on in January
2006.
Engine Mount
Completed: November 16, 2005
Total Time: 32 hours