Group 3200, Wynne 5th Bearing


I occasionally get questions about my 5th bearing design, which is Group 3200 in our manual numbering system. I developed it about a decade ago, thinking it might serve in special applications. Over many years, it has been conclusively proven that the Weseman 5th Bearing, (Group 3000) actually covers all common 5th bearing needs, and does so far more cost effectively than my design does. For this reason, my design is not in production, and all the production engine I build use Weseman bearings. The photos below are of my own personal 3,000 cc Corvair engine being assembled.




Above, My bearing is a non-splitting design, which moves the thrust bearing to the prop end of the engine. The bearing is the actual aluminum plate, machined to the shape of a 3.375″ diameter bearing with thrust faces that are 4.375″ across. The plate in the bearing area is coated by Poly-dyn in Texas, but it also flew 100 hours with no coating. Some people said it would never work, but you can tell they never saw the inside of a Lycoming, as the thrust faces on 180-200 hp 360 cid Lycomings are the crank running on the bare aluminum case.


The bearing is assembled by having the front and rear thrust journal on the 5th bearing as separate pieces. In operation the bearing stays perfectly round, because it isn’t bolted together. In the photo you are looking at the front thrust face, which only handles reverse thrust in the motor, like chopping the power and letting the plane drive the prop on landing. For 95% of the engine’s life, the load is taken by the forward thrust face which is behind the main aluminum plate and working against the rear face of the plate. Oil is fed by the AN-6 fitting at the top of the picture. The design is unusual, and it’s origins come from driving long distances alone without a cell phone nor a radio, just my thoughts.  None of my last 3 pickups, nor our Suburban have had a radio.  That is 300,000 miles of uninterrupted thinking. I have come up with a lot of good mechanical ideas in those miles.


The hub in the photo is missing it’s gold anodizing because it has been shortened. This was done so it could be the exact same length installed as a Weseman Bearing. This allows the engine to fit into a standard cowling, and use standard hybrid studs and safety shaft. The original design used custom parts and a long Gold hub, and was about 1.25″ longer.  I shortened this one so that our own plane can test engines equipped with Weseman 5th bearings.




Above, The bearing with it’s oil seal cover bolted in place.  The seal rides on the stepped down face that is 3.00″ in diameter, the same as the back of the hub.  I only ever made a handful of parts sets for this design. The protoypes were expensive, something like $3,000 a bearing. I gave one to Mark Langford in exchange for his flight testing of the design (I don’t sell things that are not flight proven) He flew it 450 hours in his KR-2S. Other than a teething problem caused by trying to run too tight of a clearance in cold weather with 20w-50 oil, it had a good record. The while item in the engine is the nylon U-shaped block I use to stop the rotation of the crank when tightening the studs and safety shaft nut on an engine. The red sealer is Loctite 515, the same stuff used to mount a Weseman bearing. This is also popular as a sealer at the base of 3,000 cc cylinders, which do not use base gaskets.




Above, Installation almost finished.  Note that shortening the hub required removing most of the front alternator pulley, leaving enough to act as the ring gear mounting point. This is OK, because my engine is set up with a Weseman rear alternator, #2950.This is another view of the nylon anti-rotation block in place. Note the case also had ARP main studs, these were installed as a test in 2003. In the long run they have proven to be a nice thought, but not required.


If my sole interest in Corvairs was making the maximum buck or having my ego polished, I would tell every builder that this was the best 5th bearing, that it is “Technically Correct” and other BS to get them to spend more money and buy it. In reality, my goal it to teach builders about engines, and get them flying with the parts that best serve their own personal aviation  goals. When it comes to 5th bearings, this means advising builders to use a Weseman bearing, just like we do on production engines.


Read More:

Sources: Choosing a 5th Bearing



About William Wynne
I have been continuously building, testing and flying Corvair engines since 1989. Information, parts and components that we developed and tested are now flying on several hundred Corvair powered aircraft. I earned a Bachelor of Science in Professional Aeronautics and an A&P license from Embry-Riddle Aeronautical University, and have a proven 20 year track record of effectively teaching homebuilders how to create and fly their own Corvair powered planes. Much of this is chronicled at and in more than 50 magazine articles.

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