In Aviation, Details Matter.


Here is another item from my hangar clean up. It stopped for its photo op on the way to the trash can. Tomorrow is trash day, and by the end of it this part will be in residence at the Clay county landfill and recycling center, but don’t let the lesson it has go to the dump with it.


This is what is inside a ‘John Deere” generator.  We have used these for more than 20 years, they are totally reliable…..the way we use them. Today you can mount one on the front or rear of your Corvair engine….or both if you like. Both positions intentionally have a ‘fuse’ to the engine incase it jams or has a bearing failure. The front has the belt, and in the back it has a shear point. It is beyond foolish to run a generator or alternator without such a consideration. Even small Continentals which appear to be straight gear drives actually have shear points in them so the motor will not be stopped. There are people who have put similar systems directly on the rear of Corvairs and combined it with starters, but it is an accident waiting to happen.


From 2004-2007, Between flying our 601XL test aircraft and the arrival of the gold hub system, we only had front alternators, driven by Black Hub systems. To slow the alternator down we developed a method of using a slightly larger pulley on the JD alternator. I modified dozens of them and they had a perfect track record. We charged about $40 to do so. Later, when Gold Hubs arrived, I designed them with a smaller integral drive pulley so the issue disappeared 12 years ago.



Above, the inside of the JD unit, This particular one was screwed up by a builder in 2006 trying to save $40 who didn’t think that details mattered. It flew a while, but easily could have broken in flight. When I saw it, I took it out of service. If you look where the screwdriver is pointing, the permeant magnet, which is bonded into the shell, is broken. This is because the builder directly welded the pulley on the other side of the shell. Welding near bonded magnets isn’t a good idea, ever.


The correct modification I did was welding the pulley onto the old pulley half, seen at the right, when it was removed from the unit. This kept all the heat away from the generator, and it was concentric because I did it in a lathe.  On the very surface, if you don’t look at the details, these were both welded pulleys. Had this one broken, do you think that the local expert observing the failure would read about the modification on my old site and say ‘you should have followed Wynne’s method or paid him to do it” or do you think they would just say “stupid car engine, can’t believe that jerk in Florida told him to weld on an electrical component”  You have to be a real optimist about people to believe the latter. 


Your Corvair engine will present 100 chances to say things like:

“These spark plugs are just as good as the ones WW says to use”

“I use this kind of gasket sealer on Yamahas, so It’s better than what WW says to use.”

“I know he says not to hang a lot of brass plumbing off an 1/8″ pipe thread in the oil system, but I got away with it on my Nissan.”

“I couldn’t find what WW said to use, so I got this, its just as good”


I would be OK with people doing these things, as long as when it didn’t work, they stood up and said, “You know, William said not to do this, and I was to cheap and lazy to listen to him, and I let my ego get in the way. I was planning on flying my family in this, wow, I was wrong.” 


Don’t be tempted to say this wouldn’t happen. I’ve actually seen it happen exactly twice in 30 years.




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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