Oil Leaking at Hub and Shaft of Aermotor A702

[Trester]

I just rebuilt an Aermotor A702 that I purchased off of Craigslist. When I was tearing it apart, I noticed that when it was rebuilt before, someone had coated the hub shaft with silicone caulk and pushed the shaft into the hub. While rebuilding the unit, I had to replace the hub shaft and the bearings for the hub assembly. After sand blasting, painting, and the rebuild, I installed the mill on the tower and find now that I have oil dripping (slow leak) out the end of the hub. The oil is leaking between the hub shaft and the hub. There is a tiny amount slop between the hub and the shaft when you wiggle the hub.

I'm guessing that my best option is probably replacing the hub and shaft assembly. But I am new to windmills so I would really appreciate getting some expert advice as to what the best options are. One of my problems is that since I am new, I just can't look at tolerances and understand what is acceptable.

[Bryon]

There should be NO slop between the hub and the shaft. They should be very very very tight ( I don't know the tolerance). You should also have replaced the oil collector that scrapes oil from the inside of the hub and routes it back into the gear case. Oil scraped problems cause oil to leak out the back of the hub. I think your loose tolerance on the hub/shaft is causing to to leak out the front. I would not run it. Would hate to see the hub come off the shaft and ruin some perfectly good blades.

[Trester]

Thanks Bryon! I thought that that was the case, but I just wasn't sure if there were any other options than replacing the hub assembly. Thanks for taking the time to respond!!

[windybob]

Yes, replace the hub, or hub/shaft. It is an interferance fit, but I can't tell you how much. Of course, Bryon is correct, as usual.

A lot of times, I will press in a shaft, drive in the key, and also weld the outside shaft to hub in front. One of the all-time problem issues for mill makers, is how to keep the hub and shaft from coming loose. They have tried almost everything possible, some with better results than others. One issue that Aermotor tried back in the (80's?) was to also include a bolt/washer screwed into the mainshaft up against the hub on the outside / front. That was a total disaster. By the way, those 802 mills came out blue.