I have a grasshopper 725D mower. This is a 3 blade ztr mower.
Blades are mounted on 1"shaft that passes through a pair of 1" x 2" x 1/2" bearings. Bearings rest on a step in the spindle case, and also have a sleave that supports the centres. The spindle housing is about 2.5" in diameter.
The blade is bolted with a 3/8" NCF bolt to the shaft. There is a metal washer between bolt and blade about 2" in diameter, and a fiber washer between blade and bearing.
In operation if you hit any plastic bailing twine it wraps tightly between the blade and spindle housing, then melts and moves into the space between the fiber washer and the bearing. There it destroys the bearing seal. Net result is a $200 repair about once a season.
I'm looking for ways to prevent the plastic from melting and getting into the bearing space.
One thought I had was to fabricate a metal cup that went between the blade and the fiber washer that covered the spindle housing. This would spin with the blade. However the top edge of this would have to have some clearance, and I anticipate that it would collect dust, mud, shattered dry grass. Not sure if this would be a win or not. I also worry about water collected there, as I frequently have to mow wet grass.
This must be a frequent problem in mechanical engineering -- running bearings in a hostile environment.
Pointers to any standard ways to deal with this.