Plastic floating seal in drive sheave

[Slick1951]

I was wondering if anyone would know why the plastic floating seal in my Melroe keeps shattering . I put a new one in [$50] and it only lasted about 2 hours. Maybe i cracked it during installation of everything. I wish I knew exactly how this works so maybe i could come up with an alternative solution to make it work. I DO NOT want a fixed variable speed! Thanks for any reply.

 

[foton]

fixed speed it is just a matter of time, been there done that, and sold that , good luck!