The bushings I use are on the edge of their spec in Valkiri3.
But that's a monster in weaponpower; Diameter 356, 4 kg going 5.5Krpm. (theoretical 6300).
Start up amps, around 120, running amps, 20.

The grit issue is solved like any good bushing in a backhoe, bulldozer or any other heavy equimpent dealing with massive amounts of dirt and sand. Grease it so the grease pushes out the crud after each use.