B7200HST
Member
- Joined
- Aug 26, 2011
- Threads
- 3
- Messages
- 11
I have a circa 1989 Kubota B7200 HST with an "RC60-72H" 60-inch belly deck. I started using it April 2008 when it had 846 hours. In Sept. 2010, at 935 hours the middle blade broke. Then again at 956, 960, and 965 hours. So the middle blade has snapped four times - 3 x with old blades, once with a new blade.
The breaks always occur about two inches from the center mounting hole. They are clean breaks, and almost look at though they had been sawed off. Sometimes the blade breaks in one place, sometimes in two places (on either side of the center hole).
I see nothing that the blades could be hitting. The blades are clearing each other, unless a blade shaft is distorting a lot, and I detect no wobble in the shafts.
The middle blade is driven directly by a gearbox, while the outer blades are belt-driven. I wonder if vibration is fatiguing the metal blade. (The outer blades would be cushioned by the belt.) The U-joints from the PTO to the gearbox seem OK, but the U-joints aren't a really tight fit on the splined PTO shaft. I can see the PTO shaft wobbling, but perhaps that's normal due to the action of the U-joints turning. It's not a very long shaft.
Any ideas what's wrong? Anyone ever heard of this?
The breaks always occur about two inches from the center mounting hole. They are clean breaks, and almost look at though they had been sawed off. Sometimes the blade breaks in one place, sometimes in two places (on either side of the center hole).
I see nothing that the blades could be hitting. The blades are clearing each other, unless a blade shaft is distorting a lot, and I detect no wobble in the shafts.
The middle blade is driven directly by a gearbox, while the outer blades are belt-driven. I wonder if vibration is fatiguing the metal blade. (The outer blades would be cushioned by the belt.) The U-joints from the PTO to the gearbox seem OK, but the U-joints aren't a really tight fit on the splined PTO shaft. I can see the PTO shaft wobbling, but perhaps that's normal due to the action of the U-joints turning. It's not a very long shaft.
Any ideas what's wrong? Anyone ever heard of this?