Morbark Chipper feedwheel shaft problem

[PineBob]

I have a 2010 Morbark MR15 chipper. Has anyone been having an issue with the lower feedwheel drum shaft breaking at the point where the shaft is tuned down to 1"? The first one broke about a year after we bought it, and the new one broke  15 months later. Morbark claims they have not heard of anyone else having problems like mi

  ne.

[Gary_C]

Morbark claims they have not heard of anyone else having problems like mi

That's one of the oldest and most worn out lies in the world of manufacturing.

Without seeing how that shaft mounts in the machine, I can say it's inevitable for that small shaft to break. Particularly in a machine subject to shock loading like a chipper. The problem is the point where it steps up to a larger diameter is a high stress point and every rotation of the shaft is a stress cycle. So it's not a question of wether it will break but how many cycles or revolutions will it take before it will break.

It would help if there was a large radius where it steps up to a larger diameter. But otherwise, it is hard to overcome that shaft design without reworking the machine.

Best way to fix just that shaft would be to bore out the large shaft for a larger diameter step shaft and then be careful to not weld near the smaller diameter part. And leave a large radius in the transition from middle diameter to small diameter. But the new shaft must fit tight in the bore or you will get wobble and be back in the same fatigue failure problem.

But that could be a costly repair. However it might still be better than a new part with the same design problem.

[PineBob]

thanks for your take on the problem. Think you hit it on the head. I might get a new shaft from them and weld it in the drum,myself. thinking about building up the weak spot with my mig welder.

[thecfarm]

PineBob,I see you are new here.Welcome to the forum. Seem like I heard the same thing from a Kubota dealer too. : I have no idea how many Morbark owners we have on here. But somewhere's out in internet land there must be others just like you and having the same problem.

[LAZERDAN]

You are hard on equipment