Mowing Kubota PTO Breaking

[Javinka]

I have two Kubota M110x, one pulling a 15' Bushhog RotaryCutter, and a 20' BHRC. My problem is this: We have had to replace the PTO shaft on each tractor at least twice. My question is, is this at all related to operating the attachments at higher than 540? I am leaning towards yes, but I am getting nowhere trying to get a definitive answer. I'm sure once the operators are in the field, they are operating at max RPM. I wam considering having my mechanic put governors on the tractors to keep them at or below 2300 rpm. Any help?

 

[Gary51]

The only PTO I ever broke was on a Ford 7740 was a result of the engagement lever not working correctly and did not feather the PTO on as it should. I would guess that the PTO is being slammed on or perhaps they are making ground strikes with the blades while at running speed.

 

[rbargeron]

I have two Kubota M110x, one pulling a 15' Bushhog RotaryCutter, and a 20' BHRC. My problem is this: We have had to replace the PTO shaft on each tractor at least twice. My question is, is this at all related to operating the attachments at higher than 540? ........am considering having my mechanic put governors on the tractors to keep them at or below 2300 rpm.

I doubt that the shaft speed is a direct cause - the engine doesn't make that much more torque at higher rpm anyway. Impact loading is the more likely cause. And the M110 should be able to soak up quite a whack without breaking. It sounds like the pto shafts may be hardened too much and are brittle. Has the factory been involved in any of these replacements? Are the gears ok? Where are the shafts failing? At the same spot? Do they twist and bend or just crack apart? Could you post a closeup picture of the broken pieces?

 

[Javinka]

It's pretty consistent in the same spot, give or take an eighth of an inch or so. We've had a warranty repair on it the first time, but the dealer felt he was actually just doing us a favor. As far as he was concerned , it had to be operator related.

 

[bucktaker]

have you checked your mowers to see if the slip clutch or shear is operating correctly?

 

[Javinka]

Here's a few more pics. The inside gears look okay. One shaft looks like it was twisted before it broke, but the other three are clean breaks.
That's as close up as I could get with this camera.

 

[Javinka]

Thanks, Bucktaker, that was just brought up to me, as well. I think my mechanic may be part of the problem. I am pulling my freaking hair out for poor maintenance? That would not be good.......:confused2:

 

[moored4]

Here's a few more pics. The inside gears look okay. One shaft looks like it was twisted before it broke, but the other three are clean breaks.
That's as close up as I could get with this camera.

Pictures 1,2,and 4 look like impact breaks to me. caused by impacting an object or start up torque! or so I think with pictures. Have you taken them to a drive line shop or someone that see's alot of these and get their ideals!

 

[equipman]

We have a Professional Mowing customer with numerous Kubotas and we saw this happen once on a M120 pulling a 20' mower. It happened after almost 5000 hrs and we figured it was just fatigue. Since you have had several occurances, I would really look at the slip clutches on the mowers first. A combination of ground strikes and non functioning slip clutches could certainly cause the PTO shaft to break.

 

[blueriver]

All good advise. I'm leaning to the operator's engaging the pto at full pto rpm. A sudden force at high rpm's.

 

[Javinka]

Thanks, all of you. Great points for me to think about! I hope you all have a Great Holiday Season!!!!!!

 

[slowzuki]

1. Check your slip clutches
2. Check your pto length with the tractor parked on the uphill of a dip and the mower on the down hill. Make sure the shaft isn't bottoming out, it will push the output shaft down and break it.

 

[rbargeron]

Those breaks have a little of everything - combined side load, twist, and brittle fracture. The spiral break is more of a torsional failure - but the first pic is a classic brittle failure. Slowzuki's idea about the shaft pushing down with a bending load rings true to me. If it was all due to torque impact some gear tooth damage would be expected too.

Dumping the clutch to spin up a big mower from stopped can overload the driveline to the breaking point for the shear bolts. Check that the shear bolts in the drive line haven't been replaced with hard (grade 8) bolts. Hard bolts transfer the abuse to a more expensive part.

I'd ask the dealer to show those parts to the Kubota service rep and get some factory eyes on them. To my semi-trained eye they look through-hardened near the bearing and maybe case hardening with a ductile center would be better for this part.

 

[Grateful11]

How well do you know and trust your operators? I've seen operators break stuff just to get down time, I'm not saying that this is happening but I know that in the field I used to work in that was done by operators and then we would have to fix the stuff. I've seen 6" axles snapped off and we had to scratch heads trying to figure out how and why. This was on rail maintenance equipment.

 

[andrehoude]

It's pretty consistent in the same spot, give or take an eighth of an inch or so. We've had a warranty repair on it the first time, but the dealer felt he was actually just doing us a favor. As far as he was concerned , it had to be operator related.

I think it's the drivers that are rough on you equipment

 

[Tx Jim]

I agree with the other posters that think it's slip clutch related(stuck from rust or too tight).

 

[Deere9986]

last yr we ran 3 9540s and 3 m100xs and broke 2 or 3 shafts on the 100s and not a 1 on the 9540s. this yr we went to deere 3 5093es and 3 5101es and have broke 3 shafts in them. funny thing is the only ones that break them are the ones that have 4 clutches on the mower slip clutches. we run 1 rhino sr15 with 4 clutches, 2 landpride 5615 with 4 clutches, and 3 bushog 2615l that have 2 clutches per slip clutch and the bushogs never broke the pto. plus its not always the driver, i broke one with 50 hours on the m100x and new mower just by turning it on at idle.

 

[grsthegreat]

I second the vote for checking the clutch and or too strong of shear pin. Man, that break looks painful. id me crying :mur:

 

[kuboman]

Check the slip clutches and pto length.:thumbsup:

 

[MHarryE]

Some look like torsional overload but at least one appears to be bending fatigue. Is it possible you have one mower with a bent drive shaft? We had one of our old IH 1456s snap its 540 rpm PTO shaft this year running a chopper and discovered a bent PTO driveline was creating a wobble that fatigued the shaft. The failure looked just like your picture of the tractor end.