ZD21-60 Engine Noise warning to owners

[Ob1kubota]

While mowing my flat pasture in 6 inch tall grass under full load, I heard a terrible horrifying noise clear through an earmuff head set listening to 'boss' singing about turning 60 yrs young and joining the AARP, a ratching metal to metal noise that sounded like the HP injection pump cam breaking the tabs off plungers. SCARY I tell you Well to make a long story short I instantly threw the pto out and pulled the throttle back to idle, threw the arms out to neutral and set the park brake, climbed off the deck and pulled the hood up to find ??????? what

Come on guys start guessing what did I find... hint nothing organic, animal, etc. no tricks here just hard facts about what happened to this Kubota 782EA-2 engine.....

 

[Theekillerbee]

A failed U-joint on the crank to hydraulic pump shaft!!! Not even sure if your model has that, but I have a 66 Ford 3500 that threw one of those...not a pretty sound or sight.

 

[Ob1kubota]

I really like Vic's answer but bee for short you are warm ... hint looking straight down at the engine with the hood pulled open it was on the left side and this is for real not a joke I've never seen this on any Forums about a ZD. After this post is over I wll get this info to my rep because this is absoultely a freakie thing. But, I want to see if anybody can guess what it is, I haven't even fixed it yet and still thinking about what I can do for it to never happen again....

 

[aquaforce]

Shaft failure to the belly mower?

 

[Ob1kubota]

Aqua to the left and up on the engine. Listen you guys will not believe what it was and all the expense I went to rebuilding the bearings ( rotating components ) to no avail.
Hint: It has something to do with natural frequency Vs forced frequency and reaching an amplitude to the resonant range. Stay with me on this one and start thinking out side the box. It can effect everybodies tractor and Kubota Engineers know there is a problem but have failed to discover how simple it can be controlled with damping before total failure of members.

 

[Ob1kubota]

Okay guys this post has been here long enough.... it was the...... woops don't have pictures ready yet ...stay tuned

 

[kdsn]

Okay guys this post has been here long enough.... it was the...... woops don't have pictures ready yet ...stay tuned

Any day now...could be today...tomorrow??? Loose nut behind the wheel?? LOL

 

[Ob1kubota]

Finally I'm getting some attention on this post. I promise I will upload pictures from work and get this done. You won't believe it and its a lot tighter then the loose nut behind the handles, no steering wheel on a ZD guys

 

[dusty-t]

Hey Ob1kubota, I don't even own one of these and I'm getting itchy to find out what's going on with this machine.

 

[Ob1kubota]

Okay I'm giving it up tonight .... it was the muffler bracket that supports the outlet end to the chassis frame rail. It sheared at a stress riser created during the mig weld at the factory. There was severe under cut where the machine weld either shut off or ran out of wire but it created the perfect shear point under the stress of vibration. My digital camera went Kaput and deleted my rework photos. I will take finished weld pictures some time this weekend and load them. ( My day job is kicking my A lately and that eats all my time )

Heres the interesting thing I learned about this incident. Kubota vendors realize there is a strong chance that resident frequencies will develop between the muffler attachment bracket and engine harmonics ( vibration of the natural cycles per second reach the mechanical frequencies which is defined a resonant) So they use a very soft metal to support the muffler in hope of damping the vibrating force of the engine to frame attachment. Damping reduces amplitude in resonant frequency range between natual and mechanical forces acting on the mechanic of materials. Now having said these basic properties for the record, I will get into my fix on these mowers vibration problem in a later post for all you great guys and ZD owners listening to needless noise created by such a simple over site by Japan ( thats where all the manufacturing engineering comes from for KAC ). When they get over here ole Yankee Engineering takes over, stay tuned...

 

[Ob1kubota]

Here are some of the photos I hope to up load for specific details of the fix. At least 60 hours after this fix, no cracks, no noise, just mowing as it should be....

 

[Ob1kubota]

Here is the exact location of the rubber dampner added to prevent Resonance between the muffler brace the frame attachment point.

 

[dusty-t]

Iv'e seen things like this before on different machines through the years, but that has got to be the best most simple fix I have ever seen. Thinking outside of the box. Very Cool !!!

 

[Ob1kubota]

Thanks Guys it was a cheap fix after I found out what it was. The hair line crack could only be heard when the machine was running and sounded just like a bearing going out, Hope this helps others with this machine. This series of ZDs had hydraulic pump issues in early serials and got a bad name but all considered its a great mower for the cost of operation.