Orange related question in Blue Froum!!

[JC-jetro]

Howdy all,

This is Kubota related design question and it is purely mechanical in nature question. On several occasions I asked the same in the Orange forum and got no response at all. I know here in Blue forum we got quality experts that I always appreciated their input.

By the way, I think Kubota is a very good manufacturer to a great extent and they like anyone other manufacturer like to keep the cost down specially in their economy line.

Now to the question. The Pto Input shaft to the pto final output shaft is coupled together by a locking cam device. As pictured below. This also provided the function of ORC (over running clutch). It would grab one way and slip the other way. Engagement is accomplished by sliding the driven coupler to engage the driving cam. Due to adjustment of the cable that engages the two sides the lips would hit and not grab good causing premature damage to the mechanism.

Old PTO Cam/Coupler:


Here is how they tried to improve it by removing the ORC function and making a more solid interface. Apparently they have less issue with this. They have also increased the oil level in the diffy higher to mask the clanking engagement noise.

New PTO Cam/Coupler


Here the Spring 80 allows the cam some fore and aft to smooth out the engagement. #130, the driven cam is sliding, and by a fork moves for and aft to engage or disengage.

PTO driving and driven cam/coupler.


Here #10 fork( if you can call it) pushes the #130 cam to engage. Cable #100 , along with lever 60 moves fork #10. it is easy to see the cheesy cable has a major impact on the proper engagement of the pto. There is also a dry contact switch there that is operated off of #130 pto engagement handle to act fas PTO safety switch.

PTO engagement mechanism and sliding cam engagement:




In my opinion this design is much inferior to a simple sliding gear coupler as the torque equally transferred from one shaft to another with much less chance of jumping out.

In kubota's design this torques is transferred to a very small surface area and much easier to damage the cam edges due to maladjustment. Their set up is much more robust with the Grand L series and hydraulically activated independent pto.

I would appreciate your opinion.

Thanks,
JC,

 

[brain55]

I'm a little confused by what you are saying. There should be no engagement of the over running clutch it should be strictly spring loaded. Did some engineer at Kubota decide to ruin a perfectly good design? I have worked on many of the B-series Kubotas with the spring loaded design, they are a must if using a rotary mower or the mower will push the machine when decelerating. The only problem they would have is if the PTO shaft got a slight twist in it the the spring loaded cam would hang up on the shaft and the PTO would freewheel.

Brian

 

[JC-jetro]

I'm a little confused by what you are saying. There should be no engagement of the over running clutch it should be strictly spring loaded. Did some engineer at Kubota decide to ruin a perfectly good design? I have worked on many of the B-series Kubotas with the spring loaded design, they are a must if using a rotary mower or the mower will push the machine when decelerating. The only problem they would have is if the PTO shaft got a slight twist in it the the spring loaded cam would hang up on the shaft and the PTO would freewheel.

Brian

Thanks Brian,

On the first picture (Old cam design), if you have transmission driven pto the momentum of a rotary cutter can push the tractor forward when the tractor is dead even with gear pushed in neutral. The graduated sloped side of the cam allows two pieces to catch in one way and slip the other way. They are still using the spring as it is quite necessary. The issue was with economy L series and adjustment of the cable. If the pto cable did not pull the pto fork lever arm enough then two pieces of the cam would not engage completely and under heavy load would separate and slowly caused damage to mating parts. You can see evidence of the damage as two cams started to slip.
My beef is, why use a cam designed as such where a robust simple sliding gear that is proven design is not used there. Obviously no one has exclusive patent or right of using a simple sliding gear. Even Ford 8n along with many other manufacturer use them. I wondered if this cam is a new improved design or they had it even for their vintage models as well.

JC,

 

[brain55]

So on the L-series instead of this being an over running clutch design, they are actually using this cam to engage and disengage the PTO. Do I have that right?

Brian

edit- Now I think I'm getting it, they were actually trying to do both, and the new gear design doesn't have the over running feature. The problem might be they are using a design that worked for machines under 20 HP but might not be strong enough for bigger HP. I have used add-on over running clutches for machines that didn't have them. B20's didn't have ORC's and if you ran a rotary cutter it would push the drive gear off the front of the HST because it was helical cut and designed to be driven and pushed against the case instead of becoming the drive and being pushed against the cir-clip. I guess they figure if you disengage the cam there is no need for an ORC since it is not engaged.

 

[JC-jetro]

So on the L-series instead of this being an over running clutch design, they are actually using this cam to engage and disengage the PTO. Do I have that right?

Brian

edit- Now I think I'm getting it, they were actually trying to do both, and the new gear design doesn't have the over running feature. The problem might be they are using a design that worked for machines under 20 HP but might not be strong enough for bigger HP. I have used add-on over running clutches for machines that didn't have them. B20's didn't have ORC's and if you ran a rotary cutter it would push the drive gear off the front of the HST because it was helical cut and designed to be driven and pushed against the case instead of becoming the drive and being pushed against the cir-clip. I guess they figure if you disengage the cam there is no need for an ORC since it is not engaged.

Yes Brian, that is my understanding as well. On big pumps and such we have resilient coupler (ie rubber coupler) to join electric motor shaft and the pump shaft. The reason for it is, if there is slight shaft misalignment, then the rubber compensate for it. The concept works okay since they are always attached and are not engaged or disengaged. In the case of Kubota cam design, it is metal to metal contact and if rotation of the pto input shaft is not completely stopped then you have a bad engagement and then all the initial torque lands on couple of small lips. On the sliding coupler, you still might have some grinding if you don't clutch right but once engaged then the torque is uniformly spread in to a concentric heat treated gear with a lot of surface area and that's a good thing.

JC,