overrunning clutch B3030?

[lil_country]

After reading the very informative PTO information on tractorsmart - http://www.tractorsmart.com/main/Tractor Power Take Off Types.htm - I am wondering if I need an overrunning clutch on my B3030. Should I be using one - especially for brushhogging?

Here is the section of the article in question;

"Some form of PTO brake is incorporated into most hydraulic independent PTO systems. The function of the brake is to overcome the tendency of the PTO shaft to continue rotating, even when it is in the OFF position. This undesirable rotation is caused by oil drag between the drive and driven discs in the clutch pack. Without a brake, light load implements, such as hay rakes, might continue to slowly rotate, even with the PTO OFF. At best, this is a nuisance; at worst it could present a dangerous situation. PTO brakes are getting more reliable, however they are still subject to accelerated wear and damage, if continually called upon to stop heavy implements. A good example is the heavy duty rotary cutters that are popular today. There is a lot of potential energy built up in those heavy blades and stump jumpers when they are rotating at operating speed. When you select the PTO to the OFF position, your are disengaging the clutch pack, and redirecting the pressurized oil to the PTO brake system. Imagine trying to bring your truck to a stop from 50 MPH, using only half of the brake pads on one wheel, and you'll get the general idea. Some of these systems have an intermediate coast position between ON and OFF, which allows natural deceleration of the implement, saving wear and tear on the brake components. In the absence of that, you may wish to consider using an over-running coupler on the tractor PTO shaft, in order to avoid costly damage when using heavy implements."

 

[ksmmoto]

I move the throttle to idle before disengaging the pto on my L3430. This lets the engine take the inertia off.

ksmmoto

 

[lawn_king]

I move the throttle to idle before disengaging the pto on my L3430. This lets the engine take the inertia off.

ksmmoto

ksmmoto stole my thunder, the 3030 manual says the same thing. I always idle down before turning on or off the pto. kubota claims you can engage/disengage on the move but i stop the tractor.

 

[Toolguy]

I don't think there is a PTO brake on a B3030. On mine, I can turn the PTO shaft by hand when the engine is off. I also have a MMM and when I shut the PTO off the mower seems to slow down in a gradual manner. No sudden stop or anything like that. I usually slow the engine down before I disengage the PTO however, sometimes I will just idle it back to half throttle, turn the PTO off and then shift up a gear to travel to another part of the lawn. I have driven gear tractors all of my life and they did not have PTO brakes. The B3030 seems to act the same as the gear tractors do when shutting off the PTO.

 

[lawn_king]

Toolguy, i can't turn the pto shaft on my 3030 when the engine is off ?

 

[Toolguy]

I stand corrected, partially. Since I do not have any rear PTO implements I was basing my statement on the MMM operation alone. I did some checking tonight. I was wrong to assume that the rear works the same. The Mid PTO can be turned when disengaged and the engine is off, but not the rear. Even when the PTO selector lever is positioned so that both the mid and rear shafts are running at the same time the mid will turn but the rear will not. However, when only the mid shaft is selected the rear will turn freely about a quarter turn and then it hits a hard mechanical stop. When the rear is selected it acts as if a brake is applied. I would like to see a parts breakdown to try to understand how and why it acts that way. At least on a B3030, an over running clutch would seem to be a good thing when operating a rotary cutter or any attachment that has a lot of spinning weight to slow down.

 

[Jdengr]

The parts diagrams are available in .pdf form from tractorsmart.com
You can see the mechanisam for the B3030 pto. Power is transmitted to the rear pto through a wet multidisc clutch. When you move the PTO on/off lever you are controlling hydraulic pressure to the clutch. To apply the clutch (PTO on) the hydraulic pressure must first release the brake on the rear PTO shaft. And when the clutch is released (PTO off) the brake is spring applied. I was concerned about brake wear/damage from stopping an implement such as a brush hog. I contacted a Kubota rep thru email and he said it wouldn't be a problem especially if you idle the tractor first.
My older tractor had an overrunning clutch and the brush hog would spin for some time after disingauging the PTO. Some tractors (like old farmalls) have the pto connected to the transmission (non-live design). An overrunning clutch was required because without it the implement would drive the tractor wheels. I think Kubota is aiming for safety here. When the engine stops, hydraulic pressure is lost so the implement stops.