I'm Confused (What's a Live PTO?)

What exactly is the definition of a live PTO? I was told that my tractor has a live PTO which means that the PTO must be engaged in order to use the hydraulics. Is that correct?

How can I tell if my tractor has a live PTO? What are the Pros/Cons of a live PTO as compared to a non-live PTO?

Thanks in advance.

Bill

In the case of an N tractor, the pto is connected to the main transmission, and not the engine. Push in the clutch, and the pto stops spinning. Which makes it darn hard to work with when manuevering around slowly. You can't creep up on thick grass on an N because every time you slip the clutch to creep forward, you slow down the pto shaft. Unlike the live pto the riding mower has, which allows you to slip the driving clutch, while spinning the pto driven mower deck fully. Can you imagine how annoying and difficult mowing with that lawn tractor would be if every time you pushed in the clutch the mower deck shut down? The only reason the N isn't quite that annoying is it's got a lot of power.

That's the main difference between live vs non-live pto's.

In the case of the N, and many others, there is a secondary issue with the non-live pto. Two actually.

One is that the pto is driven off the output shaft of the transmission. This means that the tractor must be in neutral or moving for the pto shaft to spin. It also means that if the pto shaft is spinning, the tractor is being moved, or must be in neutral to stay still. Pushing in the clutch doesn't matter, the engine is out of the picture here. You would need to be in neutral to seperate the pto shaft from the driveshaft. Hence the nasty habit of bush hogs shoving tractors around by their rotational inertia, and the need for an overruning clutch. This prevents the attachment from pushing the tractor around through the pto shaft.

Another annoying aspect of the N is that the hydraulics are driven off that pto shaft. So every time you push in the clutch, the hydraulics are dead. So when you're pushing snow out of the driveway and across the road, you have to wait in neutral with the clutch out to lift the blade, then shift again, and drive back. It can make life rather exciting and complex some times.

NOW, since the main input shaft and the counter shaft are PERMAMENTLY geared together in the front of the transmission, an N PTO cannot be live. Understand, the counter shaft is how you get the lower gears and reverse so it must turn to drive the wheels. And as has been stated, "live PTO" means the PTO is independent of the drive train to the rear wheels and can be "decoupled" independently with something like a two stage clutch or a completely separate clutch. Either way the PTO drive must be coupled directly and independently to the engine.

I hope this long and "complicated" description has given you a complete understanding of the relation for the drive train and the PTO/hydraulics in the Ford N series tractors. AND, thus the absloute need for an ORC. The blades on a bush hog are like a flywheel. They store a lot of energy, which can drive an N many feet forward if there is a solid connection from the blades to the rear wheels. The ORC "breaks" this connection but only when power is trying to come from the blades. When power is going to the blades, the ORC "locks up" to drive the blades.

Be safe mowing,
Larry