Power takeoff, or PTO, shafts are extremely important parts of any tractor system. They are the element that transfers power from the tractor to whatever implement may be connected to the tractor. The devices that may be powered by a PTO shaft include rotary mowers, feed grinders, balers and grain bin augers. PTO shafts were one of the major factors in revolutionizing agriculture in North America in the 1930s and they are still widely used. PTO shafts come in several major types.
Transmission PTO Shafts
A transmission PTO shaft is the earliest form of PTO shaft. It connected directly to the transmission of the vehicle in question. The main problem that arises with this type of a PTO shaft is that the shaft stops moving whenever the tractor does, and it is also inoperative when the tractor is taken out of gear. This can cause serious problems when mowing, and sections of the area to be mowed will not be caught. Often, tractors outfitted with this type of PTO shaft will require what is called an overrunning clutch, or a continuously running, PTO shaft. An overrunning clutch prevents the PTO shaft from exerting force upon the transmission, which could result in the tractor failing to stop when the operator wishes it to.
Live Clutch PTO Shafts
A live clutch, or two-stage, PTO shaft allows the tractor's transmission to run on two modes. Pressing halfway on the clutch will disengage the transmission but not the PTO shaft, while pressing on it all the way will disengage the transmission and the PTO. This will remove the danger of the PTO shaft stopping while the operator is switching gears on the tractor, thus not interrupting the work of whatever implement is attached to the PTO shaft at the time.
Independent PTO Shafts
Independent PTO shafts have their own clutch, which can be operated independently of the tractor's transmission. Independent PTOs come in two subtypes, mechanical and hydraulic. A mechanical independent PTO shaft comes with a separate on-off selector, which is separate from the PTO control lever. A hydraulic independent PTO shaft has a single selector for both.