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Most people have heard about PTO, but not everyone who heard about PTO knows what it does and how to use it on a tractor. If you are here to find out what PTO is and how to use it, we are glad to let you know that you will find what you are seeking here. So what is a PTO, and how can you use it on a tractor?
PTO stands for power take-off. It is a device that transfers power from a tractor’s engine to an implement or machine that doesn’t have its own engine. To use a PTO, you need to attach a PTO-driven implement to it and engage the PTO.
PTOs are available in different capabilities to transfer sufficient power to PTO-driven implements. There are certain pieces of information that can assist every operator in using PTO for appropriate implements. Kindly read on to see these pieces of information and also to understand how PTO works on a tractor.
What is a PTO on a Tractor?
PTO is a device for transferring power from a tractor’s engine to an implement or machine that lacks an engine. Without the PTO, farmers can’t use tractor’s power to run implements like the harvester, mower, and every other implement that does not have its own engine. One can find PTO on utility tractor, row crop tractor, compact tractor, etc.
Tractors with PTO have been in the tractor market since 1918 when the International Harvester Company added PTO to some production tractors. PTO soon became a sought-after device after it featured in some models of tractors in 1918. The type of PTOs that existed in old tractor models connected implement directly to the tractor’s transmission, but such connection exposed the tractor’s transmission to more damages, especially when high-momentum implements are attached to the PTO. Modern PTOs are now designed to protect the transmission from damage even while transferring energy to high-momentum implements.
Modern PTOs have standardized structures for safety and universal compatibility purposes. The PTO of a typical utility tractor has a telescoping driveshaft, yoke at the tractor, and yoke at the implement. You may not see some of the PTO parts if a power take-off shield is fitted on it for safety.
Do All Tractors Have PTO?
The things you have read so far about PTO might make you wonder whether PTO is meant only for some special tractors or it’s meant for all tractors. It really makes sense to wonder whether you will find PTO on every tractor you come across. Here comes the answer to the question.
Almost all modern tractors have PTO. It’s rare to come across a tractor that doesn’t PTO. Compacts tractors even have PTOs despite their small sizes. It’s important to note that PTOs differ in their abilities to operate for a long period. While some can continue operating for up to 10 hours daily, others can operate for only about 10 minutes a week. It’s always best to verify the rated power output and operating time of a PTO before using it.
Tractor PTO Types
This type of PTO derives its name from the point where it connects. A transmission PTO connects directly to the tractor’s transmission. This type of PTO can transfer power to attached equipment only when the gear is engaged.
Transmission PTO is the simplest type of PTO, but its simple structure can cause a problem if you attempt to use the PTO to operate a high momentum implement. Since the PTO connects directly to the transmission, it can put a great force on the transmission if the attached implement tends to drive the tractor’s transmission.
However, such a problem usually doesn’t occur in tractors that have built-in overrunning clutches. Overrunning clutches will disconnect the PTO shaft from the driven shaft whenever the driven shaft rotates faster than the PTO shaft and hence protect the transmission from damage.
Live PTO can transfer power to implements even when the gear is not engaged. Unlike transmission PTO, live PTO has a separate clutch for engaging and disengaging the PTO. An operator can change gears or stop the tractor while the PTO is engaged because live PTO uses a 2 stage clutch.
Although live PTO has its own separate clutch, it’s impossible to engage the PTO if the tractor doesn’t come to a halt. However, the PTO becomes totally independent of the tractor’s motion once the PTO is engaged. One advantage that a live PTO has over transmission PTO is that It protects both the tractor’s transmission and PTO from damages that can arise from high operating speed.
Independent PTO is very similar to live PTO. It has its own separate clutch, which makes it possible to engage the PTO without engaging the gear. This type of PTO does not depend on any other function on the tractor. An operator can engage or disengage the PTO while the tractor is moving and also when it is stationary.
There are two types of independent PTO. The two types that exist are hydraulic-independent PTO and mechanical-independent PTO. Both types feature an electrical switch for engaging and disengaging the PTO. However, the mechanical-independent has a lever clutch in addition to the electrical switch. The lever added to mechanical-independent ensures that an operator doesn’t engage the PTO accidentally.
An operator can decide to change gears while the PTO is engaged since the position of the gears does not affect the PTO. Although independent PTO protects the tractor’s transmission from damages that can arise from the excessive spinning of the PTO shaft, the tractor’s transmission can get damaged if the operator is fond of engaging the PTO while the tractor is moving at full speed. Most operators prefer the independent PTO due to the ease associated with its usage, but a few of them end up misusing the benefits that independent PTO offers.
Independent PTOs are ideal for continuous operation, and their output power is usually very high. If operators use the PTO properly, it can be used for several years without developing any fault or damage to any component of the tractor and attached implement.
What Is the Difference between Live PTO and Independent PTO?
Live PTO and independent PTO have many things in common, but they are not completely the same. The mode of PTO engagement is the major difference between independent PTO and live PTO. While it’s possible to engage independent PTOs without using the clutch, live PTOs require a clutch for engagement. Also, it’s impossible to engage a live PTO while the tractor is moving, but an independent PTO can be engaged while the tractor is moving.
All the PTO types that we mentioned above can rotate only in one direction, but they can be modified to reverse their direction of rotation when necessary. Although one-way rotation doesn’t cause problems when the PTO is transferring power to certain kinds of implements, some challenges may arise when the PTO is transferring energy to implements that can get stuck. This kind of problem can be solved by changing the direction of rotation whenever the attached implement gets stuck.
PTOs that can rotate in two directions are known as a reverse PTO. All the above PTO types can be made to reverse their direction of rotation if a PTO adapter is available. Kindly note that PTOs can’t handle high torsional force when rotating in the reverse direction. Hence the direction of a PTO should be reversed only when it is very necessary, and the PTO should not be allowed to rotate backward for too long.
Tractor PTO Shaft Types
There are two types of PTO shafts, and everyone who owns a tractor needs to know the PTO shaft type on his or her tractor. One may not see the need to identify a PTO shaft type until one needs to replace a damaged PTO shaft. Let’s mention the two PTO shaft types and show you how you can easily identify shaft type. The first PTO shaft type is known as domestic, and the second type is known as the metric.
You can identify each type by their shapes. The domestic PTO shaft is of four shapes, namely square, rectangle, round, and splined. Metric PTO shaft is of three shapes, namely star, bell, and football shapes.
Domestic PTO shaft is very common in North America, so the shaft style is usually attributed to North America. The Metric PTO shafts with star and ball shapes are attributed to Germany. The Metric PTO shaft with a bell shape is attributed to Italy. Each of the PTO shaft styles (shape) comprises many series, which vary in PTO shaft length and sizes. After one has identified shaft type, one can measure one end of its cap to another at the U-joint and the external diameter of the bearing cap in order to know the shaft series.
How Does a PTO Work on a Tractor?
We’ve already mentioned that PTO transfers power from the engine to an attached implement. Now you know what PTO does, but you probably don’t know how it works yet. We will show you how PTO works on a tractor.
The input shaft of the PTO taps energy from the tractor’s engine and transfers it to a hydraulic pump. The hydraulic pump then uses the energy to create pressure, which forces hydraulic fluid to flow until it reaches hydraulic equipment where it does useful work. Some equipment that a PTO can operate includes cotton pickers, mowers, and harvesters.
Since there are different types and series of PTO shaft, a PTO may be used only for implements that match its shaft type. Also, it’s important to note that some PTOs transfer energy faster than others. The PTOs on large tractors usually work faster and more efficiently than the ones on small tractors.
How to Engage PTO on a Tractor?
If your tractor has a transmission PTO or live PTO, you should set the transmission to neutral and engage parking break before you proceed to the steps we are about to mention. If your tractor has an independent PTO, you may proceed to the steps below without stopping the tractor, but ensure the tractor isn’t moving at full speed.
For transmission and live PTO
Start by pressing the clutch pedal down totally and let it stay in place. Thereafter, you should shift the PTO switch to “ON” position. The PTO switch is usually positioned on the dashboard. Keep holding the clutch pedal down for about 5 seconds to allow the PTO to engage properly. Release the clutch pedal slowly after 5 seconds. An indication light may come up beside the PTO switch when the PTO is successfully engaged.
For independent PTO
Independent PTO is quite easy to engage because you don’t need to bother yourself with the clutch. To engage an independent PTO, you should start by shifting the PTO selector lever away from the ‘OFF” position. Thereafter, you should flip the PTO switch to the “ON” position. The PTO selector lever and PTO switch are usually positioned on the right side of the operator’s seat.
Kindly note that some independent PTOs have only a PTO switch in the form of a lever and the PTO will engage as soon as you switch the lever to the “ON” position. The tractor models that feature both selector lever and PTO switch are designed purposefully to minimize the risk of accidental engagement.
If you follow the above steps properly, the PTO won’t vibrate excessively or make loud grounding sounds after you engage it. Kindly note that it’s important for you as an operator to protect fellow humans while you are engaging the PTO. It would be best if you verified that nobody is dangerously close to the PTO before you engage it as it may injure anyone whose cloth or body part gets caught within the rotating PTO shaft.
Tractor PTO RPM
RPM means revolution per minute, and it measures the speed of a rotating shaft. All tractor PTOs have standardized RPM. Before the year 1958, PTOs had a standardized speed of 536 rpm. The standard PTO speed was later changed to 540 rpm as the new speed increased the output power of PTO without increasing fuel consumption and noise. A new speed of 1000 rpm became the second standard in the same 1958 to provide higher power for certain operations.
One can easily know the rated RPM of a tractor PTO by examining the PTO shaft. Any PTO shaft that measures 1 38 inches and has 6 splines is meant to rotate at 540 rpm. A PTO shaft meant to rotate at 1000 rpm can either measure 1 34 inches and have 20 splines or measure 138 inches and have 21 splines.
Most tractors have a tachometer that measures both the engine speed and the PTO speed. The tachometer won’t display the PTO rpm directly. Instead, it will show the engine speed. Once the engine speed is known, one can proceed to determine the PTO speed since the PTO rpm is always expressed as a percentage of engine rpm. The tachometer usually indicates the engine speed that will rotate the PTO at the standard speed.
The most tachometer can indicate when the engine speed is too high for PTO to rotate at standard speed. If an operator allows the PTO to rotate above the rated rpm for too long, the PTO drive shaft can become twisted. Hence, it’s important to allow the PTO to rotate at the rated rpm. Kindly note that the PTO speed depends only on the engine speed and not the tractor’s ground speed.
Which Direction Does a Tractor PTO Turn?
The International Organization for Standardization (ISO) stated a standard direction for PTO rotation. All PTOs need to turn in the same direction because an implement attached to a PTO can get damaged if the PTO rotates in a direction that doesn’t match what the implement requires. Such damage is avoidable if all PTOs are designed to rotate in the same direction.
According to ISO standard, a rear-mounted PTO rotates clockwise when an observer who seats in the operator’s seat is facing the PTO while it rotates. That means an observer who is standing behind the tractor will see the PTO rotating counterclockwise.
The ISO has a standard for front-mounted PTO also. The standard says that a front-mounted PTO should turn counterclockwise when an observer who seats in the operator’s seat is facing the PTO while it rotates. However, the International Organization for Standardization is a bit relaxed on the standard for the direction of PTO rotation, which is why front-mounted PTO on tractors made in Germany and Italy turn clockwise, and not counterclockwise like the ones made in other countries.
It’s important to note that residents of North America, Britain, and a few other places prefer front-mounted PTO to rotate in the same direction as the rear-mounted PTO so that they can readily attach rear implements to front-mounted PTO and vice versa.