PTO shafts - how to select them for agricultural machinery? We're rolling out the topic from scratch!

PTOs, or power take-offs, are components that mediate the transmission of power. It can be said that they are an essential link between the driven machine and the tractor. Moreover, they function under such names as: “shafts” or articulated-telescopic shafts”, “power transmission shafts”, “power transmission shafts” or “power take-off shafts”, which certainly doesn’t make it any easier. But how do you match them with agricultural machinery? We answer!

Construction and division of articulated-telescopic shafts

Let’s start with the fact that articulated-telescopic shafts are built from such elements as:

• Bearings – they include an outer and inner ring, as well as rollers or balls to keep the rings next to each other; bearings minimize friction and wear as the shaft rotates;
• Gearboxes – thanks to them it is possible to change the speed of the shaft, they are used when the engine speed is too high or too low for shaft-driven components;
• fastening elements – these include nuts and bolts, they allow you to stably and securely attach the shaft to other components of tractors and agricultural machinery;
• couplings – thanks to them it is possible to disconnect and connect shafts to other components; as for disconnection, it is done, for example, when maintenance or repair is needed;
• Shaft hubs – they are usually metal and take different shapes and sizes – it depends on their application; they allow to connect the shaft with other elements, so for example with clutches, gears or bearings,
• Flywheels – reduce vibration and increase the stability of engine operation; allow storage of kinetic energy when the engine is running.

And here is the simplest division of the rollers:

• Milled shafts (with our store milled here all );
• rollers on the so-called. “lemon” (you will not find them in our store, they have the shape of a lemon);
• Rollers with a triangular tube – are equipped with a profiled tube with a shape similar to a triangle.

Add that Exparto’s PTO shafts are heat-treated (hardened)

Power take-offs are also used in machines

How to select articulated-telescopic shafts for agricultural machinery?

Note the torque Nm

When it comes to choosing the right PTO shafts, the first thing to pay attention to is whether the torque of the driven machine and the shaft are the same. Combining a shaft with a machine with a higher such parameter is simply a mistake. When it comes to shafts, it is usual to meet models with a speed level of 540 to 1000 revolutions per minute. However, the shaft should be selected individually for each machine. For example, a 540-rpm shaft is usually needed for a lawn mower, and a 1000-rpm shaft for large manure spreaders.

Consider the design of articulated-telescopic shafts

Another important issue is the design of the rollers. Let’s start with the fact that the basic models, with cross joints, can definitely boast a low price. They carry the drive at a 25-degree angle under heavy load. At lower speeds, they also often allow 45-degree incline operation, such as in feed wagons.

When do we recommend, on the other hand, a shaft with two wide-angle joints? First of all, when the distance between the machine and the tractor is small and a larger angle is formed between the longitudinal axis of the machine and the longitudinal axis of the shaft. In a situation where the distance is greater and there is no strong breakage of the machine, a shaft with one hexagonal joint, which is inserted from the side of the device, will be a hit. It has double crossbars located side by side, which allows for a larger working angle. Shafts with one joint are definitely more popular than those with two.

It is also important to know the specifics of the equipment in question, When it comes to trailed machinery, such as rotary mowers or balers, a wide-angle PTO shaft will also work best. Suspended machines, on the other hand, need rollers with standard joints, in which the angle for continuous operation is 25 degrees.

The homokinetic articulated telescopic hexagonal shaft can be successfully used on headlands – work will be safe as a result. It is equipped with a joint that is connected by a wheel to a fork, which makes the angle between the device and the tractor divided in half. This means that both parts of the shaft (both driving and driven) operate at the same angular speed. The CV joint allows momentary operation at angles of up to 80 degrees. We should add that information about the parameters of the shaft that is designed to drive a particular machine should be included in the instruction manual for that machine. They are often used in sprayers.

Consider the length of the shaft

Currently, you can find mainly shafts with standardized lengths on the market, which makes them able to work with a variety of machines. If the shaft is not a factory part of the machine in question, the length of the shaft can be tested. For suspended machinery, the length of the shaft should be as long as necessary to connect it to tractors in the lowest position during operation. Moreover, the shaft should twist so that the machine can be lifted into the highest transport position. On the other hand, in the case of trailed machines, it is necessary that the shaft allows the aggregate to make a proper turn.

It is worth noting that for equipment such as rakes, tedders, suspended spreaders, it is necessary to select shafts carrying a nominal 250 Nm. On the other hand, for machines such as field forage harvesters, rotary harrows or balers, you need to use a shaft with a nominal torque of 400 or 540 Nm.

Remember the right tip

It is also important to choose the right shaft end. To do this, pay attention to the type of bits that protrude from the machine and the tractor. The most popular here is the six-milling spigot (six grooves on a spline shaft), which is found, for example, on Ursus tractors. The shaft should also be adjusted to different splines (to different diameters associated with different manufacturers (standards). If you want to use the shaft to connect a machine with a different discharge from that on the tractor, you can use a so-called “shaft”. reduction. These are specially designed pins, equipped on one side with splines for the tractor’s PTO shafts. On the other side, on the other hand, there is a crotch matched to the PTO that drives the machine. However, do not “combine” like this with heavy machinery. Then it is definitely better to replace the tip on the tractor or swap the forks on the cross shaft. The use of such elements in the event of a breakdown or accident ends up in not paying compensation.

It is also important to remember that you should swap the shaft for another one when the working width of the machine changes – then you need more power. This, in turn, means that the torque of the shaft must increase, at the same speed. The best solution here, therefore, will be a shaft of higher nominal torque.

When choosing a shaft, it is also a good idea to pay attention to whether it is equipped with guards. They limit human contact with moving PTO components. If the shaft lacks a cover or is damaged, there is a risk of an accident, even fatal due to the grasping of various items of clothing.

Summary

As you can see, choosing PTO shafts may not be easy, but it’s certainly possible. We hope our article will help you choose the best model for your machine. If you are already looking to replace your PTO shaft, see what PTO shafts we have at Exparto.