Friday, June 30, 2017

What is a Power Take-Off?




The Power Take-Off or PTO is a mechanical device which is mounted on the gearbox to obtain power and a determined rpm for our application. This mechanical energy from the gearbox is transmitted to the pump and converted into hydraulic energy. When selecting a PTO we should consider different issues:


 What is the transmission brand and model? 

When requesting a PTO it is very important to know the brand and the model of the transmission.

With that information, we can advise you to select the most adequate power take-off for your application.



Which PTO opening are you going to use?

Most of the industrial vehicles are supplied with one or more PTO openings. Each window may have different transmission ratios. According to the position of the window, it can classified as follows:

Side: The window for installing the PTO is on the right or on the left side of the gearbox, always looking at the gearbox from the rear of the vehicle.

Rear: The opening window is on the rear of the gearbox, most common with ZF, MB ad Volvo transmissions.

Bottom: The window is in the bottom or "belly" of the box.




What kind of equipment is to be driven by the PTO?

Based on the application, the pto shall have different outputs. The most common outputs are:

   For pump (ISO 4 holes, UNI 3 holes, SAE A, SAE B, SAE C)

Flange to connect to a transmission (SAE 1100, SAE 1300, SAE 1400, DIN 90, DIN 100, DIN 120, etc.)





What is the power required by the application?

In order to calculate the power consumption it is necessary to know the pressure and flow of our application.

What is the rotation required of the PTO?

Depending on the number of gears of the PTO, we can choose the direction of rotation.


Bezares also offers rotation reverse adapters for those cases where there are no different options.


What will be the percentage of speed required at the output of the PTO?

Depending on the internal ratio of the pto, the PTOs can be:

Simple: Also called direct. 1: 1 ratio

Multiplied: The ratio will be 1:> 1

Reduced: The ratio will be 1: <1. 

In order to calculate the final ratio you just need to multiply the transmission's output ratio by the PTO's internal ratio.





What will be the shifter’s type required?

Depending on the type of actuator, the power take-offs can be classified as follows:

Pneumatic: If the truck has air brake, it means that it has a compressor. They are usually driven at 7kg / cm2 – 8kg/cm2.

In small vehicles, where no compressor is available, it is possible to install one using the Bezares pneumatic pressure kit. It is an independent unit without maintenance, which provides a pneumatic line.

Mechanic: They are manually operated by means of a lever or cable that connects directly to the PTO's piston. With the movement of the cab's lever, the power take-off's fork moves internally and engages it.

Vacuum: When the truck has a depressor, it works through a vacuum line.

If your vehicle does not have one, it's also possible to install it using the Bezares' simple acting shifting kit.

Electric with motor: This actuator includes a small electric motor which moves a bar which diplaces the synchronizer until the pto is enganged. This system ensures always an easy engagement.

In contrast to the electric actuator with solenoid-type, the electric motor only works when engaging and disenganging the pto. This allows long working periods of time without power consume and avoiding possible damage to the vehicles battery.

Electrohydraulic: It incorporates an electrohydraulic actuator. They are normally used in the clutch PTOs for automatic Allison or Aisin gearboxes.


Article created in collaboration with Alfonso Sabbatini e Hijo S.R.L.