Understanding power take-offs

Power take-offs, or PTOs, removes the need for a secondary engine to power a vehicle. Let’s continue to delve into the mysteries of power take-offs.

What is a power take-off?

A PTO is a gearbox that transfers power from the engine to secondary equipment through the rotation of PTO gears and the vehicle transmission gears meshing. For example, power from a truck’s engine is used to power the equipment on the vehicle.

Types of PTOs

PTOs are generally categorised as a side-mount, rear-mount, and top-mount.

What determines the PTO output speed?

How fast a PTO spins depends on the internal gearing of the PTO and the internal ratio of the transmission as it relates to the PTO driver gear. For PTO operation in an automatic transmission, it’s necessary to maintain the minimum input speed higher than torque converter lock-up.

How do you find the input horsepower for the equipment?

Horsepower is the capacity measurement for doing work per unit of time. Torque is the energy necessary to perform a twisting or turning motion. When specifying a PTO, horsepower is used in an equation to determine the torque requirements for the proper PTO.

The equation is: Torque (T) = horsepower (HP) x 5,252 / revolutions per minute (RPM)

Hydraulic PTO vs mechanical shift-type PTO

A hydraulic shift PTO needs a clutch mechanism to engage traditional automatic transmissions. A mechanical shift PTO engages by shifting one gear into another through a lever, cable, or air pressure and applies to manual transmissions.

Common parts and terms relating to PTOs

Spur gears have teeth cut straight across the gear face.

Helical gears have teeth cut on a diagonal angle across the gear with a right or left-hand slant. Therefore, in combination, one helical gear must slant to the right and the other to the left.

A pitch line is a point on the gear tooth halfway between the base and the tip of the tooth.

Pitch line velocity is the speed of rotation in a gear measured at the pitch line. It is measured in metres per second.

The gear ratio is established when you divide the number of teeth in the driven gear by the number in the driving gear.

PTO maintenance

Periodic PTO maintenance is essential for the correct and safe operation of the PTO. Therefore, this is a suggested maintenance schedule.

Daily: Check the air, hydraulic, and working mechanisms before operation.

Monthly: Inspect the PTO for possible leaks. Tighten air, hydraulic and mounting hardware as required. If necessary, ensure that splines are adequately lubricated.

Contact Vortex Transmissions

If you want to know more about power take-offs or need repairs done to a PTO, get in touch with a Vortex Transmissions representative today. We specialise in Chelsea PTO repairs.

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