Power Take-Off Systems

Spec'ing power take-off systems


Choosing the wrong power take-off (PTO) is a recipe for disaster. However, by properly selecting, installing and maintaining the PTO it should give tremendous life and value, and avoid equipment problems down the line. The first step in the process is to decide upon the correct power take-off for your application and truck, says Jeff King, marketing manager, Chelsea Products Division of Parker. www.parker.com.

Parker, the global leader in motion and control technologies, has eight product groups which span the core motion technologies - electromechanical, hydraulic and pneumatic. The groups offer a full complement of fluid handling, filtration, sealing and shielding, climate control, process control and aerospace technologies.

“Proper selection will go a long way in establishing a lengthy, productive lifecycle with little or no vehicle downtime resulting from a mismatched PTO,” he says.

TRANSMISSION DETAILS

“First, nail down transmission details,” advises King

Essentially, a PTO serves as an extension of a vehicle’s transmission. It transmits its power to the output shaft.

“Therefore, it is imperative to begin the selection process by noting the make and model of the transmission about to receive a PTO,” he says.

More and more vocational vehicles are equipped with automatic transmissions, which have special PTO application considerations. With automatic transmissions, King says the PTO choice should include an option for pressure lubrication.

“Most automatic transmissions are not designed to concentrate the lubrication fluid near the PTO opening in quantities adequate enough to effectively lubricate the components within a PTO,” he points out. “To overcome that, Chelsea can assemble these units with special, drilled idler shafts which allow input gear bearings to be pressure-lubricated during operation.”

There may be some applications where pressure lubrication is not necessarily recommended, says King. This is the case, for example, where minimal torque requirements exist.

“But, in most vocational automatic transmission applications, a clean, cool supply of oil to the input bearings will extend PTO life.”

MANUAL TRANSMISSIONS

For those fleets using manual transmissions, pressure lubrication criteria need not be considered since the PTO is flooded with oil.

“Always take into consideration, however, that a cavity has been added onto the transmission and additional oil may be needed to bring the transmission up to its required fill level,” King says.

With manual transmissions, a broader selection of PTOs will be available.

POWERSHIFT UNITS

Most waste company fleets require a PTO that can be engaged while the vehicle is moving. These are known as powershift or hot shift PTOs.

These types of PTOs are also designed for use on automatic transmissions.

Powershift or hot shift PTOs may be shifted while the engine is running without clashing gears, even while the transmission is engaged.

UNDERSTAND CLEARANCE ISSUES

Every truck can have its challenges when mounting auxiliary equipment such as PTOs and hydraulic pumps, observes King. Depending upon the chassis, engine and transmission combinations, every truck can have a potential clearance issue.

After nailing down transmission make and model, the next item to note is the type of equipment to be driven, he says.

Since hydraulic pumps are extremely popular in the waste industry, this will serve as a good example.

Pumps, like most other PTO-driven equipment, require a fixed amount of horsepower and input speed (rpm) to produce a required flow of fluid measured in gallons per minute (gpm), explains King. Pump makers can supply these figures.

The formula to determine the horsepower required to operate a pump is: Hydraulic HP = (GPM x PSI)/1,714 x Pump Efficiency

PTOs are typically rated according to torque capacity. In simplest terms, torque is that amount of force needed to make something move or run. Torque is directly related to horsepower and rpm.

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