Road planers, dredges, and other equipment require power from some sort of engine in order to perform their designed function. Without a power take off, it would be necessary to add a second engine to provide the power necessary to run hydraulic pumps and other driveline attached equipment.
Adding a second engine simply is not practical, which makes power take off (PTO) a valuable element in providing power to secondary functions. To recognize their value requires a better understanding of these systems, their various types, and their various applications.
Understanding Power Take Offs
A PTO is a device (mechanism) usually seated on the flywheel housing, which transfers power from the driveline (engine) to a secondary application. In most cases, this power transfer applies to a secondary shaft that drives a hydraulic pump, generator, air compressor, pneumatic blower, or vacuum pump. Power take offs allow mobile crushing plants, road milling machines, and other vehicles to perform secondary functions without the need for an additional engine to power them.
Selecting the Right PTO
PTO choice is critical in order to provide sufficient power to the auxiliary equipment without severely limiting the primary function of the prime mover. Selection of a power take off requires specific information relating to the application and the power needs of the secondary or driven component.
Here is a quick list of considerations for PTO selection:
- Torque and horsepower requirements of the driven component
- Intermittent or continuous operation
- Application usage
- Speed requirements of the driven component
- Mounting face dimensions and options
- Space allocation
- Method of PTO engagement
Having these specifications available makes the proper selection of a PTO a simple task.
PTO Torque and Horsepower Requirements
Speed and rotation requirements of a PTO are among the most important specifications in the list above, with speed being necessary for calculating torque. The torque and horsepower requirements of the driven component are critical for optimal performance.
In most cases, the owner’s manual of the driven component will provide this information, but calculation of these requirements, if necessary, is relatively simple using two basic formulas.
- HP = GPM x PSI ÷ 1714
HP (horsepower) = GPM (pump flow in gallons/minute) x PSI (pump pressure required pounds/inch) ÷ 1714 (conversion factor to yield HHP or hydraulic horsepower). This formula provides the horsepower requirement for the driven component, used in calculating the torque requirement.
- T = HP × 5252 ÷ RPM
T (torque) = HP x 5252 (the rpm rate where both torque and horsepower intersect) ÷ RPM (RPM rate of the drive shaft of the driven component).
Keep in mind that these calculations only apply to PTOs that drive a hydraulic pump. In cases where power take off is providing power to a different type of drive component, it will require the manufacturer’s specifications of the driven component.
The Different Types and Industrial Applications of PTOs
Though they perform the same general function—transferring power from the primary drive shaft to a secondary drive shaft for a driven component—there are a variety of different PTO types that each serve specific industrial applications. This is why WPT Power supplies OEM’s units in agricultural, energy, off-highway, and road building sectors, among others.
The distinguishing characteristic of this type of PTO is the designed removal of the pilot bearing. Benefits of this design feature come with an increased side load capacity, reduced inventory, increased uptime and engine life, and a quicker and easier installation. Industrial uses of the Pilotless Mechanical PTO include:
- Asphalt grinders
- Irrigation pumps
- Water blasters
- A wide variety of other heavy-duty industrial/construction applications
This type of flywheel PTO applies to either inline or side load uses. It includes a sealed-for-life pilot bearing, utilizing a lever-actuated manual clutch. The benefit of this type of PTO is a straightforward installation minimizing downtime and maintenance requirements. This type most commonly applies to:
- Engine packages
- Pump jacks
- Irrigation pumps
- Wood chippers
This is a rugged, high-capacity type of power take off used in a broad range of industrial functions. Characteristic of this type of PTO are the sheaves between heavy-duty spherical roller bearings designed to utilize their full load potential. This bearing arrangement reduces the damage produced by crankshaft loading. Among the most common applications for the Type 1 PTO are:
- Mud pumps
- Rock Crushers
The design of the Type 2 PTO features a heavy-duty side loading capacity using large spherical roller bearings. Actuation of this PTO can be either hydraulic or pneumatic. It is self-adjusting and removes the need for the pilot bearing inside the engine flywheel. Features include reduced maintenance, less chance of premature failures, and improved engine and bearing life since there is no direct loading to the crankshaft. Common applications for Type 2 PTOs include:
- Road building equipment (milling machines, stabilizers)
- Portable Rock Crushers
- Tub grinders
Type 1 vs Type 2 PTO Clutches
The difference between these two PTO clutch types is in their different functional designs.
- Type 1 PTOs include 2-4 times the side load capacity of a Type 2 PTO, so they best suit heavier, industrial applications with high impact loading.
- Type 2 PTOs allow for high-capacity loading in a smaller footprint and are best for light-to-medium capacity side loading.
This PTO design eliminates the need for the pilot bearing while providing increased side loading or inline potential. Its engineering accommodates the most demanding requirements of high-loading diesel engines. Features include simple installation, reduced downtime, and improved engine service life. This style PTO is used for in-line applications with its hydraulic and air fittings mounted near the bell housing instead of at the rear of the shaft like type 1 and type 2.
The GM Style PTO reduces maintenance time and cost by using sealed main bearings and eliminating the need for the pilot bearing. This PTO is designed to mount directly to GM® style engines without the need for any special PTO or engine adaptations. Notable features include clutch adjustments using an external ball stud and jam nut adjustment points.
Also known as “flat-faced” style PTOs, incorporates similar design characteristics, features and benefits to the GM style PTO. It is a spring-loaded clutch making it easier to engage and disengage than over the center power take-offs. Typical uses include irrigation units, brush chippers or any other gas or diesel engine applications.
Common Operational PTO Clutch Problems and Solutions
PTOs are relatively simple mechanical units with few operational problems, but there are a few common issues associated with them—each with straightforward solutions. Here are some of the most frequently encountered issues:
- Clutch will not disengage. Slipping and overheating are common causes of this issue. To fix this problem, disassemble, inspect, and replace if necessary.
- Clutch will not stay engaged. Improper adjustment is the most common cause, remedied through adjusting engagement torque.
- PTO is hot. Several issues contribute to overheating (220º F measured by infrared thermometer at the bearing carrier), including too much or too little grease, excessive side load, or a new installation. Follow proper lubrication specifications and reduce the side load to remedy the first two problems. A newly installed PTO will run hot for the first 10-20 hours of operation after installation.
Get the Right PTO for Your Needs at WPT Power
Getting the appropriate PTO to meet your operational needs is a priority at WPT Power. Manufacturing of our PTOs takes place in our ISO 9001:2015 facilities where all our products are engineered to meet the highest standards of quality demanded by our customers. ABS type approvals and ATEX certifications minimize risks, time and costs.
When you call for technical questions, application design or to place an order, you talk to a real person. Sales, Customer Service and Engineering are available without all the phone menu options and department shuffling. WPT serves many types of markets globally that includes:
- Steel and Metal Forming
- Road Building
- Paper Converting
Our broad range of products are developed to meet most requirements on standard industrial applications. Custom or modified PTOs are available for original equipment manufactures requiring specialized design and where volume is needed.
Power take offs play an important role in allowing for the transfer of power from a primary mover to a secondary or driven component without the need for an additional separate engine. Various PTO types serve in a multitude of applications from smaller scale operations to major industrial and construction projects. Choosing the right PTO for a specific application is critical to proper performance of the driven component.
Contact us for more information about the range of solutions offered by WPT Power Corporation, for assistance in selecting the right PTO to fit your specific application, or to request a quote from one of our experts.