A power take-off (PTO) is a mechanical device that transfers power from an engine or other prime mover to secondary equipment. In industrial applications, that transferred power can operate hydraulic pumps, generators, compressors, blowers, chippers, crushers, fans, and other driven components without requiring a separate engine.
Power take-offs are used across equipment such as road milling machines, rock crushers, dredges, wood chippers, irrigation systems and other heavy-duty machinery. Depending on the application, a PTO may transfer power through a shaft or belt-driven system and may use mechanical, hydraulic, or pneumatic engagement.
There are several types of industrial PTOs, including Pilotless® Mechanical PTOs, traditional Mechanical PTOs, Type 1 and Type 2 PTOs, Pilotless® Over-the-Shaft PTOs, GM® Style PTOs and Automotive Style PTOs. The appropriate design depends on factors such as engine torque and horsepower, operating speed, side-load requirements, available space, drive configuration, and equipment duty cycle.
In this guide, we’ll explain how a power take-off works, the major types of PTOs and their applications, how PTO torque requirements are calculated, what to consider when selecting a PTO, and how to troubleshoot common PTO clutch problems.
Understanding Power Take-Offs
Power take-offs allow mobile crushing plants, road milling machines, and other equipment to transfer engine power to perform primary and auxiliary functions. A PTO is a device (a mechanism) usually seated on the flywheel housing, which transfers power from the engine to a secondary application.
In most cases, this power transfer is applied to a secondary shaft or belt system that drives a hydraulic pump, generator, air compressor, pneumatic blower, vacuum pump, chipper disc, crusher drum, or fan.
Selecting the Right PTO
PTO choice is critical for providing sufficient power to the equipment without severely limiting the prime mover’s main function. Selecting a power take-off requires specific information about the application and the power requirements of the secondary or driven component(s).
Here is a quick list of considerations for PTO selection:
- Torque, power, and speed of the engine
- Intermittent or continuous operation
- SAE flywheel housing and flywheel sizes
- Method of PTO engagement
- Drive configuration (belt or shaft)
- Space allocation
- Application usage
Having these specifications available makes the proper selection of a PTO a simple task.
PTO Torque and Horsepower Requirements
Torque, power, and speed of the engine are among the most critical specifications in the list above. Knowing this information is essential for optimal performance.
In most cases, this information can be found on the engine specification sheet or data label affixed to the engine. Once you have this information, determining the recommended torque capacity for the PTO is a relatively straightforward calculation using the formula below:
- RTC = Rated Engine Torque x SF
RTC (recommended torque capacity) is the calculated input torque capacity required from the PTO. SF (service factor) is the ratio between the PTO’s rated input and the engine’s rated output and is based on the application. It ranges from 1.5 for light-duty to 1.75 for medium-duty and 2.0 and above for heavy-duty applications. Please consult WPT Power for details on selecting the proper service factor.
If you do not know the rated torque output of the engine, you can estimate the value using the horsepower (HP) and speed of the engine using the formula below:
- RTC = (HP x SF)/RPM x 5252
HP is the rated engine power. RPM is the speed of the engine at the rated power.
Keep in mind that these calculations are estimates and should only be used to provide tentative selections. For a complete application review and guidance, please get in touch with WPT Power Applications Engineering.
The Power Take-Off clutch applications shown are a mobile track chipper, an irrigation pump package, and a trailer-mounted jetter.
The Different Types and Industrial Applications of PTO Clutches
Though they perform the same general function—transferring power from the primary drive to a secondary drive shaft for a driven component—there are various PTO types available that serve specific industrial applications. These diversifications are why WPT Power supplies OEM’s units in agricultural, energy, forestry, and road building sectors, among others.
Pilotless® Mechanical PTO
The distinguishing characteristic of this type of PTO is the intentional removal of the pilot bearing. The benefits of this design feature include increased side load capacity, reduced inventory, increased uptime and engine life, and quicker, easier installation. This PTO can be used in inline or sideloaded setups and features the time-tested lever-actuated mechanical over-center clutch.
Industrial applications of the Pilotless® Mechanical PTO include:
- Chippers
- Rock crushers
- Pump jacks
- Water blasters
- A wide variety of other heavy-duty Road Building & Construction machines
Mechanical PTO
This type of flywheel PTO is a staple in the industry. It includes a sealed-for-life pilot bearing and utilizes the same lever-actuated manual clutch as the Pilotless. The benefit of this type of PTO is compatibility with existing units.
This type most commonly applies to:
- Engine packages
- Irrigation pumps
- Barge pumps
- Hand-fed wood chippers
Type 1 PTO
This is a rugged, high-capacity power take-off used in a broad range of industrial functions. The main characteristic of this type of PTO is the sheave mounted between two heavy-duty spherical roller bearings. This design is engineered to maximize the bearings’ potential under full-load conditions.
Among the most common applications for the Type 1 PTO are:
- Mud pumps
- Dredges
- Rock crushing plants
- Whole tree chippers
Type 2 PTO
The design of the Type 2 PTO features a heavy-duty side-loading capacity using sizeable spherical roller bearings. The actuation of this PTO can be configured either hydraulically or pneumatically. It is self-adjusting and removes the need for the pilot bearing inside the engine flywheel. Features include reduced maintenance, a lower risk of premature failure, and improved engine and bearing life, since there is no direct loading on 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 lies in their distinct functional designs.
- Type 1 PTOs have 2 to 4 times the side-load capacity of a Type 2 PTO, so they are best suited to heavier, belt-driven 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.
Pilotless® Over-the-Shaft PTO
This PTO design eliminates the need for the pilot bearing while providing increased side loading and hydraulic or pneumatic actuation in an inline application. 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 of PTO has the hydraulic/pneumatic fittings mounted on the bell housing rather than at the rear of the shaft, as with the Type 1 and Type 2.
GM® Style PTO
The GM Style PTO reduces maintenance time and cost by using sealed main bearings and eliminating the need for a pilot bearing or bushing. Designed to mount directly on GM®-style engines, these operate without the need for any specific PTO or engine adaptations. Notable features include clutch adjustments using an external ball stud and a high-capacity version for belt-driven setups.
Common applications for the GM-style include:
- Irrigation pumps
- Sawmills
- Wood chippers
Automotive Style PTO
Also known as “flat-faced” style PTOs, they incorporate similar design characteristics, features, and benefits of 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
- Engine packages
- Other gas or diesel engine applications
Common Operational PTO Clutch Problems and Solutions
PTOs are relatively simple mechanical units with minimal operational problems. There are a few common issues, but each has a straightforward solution. Here are some of the most frequently encountered issues:
- The clutch will not disengage. Slipping and overheating are common causes of these issues and can be fixed by disassembling, inspecting, and replacing components as needed. To prevent this type of problem, be sure to check and adjust the engagement torque often.
- The clutch will not stay engaged. Improper adjustment is the most common cause, remedied by adjusting engagement torque.
- PTO is hot. A newly installed PTO will run hot for the first 10 to 20 hours of operation after installation. Several issues contribute to overheating (220º F measured by an infrared thermometer at the bearing carrier), including too much or too little grease, excessive sideload, or a new installation. Follow proper lubrication specifications and reduce the sideload to remedy the first two problems.
Get a Quality PTO to Meet Your Needs at WPT Power
Delivering a quality PTO to meet your operational needs is a priority at WPT Power. That is why our PTO manufacturing and engineering take place in our ISO 9001:2015 facilities. Here, all our products are designed to meet the highest standards of quality our customers demand.
In-house testing facilities and certification, including ABS, DNV, and ATEX, help to minimize risks, time, and costs.
Unmatched Customer Service, Sales, and Engineering
Our unmatched capabilities in customer service, sales, and engineering set us apart from the competition. The friendly, knowable WPT staff are available without all the phone menu options and department shuffling that has become standard with these larger companies. When you call for technical questions, application design, or to place an order, you talk to a real person. It’s as simple as that.
Global Markets and Service
WPT serves many types of markets globally, including:
- Steel and Metal Forming
- Marine
- Agriculture
- Forestry
- Dynamometer
- Energy
- Road Building
- Mining/Aggregates
- Paper Converting
We also have an extensive network of knowledgeable distributors to ensure your product needs are met quickly and with minimal downtime – when and wherever you are, worldwide.
Custom or Modified OEM Solutions
Our broad range of products has been developed to meet most of the requirements for standard industrial applications. Custom or modified PTOs are available for original equipment manufacturers (OEMs) requiring specialized design and where volume is needed.
WPT’s sales and engineering teams work directly with the OEM engineering team to design a solution to meet the application requirements. If you don’t see a standard WPT product that fits your application, don’t hesitate to get in touch with us today to discuss custom solutions.
More Information
Power take-offs play an essential role in transferring power from a primary mover to a secondary or driven component. Various PTO types serve many applications, from smaller-scale operations to major industrial and construction projects. Choosing the correct PTO for a specific application is critical to the proper performance of the driven component.
Contact us for more information about the range of solutions offered by WPT Power Corporation, assistance in selecting the right PTO for your specific application, or a quote from one of our experts.
Power Take-Off FAQ’s
How do I choose the right power take-off for my equipment?
Choosing the right power take-off starts with understanding the engine and driven equipment requirements. Important considerations include engine torque, horsepower, and operating speed; whether the equipment will operate intermittently or continuously; SAE flywheel housing and flywheel dimensions; PTO engagement method; belt or shaft drive configuration; available installation space; and the intended application.
The PTO must also have sufficient torque capacity for the application. Because service factors vary with operating conditions and duty level, PTO sizing should account for more than just engine horsepower. Heavy-duty or high-impact applications may require greater torque capacity and side-load capability than lighter-duty equipment. For applications where PTO sizing is uncertain, an application engineering review can help determine the appropriate configuration and capacity.