It is very important to have specific information to select the proper Power Take-Off (PTO) to match the transmission on a vehicle. A PTO is not transferable from one vehicle application to another especially with different transmissions. PTOs are available in many sizes and provide various capabilities that are tailored to fit the specific context of the application.
The following ranges of categorized sizes of PTO Series are as follows:
- Medium duty – mechanical and hot shift – 442, 489, 272, 282
- Heavy duty – mechanical and hot shift – 660, 680, 280
- Extra heavy duty – 870, 890, 823
- Forward and reverse operation units – 340, 352 & 863
- Rear mounts –524, 541
It is recommended to begin analyzing a PTO application using pre-determined necessary technical information about the work output and installation requirements. Go through the following steps to specify a PTO.
- Determine the transmission information being used (i.e. automatic or manual, make, model, side of installation). Parker Chelsea has an application guide that will help organize the necessary information needed. There are identification tags on the transmission itself that provide the make and model of the transmission which is required for the application worksheet.
- Determine what type of equipment is being driven by the PTO (i.e. hydraulic pump, winch, blower).
- Find the input horsepower (HP) required of the driven equipment. The power requirements of the driven equipment should be provided by the manufacturer of the driven equipment.
- Find the desired operating speed of driven equipment. This will be determined by the driven equipment operating parameters.
- Establish the approximate engine speed desired during operation or PTO ratio (if known). PTO speed is stated as a percentage of engine speed. An example being, required pump speed of 1000 RPM and having an engine operating speed of 1500 RPM. The percentage of PTO to engine speed would be calculated to approximately two-thirds, or approximately 67 percent (e.g. 1000/1500 = 66.67, or 67%).
- Define the direction of the Driven Equipment Shaft Rotation with there being two choices, engine and opposite-engine. The PTO requirements will be determined by the driven equipment. It is important to note the PTO output shaft rotation listed on the application page is in relation to the vehicle crankshaft rotation as viewed from the rear of the vehicle. (See Figure 1).
- Clarify the type of connection between the PTO and driven equipment with there being a remote and direct connection.
- Define the duty cycle as intermittent or continuous. Intermittent duty cycles are defined as PTO operations that last for less than five minutes in any fifteen-minute period. Conversely, continuous duty cycles are defined as PTO operations for more than five minutes out of every 15. If an intermittent PTO is used for continuous operation, the required torque must be divided by .70 to get the torque requirement for the driven equipment. The PTO will need to de-rated if it was not designed for continuous duty.
- Determine if there are reverse gear requirements (yes/no).
- Determine the type and size of the PTO output required (i.e. driveshaft – size of output required, direct mount pump – mounting flange and shaft type/size).
Here are useful formulas to help Specify a PTO:
- Pump Output Horsepower: HP = (GPM x PSI) / 1,714
- Pump Input Horsepower: HP = (GPM x PSI) / (1,714 x E)
- Pump Input Torque (Lbs. Ft.): T = CID x PSI / 75.63
- Gallons Per Minute: GPM = (CID / 231) x (RPM)
- Cubic Inches Displacement: CID = (GPM x 231) / RPM
- Horsepower: HP = (T x RPM) / 5,252
- Flow in GPM using PTO: GPM = (Engine RPM x PTO%) x (CID / 231) x E
- CCM Conversion: CCM = CID x 16.39
- CID Conversion: CID = CCM x .06102
- PTO Ratio Calculator = Pump RPM / Engine RPM
Figure 2 (Remote on top, Direct on bottom)
While not all information is always available, here is an information guideline that can get you started with the right information to help you select the right PTO for your application.
It is important to remember when the appropriate PTO has been selected through the concluded gathered information, review the application guide and make sure that all the necessary information has been included. When searching for a PTO in a catalog, please remember to read the footnotes as there may be additional information to consider for specifying a PTO. This can include transmissions not being able to withstand torque capacity of the PTO and the application or some other unique feature of the unit may be mentioned through the footnotes.
To further investigate what different PTOs are being offered, including the new 210 series PTO for the 2020 Ford Super Duty 10R140 Transmission, be sure to check out www.parker.com/chelsea to learn more.
This article was contributed by Michael Mabrouk, marketing leadership associate, Chelsea Products Division, Parker Hannifin Corporation.