What You Should Know
Understanding your PTO may greatly improve the performance of the system and reduce the opportunity to waste time and money.
By Mikel Janitz
When you are ready to fit a truck for a mobile hydraulic power application with a power take-off (PTO), there are some basic questions that you need to know to help ensure that you get the productivity, reliability and longevity from the PTO that the end operator needs.聽 By following these steps, the guys in the shop can size the right power take-off to fit the transmission and to fit the correct pump. There are about eight steps needed to make sure that you get what you need and ensure that it will fit up with minimal problems. Everyone can appreciate as few problems as possible.
The fellas in the garage asked the other day about their truck and a refuse PTO applications. They had someone come in wanting to fix the equipment. The truck had been out of service for a while and was not in good working order when they parked it. The tricky part was that no one knew where the PTO and pump were. They got up under the truck and saw that the stickers had fallen off a long time ago. They did not know what was on there. Given that situation, they need to follow some basic steps to select the right PTO and size the correct pump for it. As far as mobile power PTOs go, there are about eight steps or questions the technician needs to answer to ensure that they get what they need.
#1: What is the Make and Model of the Transmission?
If no other question is asked, this is the most important item to know. The PTO fits in an aperture with a matting gear that meshes with the transmission gear. If this is not right, then there are huge consequences. First and foremost, the wrong gear can severely damage a transmission and cost thousands of dollars to repair or replace. Secondly, there is an aperture on the tranny. You need to know if it is a 6-bolt, 8-bolt or 10- bolt or it just will not fit. Most PTO manufacturers have Web sites to help define this or a customer service representative who can assist you.
#2: What Will the PTO Drive or Operate?
There are basically two options鈥攄irect mount the PTO to a pump or have the PTO with a flange, which will connect to a driveline. This is very important. The output on the PTO is typically an option when you order it and you need to know if you are driving a gear pump or driveline. If it is a gear pump, then there are about four standard types鈥擲AE 鈥淏鈥�,鈥滲B鈥� and 鈥淎鈥� plus ISO.聽 Then there are DIN and SAE 1300 and 1400 flanges typically on a 1 录鈥� shaft.聽 Make sure you talk to your customer service rep to ensure you get what you need.
#3: What Speed (RPM) Do You Want to Run The Pump, Blower or Winch?
The vast majority of applications for PTOs are when the truck engine is idling or parked. There are also some applications for a moving vehicle. Either way, you need to know the engine鈥檚 RPM so that the PTO ratio can be determined. This is important so you can run the pump or other application at optimal speeds and efficiencies. If the PTO ratio is too low, then the pump鈥檚 flow rate may be slow and the system may run too slow and/or bog down the engine. This can cause the engine to stall while in operation. If the PTO ratio is too high, then you run the risk of spinning the pump too fast and burning it up. Note: it is easier to use a lower ratio and speed up the engine鈥檚 RPM than it is to have a higher PTO ratio and try to run the engine slower.
#4: Do You Know the Horsepower Needed for the Pump, Blower or Winch?
The horsepower requirement is needed as a check to ensure that you don鈥檛 underside your PTO/pump combination. It is vital to make sure that the PTO is rated for your application so you don鈥檛 burn up the bearings and reduce the useful life of the PTO and system.Also make sure to run the equipment as efficiently as possible. Time is money!
#5: What Side or Location Do You Want to Mount the PTO?
When you order a PTO, it is important to identify where the PTO goes, fits and connects to the transmission. A lot depends on the transmission鈥檚 original equipment manufacturer (OEM).聽 There are many options to choose from. Most popular transmissions fit PTOs on the bottom of the tranny with an 8-bolt PTO. The next most popular are the driver side (left) with a 6- or 10-bolt PTO. Then, the least popular are right side and top mounted PTOs. It is nice to have the options and to know your limits because vehicle space is tight and at a premium. Since this is the case, rear mount PTOs are gaining popularity here in the U.S. Rear mounted PTOs are very common in Europe. These are great solutions for tight spaces and typically easier to install and set up. Select a PTO engineered for your transmission by an OEM respected and known for their quality.
#6: What is the Rotation, Clockwise (CW) or Counter Clockwise (CCW)?
Once the PTO location is identified, it is easy to determine the output shaft rotation. However, you need to make sure that you match the CW or CCW direction to your pump, motor or winch.聽 Another option to ensure this is to get a bi-rotational pump. That way it will work in either direction. If that is not an option, then consult with the customer rep to ensure you get the output direction you need. One other option is to get a reversible style PTO if it meets your horsepower and torque requirements. There are a couple of other options to help solve location and rotation limits. One is the use of a gear adaptor, which allows the output direction to change with minimal negative effect on performance. The other option is that some PTOs are reversible so the operator can shift rotation if need be. These are common in winch applications.
#7: How Do You Want to Connect from the PTO to Pump or Winch?
This question deals with mounting style. The PTOs have many output options. For example:聽 output options can be 1 录鈥� round shaft or SAE 2/4 bolt splined shaft, to a DIN standard or SAE 1410 flange. Whatever it is, it needs to mate up from the PTO output to the next part (pump or driveline) in the system, whether that part is a winch or hydraulic motor, etc.
#8: Is this Application Going to Run for Short Periods or for a Long Time?
Continuous duty vs. intermittent duty is critical information. This depends on and is directly related to what kind of work is being done. In a nutshell, if the PTO is going to run five minutes or more in a 15 minute time frame, it is considered continuous. This is an industry norm and can be reviewed and modified by the PTO鈥檚 engineering team and application experts. Just remember this, the more the PTO is used at elevated speeds and higher torques, the shorter the life of the bearings, shafts and gears, not to mention the life of the transmission can be reduced. It is a better idea to get a more robust PTO and run it at, or below, limits if you want the PTO, pump and your transmission to last a long time.
This is quite a bit to remember, but understanding the answers to these questions may greatly improve the performance of the system and reduce the opportunity to waste time and money. A good and reputable PTO OEM manufacture will have the right people in place to help you with all your questions and concerns surrounding your truck, transmission and your application. They are only a phone call away. If you don鈥檛 want to call, reputable PTO manufactures have Web sites that can help you navigate these questions as well. They are here to help you get the most out of your mobile power system and keep you building our world.
Mikel Janitz聽is the OEM Applications Engineer for Bezares USA, a global leader in PTO design and engineering based in Houston, TX. Mikel lives in Tulsa, OK, but covers most of the U.S.鈥� mobile power industry vocations. He graduated from Oklahoma State University with a BS in Engineering and MS in Engineering Management and holds several patents. He can be reached at (918) 953-9062 or via e-mail at聽[email protected].