Power Take-Offs (PTOs) are designed to pick up engine power through rotation and transfer the power to another piece of equipment. For this to work, a piece of equipment can be mounted to the PTO or it can be connected by a driveshaft. The process begins with the PTO input gears meshing with one of the gears in a vehicle’s transmission starting the rotation. This rotation created from the engine drives the transmission and results in turning the PTO gear and rotating the PTO output shaft. Input gears must mesh properly with the transmission’s PTO drive gear for the PTO to work. But there are a series of gears that must be considered to determine the final output ratio of the PTO.

When analyzing the gears, a measurement term to be familiar with is gear pitch. Gear pitch is the measure of the size of the teeth and is determined by the number of teeth in a given area. To calculate the gear pitch, you would divide the number of teeth by the pitch diameter of the gear. Knowing the gear pitch is important since the PTO gear must have the same pitch as the transmission gear to function properly.

Another measurement term to be familiar with is gear ratio. Modification of the operating speed of the engine to the PTO driven device can be created through the gear ratio. To understand the PTO gear ratio, it measures the revolutions of the small and large gears. Looking at a smaller gear with 12 teeth driving a 24 teeth gear, the small gear makes a revolution with the larger gear only making half a revolution during the 1 small gear revolution. This means that the speed of the larger gear is half of the smaller gear, but the torque and twisting force is twice of the smaller gear.

The gear ratio in this scenario equates to the number of teeth in the driven gear (24) divided by the number of teeth in the driving gear (12). This results in a gear ratio of 2 to 1. The change in torque in this scenario is 1 to 2 resulting from dividing the number of teeth in the driving gear (12) over the driven gear (24).  With the assumption of knowing the engine horsepower and the revolutions per minute (RPM) of the smaller gear, torque can be determined.

T = Horsepower x 5252/Speed (RPM) = Lbs. Ft. Torque

(As you can see from the above photograph, the two gears would lock as so with the red marked teeth)

Product series can have multiple gear ratio options or have just one gear ratio option. To select what ratio makes the most sense, you must know the RPM you want your vehicle’s engine running at for the application and the required operating speed of the driven equipment being used in the application. The ratio of a series of gears creates the speed for the output shaft. Those gears include the input driver gear, the input ratio gear, and the output ratio gear. Their relationship to one another will determine how fast the output of the PTO is spinning in relationship to the engine. The required speed for the driven equipment must be known in order to select the proper PTO ratio. When utilizing pumps, flow rate and displacement are needed to be determined beforehand to make sure the pump input shaft will work with the given speed from the PTO.

When looking into specific product series offered by Parker Chelsea, we want to highlight two different scenarios for series model codes. Starting with our new 210 Series for 2020 Ford Super Duty 10R140 transmissions, this series only has one gear ratio being 46/36 (internal ratio).  When all of the gears in series are considered, the final output ratio is 144% of the engine speed. With this gear ratio, and using a 90% efficiency rating, specific pump options are offered for the 210 Series which include the CGP-P11, PGP-315 and P16 pumps. It is important to remember pump productivity is determined by the pump size in relation to the pump speed.  Therefore, certain pump options may be more suitable than others depending upon the requirements of the application.

The 524 Series Rear Mount PTO is a little different compared to the 210 Series in relation with the gear ratio(s). The 524 Series has gear ratios of 1:1.00, 1:1.33, and 1:1.80. The design of the PTO itself is a two gear mechanically shifted Rear Mount PTO that is attached to rear mount apertures of a transmission. Rear mount apertures are becoming more common in the U.S. with European based transmissions becoming more popularized in the U.S. market. With the three gear ratios, this leads to different torque ratings being available in the market therefore increasing the number of applications that can be used with the 524 series along with optimizing the driven equipment.

Learn more about our 524 Series rear mount and 210 Series ten speed PTO today.

This article was contributed by Michael Mabrouk, marketing leadership associate, Chelsea Products Division, Parker Hannifin Corporation.  

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Parts 1 and 2 of this series discussed the theory behind CSR testing and what to look for in a CSR result curve.  This 3rd and final section will focus on how to use CSR data and apply it to real world applications and how to incorporate it into a material specification.

For the reasons discussed previously, it is important to view a full CSR curve, rather than a single data point, and to resist the urge to draw conclusions from incomplete data.  For example, Figure 1 compares a FKM to an HNBR material.  Because the fluorocarbon material has a larger viscoelastic loss within the first 24 hours of the test, it appears to be worse (less retained seal load) than the HNBR for most of the test duration.  However, the slope of the HNBR curve is steeper than that of the fluorocarbon, and the curves of retained load force cross at about the 2,300 hour point.  If these curves are extrapolated, the HNBR is predicted to reach the point of zero residual load force at 4,262 hours, whereas the fluorocarbon is not expected to reach the same point until 8,996 hours have elapsed.  Had the HNBR material been selected for this application based solely on the higher percent retained load force observed at 1,008 hours, the end user would have achieved roughly half of the service life they could have enjoyed had they selected the FKM compound instead.

Figure 1: An HNBR and a fluorocarbon in engine oil.

Several caveats remain in attempting to use CSR curve data to predict real-world performance.  First, a CSR procedure cannot mimic real-world application conditions.  In fact, it is not intended to.  CSR testing is meant to be an accelerated aging test, where specimens are exposed to constant temperatures hotter than anticipated in the actual application.  While some continuous CSR test machines are capable of temperature cycling, no CSR test can realistically replicate the actual temperature conditions, pressure fluctuations, or vibration seen in a real-world application.  Second, CSR testing cannot replicate actual fluid exposure conditions seen in typical seal applications.  CSR testing completely immerses a rubber specimen in a small amount of fluid that is kept at a high temperature – typically hot enough and with enough air exposure to cause the fluid to degrade.  In a real-world application, a seal is usually installed in a groove with fluid exposure on one side and air on the other.  In many applications, the fluid is contained within a sealed system that minimizes oxidative degradation of the fluid.  Third, there is as yet no definitive correlation between the onset of leakage and residual load force, regardless of whether that force is expressed in absolute terms (Newtons or pounds-force, for example) or as a percentage of the initial developed load force.  Finally, because low temperatures are more challenging for a seal, cycling the temperature to include load force measurements at -40°C would be considered a worst-case scenario.  Continuous measurement CSR devices are now commercially available with the capacity for running such a temperature cycle, but their use to date has been extremely limited due to the cost of the equipment.

Several factors should be considered before incorporating CSR testing into a material specification.  CSR is a more expensive procedure than compression set, and it requires dedicated and expensive test equipment.  As a result, it is not always appropriate to replace compression set testing in a material specification with CSR testing.  Second, establishing limits for “what good looks like” should never be done arbitrarily.  It is extremely difficult to convert a real world application service life into a number of test hours at a set temperature.  Therefore, it is more practical to start with a material that is known to maintain a satisfactory service life in the application, test it for CSR at a relevant temperature, and establish meaningful limits based on the performance of that material.   Finally, resist the temptation to get too exotic with specification limits.  For example, it may seem valuable to impose specification limits related to the slope of the CSR curve or to the extrapolated “time to zero load force”.  These can be valuable tools for gathering engineering insight, but they are far too complicated to incorporate as specification limits.  CSR is a more complicated test than compression set, and it requires more “homework” to set proper limits and test conditions.

In conclusion, Compressive Stress Relaxation is a powerful tool for comparing the performance of two or more materials in a particular application, provided it is done on an apples-to-apples basis.  It also serves as a reasonable means of (roughly) estimating the long-term service life of a seal material in a given application.  There are too many assumptions for it to be used to guarantee a specific level of performance, and there remains much work to be done in correlating results to real-world observations, but it currently offers the best laboratory-scale means of evaluating a seal material for long-term use in a given application.

This article was contributed by Dan Ewing, senior chemical engineer, Parker Hannifin O-Ring & Engineered Seals Division.

How Much Do You Know About Compressive Stress Relaxation? CSR Part 1

How Much Do You Know About Compressive Stress Relaxation? CSR Part 2

How to Read a Rubber Test Report: The 4 Most Common Misunderstandings

Reduce Downtime and Costly Seal Replacements: Seal Failure Diagnosis Part 1

Quick connections for high-pressure, hydraulic applications have evolved immensely over time to satisfy new processes and operational needs. As industries advance their capabilities, the demand grows for coupler capabilities. Today, couplers must ensure fluid handling applications meet both safety and regulatory standards while simultaneously provide optimized containment of a wide range of fluids that can have different operational conditions.

Operators have continually depended on reliable connections for a “non-spill” experience under the most extreme conditions, such as temperature or high pressure. Manufacturers saw this as an opportunity to introduce new and enhanced couplers to the market.

Couplings, specifically non-spill, are engineered to combat hydraulic leaks and spills with a unified design incorporating sophisticated components. For reference, the term “non-spill” regarding a coupling means a specific type of connector can reduce fluid spillage to near zero whenever a coupling is connected and disconnected. Designed initially as heavy-duty metal couplings for high-pressure, industrial applications, non-spill couplings have evolved into a variety of materials to complement a wide range of applications requiring minimal spillage and air inclusion.

The flush face design became a significant advancement in quick coupling architecture. A “no-drip” valve means no more than a coating of liquid will appear on the valves’ surface, establishing repeated dripless connections and disconnections for a cleaner, safer work environment. Also, inclusion, which represents the air put into the fluid system during each connection, is drastically reduced through a flush face valve. The benefits of near-zero spillage and air inclusion have become critical in many applications, from heavy-duty construction equipment to hydraulic hand tools and general industrial machinery.

Parker is the global leader in quick couplings, delivering a spill-free and lasting performance, with a wide range of non-spill coupling solutions to fit versatile fluid applications. The FEM Series, FET Series and 59 Series all provide minimal fluid loss and air inclusion, as well as chemical compatibility when necessary.

This non-spill quick coupling satisfies the design and performance requirements set forth by the ISO 16028 International Standards for quick coupling interchangeability. Featuring a push-to-connect design, FEM Series delivers an extra level of security for simple connections without causing any joining, crimping or soldering materials, eliminating spillage and air inclusion during connecting and disconnecting.

In addition, Parker provides an optional FEC male nipple, which allows connect-under-pressure capabilities with the FEM female coupler. This option is designed for applications where residual pressure makes connection difficult.

The FET Series non-spill quick coupling, engineered for reliable performance with equipment experiencing powerful impulses, accommodates the most demanding hydraulic applications. Parker’s FET Series couplings connect under pressure at 6,000 psi and disconnect up to 2,500 psi in environments that desire the security of a threaded connection under residual pressure. These couplers are built to operate under high-impulse mobile circuits, including excavators, and oil and gas equipment, such as umbilical lines and mobile drill rigs. Constructed of high-grade materials and a stainless steel valve, the FET Series features a robust Brinell resistant design and plating for extended durability and corrosion resistance.

Ideal for use in high impulse applications with multiple high-pressure hydraulic lines, the 59 Series ensures consistent connections and disconnections under residual pressure. A powerful ACME thread utilizes a double start feature and allows a full connection to be completed in 2 – ½ turns, saving time and eliminating frustration. Its size and shape of the heavy-duty ACME thread make the coupling resistant to damage, easier to clean and ready for operational use.

An internal bearing between the collar and body eases resistance and minimizes the challenge of handling pressurized lines. In addition, the coupler and nipple have non-spill stainless steel valves and can be connected under pressure up to 5,000 psi and disconnected under a pressure of 2,500 psi.

Review our non-spill product pages for your specific applications. Or contact one of our product experts for more information or a price quote.

Contributed by Lori Aus, product sales manager, Quick Coupling Division, Parker Hannifin.

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Electrically conductive elastomers are elastomeric polymers filled with metal particles. They can be grouped by filler type and elastomer type. Then within each of these classes, there are standard materials and specialty materials.

Parker Chomerics manufacturers electrically conductive elastomer gaskets, also known as EMI elastomer gaskets, under the CHO-SEAL brand. We won't get so much into gasket configurations and dimensions here, we'll just stick to classes of materials. So what is available? Let’s find out.

Conductive elastomers are metallic particle filled elastomeric polymers, the particles giving the shielding performance and the polymer making them “rubber." There are many materials within this generic material type, but we'll focus on the below.
 

Setting up the grades of conductive elastomers by filler types involves six different particles:

• Silicone
  A polymer that has a large temperature range especially on the low end down to -55F. It is a very soft material with a low compression set. 
   
• Fluorosilicone
  Close to silicone, but will not swell and degrade when exposed to solvents, fuels hydraulic fluids and other organic fluids. Although slightly harder than silicone, it is still relatively soft with low compression set properties.
   
• Ethylene propylene diene monomer (EPDM)
  Does not have the temperature range nor the softness of silicone, but is resistant to highly chlorinated solvents used for compliance with NBC decontamination and is only used for applications with those needs.

All of these materials are cured or cross linked when the gasket is made. The cure either happens with heat or atmospheric moisture.
 

• Compression molding - uncured material is placed into a mold that has a cavity machined into it. The mold is closed, put into a press, then with heat and pressure the material is formed into the gasket shape mirroring the cavity and cured with heat. This process is used for sheet stock also.
   
• Injection molding - instead of hand loading the mold with approximately the proper amount of material, the mold is closed, then the proper amount of material is injected into the cavity. The process is much faster and because the right amount of material is injected tighter size tolerances can be obtained. Injection molding tooling is more expensive than compression molding.
   
• Extrusion - raw material is pushed through a die with the cross section machined into it to create extruded cord stock. Heat is applied on the die and a finished continuous gasket strip is made. These gasket can be supplied in lengths or cut to size and then corners or intersections glued or spliced together to make a ready to use gasket.

In general, for small cross sectional electrically conductive elastomer shapes, the smaller the particle the more producible the part will be. Particle fillers have little to do with mechanical properties of the gasket except that they simply increase hardness.

Now that you have more information about how to select particle and polymers for electrically conductive gaskets, download or Electrically Conductive Elastomer Handbook and get started today!

This blog contributed by Jarrod Cohen, marketing communications manager, Chomerics Divison.

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