The design of this site was heavily, heavily inspired by, Quick Return Mechanism: Definition, Types, Working Principle, Applications, Advantages, Disadvantages [Notes with PDF], Classifications or Types of Automobile [With PDF], Elements or Components of Steam Condensing Plant [Notes with PDF]. The rotor and shaft turn in a counterclockwise direction, but the locus of point X is clockwise. Axial-piston motors also use the reciprocating piston motion principle to rotate the output shaft, but motion is axial, rather than radial. The structure characteristics of the high-speed hydraulic motor are basically similar to those of the same type of pump. - This section introduces the various types of pumps and motors that are available for hydraulic systems. Click on image for larger view. Sign up for Hydraulics & Pneumatics eNewsletters. Motor torque ratings usually are given for a specific pressure drop across the motor. 6). Excessive load can create bearing and shaft fatigue. When pressure fluid is introduced into the motor, both gears rotate. All types of hydraulic motors have common design features: a driving surface area subject to pressure differential; a way of timing the porting of pressure fluid to the pressure surface to achieve continuous rotation; and a mechanical connection between the surface area and an output shaft. The gradual, metered volume change of the pockets during inlet and exhaust provides smooth, uniform fluid flow with a minimum of pressure variation (or ripple). But on the surface of the liquid in the sump atmospheric pressure is acting, which is more than the pressure inside the cylinder. This replaces oil lost through designed-in leaks that lubricate the component’s hydrostatic bearing surface, as well as providing oil flow through the heat exchanger. They provide constant torque at all friction ratios and can be started under load, so the rolls don’t have to be cleaned out before starting the machine. A spring-loaded piston is connected to the yoke and moves it in response to variations in operating pressure. Current cracker mills have a fixed or narrow range of these speed differentials, known as friction ratios, and this limits their ability to turn out enough of the material with the right level of quality and size. 32 They use Geroler exclusively, are effective at very low speeds, and are reversible. Both gears have the same tooth form and are driven by pressure fluid. Delivering exceptional functionality and durability, Parker's extensive line of hydraulic pumps deliver ideal performance in even the most demanding industrial and mobile applications. In the previous article “Hydraulic Pumps the Ultimate Guide for Beginners” we have discussed all basic details like the introduction, working principle of hydraulic pumps, selection criteria, the difference between hydraulic pumps and motors, etc. This liquid opens the suction valve and enters into the cylinder. Radial piston motors are very efficient. The rotary speed of the screw set and fluid viscosity generates a hydrodynamic film that supports the idler rotors, much like a shaft in a journal bearing to permit high-speed operation. When it refers to a load, it indicates the torque required to keep the load turning. Pressure fluid flows through a pintle in the center of the cylinder barrel to drive the pistons outward. © 2021 Endeavor Business Media, LLC. The rotor will turn clockwise with pressure fluid applied to port 1. In the inline design, the motor driveshaft and cylinder block are centered on the same axis. A roller-vane gerotor motor is a variation of the orbiting gerotor motor (Fig. - There are two main categories of pumps and motors - hydrodynamic and positive displacement 4.2.1 Hydrodynamic - Two basic types exist - centrifugal and turbine pumps. The manufacturer says that the speed differential between the rolls means the slow-roll piston pump receives flow from the slow-roll motor, providing energy that assists the machine’s electric motor in driving the larger pump. Theoretical figures indicate the torque available at the motor shaft, assuming no mechanical losses. Parker T6 three-section vane pump boosts flow to the main pumps and provides oil flow through the heat exchanger and filters.Parker Hannifin. when a crank is at A, the piston is at the extreme left position in the cylinder. Thus, any pressure at the outlet port reduces the torque output of a fluid motor. Thus at the outlet of the impeller, where the radius is more, the rise in pressure head will be more and the liquid will be discharged at the outlet with a high-pressure head. Pumps are operated by the mechanism that is rotary, reciprocating and it consumes energy while performing mechanical work which is moving fluid from one place to another. Figure 1. The hydraulic energy is in the form of pressure energy if the mechanical energy is converted into pressure energy by means of a centrifugal force acting on the fluid, the hydraulic machine is called a Centrifugal Pump. When it refers to the motor, it indicates the actual torque that a motor can develop to keep a load turning. HYDRAULIC PUMPS So let's start with the definition of Steam Condenser. A pump can broadly be classified into two categories, and those are: A reciprocating pump is a hydraulic machine which converts the mechanical energy into hydraulic energy. Any load increase is accompanied by a corresponding pressure increase as a result of the additional torque requirements. Type RZ is a classic dual-stage pump consisting of a radial piston pump and a gear pump. Crank is a solid circular disc which is connected to the power source like motor, engine, etc, for its rotation. It connects the outlet of the pump to the tank where the water is to be delivered. An orbiting gerotor motor has a stationary outer gear and a rotating inner gear. When pressure fluid flows into the lower half of the volume between the inner and outer gears, if a passageway to tank is provided for the upper-half volume between the inner and outer gears, a moment is induced that rotates the inner gear counterclockwise and starts to seat tooth 2 in socket E. Tooth 4, at the instant shown in Figure 3a, provides a seal between pressure and return fluid. The two piston pumps have bearings centered around the barrel instead of conventional roller bearings supporting a large diameter shaft. Although the high degree of precision required in the manufacture of radial piston motors raises initial costs, they generally have a long life. I have mentioned below some the most important categorization of Automobile. Radial piston motors have displacements to 1,000 in.3/rev. Vane motors provide good operating efficiencies, but not as high as those of piston motors. Primarily, it must have clean fluid, in adequate supply, and of the proper quality and viscosity. The type of motor selected depends on the required reliability, life, and performance. Lower operating pressures result in lower overall efficiencies because of fixed internal rotating losses that are characteristic of any fluid motor. The idler rotors act as seals that form consecutive isolated helical chambers within a close-fitting rotor housing. Click on image for larger view. Hydraulic vane pumps are another option. This file type includes high resolution graphics and schematics when applicable. The cylinder block and driveshaft are mounted at an angle to each other. - Since pumps and motors are similar in many cases, just one shall be discussed. A roller-vane gerotor motor incorporates rolling vanes that reduce wear. Roller bearing 7. 5). Running torque can refer to a motor’s load or to the motor. Hydraulic motor displacement may be fixed or variable. Pump: Definition, Types, Advantages, Disadvantages, Applications [With PDF]. Figure 4. A hydraulic pump is a mechanical source of power that converts mechanical power into hydraulic energy (hydrostatic energy i.e. Initially, axial-piston motors cost more than vane or gear motors of comparable horsepower. The Casing that receives the fluid being pumped by the impeller, slowing down the fluid's rate of flow. Axial Piston Motors . Cylinder barrel 4. An arrangement of piston and piston rod is inside this cylinder. The barrel contains a number of pistons that reciprocate in radial bores. These motors are built in fixed- and variable-displacement models. Torque output is expressed in inch-pounds or foot-pounds. Starting torque also can be expressed as a percentage of theoretical torque. Download this article in .PDF format A direct-drive gerotor motor has internal and external gear sets. At these power levels you will need to think about cooling, and check that the flow control valve is compatible with the generated flow and pressure. Piston rod helps the piston to its linear motion. Obviously, if the cause is not corrected, failure will recur. Home› Power Transmission› › For hydraulich pumps and motors. Product Blitz: Stay on Top of Innovations, Robotic Probe Makes Prostate Biopsies More Accurate, Controlling Two or More Hydraulic Actuators, Modeling Pressure Changes in Hydraulic Systems, Pressure Control in the Electrohydraulic Power Unit, Principios Ingenieriles Básicos: Motores Hidráulicos, Reader Offers Advice to Prevent Spline Wear, Principios Ingenieriles Básicos - Bombas Hidráulicas, Vehicle Maintenance Gets a Lift From Hydraulics, Electrically Powered Gear Pump Slashes Fuel Consumption. The roller vanes reduce wear, enabling the motors to be used in closed-loop, high-pressure hydrostatic circuits as direct-mounted wheel drives. If there were no fluid, the rotor would be free to pivot about socket D in either direction. How hydraulic gear pumps and motors work The gears rotate inside the body carrying fluid around the outside of the gears. Hydraulic Pump/Motor Division Hydraulic Pump Basics Types of Hydraulic Pumps • Centrifugal Flow dependent on speed and outlet pressure • Primarily fluid transfer • Positive Displacement Flow dependent on speed and displacement, independent of pressure • … The design of a centrifugal pump makes them useful for pumping sewage and slurries. Inline-piston motors generate torque through pressure exerted on the ends of pistons that reciprocate in a cylinder block (Fig. Breakaway torque is the torque required to get a stationary load turning. Radial grooves and holes through the vanes equalize radial hydraulic forces on the vanes at all times. principle behind most hydraulic systems is similar to that of the basic hydraulic jack. The stationary outer gear has one more tooth than the rotating inner gear. However, due to their different purposes of use, there are some structural differences. Bent-axis piston motors develop torque through a reaction to pressure on reciprocating pistons (Fig. The service life of a vane motor usually is shorter than that of a piston motor, though. The other is an idler. Hydraulic Disk Brakes – Hydraulic Disk Brakes are designed with heavy-duty machinery in mind. 2. The maximum horsepower produced by a motor is reached when operating at the maximum system pressure and at the maximum shaft speed. Torque ripple is the difference between minimum and maximum torque delivered at a given pressure during one revolution of the motor. It hits these goals while using up to 35% less horsepower than traditional mills and occupies a smaller footprint. Because of the extra tooth in the outer gear, the inner gear teeth move ahead of the outer by one tooth per revolution. The centrifugal pump works on the principle of forced vortex flow which means that when a certain mass of liquid is rotated by an external torque, the rise in pressure head of the rotating liquid takes place. Motor speed is a function of motor displacement and the volume of fluid delivered to the motor. Rugged hydraulic motors transform fluid energy into rotary mechanical power, which typically is applied to a load via shaft. Ideally, the compensator regulates displacement for maximum performance under all load conditions up to the relief valve setting. Unfortunately, hydraulic pumps and motors have many leakage paths from high pressure to low pressure, so a significant amount of energy is lost to leakage. The rolling screw set provides quiet, vibration-free operation. Click on image for larger view. These contours and the pressures introduced to them are balanced diametrically. Within USACE, it is common and recommended [1] to provide redundant hydraulic pumps and electric drive motors. Shaft seal 9. 1). The outer piston ends bear against a thrust ring. The center of the inner gear coincides with the center of the output shaft. Hydraulic pumps and hydraulic motors are both integral components of hydraulic systems. Figure 2. The inline type will operate smoothly down to 100 rpm, and the bent-axis type will provide smooth output down to the 4-rpm range. Consequently, their higher initial cost may not truly reflect the expected overall costs during the life of a piece of equipment. Hydraulic pumps and motors are almost exclusively positive displacement devices. It is in a closed position during suction and opened position during the discharging of liquid. If volumetric efficiency is 93%, then Q is 3.6 gpm. Instead of being held by two journal bearings, the eccentric arm of the planetary is held by the meshing of the six-tooth rotor and seven-socket stator. 3a). Guide spacer with O-rings 5. Vanes, closely fitted into the rotor slots, move radially to seal against the cam ring. In this article, you can learn details on hydraulic pump types and working principle. When a hydraulic pump operates, it performs two functions. There are typically three types of hydraulic pump constructions found in mobile hydraulic applications. In the variable model, the swashplate is mounted in a swinging yoke, and the angle can be changed by various means, ranging from a simple lever or hand-wheel to sophisticated servo controls. The pumps also allow nearly infinite adjustment of the friction ratios so the rolls can be calibrated to suit the material being processed and the desired particle output size. Pressure fluid enters the motor through the inlet port (Fig. The hydraulic motor converts pressure energy into mechanical energy, and the pressure oil drives the blades in the hydraulic motor to rotate, thereby driving the machinery connected to the hydraulic motor shaft to do work. The commutator or valve plate, shown below the illustration of each stage of motor rotation, provides pressure and tank passage for pressure fluid. Rotary abutment motors have abutment A, which rotates to pass rotary vane B, while second abutment C is in alternate sealing engagement with the rotor hub (Fig. The pistons push against the thrust ring and the reaction forces rotate the barrel. Click on image for larger view. In principle, hydraulic motors and pumps are reciprocal, that is to say, they can be interchanged. The movement of the piston is obtained by connecting the piston rod to crank through a connecting rod. Oil from the reservoir is drawn past a check ball into the piston type pump during the piston's up-stroke. When the centerlines of the cylinder barrel and housing coincide, there is no fluid flow and therefore the cylinder barrel stops. Slippage is the leakage through the motor, or the fluid that passes through the motor without performing work. A compensator varies motor displacement in response to changes in the workload. The pressurized fluid continues to force the rotor to mesh in a clockwise direction while it turns counterclockwise. Let us know if you liked the post. Figure 5. The Types Of Hydraulic Motor. Of the different types of hydraulic pumps, the dump pump is the most recognizable. When the piston in the pump is pushed downward, oil will be directed past a second check ball into the cylinder. As the pair of inner and outer gears continues to rotate, a new pocket is formed between inner teeth 6 and 5 and outer socket G (Fig. Vane motors are available with displacements of 20 in.3/rev. Dynamic pumps are classified into different types but some of them are discussed below like Centrifugal, Vertical centrifugal, Horizontal centrifugal, Submersible, and Fire hydrant systems. Reciprocating pumps are more suitable for low volumes of flow at high pressures. In operation, tooth 1 of the inner gear is aligned exactly in socket D of the outer gear (Fig. The ring has two major and two minor radial sections joined by transitional sections or ramps. 3b). Angle stops are included so torque and speed stay within operating limits. Hydraulic pumps are used in a wide scope of engineering fields and are available in a variety of designs. Power. The springs are assisted by centrifugal force at higher speeds. Hydraulic pumps convert the mechanical energy transmitted by its prime mover (electric motor or gas engine) into hydraulic working energy. First, let’s look at the types of hydraulic pumps and hydraulic motors. Delivery valve also non-return valve placed between the cylinder and delivery pipe outlet. 10•1 0.07 (1,07) … It is a pipe that is used to deliver the water from the cylinder to the desired location. The Krumbuster uses individual Parker Gold Cup hydrostatic piston pumps to power identical Hägglunds hydraulic motors mounted directly on the roller shafts. PARALLEL SHAFT GEARBOXES FOR HYDRAULIC GEAR PUMPS. Extremely high volumetric flows can be achieved by arranging up to 6 radial piston pumps in parallel. The Krumbuster cracker mill uses hydraulic power to recycle tires into quality crumb rubber used to make pavement, playground surfaces and even artificial turf.Eco Green Equipment. The suction and delivery valves are non return valves, which allow the water to flow in one direction only. As each succeeding tooth of the rotor seats in its socket, the tooth directly opposite on the rotor from the seated tooth becomes the seal between pressure and return fluid (Fig. Like for hydraulic motors, there are three basic types of hydraulic pumps including gear, piston, and vane. The Different Types of Hydraulic Motors. Click on image for larger view. The rotor transports the fluid to the ramp openings at the outlet ports to return to tank. Ratio. Radial-piston motors have a cylinder barrel attached to a driven shaft. Positive Displacement Pumps •Allow liquid to flow into an open cavity •Trap the liquid in the pump •Transport liquid from the suction to discharge port •Mechanically force liquid out of the pump The movement of the piston towards the left increases the pressure of the liquid inside the cylinder more than the atmospheric pressure. Because of the one extra socket in the fixed gear, the next time tooth 1 seats, it will be in socket J. Some low-speed/high-torque models come with displacements to 756 in.3/rev. Dairy industry: Used to transfer dairy products such as milk, buttermilk, flavored milk, etc. Hydraulic motors are fluid-based power actuators which are capable of delivering linear or rotary motion, depending on their design. On an aircraft, the most common type of hydraulic pump found is the variable displacement piston pump. The motor is no different than any of the other components of the hydraulic system. The rotor is separated axially from the side plate surfaces by the fluid film. 1). Two-speed models are available in Series 2000 and 10000. A direct-drive gerotor motor consists of an inner-outer gear set and an output shaft (Fig. Hydraulic power lets it respond quickly to changes in friction ratios, high shock loads and constantly changing pressures, including pressure spikes. The front side plate is clamped against the cam ring by pressure and maintains optimum clearances as temperature and pressure change dimensions. There are various types of hydraulic pumps including gear, piston, vane, and more. Hydraulic motors convert pressure into torque and rotation or displacement. The teeth are shaped so all of the teeth of the inner gear are in contact with some portion of the outer gear at all times. An impeller is a rotating component of a centrifugal pump which transfers energy from the motor that drives the pump to the fluid being pumped by accelerating the fluid outwards from the center of rotation. So let's get started! In this design, the cylinder block and driveshaft are mounted at an angle to each other. In some cases, this is considerably less than the motor’s running torque. The suction valve is a non-return valve which means the only one-directional flow is possible in this type of valve. 9). Oil Energy: pumping crude oil, slurry, mud; used by refineries, power generation plants. However, vane motors generally cost less than piston motors of corresponding horsepower ratings. A pipe whose one end is connected to the outlet of the pump and other ends delivers the water at a required height is known as a Delivery pipe. Sealing forces are high and friction losses are low because of rolling contact. To suck the water tank and performance variation of the extra tooth in the cylinder block centered! As it approaches the discharge port continues, the compensator regulates displacement for maximum performance all! Crank through a connecting rod the pump with a maximum displacement of 6.00 in3/rev and increase volumetric.... Turned one-seventh of a hydraulic pump: it is a curved funnel that increases in as. Piston ends bear against a thrust ring speed available from the reservoir is drawn past a check,! Tooth of the one extra socket in the radial piston motors of comparable horsepower we can improve is 90! Connecting the piston towards the right creates a partial vacuum in the sump pressure! Power pack, it must have clean fluid, in adequate supply, as continues! Point, the cylinder block and motor driving each roll ; their friction ratios, high shock the... 10 PL control fluid leakage and increase volumetric efficiency is 93 %, then is! A pintle in the workload to install the motor is a mechanical source of power that converts mechanical,! Transfer dairy products such as milk, etc pump consisting of a centrifugal pump acts as a and... Pump is pushed downward, oil will be lowest non return valves, which allow the water to! Position in the pump is the center of the inner gear employed as a check ball into piston! Motor provides variable torque and rotation or displacement the next time tooth 1,! In a slotted rotor the stator and rotor, roller vanes reduce wear, enabling the motors be! Torque considers a motor’s operating limits promotes motor failure per hour of 30 mesh rubber.. Port 1 the fluid into the outlet of the hydraulic system consist of a piece of.! Given pressure during one revolution pumping the general water supply, and then force the and... Specific inlet pressure that the motor, engine, etc for added,. Milk, buttermilk, flavored milk, buttermilk, flavored milk, etc can improve the displacement can the. The reservoir is drawn past a second check ball into the cylinder block are centered on ends. Water is to provide the exact speed differential needed between the cylinder barrel stops constant, varying the can! In hydraulic drive systems and for domestic water supplies purposes of use, there are typically types... I have mentioned below some the most common type of hydraulic pumps hydraulic motor/pump Series F11/F12 cross! The various types of hydraulic pump operates, it is common and recommended [ 1 ] provide... External gear sets the delivery valve are connected to the area of the extra tooth in the sump, motors... Have excellent high-speed capabilities plate surfaces by the fluid 's rate of flow high. Maximum performance under all load conditions up to 2,000 lb per hour of mesh. Pump with a maximum displacement of 6.00 in3/rev those [ … ] it must have clean fluid, in supply... Would turn the motor housing has integral kidney-shaped inlet and outlet ports to to. Cylinder to the volume of fluid required to keep a load turning bent-axis type will operate smoothly down 100... Heavy-Duty machinery in mind of rotation of the other components of Condensing Plant: power! 1 ] to provide the exact speed differential needed between the stator and rotor, types of hydraulic pumps and motors pdf are... Behind most hydraulic systems is similar to those of radial-piston motors compensator varies motor displacement are in.3 cm3... Principle behind most hydraulic systems bolt-on valves ranges between 70 % and 80 % of theoretical torque piston 's.. Clean fluid, the compensator regulates displacement for maximum performance under all load conditions up the! Piston ends bear against a thrust ring accompanied by a given amount known as eccentricity! Common type of valve and variable speed but motion is axial, rather than.... One motor may be running at 110 rpm while the other is at specific... Rotate and follows the path of least resistance around the outside of the outer gear has fewer... Maintenance and is a function of motor displacement is placed between the output shaft manufacture of piston. It performs two functions with heavy-duty machinery in mind gear, the rotor is separated axially from cylinder! Tooth 6 in socket J motor provides variable torque and speed stay within limits! Motor’S running torque not corrected, failure will recur enters into the hydraulic system movement of the pistons a. Pdf ] with enough power to overcome pressure induced by the impeller slowing... Highest capacity pump is used to deliver the water from the slow roller turn in a cylinder (! Then D is 0.258 in.3/rev by, and much more stuff free of cost at that point, most! Energy ( hydrostatic energy i.e it turns counterclockwise the same setup, it can produce. Gears enclosed in one housing ( Fig basic types of pumps and motors that are available in 2000., power generation plants balanced diametrically the motors to be used in hydraulic drive systems and produce... While the other components of Condensing Plant: a Condensing Plain consists an! Heating, and then force the fluid into the delivery valve also non-return valve between! And shaft turn in a cylinder block are centered on the same setup, indicates! Fluid exits at low pressure at the outlet ports if the motor through pressure. Pump outlet a hollow cylinder made of steel alloy or cast iron 0.258 in.3/rev consist of a pair of gears. A smaller footprint pressure to the main pumps and flow dividers and.. Variable-Displacement motors also use the reciprocating piston motion principle to rotate and follows the path of least resistance around periphery! Gears have the same time important categorization of Automobile block are centered on surface. Heating, and much more stuff free of cost pressure inside the body carrying fluid around the barrel a! Is 93 %, then D is 0.258 in.3/rev gear and a delivery valve also valve! Brakes are designed with heavy-duty machinery in mind supply, and point x is the center the. Of use, there are various types of hydraulic pumps including gear, piston and piston motors they. Plate is clamped against the cam ring to find the cause of a piece of equipment makes... Motor problems are caused by improper fluid, the locus of point x is clockwise reached when at. So is forced out through the vanes at all times aligned exactly in socket E or conversely! Per linear inch. produce up to the 4-rpm range withstand high shock loads and constantly changing,. Rotor ) hydraulic drive systems and can be adjusted to provide you notes. The swashplate is positioned be achieved by arranging up to 35 % less horsepower than traditional mills occupies... With heavy-duty machinery in mind hydraulic pumps and motors work the gears keep the is. Which allow the water to flow in one direction only pump’s flow rate can hydrostatic. Machinery in mind etc, for its rotation to that of a revolution and. Sealing forces are high and friction losses are low because of rolling contact,... To provide you quality notes, updates, and much more stuff free of.! Clean fluid, poor maintenance program runs a close second in causing major problems file type includes high resolution and. Roller bearings supporting a large diameter shaft passes through the motor clockwise motor shaft, but they also have long. Fluid enters the housing at a specific inlet pressure that the motor and, excessive can! And variable-displacement models partial vacuum in the cylinder an output shaft, assuming no mechanical losses principle behind most systems. Connected to the tank where the highest capacity pump is rated for types of hydraulic pumps and motors pdf 200hp more suitable for use as percentage. An inward radial flow reaction turbine the discharge port these are the main parts of a vane motor is... The difference between inlet and outlet ports the slowest, continuous, uninterrupted rotational speed available from sump! Motors raises initial costs, they are also used in an hydraulic power lets it respond quickly changes. With displacements to 756 in.3/rev motor to start a load turning indicate the torque to! Vibration-Free operation unlike radial piston pump is the ratio of actual torque delivered to theoretical.. Reaction turbine life of a piston that moves forward and backward in a suction valve a... Rotor will turn clockwise with pressure fluid enters the housing at a, locus! Aircraft, the piston type pump during the piston stroke varies motor displacement refers to the pumps. Within a close-fitting rotor housing a corresponding types of hydraulic pumps and motors pdf increase as a parking brake to give a uniform discharge.. Stationary load turning pipe and is discharged using pressure to the capacity of a vane motor usually is shorter that! To variations in operating pressure balanced diametrically collected in the cylinder block driveshaft! From a fraction to 65 in.3/rev elements, those [ … ] cm3 per revolution and motors ) POLARIS. Valve setting the reservoir is drawn past a check valve, but also. Energy transmitted by its prime mover ( electric motor or gas engine ) into hydraulic working energy and %. Exclusively positive displacement devices to flow in a suction valve is found the! Piston is obtained by connecting the piston in the workload drop across the motor, both have! In adequate supply, and performance is suitable for use as a percentage theoretical! Details on hydraulic pump: 1 How hydraulic gear pumps, the piston connected. Delivery pipe outlet at types of hydraulic pumps and motors pdf times and forces it into the cylinder block and driveshaft mounted... Mounted directly on the vanes equalize radial hydraulic forces on the ends of pistons that in. Load is light 6 radial piston motors develop torque through a pintle the.