Or perhaps larger parts are to be manufactured which will require twice the torque but at the same production rate. Again, twice the horsepower will be required. Suppose the new machine is to manufacture the larger parts and at twice the rate of the existing machine. Then four times the HP is needed. Estimation is by comparing horsepower; then the HP can be divided by speed to find the hydraulic motor torque. If the existing machine is powered with an electric motor and the new machine with a hydraulic motor, and if high starting torque is required, the hydraulic motor must be selected by comparing its starting torque with the starting torque of the electric motor on the existing machine.
An induction type electric motor can produce about 3 times the starting torque of most hydraulic motors of the same horsepower rating. Torque Estimation by Calculation On machines of new design- where there is no way to measure input torque, nor to compare performance with an existing machine, torque and HP must be calculated. Since the final output of the machine will be mechanical, the starting point for calculations is to compute the mechanical output HP.
F is the linear force output, in lbs. T is the torque produced, in ft. No calculations are possible unless the force, and travel distance during a specified time interval are known or assumed.
After HP output is determined, work backwards toward the input shaft of the machine, one step at a time, adding sufficient HP at each step to make up for friction losses in gear boxes, bearings, etc. This will give the estimated HP required from a hydraulic motor coupled to the input shaft. In a similar manner start with the output speed and work back toward the input, adjusting for speed changes through chain drives, gear boxes, etc. From these estimations of input HP and speed, the hydraulic motor torque can be computed:.
Mechanical HP is calculated as follows:. Drum RPM is computed from Formula D in box; input speed for the hydraulic motor is computed as described above in this column. Drilling Machine. On a machine for drilling, the drill manufacturer will usually furnish HP and recommended speed specifications. These figures can be adjusted back to the input shaft of the drilling machine, making allowances for frictional losses and speed changes.
Vehicle Wheel Motor. Calculate the total drawbar pull horizontal thrust to overcome all road and operating conditions. Using the wheel radius, calculate wheel torque with Formula C in the box below. Convert travel speed into wheel RPM. Select hydraulic wheel motor to meet these conditions. Motors are similar in design to pumps only where a pump takes a rotary actuation to move hydraulic fluid out of the unit, whereas a motor will take flow into itself and put out a rotary actuation.
The motor selection comes first in the process because application design best practices require that you start with the load requirement, then work back to the prime mover—the pump that will put the fluid power into the motor selected to deliver the performance goal. Each motor type—gear, vane, in-line piston, bent-axis piston and radial piston—has a specific performance profile. So, knowing the application performance requirement and which motor type best meets the objective is the first step.
Some have severe duty cycles, while others do not. If, for example, you consider running a low-efficiency, lighter-duty motor into a higher-duty cycle application, the life of the motor will be less than the life of a higher-duty cycle motor that is designed to operate in those types of environments.
It is important to understand what operating pressures and flows are required for the motor selected to achieve the application performance expectations. Each motor type has its own set of applications where they are a better choice than others.
The better motor choice would be a motor with higher ratings that will live longer in the application. Granted, there is a greater cost in going with a higher rated motor. The final decision always will depend on what is required in terms of application performance and motor life versus where you want to be with cost. How motors are rated Motors are rated by displacement , with displacement defined as the volume of fluid that it takes to rotate the shaft of the motor once.
Motors are also rated by torque —the amount of twisting force the motor can deliver. The common measurements of torque are inch-pounds in. The torque of a motor is a function of motor displacement and system pressure.
Starting torque is the torque the motor can generate to turn a load when starting from a stop. In general, starting toque is the lowest torque rating of a hydraulic motor due to inefficiencies. Stall torque is the maximum torque the motor will generate before it stops rotating. Sometimes this is also referred to as running torque. The rotational speed of the motor shaft is measured in units of rotations per minute rpm.
Motor speed is a function of hydraulic input flow and motor displacement. Pressure is generated by resistance to hydraulic flow. The more resistance, the higher the pressure. They consist of a matched gear set enclosed in a housing. When hydraulic fluid is moved into the motor, it causes the gears to rotate.
Key features include:. Applications include mobile hydraulics, agricultural machinery to drive conveyor belts, dispersion plates, screw conveyors or fans. Their biggest drawback is that they have a higher noise level. Vane motors are typically classified as HSLT units. However, larger displacements will fall into the LSHT range.
Hydraulic fluid enters the motor and is applied to a rectangular vane, which slides into and out of the center rotor. This center rotor is connected to the main output shaft. The fluid being applied to the vane causes the output shaft to rotate. They are used in both industrial applications, such as screw-drive and injection molding, and mobile applications such as agricultural machinery.
In-line piston motors are classified as HSLT. Hydraulic fluid enters the motor and is applied to a series of pistons inside a cylinder barrel. The pistons are pressed against a swash plate, which is at an angle. The pistons push against this angle, which causes the rotation of the swash plate that is mechanically connected to the output shaft of the motor. The swash plate can be a fixed or variable angle.
Variable angle motors can have their displacements adjusted between a maximum and minimum setting. The command signals to change the displacement can be electrical, hydraulic or a combination of both. Bent-axis piston motors are classified as HSLT. They are similar to inline motors except that the piston barrel is at an angle in relation to the swash plate. Unlike a linear, force-moving cylinder, the hydraulic motor uses hydraulic pressure to rotate. A hydraulic motor is built very much like a pump.
However, when operated, oil enters the hydraulic motor and turns the shaft. The amount of oil supplied by the hydraulic pump determines the speed of a hydraulic motor. Subsequently, the torque is dependent on the amount of pressure supplied.
Radial piston motors are highly efficient and generally have a long life. Furthermore, they provide high torque at relatively low shaft speeds, as well as excellent low speed operation with high efficiency. The low output speed means that, in many cases, a gearbox is not necessary. We supply radial piston motors from brands worldwide, including Bosch Rexroth, Staffa Kawasaki and the Italgroup.
Radial piston motors are commonly fund in: excavators, cranes, ground drilling equipment, winch drives, concrete mixers, trawlers and plastic injection moulding machines. Generally, there are two basic types of radial piston motors. These are explained further here. The Crankshaft radial piston motor has a single cam and pistons pushing inwards.
And, some can run seamlessly up to rpm with virtually constant output torque. To sum up, the Crankshaft radial piston motor is the most versatile hydraulic motor. This type is constructed with a cam ring, which has multiple lobes and piston rollers that push outwardly against the cam ring. In essence, this produces a very smooth output with high starting torque. However, they are often limited in the upper speed range.
Moreover, these high power motors are particularly good on low speed applications. Other types of radial piston motors include: compact radial piston motors, dual displacement radial piston motors and fixed displacement radial piston motors.
And in addition, we can also help you source: low speed high torque radial piston motors, two speed radial piston motors and variable displacement radial piston motors. Gears are used to reduce the shaft output speed for applications that require a lower speed. In addition, some of the more modern gear motors operate at, up to, bar continuous pressure. However, the downside is that this motor can be rather noisy. To sum up, gear motors are generally lightweight and small units with relatively high pressures.
In addition they are known for their low cost, variety of speeds, broad temperature range, simple design and large viscosity range. Hydraulic vane motors are used in both industrial and mobile applications.
For example, screw-drive, injection moulding and agricultural machinery. These motors tend to have less internal leaking than a gear motor. And subsequently, they are better to use in applications requiring lower speeds. Hydraulic vane motors feature reduced noise level, low flow pulsation, high torque at low speeds and a simple design.
Moreover they are easy to service and suitable for vertical installation. To function correctly, the rotor vanes must be pressed against the inside of the motor housing.
This can be done through spiral or leaf springs. But rods are also suitable. The speeds range from to 2, rpm. Maximum torque of up to Nm. Axial piston motors use a bent axis design or a swash plate principle. The fixed displacement type works as a hydraulic motor and can be used in open and closed circuits. In contrast to this, the variable displacement type operates like a hydraulic pump.
In the bent axis design, pistons move to and fro within the cylinder block bores. This movement is converted into rotary movement via the piston ball joint at the driving flange. In the swash plate design, pistons move to and fro in the cylinder block.
Subsequently it revolves and turns the drive shaft via the connected cotter pin.
0コメント