This article takes an in depth look at dynamometers.
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A dynamometer is a measuring device used to determine the torque, force, speed, and power required to operate the drive on a machine or motor, which can be measured by evaluating the torque and rotational speed of a motor simultaneously. Beyond the common use of dynamometers, there are other uses for them, such as tests of engine management controllers and the examination of combustion.
When force is applied to a flexible metal ring on a dynamometer, it bends and measures the applied force. The measurement of force using dynamometers is an essential part of automobile production to determine horsepower, power absorption, and rotary speed.
To maintain their instruments and ensure the accuracy of readings, users regularly calibrate and test dynamometers.
The best explanation of how a dynamometer works is to envision a spring in a two part mounting. One end of the spring is anchored to a base with the other end connected to the force to be measured. As the spring is stretched by the force, a reading registers on a scale. This simplistic representation of a dynamometer is very similar to a spring balance but provides readings in units of force or Newtons (N).
Though this simple example can provide a reading, it does not have the strength to measure the power of a 250 hp engine. A more sophisticated and technical device is required for that type of job, which is much larger and resembles an electric motor or gas engine.
A large dynamometer is a variable load that is attached to the drive of an engine or motor. As the motor powers up, the dynamometer absorbs the power being produced to provide data on the torque and power of the motor. As the power is absorbed, the dynamometer dissipates the massive amount of power generated through electromagnetism.
As can be expected in the modern era, the data produced by a dynamometer is fed into a computer. There are several varieties of software available to collect dynamometer readings. Though DOS tends to be going out of existence, a few versions of DOS software are still being used. The most common type is Windows based.
The readings from the software include:
With the use of dynamometer software, it is possible to measure, record, observe, and assess any kind of data from an engine. Most manufacturers and producers use dynamometers for basic data readouts. Dynamometer producers know that the more things you measure and quantify, the better will be the quality of the final product. With every test being performed consistently since any aspect of the process can create variations in the results. Compiling a wide range of data can account for any possible fluctuations and variables.
During the design process, engineers want to know how big an engine or electric motor will be necessary to operate a machine. The type of dynamometer for such an application is a driving one, which is an engine or electric motor that has monitors and meters that are able to measure the power, force, and speed being used by the motor.
Though the use of dynamometers may seem to be restricted to motors, engines, and other mechanical devices, in reality, they have found use in other fields as a means for measuring power and force. Dynamometers may seem to be a valuable technical instrument that is necessary for manufacturing. As modern as they are, dynamometers began over 220 years ago to measure the pulling force of horses.
Emission testing measures the emissions and power of a motor when it is on the road. The results of the testing are compared to chassis tests. A dynamometer for this purpose is portable and placed on the vehicle with devices for measuring emissions, performance, and driving. The data is downloaded to a chassis dynamometer to produce the loads that were seen on the road test. Required real time compensations include grades, wind, temperature, and altitude.
Motor testing using a dynamometer takes place in a controlled setting. The vehicle to be tested is placed on roller beds, which provide the driving force to the wheels, with the motor’s torque being the primary source of power. Data recording and collecting devices are attached to the vehicle that establishes a controlled, accurate, and precise set of readings about the motor. The nature of the setting allows for control of the amount of force that can be distributed using a variety of methods as well as the speed. Measurements are taken at static power at a constant velocity.
In the medical field, practitioners need to know the muscle strength of a patient to determine mobility and the ability for self-care. Hand held dynamometers provide data regarding a patient's ability to hold a standard position. The testing includes a length tension of a muscle, which is the relationship between maximum tension versus the length of the muscle. For the best results, the muscle is tested in its maximum length tension position.
A specialized form of dynamometer is a hand strength tester that is used to measure the amount of loss of muscle strength in the hands. The reasons and concerns regarding hand testing include carpal tunnel syndrome, nerve and tendon damage, and various forms of neuromuscular disorders. Hand strength dynamometers serve a variety of purposes, such as diagnosing diseases, evaluating treatments, and providing data regarding the improvement of muscle strength during recovery.
A speedometer is a form of dynamometer that uses electromagnetism to provide data. A metal disc that is connected by a cable to the wheels of a car causes a magnet to rotate inside a metal cup. While the magnet is rotating, it creates eddy currents that work to slow down the magnet. In the process, the cup rotates and produces a speed reading by making the needle on the speedometer move or creating a digital readout.
A towing dynamometer is a mechanized trailer that is towed behind a vehicle. It uses an eddy current absorber connected to an axle system to absorb energy. Measurements are taken by a load cell on the drawbar of the trailer. A towing dynamometer is used to determine a vehicle’s performance and develop any adjustments that may be necessary.
The testing of electric motors using a dynamometer is very similar to tests performed on other motors. A dynamometer provides data regarding the torque, force, power, and rotation of an electric motor. Dynamometers do full and variable testing to determine the optimum performance of an electric motor.
One form of electric motor testing involves the application of water flow that is proportional to the load, which creates resistance in the motor. The acceleration and deceleration of the water flow allows the dynamometer to adsorb the power generated by the motor.
The different aspects of a locomotive are tested using a dynamometer car. The main purpose of a dynamometer car is to measure the power output of a locomotive, which include pulling force, power, brake pipe pressure, and drawbar pull. The main pieces of data, which are force and speed, are used to calculate the effectiveness of a locomotive.
PTO testing is a series of tests performed by a dynamometer when connected to an engine’s output shaft. The parameters for the testing are much like those of other engine tests and include speed, torque, power, and fuel consumption. PTO dynamometers are easy to connect and disconnect. Accurate and detailed PTO readings assist in lowering maintenance costs and improving equipment reliability.
Several tests are performed on the motors of electric vehicles using a dynamometer. The most important part of the testing includes the performance parameters, which are calculated by the dynamometer.
The measures tested on an EV motor include rotor current, temperature rise, continuous electrical operation, max speed, and over speed. Each dynamometer for testing EV engines is specially designed to meet the parameters of the engine to be tested. The specifications of the motor are identified such that they apply to the specific motor.
The various types of dynamometers are designed to be attached to a machine to apply a breaking force to calculate the RPMs of the machine. The main types of dynamometers are absorption or passive and universal. The absorption type is used for driving purposes, while the universal type is for absorption and driving.
Though the general definition of dynamometers breaks into the two types, under each type are a wide variety of specialized dynamometers designed to perform a specific form of test to meet the needs of an application. The description of dynamometer types consists of a long list of devices designed to provide information and data.
Absorption dynamometers create torque by placing constraints on a turning shaft through mechanical or fluid friction or electromagnetic induction. The torque inducing components are arranged in pairs such that the effects of a transverse load is avoided. Absorption dynamometers are very accurate and are used where continuous transmission of the load is required.
The purpose of absorption dynamometers is to measure and absorb power. Eddy current, hydraulic, and Prony dynamometers use the power absorption principles as their means of measurement.
An AC dynamometer applies power to an engine and absorbs power, such as braking force, from the driveshaft. This permits the dynamometer to simulate the external forces on the engine. AC dynamometers can use direct current (DC) as well as AC and can be a load or prime mover to measure rotational power and torque. The prime mover can be an electric motor, or a turbine driven by wind, water, or steam. It is a simple testing device that can provide a range of torque values.
AC dynamometers are a convenient method for developing a comparison between actual execution and design specifications. They have been a major step in improving marketable products and enhancing product life and performance.
Chassis dynamometers are torque measuring devices that measure what is produced by the movement of a vehicle's wheels. They are available in fixed configurations or portable units. The purpose of chassis dynamometers is to simulate road conditions, including all the forces that attack a vehicle during operation. The test includes accelerating, braking, and decelerating the test vehicle to get the necessary data. There are several designs of chassis dynamometers designed to test several driving conditions and challenges for vehicles.
A driving dynamometer is used to determine what type of a motor is necessary to operate an engine or electric motor. The components of a driving dynamometer include a motor with measuring meters and monitors that are attached to the device to be measured. The readings from the monitoring equipment supply information regarding how much power, force, and speed are being used.
An eddy current dynamometer measures the torque and power of the prime mover, which is a motor or engine. The rotor turns by the force of the prime mover shaft, and voltage is applied to the stator housing. Magnetic flux is generated, which is cut off by the rotor. An eddy current that is opposite to the change in the magnetic flux is generated in the rotor. The rotor attempts to contain and reduce the rotational speed, while the prime mover maintains speed using its torque. The amount of torque is measured by an eddy current dynamometer. There are a wide range of functions that use eddy current dynamometers including various turbines and mining and drilling equipment.
The process of using an engine dynamometer is slightly more complicated than the use of other dynamometers. The size, weight, and performance of the engine are the determining factors related to selecting a proper dynamometer. Unlike chassis dynamometers, engine dynamometers test and tune engines.
Engine dynamometers produce a great deal of information and require a computer interface to record and display what is ascertained by the dynamometer. The main dividing factor between the different types of engine dynamometers is whether the engine is for street use or heavy duty use, such as race cars or trucks since there is a great deal of variance in torque between the two classes of engines.
Fluid dynamometers use the same process as water brake dynamometers but use water or oil to spin the crankshaft. As with water brake dynamometers, the heat caused by the turning of the impellers produces heat that is read by the dynamometer. Gears that are connected to the shaft of the dynamometer send the recorded data to a device that measures the force.
A hydraulic dynamometer has semicircular vanes placed in a rotor and stator. Water flows in a toroidal vortex around the vanes and creates a torque reaction in the dynamometer casing that is resisted by the dynamometer and measured by a load cell. The construction of a hydraulic dynamometer is similar to a fluid flywheel that measures the frictional force between impeller vanes and a moving fluid.
A Prony brake dynamometer is the simplest form of dynamometer that Prony developed at the beginning of the first industrial revolution. It is made up of brake blocks that press against a rotating wheel attached to the motor. The braking blocks create friction force to slow the velocity of the wheel. The purpose of a Prony brake dynamometer is to measure braking power.
A rope brake dynamometer is another method for measuring the power of an engine and includes a rope that is wound around a drum that is attached to the output shaft. One side of the rope is connected to a spring balance, with the other side attached to a loading device.
In a rope brake dynamometer, power is absorbed between the rope and the drum. The amount of friction produced by the interaction of the rope and drum necessitates some form of cooling mechanism. The mechanics of a rope brake dynamometer can be easily made, but the device does not provide accurate data due to the changes in the friction coefficient.
A universal dynamometer is different from an absorption dynamometer in that it can measure absorption and drive of the device being monitored. As the dynamometer absorbs the force and power, it drives the engine to measure friction and pump loss, to name a few factors.
Water brake dynamometers are designed to work with high torque low speed diesel engines that are used in mining, marine, and naval applications. They can test engines with clockwise and counterclockwise rotations. Water brake dynamometers are hydraulic type absorption dynamometers, which are connected to the crankshaft of the engine while water is fed into the meter.
A rotating blade in the dynamometer turns the water to create the braking force against the crankshaft. The measure of the power of the engine is decided by the heat that is generated. As the amount of water increases, the necessary braking force increases.
The basic processes of a dynamometer are to measure torque or force and power. Each of these functions is completed following a set of procedures: step test, sweep test, and transient test. The various procedures are used in conjunction with the type of data to be collected.
A dynamometer has a data acquisition system that includes a commander and workstation. As with all modern testing devices, the dynamometer is linked to a computer that sends commands to the workstation. Once the commands have been implemented, the workstation operates the dynamometer and collects the programmed data that is fed back to the command computer.
Step testing procedures are performed by brake dynamometers and are tests where an engine is kept at a set RPMs for a predetermined amount of time. After collecting data at one level of RPMs, it is stepped up to the next level. The advantage of the step test is the lack of acceleration so that inertia and the dynamometer do not influence the torque readings.
The sweep test accelerates the engine at a constant steady rate, such as 100 rpms per second. Its purpose is to simulate as closely as possible actual driving conditions. The key to the success of the sweep test is precise control of the acceleration such that it remains constant and consistent. The dynamometer control system is responsible for the reliability of the acceleration rate.
The inertia sweep test is as close as possible to actual driving conditions. Though the test does not provide the same type of data that can be acquired during driving, it does come very close. The purpose of the test is to measure the inertial resistance of an engine.
The loaded sweep test has two versions, which are simply fixed and controlled. With the simple fixed test, the engine accelerates at its own rate. Power is determined by the power required to accelerate the dyno. As the name indicates, the controlled version of a sweep load test controls the acceleration rate.
The transient test was developed to examine various driving patterns that a vehicle will encounter during its use. The testing procedure is designed to include throttle movements, speed changes, and other engine patterns.
Variations in the transient test include cold starts that are immediately followed by hot starts. The test’s main purpose is to measure emissions as outlined in Federal Test Procedure (FTP) documentation. Under FTP guidance, the load factor during the test should be 20% to 25% of the maximum engine power.
In the majority of cases, the first place an analyst looks when reading data from a dynamometer is at peak power. Though this is an essential statistic, it is more important to examine the average power that covers a useful rpm range. The provided readings of the useful range are the minimum rpms of an engine at wide open throttle.
A concern for managers and supervisors in industry is to ensure top performance from the equipment being used. Inspecting, assessing, examining, and testing of machines and engines is a necessity. A dynamometer is an ideal tool for determining the power and capabilities of essential equipment. The use of a dyno is a way of guaranteeing that a procedure works smoothly and efficiently.
A dynamometer is a tool that can scientifically calculate the speed, torque, and power of any engine, machine, or powered tool. The general use of a dynamometer includes collecting data on motors, engines, pumps, and generators, making them applicable in a wide range of industries.
An important function of a dynamometer is providing accurate and precise data. They are an ideal instrument for determining the best use of fuel and whether fuel is being wasted. The provided data assists in fine tuning and adjusting machines and motors at little cost.
Though testing devices are an excellent idea, they are only as good as the data they provide. Dynamometers provide the highest quality of precise and accurate data in a clear and concise manner. They are capable of examining large and small weight equipment and are available as portable units.
Manufacturers of dynamometers have a wide range of sizes to fit any type of application. Water brakes are ideal for large engines while eddy current brakes measure engines up to 250 hp. The many options make it possible to purchase a dynamometer that specifically fits your needs.
The key attribute for any industrial instrument is the ability to withstand and endure the conditions where they are used. Dynamometers are solidly built from metal alloys. Producers are well aware of the conditions where their devices will be used and plan them to be durable and strong.
There are general parameters regarding the performance of engines that require testing to provide data for making adjustments and maintenance. The requirements for rigging and lifting operations are slightly different than those of engines and motors. Specially designed dynamometers provide data that assist lifting and rigging operations to be efficient and safe.
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