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Dynamometers

Proof testing and Performance Evaluation are an integral and crucial part of Product Development, creating "near to actual" condition with measurement is essential. At K-E Material Handling, we have built "Load Simulators", also called "Test Rigs" for various applications.

One such Simulator is the "Brake Pad Dynamometer" built to simulate a proportion of the reject take off energy level of a Fighter Aircraft and to establish the Temperature and Wear Characteristics of the Carbon fiber material used as the brake surface element.

Application

The Under Carriage Wheel Set of a Fighter Aircraft comprises of a pair of Pneumatic tires on Aluminum Alloy Hubs. The Brake system is housed inside the Hub and is actuated by Multiple Hydraulic Pistons, which press a set of Rotors against a mating set of Stators. The friction force developed between the relative surfaces of the Rotor and Stator provides the retardation required to control the velocity of the Aircraft during Taxing and Takeoff. Considering that the temperature rise is in the region of 1300 deg.C, the material characteristic of the Rotor and Stator pads is of crucial importance.

This Machine is required to develop varying levels of Kinetic Energy and dissipate this Energy in specific time using the prototype Brake Pads as the media. A set of 4 independently coupled Fly Wheels with specific Inertia properties, and rotating at controlled velocity develop the energy that needs to be dissipated. The axial force needed to simulate the Braking action, is provided by a single Hydraulic actuated Ram.

Data Acquisition System:

Online information is generated, displayed and stored through a DAS, covering:

Brake Force:

The Ram equipped with a faceplate on which the Stator is mounted, is moved linearly by a hydraulic actuator. On achieving contact with rotating Rotor pad (also mounted on a face plate) the required force is generated and maintained using a Servo Valve circuit. The axial force is measured and recorded continuously via compression Load Cell placed between the Ram fixed end and the support.

Maximum Torque:

The Ram has a freedom to rotate along its axis, and a restraint is provided to prevent sympathetic rotation at time of contact with the Rotor. The restraint force is measured by a strain gauge, and used to compute the torque. Peak values and average values are recorded.

Temperature rise:

The Stator faceplate has a recess to insert a Thermocouple sensor making contact with the rear surface of the Stator pad during the test run. Duration of test:

The complete test is conducted in "Auto" made, thereby providing for absolute measurement of time. Corollary Data:

Run down time, Run down distance, Energy dissipated.

Safety Feature:

Accelerometers are provided at critical locations and interfaced to shutdown test immediately on detection of mechanical vibrations beyond preset level.

Construction:

The concepts used are fundamental, and based on using indigenous components and technology adapted from Material Handling experience. The whole Simulator is a rotating machine with all the elements mounted co-axially on a common steel base bed. On account of the high energy and frequency vibrations developed the base is stress relieved and machined for level accuracy. Four solid steel fly Wheels having calibrated mass to achieve the gross MI of 16 units (1 unit = 1.0 kg-m-sec^2) are fitted with a Taper lock mechanism to toughened steel axles. To limit the deflection of the axles, two fly wheels are coupled to a single axle and then integrated to the drive by flexible gear couplings. The operating speed range goes up to 3300 Rev / min and this facility provides for simulating the actual contact speed between Rotor and Stator in true application. The behavior of brake pad material is dependent not only on the energy dissipated in specific time, but also on the relative velocity between surfaces.

The energy level desired for different operating condition simulation viz: taxing, normal takeoff and Reject Takeoff (RTO) is obtained by changing the combination of the flywheels during a Test Run. The MI of flywheels are 8.0, 4.0, 2.0, 1.0 units, with the drive system being a constant 1.0 unit. The energy level can be therefore varied by having MI in any range between 1.0 and 16.0 units.

The process of Coupling and di-coupling the individual flywheels from the axels is simplified using a "Taper Lock" mechanism. Each fly wheel is provided with a Roller support below, on which it rests when not coupled. When coupled to the system, the Flywheel leaves contact with the support roller by moving a small amount in the axial direction, through a special hydraulic puller facility. The co-axial alignment of all fly wheels does not change irrespective of individual coupled or idle status.

To get to the operating speed of 3300 rpm a Step up spiral helical Gear Box is used. Forced lubrication with an auxiliary pumps and heat exchanger is incorporated.

The DAS system provides for an auto sequence of operation during a normal test. The startup of the Drive, attainment of required speed plus 5%, shutdown of Drive power, coasting down to required speed, actuation of brake pad, measurement of retardation time, temperature change and retraction of ram are fully automatic. Graphical and digital displays of input and output parameters are available for evaluation. Foundation:

The entire foundation bed is in an excavated pit, such that the steel base frame only is at the finished floor level. A Mass Concrete bed having a weight ratio to equipment in excess of 8.0 is used to anchor the Equipment firmly. Vibration isolation to the surrounding earth is through a Sand bed media all round. The frequency of the entire mass is checked against the operating speed of the individual flywheels and a safe limit specified and built into the Program.

Conclusion:

This "Simulator" provides the user with a reliable and economical method of proving his Product for a crucial application, using completely indigenous technology.

Brake Disc Dynamometer, installed at DRDL, Hyderabad is used for Brake Torque Simulation on Carbon-Carbon Rotor and Stator of the LCA

Performance Data:

Energy Generated: 7.64 M Joules
Braking Force: 10,000 KGF
Velocity: 3,000 RPM
Power: 125 HP DC