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Wheel Roll

This is an Aircraft Wheel test rig for evaluating fatigue limits of Fighter Aircraft Wheel assemblies, using Axial force with Yaw and Camber component to validate material selection.

A brief description of the design and construction of this equipment is furnished below

Application

The Under Carriage of the Fighter Aircraft comprises the Main Wheel set below the wings and a single Nose Wheel in the front section.

The wheel hub is a lightweight alloy designed to accommodate the disc brake system and support Axle. To test the mechanical and thermal properties of the alloy Hub under the loads that will occur in operation, simulation equipment is required

The wheel hub is a lightweight alloy designed to accommodate the disc brake system and support Axle. To test the mechanical and thermal properties of the alloy Hub under the loads that will occur in operation, simulation equipment is required

General Description:

This Rig develops varying levels of Axial Force on the Wheel assembly while simulating taxing condition. Two load stations are provided, one for purely axial load application called Station "A" and the other for a combination of Axial load with Camber and Yaw conditions, Station "B".

The Camber represents the pre load deflection of the cantilever Wheel bracket assembly while the Yaw induces the drag that occurs when the Aircraft changes direction during ground motion.

A hydraulic powdered Ram provides the Axial Force, while the Camber and Yaw positions are achieved by manually setting a mechanical position device for specified conditions.

Data Acquisition System:

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

Axial Force:

The Ram equipped with a faceplate on which Wheel bracket is mounted, is moved linearly by a hydraulic cylinder. On achieving contact with the rotating Drum surface the required force is generated and maintained using a sensitive valve circuit. The axial force is measured and recorded continuously via compression Load Cell placed between the Ram fixed end and the support.

Linear Speed:

The surface velocity of the Wheel assembly is variable by modifying the rotation speed of the Drum unit. A DC Thyristor controlled drive unit provides a smooth acceleration as well retardation.

Duration of test:

The parameters of the test are to be compiled and the basic axial force set manually. The run time duration can however be set and achieved in Auto mode.

Safety Feature:

In the event of Tire burst, the Ram will retract automatically and shut down the drive. The sensing for this condition is dependent on individual wheel specifications and needs to be set in position prior to test run. A canopy type slide cover with mesh covering is available to ensure Operators are protected from tire pieces.

Construction:

The Rig is simple in concept and construction, using indigenous components and manufacturing technology. Two Stations are provided, one for purely Axial load application and the other for a combination of Axial with Camber or Yaw.

The rolling effect of Wheel on tarmac is created by a 2.0 meter diameter drum having a face width of 0.5m, and supported on live axle in steel bearing housings. The supporting framework is an integral steel bed anchored to a RCC bed. All the force and reactions are confined within the frame itself and only self-weight and dampening are absorbed by the civil foundation.

The Axial force is generated using hydraulic cylinder acting on a square Ram in a slide guide. The cylinder itself is floating on horizontal guides, and the reaction is transferred to a standard compression Load Cell at the rear.

The Yaw effect is achieved by a rotation facility available on the Face Plate of the Ram at Station B. The extent of Yaw required is set manually and locked into position using a quick acting taper lock mechanism. During the test, considerable torsion is generated on the Ram assembly, and is effectively absorbed by the square construction.

The Camber position is available by moving the whole Ram assembly on a cross slide, by a manually operated lead screw mechanism. The Ram slide guide housing is pivoted on a central shaft and will then need to be aligned to ensure that Tire make contact with the middle of the Drum face. The pivot restraint is through a shear beam load cell, and the reaction generated during the test provides the input for computing the Side load induced on the Tire assembly.

The process of mounting the wheel assembly is made easy by having a bracket and matching axle to suit each type of unit; heavier load application an additional support arm is provided and attached to the same faceplate.

Controls:

The 75 HP DC motor is selected to build up the speed of the Drum through a helical step down gear box. The Axial force is applied after achieving the set speed and the power is required to maintain this speed under wheel drag condition. The stability of the load on the wheel during test is ensured by a combination of hydraulic force through a variable displacement pump and natural tire pneumatic cushioning effect.

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.

Conclusion:This Test Rig enables a comprehensive and user-friendly method of simulating stresses on the components under design and development. Strain gauges fixed to the hub of the wheel will be able to analyse deflection and transmit the data to the DAS via slip rings or telemetry. The first Indigenuous Test Rig for Aircraft Wheels is installed at Hindustan Aeronautics Ltd., Lucknow, for testing of LCA Wheel Assemblies.

Performance Data:

Taxiing Speed: 55 Km / Hr
Max. Axial Force Available: upto 8000 Kgf.
Load Application:
Yaw: +/-10%%D
Chamber: +/- 15%%D