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round
Specifying an electromagnetic retarder can lead to significant operational cost savings, plus a smoother ride!
Not long ago, retarders were considered as an option only found on coaches, buses and perhaps a few heavy goods vehicles operating in the Alps. Now a greater awareness-and an increased demand on brakes-has expanded the market substantially, broadening it to create a large number of specialist applications. The wide range of different manufacturers and technologies-engine and exhaust brakes,
hydraulic and electromagnetic retarders-has contributed to this growth.
While safety remains a prime concern for all operators, commercial pressures and operational requirements have seen the use of retarders grow, not only in the more traditional areas such as tippers and international haulage, but also in many new niche applications.
Stop-go urban applications such as waste collection, for example, or slow speed heavy haulage, benefit from the Telma electromagnetic system due to an impressive performance right across the road speed range. Not only are the benefits significant at high road speeds, but almost full retarder performance is also available at very low speeds right down to a standstill.
Front-line emergency vehides, from 3.5-tonne ambulances to 12-tonne fire engines, generally operate in high-density urban environments and have to respond in minutes. This type of use places a huge demand on service brakes, and Telma believes it has made major contributions to improving safety through eliminating brake fade. In addition, an electromagnetic retarder has the knock-on effect of making a major contribution to cost reductions, by minimis ing wear of friction linings and disc or drum cracking from excessive heat.
The Telma electromagnetic system consists of the retarder itself, together with the control system appropriate for the application. The retarder itself has two basic components-the stator assembly mounted to either the chassis, the rear of the gearbox or the driven axle, and the rotor which is permanently coupled to the propshaft. There is no contact between these two components, ensuring friction-free retardation.
The driver activates the control system, and current flows within the coils mounted in the stator, creating a magnetic field. The rotors attached to the propshaft revolve within this field, creating secondary and opposing magnetic fields, which in turn creates the braking torque acting through the driven wheels.
The flexible control system can be designed to suit the operational needs oi the application, from a simple hand control built into the dashboard, to fully automatic control integrated through the foot-brake pedal for urban delivery and emergency vehicles. Optional downhill speed regulation enables the driver to set the speed on long downhill descents, for maximum comfort and safety.
The wide range of Telma electronit. controls allow the optimum integration with the latest vehicle systems, including ABS/ASR, Electronic Braking Systems (EBS) and the latest CANBUS multiplex technology.
The next generation of Telma retarders for heavy trucks-the Hydral-ix expected to be available shortly and will see substantial reductions in weight and power consumption, yet giving ar unequalled performance on the road.
Ruing and maintenance Telma provides a highly flexible system and these retarders can be fitted to more or less all types of commercial vehicle, with complete independence from engine type, gearbox and cooling system. The majority of Telma installations are specified as factory options on new vehicles, but retrofits can be cost-effective and straightforward on dealer stock, or even vehicles in operator fleets. Whole life costs are extremely low. The Focal range, for example, is designed for gearbox or axle mounting. A physical Inspection and function test is all that is required as there are no wearing components whatsoever. On the Axial range, a physical inspection and greasing at 6o,000km intervals is recommended—but this will no longer be required with the new generation of sealed units due to be released shortly!