Volting ambitior is meeting resistance
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Progress in electrical systems has been limited in recent years but Lucas is hopeful that a production breakthrough will lead to big savings in the weight of components. Bryan Jarvis reports on developments
VEHICLE electrical systems of commercial vehicles have changed only slowly over the past few years. I learnt this when I went along to Lucas Electrical Ltd at Birmingham to find out what developments have already taken place and what others we can expect to see in the future.
It has been very much a case of steady and unspectacular development with the emphasis placed on weight-saving and cost-effectiveness for many components.
There are still many vehicle parts which are manufactured from mild steel because plastics are not suitable. Although Lucas was reluctant to explain the process to CM it is using a nitrocarburising treatment of mild steel which it says achieves a considerable increase in tensile strength with improved anti-corrosive qualities. The result is that in many applications less metal is used, thus offering a considerable saving in the weight of components.
It seems that the process will be developed beyond the realms of electrical components and, who knows, might even herald the arrival of "off the shelf" exhaust systems which will survive more than one winter's salting season, Conventional mild steel thin links for windscreen-wiper mechanisms are being replaced by nitro-carburised mild steel ones which weigh only a third of the weight of a link currently used.
Lucas has carried out 500 hours of continuous running and salt-water tests on fan motors of nitro-carburised mild steel build. From the results, it believes that these motors can successfully replace motors of conventional mild steel without the need for shaft support bearings.
A smaller and lighter electric horn has been developed and is being produced using "treated" mild steel reducing the weight and improving its anti-corrosive quality. Lucas assures me that there is no reduction in volume. Each horn is electronically tuned to meet the required standard and 10 per cent of each batch is sample-tested.
The new horn will soon re place the larger existing ones fitted to cars, light vans and some commercial vehicles. The mounting brackets will also be constructed from nitrocarburised mild steel.
At their Cannock factory Lucas is using a thermosetting compound in the manufacture of horno-focal headlights for cars and light vans, with weekly production currently at 10,000 units. Conventional five-and-a-half inch diameter headlights for commercial vehicles are also manufactured by this method but in much smaller batches.
Headlights made from pressed steel are still being produced but the thermo-plastic method is proving more cost effective.
According to Fred Annis, production engineer at Lucas' Cannock factory, homo-focal units are press-moulded so accurately that few metal attachments are required, which means a much lighter headlamp unit.
This type also has the advantage of being corrosion resistant and does not react to extreme temperatures.
Before production is set up, the photometric performance of each prototype is examined under laboratory conditions, The finished moulding receives two wax coats and is then baked at 250°C which removes all imperfections in the reflective surface. This is followed by a vacuum-induced aluminium coating, a silicone-monoxide film coating and a final plating to complete the process.
Before being dispatched to Lucas' customers each unit is tested electronically at Cannock to ensure that it complies with UK and European lighting requirements.
Lucas currently manufactures over 36 different types of headlight by this method, which indicates how the range of shapes required is dictated by vehicle styling trends.
Its policy on starter motors is one of continuing development on a range which will feature epicyclic gearboxes with a performance equivalent to its M50 starter.
Within this range will be both wound field and permanent magnet designs, with the latter being more suitable for lowerpower requirements such as petrol or small diesel engines.
The characteristics of the gear type starter motor differ considerably from its conventional counterpart. The cranking cycle obtained from a geared starter motor has a higher stored inertia in the armature which results in lower speed fluctuations. Lucas is presently studying this and other effects on possible future applications.
Its electronics and systems division is continually extending its field of influence and many of its products will find a place on commercial vehicles.
In current production are vehicle condition monitoring (VCM) systems which continuously sense the state of subsystems. A typical VCM system comprises a sensor, a control module and a display.
Many types of sensing devices are being produced, among them float switches which are suitable for operating in solutions of glycol or alcoholbased antifreeze mixes, windshield washer fluids or lubricating oils. As the fluid level falls, the angle of the float arm increases to a predetermined value and the sensor contacts operate to activate the warning display.
Another type, the model 6SR oil probe is designed as a flexible dipstick with a hot-wire element incorporated in the lower end to monitor automatically a low oil level in the sump (with the engine stationary).
These devices can be used on petrol or diesel engines as part of a single or multi-channel VCM system from a 12 or 24-volt source. Battery temperature sensors, which are mounted in the base of the battery tray, are designed for use with specific regulators fitted to the Lucas range of 12 or 24-volt alternators.
These sensors cause the alternator-regulating voltage to be adjusted in keeping with battery temperature.
Displays of information from sensors are normally designed by Lucas to meet customer needs. Lucas display systems can operate with bulbs, vacuum fluorescent, dotmatrix, led and lcd displays.
Multi-channel control modules are designed to control a number of sub-systems, such as the coolant, screen wash fluid, oil level, brake fluid level, brake pad or lining wear and low air temperature outside the vehicle.
Modules incorporate delay circuitry to avoid false indications. The state of the oil level is "stored" should the engine be restarted before sufficient oil has had time to drain back into the sump, to produce a true readout.
Control modules also feature an automatic dimming of warning lamps to prevent dazzle when switching on side lights.
An extension of the VCM system is the trip computer which is designed at the moment for use on vehicles having carburetters or petrol-injection equipment.
The trip computer provides a digital read out of fuel, speed, mileage and time data from a 12volt negative earth supply, drawing a current of approximately 10mA.
Data computed includes fuel consumption (both average and instantaneous) distance travelled, average speed, and actual and elapsed time.
Press buttons will select the data for display. Metric or Imperial measurements can be selected from the trip computer which can be supplied to compute fuel in litres or gallons (Imperial or US) according to the market.