Noise, micro-chips and the death rattle tesi
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All subjects covered by distinguished engineers at this get together last week. Graham Montgomerie was there to report on the latest developments
STEPPING in at the last minute at the Institute of Road Transport Engineers' conference to replace Transport Under-Secretary Lynda Chalker, Dr Cedric Ashley, director of the Motor Industry Research Association described current developments in vehicle noise, aerodynamics, safety and micro-electronics.
The Armitage Report suggested that the heavy lorry of 1990 should be no noisier than 1981 model year cars on a driveby test, which Dr Ashley regards as "a very real target." Since the White Paper, based on the Armitage findings, was published, the EEC has circulated a draft directive which suggests new noise levels for all vehicle classes. If agreed, these levels will apply to all new models submitted for Type Approval after 1986 and to all vehicles built after 1989.
Dr Ashley mentioned that these EEC noise levels would be measured under new test procedures. With the present drive-by test there is comparative freedom of gearing but under the new procedure the specific gear for the test would be clearly defined.
In describing some of the aerodynamic work carried out at Mira Dr Ashley said that it is possible to reduce vehicle spray by aerodynamic means. He quoted the example of a typical cabroof-mounted deflector which could reduce the downwash of
air and thus cut down on the airborne spray.
Although sideguards are only now becoming compulsory on certain classes of vehicle, the Mira safety vehicle of 1980 was fitted with such devices. Dr Ashley said that the complete surface type used added some 93kg (190 lb) per side to the unladen weight of the trailer. He suggested that 50kg (110 lb) was now easily achievable and that this could be reduced still further using composite materials.
On the subject of microelectronics as applied to the commercial vehicle, Dr Ashley stressed that such devices should increase the reliability of the vehicle and not decrease it. He suggested that manufacturers are currently applying microelectronics to non-safety related items in order to gain experience.
Taking up Dr Ashley's points on future legislation, Brian Hancock from National Bus suggested that the public might agree on the environmental benefits of such legislation but did not appreciate that such benefits normally carry a cost penalty. Dr Ashley agreed and said that it was necessary to make the best estimates possible on the sometimes conflicting areas of environmental benefit and cost and to put this information "back into the system so the government is as well briefed as possible."
The first day of the IRTE conference was devoted to engines for commercial vehicles in the UK and began with John Bendrey of Ford who described the background to the 90-150 diesel engines — otherwise known as Dover — which were developed for the Cargo range.
Mr Bendry told of the market research carried out, which included questioning 472 Ford operators and 775 operators of competitors vehicles in the UK, France, Germany and Sweden. From these, Ford analysed what was required for the 1980s and in what order these requirements were listed.
To establish the durability of the Dorset engine (which Dover was scheduled to replace) Ford obtained 32 high-mileage customer engines with a known history. These units were then stripped and measured.
According to Mr Bendrey, one result of the analysis was to show that the naturally aspirated versions suffered from very heavy top ring groove wear compared to turbo engines where this was negligible, with the comparison being made on an equivalent mileage basis.
The turbo Dorset engine had a cast-iron insert whereas thi naturally-aspirated version rai the ring in the aluminium pistol base metal. "Needless to say, al Dover engines have an insert,' said Mr Bendrey.
Continuing through the de velopment programme, M Bendrey recalled that the o pump and its skew gear driv. had caused problems on the SiY cylinder Dorset. "We spen hours and hours hating th• thing," he said. Accordingl Dover has a completely new de sign of pump.
One interesting test which wa described by Mr Bendrey wa the so-called "death rattle test designed to simulate a fan be failure on the motorway. Thi involved running the engine a. full load to obtain high stabilise. temperatures and then remo% ing the fan belt. He claimed the the engine has to survive fou minutes of this at full speed an full load with no malfunction c adverse effect on the pistons.
Representing Leyland Truck: John Tucker outlined the irr provements in technology no available to develop new powe units and transmissions. He suE gested that the most efficier automotive diesel of the 1990 II be the adiabatic turboarged engine, in which small creases in power over a arge-cooled engine would be ssible with the main advanpas being good thermal effisncy.
Mr Tucker maintained that turally-aspirated engines will rgely be discounted on ounds of cost and noise expt for developing territories 'sere more sophisticated enles may be "inappropriate." Thermal efficiency will imove, claimed Mr Tucker, ainly through reduced heat 55, and he quoted the current syland 400 engine as an ample. This has a minimum soled cylinder head which ves a 42 per cent reduction in at to water yet with a flame ce temperature of only 375°C 07°F). Mr Tucker mentioned rther developments in cornistion chamber insulation inding ceramic insulated pisns and valves.
Describing the engine perrmance characteristics which s thought would be necessary achieve maximum vehicle Dnomy with multispeed fixed tio gearboxes, Mr Tucker listed following: a rating of 30bhp/litre air to air charge cooling good specific fuel consumption good torque back-up (about 20 per cent) good lugging speed range about 40 per cent rated speed.
Mr Tucker suggested that bad irque curve shape and driveline latching can lose the benefits f an efficient engine. "Good latching can, at best, realise the Jvantages of the good engine," a said.
Steve Cowling, manager-test perations at Perkins, mainlined that more engine power in conjunction with a suitable drive line can result in reduced journey times and improved fuel consumption.
He illustrated his argument by quoting results from a 16-ton test, with a turbocharged T6.3544 against the naturally-aspirated version of the same basic engine. The result was a five per cent reduction in journey time allied to an eight per cent improvement in fuel consumption.
Lower fuel consumption is a major objective for engine and vehicles builders alike said Mr Cowling. He suggested that a 10 per cent improvement on a typical 32-tonner could lead to an annual saving of approximately £1,500 at current fuel prices.
A vital element in diesel performance is the use of pressure charging. As Mr Cowling explained this is virtually synonymous with turbocharging in the road transport industry, where an essentially single-speed device uses the exhaust energy to increase the quantity of inlet air to increase the power output for a given swept volume by up to 25 per cent.
Although improvements in fuel consumption of up to five per cent and reductions in bare engine noise levels of up to 6dB(A) have been obtained with turbocharging, Mr Cowling admitted that because of the limited speed range capability of the turbocharger it is only ideally matched to the engine requirement at a single speed. Therefore compromises must be made in matching to obtain adequate torque outputs and low emissions at low engine speeds without excessively high cylinder pressures being developed in the upper speed range.
Because of this limitation Mr Cowling suggested one solution in the shape of a variable geometry turbine which could match the engine requirements over a range of speeds by varying the angle of the inlet guide vanes of the turbine. Although the problems of optimised gas flow paths and mechanical reliability have yet to be overcome, Mr Cowling maintained that the variable geometry turbocharger "will be a significant feature in the diesel industry of the late 1980s."
As Mr Cowling explained, it has long been accepted that driver technique plays a major part in determining overall vehicle productivity and durability. He suggested, that, in order to improve these techniques, a greater degree of "on line" information is required by the driver on engine operating conditions.
In Mr Cowling's opinion, the trip computers, which he regarded as today's toys for the passenger car market, will become vital tools in maximising operating efficiency.
In the question time which followed, the Ford/Leyland/Perkins panel was asked if there was a possibility of a simpler cooling system which used neither water nor fan. All three speakers were in agreement that it is perfectly feasible to reduce the capacity of the cooling system, which in turn means a reduction in radiator and fan size, but thought that this was about the limit with current technology. John Tucker suggested that a minimum cooled adiabatic engine could reduce the heat to coolant from 22 to 14 per cent. "Going beyond that to perhaps vapour phase cooling is not on," he said.
The other side of the question was illustrated by John Bendrey who reminded the audience that the cooling system was a conve nient source of heat for the vehicle heater. He suggested that some current designs of minimal cooled engines are already marginal in this respect.
Brian Hancock of National Bus asked the panel what was being done to improve air compressor and fuel injection equipment performance. "About 30 per cent of our problems relate to such auxiliaries," he claimed.
Mr Cowley replied that bus application gives the compressor "a bad time" because of the continuous stop/start nature of the operation. He explained that Perkins specifies a compressor against "typical" useage, which required great care with buses. Because of this his company insists on involvement with the chassis manufacturer on installation detail.
In his paper entitled "Trends in heavy duty truck diesels" Stan Hartshorne of Cummins said that turbocharged and chargecooled engines of the future will attain 34bhp/litre without exceeding the known "state of the art", that is by still using a single turbocharger and without any unconventional materials.
Mr Hartshorne mentioned that the current generation of more powerful engines has permitted the use of higher axle ratios, thus allowing a reduction in engine revolutions at vehicle cruising speed with a consequent reduction in engine revs per mile of road.
He said that initially there was a negative reaction to fast gearing although it is now a universally accepted practice. "We should not be hesitant to adopt fast-geared speeds with appropriate driver instruction," he maintained.
Moving further into the future, Mr Hartshorne claimed that thermal efficiencies of 45 per cent will be possible by the mid 1980s and by using turbocompounding with some non-stressed ceramic insulation a figure of 48 per cent can be demonstrated.
He added that electronic fuel systems will optimise the fuel timing against speed and load demand with electronics also playing a part in optimising the engine and transmission matching to the road load.
On the subject of lubricant development, Mr Hartshorne predicted that 25,000km (15,550 miles) oil-change intervals are now very near with the lubricant itself also having a higher temperature capability.
Lubricant development also featured in Ken Bresser's paper called "The pursuit of minimum cost ownership". Representing Rolls-Royce, Mr Bresser agreed that longer oil-change periods are certainly possible but stressed that the oil specification must be appropriate and "not one of your wonder oils."
He went on to mention future Rolls-Royce developments up to 1984/85 which included a five per cent improvement in fuel economy and on oil consumption of 0.2 per cent. An engine weight of 1,000kg (2,204 lb) is a Rolls-Royce target as is a bare engine noise level of 98/99dBA. Mr Bresser emphasised that Rolls-Royce will continue with the basic 12.17 litre (742 cu in) block although there will be changes to the cylinder head specification.
Turning to the subject of inchassis overhaul targets, Mr Bresser claimed that 482,700km (300,000 miles) was possible with today's engines and that this could rise to 800,000km (500,000 miles) by 1985. In this case, "in-chassis" overhaul would include any necessary piston removal.
Further into the future the Rolls-Royce targets include a further reduction in engine weight to 907kg (2,000 lb) and in noise (93/94dB(A) at one metre). Mr Bresser suggested that the adiabatic engine will appear first in military guise as it will be some years before a realistic price will make it commercially feasible. In this context, Mr Bresser claimed that the Rolls-Royce experience in ceramics via its aero engine division would be helpful.
The automotive power unit of the future will continue to be diesel according to Paul Gardner of L. Gardner and Sons. He hoped that power stations and other static users of energy could be persuaded to use other energy sources leaving the transport industry among the last users of oil fuel. Emphasising the point Mr Gardner said that he found the idea of solar panels for lorry application "mind boggling". And I don't hold out much hope for a wind mill powered bus, he added.
Mr Gardner stressed the importance of fuel consumption in the total operating cost of a fleet by quoting some statistics from the National Bus Company, who in 1981 spent £46m net on fuel. According to Mr Gardner even a one per cent reduction in overall fuel consumption would represent a saving of £500,000.
The effect of aerodynamics on vehicle performance and fuel consumption is obviously of great interest to Mr Gardner, who suggested that sun visors and name boards on the cab roof should be ruled out. He also queried the common sense of fitting a cab roof wind deflector and leaving it upright when running empty.
Echoing the views of the other speakers on road speeds Mr' Gardner appreciated the need for higher gearing but, at the same time, said "if you don't need the speed, don't use it."
Predictably the open forum featuring the Cummins, Gardner and Rolls trio was a stimulating affair. The subject of lubricant specification was raised by Mr Ken Poulson of Eastern Counties Bus Company and brought forth an interesting diversity of opinion. According to Ken Bresser, "the oil should be as good as you can get with the biggest safety margin you can buy."
Stan Hartshorne stressed that caution was necessary in matching new lubricant specifications with longer oil-drain periods. He suggested that operators should carry out their own tests but emphasised that it was definitely a case of "hurrying fairly slowly."
Paul Gardner felt that it was possible to overspecify a lubricant. Providing the operator followed the laid-down engine maintenance procedure, Mr Gardner did not think there was any need to go to the ultimate in oils.
Brian Hancock of National Bus said that his greatest problem with oil was deterioration through dilution and asked for the panels views on regular sample monitoring of the sump contents for laboratory analysis. In reply, Mr Hartshorne said that Cummins experience did not show dilution as a difficulty. "Additive depletion is our major problem," he said.
Paul Gardner said that sample oil analysis could be a useful indicator but he stressed the word "indicator". If a dubious result showed up, second and thi samples would be necessai "Do not over-react on the bal. on one report," he said.
Most of the wasted time workshops is down to poor dia nosis and repeat repairs wan ing to Frank Austin, Doug Gro and Ivan Ward who discuss. transport engineering manac ment. It was suggested that h nus systems — in which mu time, effort and money a invested — are wasted by fau workmanship and lack of be: knowledge.
Although the panel said tlmany management tools a available to today's engineer, would appear that instead making his work easier the a posite prevails. Ivan Wa mentioned that detailed analy: of vehicle records is useless u less action is taken on the suits. He said that unless ti manager has sufficient eni nearing expertise to interpret ti information and guide h workshop staff, then his reco system becomes redundant cost-effective aid.
This could also applay to oi information. Mr Ward said thal is easy to hear what we want hear but information given I mechanics and drivers can or be useful if correctly interprete
With many workshor working bonus systems and tl relatively low cost of unit r placement, Mr Ward said th many mechanics had becon just unit part fitters. This in itsi was not a bad situation provi ing they are competent at fittir the units. However, it was mai tamed that a percentage of the mechanics must be fully skilli with a full understanding basic principles to help guide ti "unit fitters."