The equipment operators need
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:OMMERCIAL vehicle pecification and performnce was the theme of the nnual conference of the Intitute of Road Transport Eniineers held at Solihull last weekend.
The subject matter of the rarious papers encompassed he psv, the heavy lorry, the Jngine and vehicle costing.
The best results obtained luring the past 40 years of bus )peration have pointed the user awards large capacity engines, noderately stressed and with he minimum of appendages, iccording to A Gurley of the Vational Bus Company in his )a per.
As far as the appendages are 7.oncerned, Mr Gurley said that his applies particularly to those omponents whose efficacy lags ehind that of the engine. -Turbochargers came to mind n this context," he said.
Bearing in mind operator experience with rear-engined vehicles, Mr Gurley said that having a high temperature device (eg an engine) in an encapsulated compartment is inviting trouble — maybe as serious as a fire and certainly incurring "ongoing cost" with frequent replacement and poor accessibility.
Auto transmission
Automatic transmission now an offer fuel consumptions on a par with current automatic and semi-automatic fluid flywheel transmissions. With an increased proportion of the vehicle's journey time spent stationary, Mr Gurley argued that a fluid coupling wastes fuel while idling in gear at stops. "A return to neutral gear when a bus-stop brake is applied would benefit both types, but the hydraulic couplings' days are numbered, surely," he said.
Mr Gurley claimed that foundation brake problems are now severe, arising partly from the weight of the modern vehicle and partly from its very poor weight distribution. Figures for brake lining life were quoted at 14,500km (9,000 miles) for the rear and 54,000km (40,000 miles) for the front — nearly a 1 to 5 relationship. There is, he said, scope here for better ventilating wheels, ie more holes, bigger holes or even spokes.
Owing to the introduction of retarders, hub-reduction axles will be seen on future psv conferring a better matched crownwheel and pinion, he said.
Mr Gurley believed power steering is here to stay, but he stressed that high quality integral units are a must as the present life between overhauls is only 18 months to two years.
Operators' view
Hammering home the operators' point of view, Mr Gurley said that they want better air compressors with much reduced oil carry-over, and the air to be dried by an air dryer.
He explained "It is difficult to comprehend when the additional cost of hydraulic brake installations is known. There is a lot of life in air systems if properly provided with quality and protection."
The all-hydraulic bus (horn and doors included) will not be possible, according to Mr Gurley. Some functions cannot be carried out satisfactorily electrically so he concluded that the vehicle is finalised with both air and hydraulic systems. But, on the other hand "The all air bus has been here for many years. I believe that if the industry spent
a little on improving the quality of its air equipment it would save the money it will cost to learn hydraulics.
Mr Gurley insisted that shapes, flat backs and a minibodies must be improved to assist the bus washing machine and the cleaning staff. By "improved" he meant smooth exteriors and interiors, simple mum of recesses, holes and protrusions. Also corrosion protection must continue to be improved.
Heating and ventilating must be updated, he stressed. If it is necessary to use the engine as a source of heat — and he thought it desirable in view of future limitations on crude oil supply — then modulation of fan speed, water pump speed, radiator shutter opening and heater motor speed all seem necessary.
Tyres with aspect ratios of less than 1 to 1 have not conferred all the advantages expected, according to the National Bus Company. In Mr Gurley's opinion the gain in reducing the step height does not justify their use and the need to save fuel might be their sole justification, as such tyres have a reduced rolling resistance.
Reduced weight
Mr Gurley maintained that reduction in vehicle weight will be of paramount importance for fuel economy. Although he thought that a body lightening exercise is limited in scope, 66 seated plus eight standing
passengers on around 53/4 tons might still be the ratio to aim for.
He said that there is scope for closer co-operation between the chassis builders and the bodybuilders.
The official title of Roger Wilsdon's paper was "Selecting engines on 'total cost' considerations." However, his subsidiary title gave a clue to the line his paper took — "Specifications like ideas are easy. Performance, like implementation, isn't!"
Mr Wilsdon, who is manager — field sales, Cummins, said that it is economy in isolation without balancing fuel costs against those other factors which can vary from one engine type to another.
Of these costs the most significant are • Routine maintenance costs; • Unscheduled repairs including downtime costs; • Payload capacity (determined by engine/driveline weight); • Trip times (determined by engine/vehicle performance); • Vehicle replacement life and residual trade-in value.
To put this into perspective, Mr Wilsdon suggested that no operator would buy a 32-ton tractive unit capable of around lOmpg fully laden if the asking price was £40,000 or if it had to spend one day a week in the service bay, or if it broke down at fortnightly intervals 2.00 miles or more from base, or if it could carry around 15 tons of payload, or if it had a top speed of only 35mph, or if it was worn out after 18 months when a man had to be paid to take it away!
When Cummins introduced the new Formula £290 engine earlier this year, many operators welcomed the promise of a 12 to 15 per cent improvement in fuel consumption, said Mr Witsdon. "But they wanted to know if there were hidden drawbacks. An improvement from 6.5 to 7.6 mpg would surely have to
be paid for in higher running costs?'" The tremendous advances in diesel technology which have been made in the past five years have produced a genuine increase in diesel efficiency. This has been partly as a result of the 1973/74 oil crisis and partly under the stimulus of possible competition to the diesel from gas turbines, Stirling engines and the like, he said.
Cummins drum • Banging the Cummins drum, Mr Wilsdon claimed that their vehicles. fuel economy has been improved without a price increase, without maintenance procedures being more complex, with no weight penalty and without impairing performance.
Fuel savings, in miles per gallon terms, obviously became more significant as annual mileage increases, said Mr Wilsdon. The operator with 32tanners averaging around 100,000 miles a year would find it easier to justify the extra initial cost of an engine with proven economy than his counterpart with low mileage heavies on urban or inter-urban running.
In comparing different aspects of vehicle costing, Mr Wilsdon quoted some interesting figures.
For example the break-even mileage between two engines can soon be calculated if engine A adds, say, £1,500 to the price of a chassis compared with engine B but engine A gives one mpg better fuel return. Covering 50,000 miles a year on diesel fuel costing 75 pence per gallon, the operator using engine A will save £767 a year per vehicle on fuel. Thus the initial £1,500 penalty would be recouped in under two years.
Low mileage Mr Wilsdon suggested that when looked at from the very low-mileage operator's point of view, the £1,500 extra spread over, say, a seven-year chassis life would be justified on present fuel costs at an annual vehicle mileage of only 14,000.
Traditionally greater engine horsepower has meant greater thirst, said Mr Wilsdon, but he went on to claim that there are distinct indications that the latest diesel technology, applied to turbocharged engines in particular, is reducing the relative thirst penalty of big horsepower units even when they are driven
hard and full advantage is taken of their performance.
Cruising speed The ability to sustain cruising speeds on motorway gradients is now a prime consideration in determining productivity, Mr Wilsdon concluded.
In his paper on "Costing commercial vehicle maintenance," K. J. Button, of Loughborough University, said that although the maintenance component varies considerably from fleet to fleet it is generally in the order of 15 to 30 per cent of the total operating costs.
Maintenance costs
Most knowledge concerning maintenance costs comes from engineering studies in which commercial vehicles have been tested in various, frequently simulated, conditions for wear and tear on their different components. Although this type of work tends to produce quite accurate results, it was Mr Button's contention that, because of the controlled conditions under which the test is carried out, it often fails to reflect the particular circumstances confronting those actually running a vehicle fleet.
Mr Button claimed that by adopting techniques in widespread use in applied quantitative economics it is possible, using data already available to a well organised operator, to isolate the main contributory causes of maintenance outlays and hence provide information which could lead to reductions in overall operating costs.
In the past these techniques have tended to be the tool of the academic rather than the industrial economist, he suggested. Although economists often tend to be thought useful for considering problems on the
demand side of a firms ape! tions (-Is business going to pi up next year?-), they are le frequently employed on the cc side, he said.
The specifications and pt formance criteria of the futL were covered by P. M. Kenni technical journalist when I stated that the design and de■, lopment of vehicles governmed not only by e gineering experience ar operational demands but alsol legislative controls.
The steady pattern of relati costs over the last decade shol little sign of changing radical he said. That trend is for ti initial purchase cost al operating cost to increase at greater rate than the reven earned through freight carriac
Tractive unit cost
Mr Kennett argued that 38/40-tonne tractive ur would cost at least £80,000 I the beginning of the 1990s the rate of price increase ov the last dozen years continuE He suggested that, to balan these equations, three are must be studied • Changes in operatit patterns needed to fit mo working hours or tonne-km in a working month; • Rethink on design to reta initial cost levels as much possible and, at the same tim make the vehicles more accel able to the buyer;
• Retain operating cost creases by improving durabili and reliability, extendir maintenance intervals al generally increasing workir time as against down-time.
Mr Kennett stressed th these factors all need attenth — they cannot be treated isolation.
Coupled with these thri search areas, he mention( other fields of technology vv( thy of examination. As far ; engines are concerned, the areas include moves towari higher torque at lower engir speeds to give the requirE journey time with low we, rates.
In Mr Kennett's opiniol transmissions for general o highway use are unlikely to i clude many automatics exce where the shift requirement either very severe or ve frequent, le the COnStructic industry and the door-to-do distribution business.
The report on the conferen, discussion and the vehic equipment display is on pa( 21.