Driver training
Page 32
Page 33
If you've noticed an error in this article please click here to report it so we can fix it.
Paper by Alan Bunting, CEng, MIMechE, ASAE Since the first world oil crisis of 1973/74, fuel economy has taken on a previously undreamed-of importance. For the first time, fuel consumption considerations can now influence truck buying decisions — often outweighing cab comfort, ride and even outright performance potential.
TRANSPORT fleets have been put under greater costing pressures than ever in the last decade, and particularly during the five years of recession. This has had the effect of tightening the "fuel economy screw" even more, as fleet operators have come to recognise fuel saving as the most achievable means of trimming costs.
In a haulage concern, a 10 or 12 per cent improvement in miles-per-gallon, across the fleet, can tilt the balance back into commercial competitiveness and therefore into profitability and survival.
For own-account companies, the distribution element of product cost can be reduced, giving greater margins and/or the chance to be more price competitive.
Heavy manufacturer investment
It is not surprising that over the last decade manufacturers of vehicles and driveline components — notably engines, fuelinjection equipment, turbochargers and transmissions — have ploughed so much investment into fuel-saving research and development.
Some of the results of costbenefit calculations made by manufacturers in this context in the mid-1970s, make fascinating reading.
In many boardrooms, throughout Europe, the United States and Japan, marketing directors were asked the same question. It was along the lines: how much of an increase in sales penetration can be expected if we can improve fuel economy?
a) by 5 per cent at an R & D cost of Lx million?
b) by 10 per cent at an R & D cost of fy million?
c) by 15 per cent at an R & D cost of fz million?
They needed to know separate answers for each market territory. In Scania's case, for example, 10 per cent better fuel consumption from the company's 11 litre engine would attract a greater percentage gain in sales in Britain than it would in Sweden.
British transport operators were, and remain, the most overtly cost-conscious in Europe. The extent to which they are influenced by total lie wholelife) costs, taking into account chassis durability and reliability, is another question, of limited relevance here.
A haulier or an own-account distribution director in Britain, faced with renewing part of his fleet, is likely to be influenced more heavily than his counterparts elsewhere in Europe or Scandinavia by the "carrot" of fuel-saving potential.
Manufacturers have spent millions of pounds, kronor, deutschmarks, francs, guilders, even lira, in fundamental research during the 1970s. The expenditure goes on — aimed specifically at raising fuel efficiency.
Cabs have been made more aerodynamic, with factory-approved cab-roof air deflectors listed as standard options. Rolling resistance of tyres and final drive gearing has been reduced.
Diesel's new lease of life
Most significantly of all, the diesel engine has been made more and more efficient. Some engineers have claimed that the extent of the reciprocating diesel's inherent superiority over rival power units, like the gas turbine, Sterling engine and the now almost forgotten Wankel diesel, only became apparent through intense 1970s R & D activity.
At the beginning of the 1970s, there were those who thought the diesel, as a genus, would be finished by about 1990. Today they confidently predict a rosy future for it, well into the next century. Indeed, with hindsight, the possible imminent demise of the diesel can now be seen as almost laughable.
It is a brutal fact of life that the cost of research and development has to be passed on to the customer — in this case the fleet operator. A 1984 engine which is 10 or 15 per cent more economical on fuel than its 1974 predecessor will inevitably be more costly. And while today's chaotic discounting war in Britain has thrown selling prices into a world of unreality, the laws of supply and demand continue to operate.
A 38 tonne tractor with a proven capability of returning a laden consumption of 7.5 miles per gallon will command a higher price than an otherwise comparable chassis which can manage only 6.5mpg.
Having taken delivery of an expensive new 1984 chassis and put it into service, the operator might well find its fuel economy falling short of expectations. The right axle ratio for the application is specified and nothing is out of adjustment ... except the driver!
Driver-dependent economy
A profound, even disturbing, truth about road transport today is that good fuel economy is as dependent on driving style as it is on the skills and experience of the most highly-paid and highlyqualified diesel and vehicle designers and development engineers.
Millions of pounds worth of R & D expenditure, along with the
time and effort involved in fuelsaving research — can effectively be squandered if drivers pay no heed to engine and driveline characteristics.
There is little point in formulating a vehicle selection policy where fuel consumption is a key criterion, if the economy merits are thrown away as soon as the driver gets into the cab.
Making the driver want to save fuel is three-quarters of the battle towards the realisation of a vehicle's full fuel-economy potential. The conference paper by the representative from the NFC will deal with the incentive issue, so ills not appropriate to dwell on it here.
Having instilled in the man in the cab the desire to save fuel — which for owner-drivers is of course instinctive — the question of training arises. Many hgv drivers resent any implication that their driving style could be improved. But if it can be shown that over a given route they can save fuel, with no consequent increase and possibly with even a reduction in journey time, then such resentment is likely to disappear.
Training drivers to be fuelconsumption conscious can bring additional fleet cost benefits, over and above those seen in month-end or year-end fuel bills. Fuel is saved, but so is wear and tear — on the vehicle itself and on the driver.
Consumption-conscious driving means in many ways "lazy" driving. Less gearchanging is needed, so that clutch and gearbox wear is reduced. Engine revs are deliberately kept down so that engine life is inevitably prolonged.
Scania was one of the first heavy truck producers to recognise the vital role of the driver in any fuel-saving measures and to develop a programme of driving style recommendations and training for the benefit of operators.
In 1978 Saab-Scania mounted an energy-conservation campaign which examined the possibilities of cutting fuel consumption in cars and commercial vehicles through driver training, with a view to conserving the earth's dwindling energy resources as well as raising vehicle efficiency.
Since 1978 diesel engine development has advanced significantly, under the stimulus of operator demand. However, the characteristics of today's highlyefficient diesel engines, as shown in their power, torque and specific fuel consumption curves, make good economy more dependent than ever on the driver.
Greater benefits from diligent driving
That is to say, diligent driving in a vehicle built in 1974 might have brought fuel savings of 5 or 6 per cent (corn pared with 'thoughtless' technique). Whereas a similar comparison made with a 1984 vehicle powered by a new-technology engine would result in a 10 to 12 per cent improvement.
A driver training scheme has now been launched by Scania (GB) Ltd, which sets out to educate the man behind the wheel in this technical background, as well as in pure driving technique.
It is explained to each driver that today's engines are happy to "lug" at much lower rpms than their forebears. Torque, the indicator of lugging ability (or tractive effort), is higher at the top of the curve than it used to be, in an engine of given horsepower rating.
More importantly, torque curves are flatter than they were. In many cases the word "peak" is no longer appropriate to describe the top of the torque curve, which in any case now occurs much lower in the rev range — typically at 1250 rather than say 1500rpm a decade ago. In an engine governed at 2000rpm, the torque improvement at around 1100rpm, corresponding in today's heavies to a top gear road speed of about 40mph, is even greater in percentage terms than the gain in maximum torque.
Specific fuel consumption curves have also changed their shape. The least fuel is being burned at just those speeds where torque levels are usefully generous.
With Scania's two larger engines the DS11 and DS14, in both turbocharged and turbo-intercooled versions, the most economical range of engine speed is between 1200 and 1800rpm. The rev counter face in 112 and 142-series trucks is marked accordingly with a green band. In fact the trough of the sic curve on both engines occurs at just about 1600rpm.
Practicalities of economy driving
Candidates on the new Scania (GB) economy driving course are broadly familiarised with the characteristics of the modern turbocharged diesel engine, particularly with its meagre appetite for fuel at low revs. With that background established, they are able to see why driving techniques can influence fuel economy.
In essence the overall message directed at the trainees is to "reduce engine speed" and so keep the engine working close to peak efficiency and, at the same time, to reduce the average number of fuel-consuming engine revolutions per mile.
When they get behind the wheel they discover, under "tuition", that today's engines (a 333bhp intercooled DSC11 in the 32/38 tonne artic assigned initially to the training programme) will pull strongly down to 1100 or even 1000rpm.
Gearbox downchanges are discouraged as road speed begins to fall. The driver is told, first and foremost, to watch his rev-counter, keeping the needle in the green sector, preferably towards the lower end.
He is also encouraged to drive "with the rhythm of the road", when upward and downward gradients are encountered, allowing the vehicle's momentum to provide the energy which the man might normally expeCt to come from the engine.
Anticipation of the road and traffic conditions ahead is another key element in the "sympathetic" style of driving which leads to fuel economy. On the Scania course, drivers are encouraged to be "one step ahead" in their assessment of the road and the traffic in front.
If a definite halt is indicated up ahead, at a 'stop' sign or behind a stationary queue of traffic, then easing of the accelerator pedal — rather than application of the brake pedal — becomes the primary requirement. Trainees are reminded that braking represents thrown-away or wasted energy.
Similarly, harsh acceleration, taking engine revs well beyond the green sector of the rev-counter, is wasteful of fuel. In the circumstances, with foresight, gentle application of the pedal could achieve the same result, in journey time and average speed terms.
Anticipation of the road ahead not only saves fuel. It is a safety "plus". And it cuts down on engine (and brake lining) wear and tear.
Except for downhill restarts, drivers are encouraged to use every gear in the 10-speed Scania range-change box, thereby keeping engine revs close to the "economy optimum" for a greater part of acceleration/deceleration periods. Skipping gears, on either upward or downward changes, leads to over-revving or painfully low-rev lugging.
Sixth gear in particular, because of its position in the gate, is commonly skipped by Scania drivers, under conditions where it is a natural choice of ratio — negotiating urban roundabouts and 90 deg bends at about 15mph for example. Gearchanging part-way through curves and roundabouts is a small but worthwhile fuel-saving ploy, avoiding the engine having to race up into the yellow part of the rev band and "head for the red".
Despite the "light-footed" approach, average speed is not normally affected adversely by an economy-driving style. This is because candidates are told to maintain as high a speed as practicable, consistent with legal limits and safety. They are told to get up to speed as soon as possible and use the economydriving technique to maintain that speed.
Drivers taking the course who are new to syncromesh gearboxes on heavies are reminded that they don't need to double declutch and that to do so wastes fuel. This is largely because of the mid-change accelerator application during downchanges which is invariably part of the constant-mesh "habit".
Normal procedure on the course is for the candidate to drive the laden 112 artic around a prescribed route of about 30 miles in length, with Scania's instructor beside him, but with the man adopting his normal driving style. The instructor remains silent, merely observing the man's technique.
Fuel consumption, speed and elapsed time are monitored continuously. The candidate then takes the vehicle round the route for a second run, this time with the instructor advising him on speeds, accelerator and brake applications, and timing of gearchanges.
Afterwards the two sets of results are compared. Invariably fuel consumption shows a significant improvement, sometimes as much as 25 per cent, but almost always over 10 per cent. Journey time is in most instances reduced, into the bargain, serving to highlight the allround productivity attractions of economy driving.
A digital read-out AIC meter in the cab of the training vehicle gives the instructor and his pupil instantaneous second-bysecond readings of fuel consumption, to provide immediate "supporting evidence" for the driving style recommendations.