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IRTE conference
Page 64
Page 65
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reported by Photographs by Graham Montgomerie Harry Roberts
How much bhp for 32 tons?
THE NINE papers presented to the Institute of Road Transport Engineers' conference at Solihull last Friday and Saturday prompted interesting exchanges between the speakers and the audience.
Following the paper by Mr B. B. Leverton (Rolls-Royce) on ",Possible power units for the future," Mr W. V. Batstone (NFC), asked the speaker what he considered the optimum horsepower requirements for the present gross weight limits and at what maximum engine speeds ?
Mr Leverton replied that the optimum power level would probably be determined by fuel economy. It was a fact of life that trucks usually operated at part engine load, which was not the most efficient area of operation. He thought that an output of 187kW (250bhp) was optimum for a 32-tonner increasing to 215/225kW (290/ 300 bhp) for 38 and 40-tonne operation. So far as optimum engine speed went "I am a great believer in 1,900/ 1,950rpm," said Mr Leverton.
Following on from this Mr Batstone asked if specific fuel consumptions better than 0.341b/bhp hr were possible. Mr Leverton replied that he thought specific consumptions in the order of 0.33 were possible, but he stressed that this was a cautionary figure because "it depends on what the civil servants get up to regarding emissions."
Constant hp
Both Mr Leverton and Mr K. E. Lea (British Leyland) were asked for their comments on constant horsepower engines and differential super charging, and both gave very cautious replies.
Mr Leverton said that it was essential to look at the partload economy of the engine and that he did not think the constant horsepower engine would be with us for some time. "But it's coming," he said.
He thought that the differential supercharger was a complex device and, while he was reluctant not to examine it further, he thought it was going to have an uphill battle to greater acceptance because everybody wanted engines which were as simple as possible. In the future they really had to get away from "the Stone Age approach to putting the fuel in." A breakthrough in fuel-injection equipment was needed along the lines of piezo-electric injection, which put the fuel in where the designers wanted it. It was easy to make a constant horsepower engine by taking a big engine, turbocharging it and then chopping off the top end of the power curve. "But this gives a very heavy engine—so you've got to make a compromise and look at the torque-rise characteristics." One avenue the engine manufacturers would have to look at more closely was the control of the timing both on the test bed and in the field.
Mr Newman asked what the panel thought about the development of gas as a vehicle fuel. In reply Mr Lea said that it was necessary to recognise that diesel and petrol could be easily transported and stored whereas pressure vessels were necessary for gas. The distribution network would thus be more expensive. Although gas was smoke-free, it had not been proven to be any better on invisible emission.
How much methanol?
Mr Lea explained that he thought methanol was attractive as a fuel but he could not find out how much methanol was commercially available.
Gas could be considered as an attractive possible fuel at the moment, but his view was that the Government could make or break the idea by fiscal measures in terms of tax.
Mr Leverton added that the dangers of gas should not be magnified. "Petrol, after all, isn't the safest thing to handle." He agreed with Mr Lea on the future possibilities of gas, but said that it would depend upon the tax situation.
Questioning Mr B. Barber of Shelvoke and Drewry Ltd on the design of municipal vehicles, Mr Hill asked from the floor what evidence there was to support the use of automatic transmissions. He thought that it was about time that the whole concept of municipal vehicles was reassessed and that the present situation was due to the fact that "there is evidently an exclusive club of municipal manufacturers. They might talk to each other about design, but they don't talk to us—the operators"
Standard rubbish
Mr Barber countered by saying that the manufacturers could not design a refuse vehicle without guessing at what the vehicle would have to handle. "Until somebody comes out with a British Standard for refuse ! "
It was necessary to be sophisticated on such points as compaction because some people had to carry the refuse a long way before it could be tipped. It was necessary to compress and crush the rubbish because if this was not done, the operator would need a dozen ordinary side-loaders to transport the same volume.
So far as automatic gearboxes were concerned Mr Barber made the point that the stop/start type of operation for a refuse vehicle was far more severe than the equivalent for either buses or milk floats due to the shorter distance between stops. Because of this the rate of wear on the clutches often reached an unacceptable level forcing the use of automatics. Mr Barber commented that S&D did not like British automatic gearboxes and so they used American units.
In his paper on "The commercial vehicle—some problem areas in future legislation" Mr J. W. Furness of the DoE had highlighted the problems of the spray caused by heavy trucks and the necessity for effective load-restraining aids. Mr R. Denniss (Bass Charrington) said that he had been horrified to see the slide showing an encapsulated mudguard on a trailer in an experiment to cut down on spray as he thought this made it extremely difficult to check the condition of the tyres satisfactorily.
Mr Furness replied that he thought Mr Denniss would be glad to hear that the design illustrated had not worked in practice! "You were meant to be horrified by the slide. I used it to illustrate the fact that present mudguards are woefully inadequate."
Mr Furness stressed that the DoE had no intention of ignoring the practicality of an antispray system with regard to checking the tyres.
Answering Mr Denniss's comment that it was sometimes possible for a vehicle load to be too secure in that the complete truck turned over, Mr Furness said he agreed that this was a possibility "but the majority of cases are not like this."