Would Cheaper Buses Show a Saving?
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P LA. Conference Scarborough
., ' THROW-AWAY ' type of vehicle would eliminate many overhead expenses now incurred in workshops. Too much money is now spent in attempting to maintain vehicles in 'as new' condition in the last years of their life, There is a distinction not always appreciated between safety and shabbiness," said Mr. Little.
Taking as a basis the present rather heavy orthodox chassis, recent experience showed that quite startling fuel economies could be achieved with truly lightweight body construction. Fuel costs, he said, now formed such a large proportion of working expenses that savings under that heading might well be greater than any additional costs incurred with a different type of vehicle.
Lightness and Cheapness
There was no real reason why light weight and reduced initial cost could not go hand in hand. That approach had been seen, to some extent, on single deck vehicles. It was, however, more difficult to apply to double-deckers, but it was in the sphere of town and city stage work that the greatest benefit from reduction in weight could accrue.
With the weight reductions that could be applied with orthodox construction, the fuel consumption rate had improved from 8+ m.p.g. to 10 m.p.g., and those figures could be further improved upon if a straight clutch and gearbox were acceptable.
Apart from the loss in miles per gallon, driving abuse with automatic or semi-automatic transmission systems tended to react on maintenance. Brakes, final drive and bodywork, as well as the passengers, suffered, and until the introduction of the most recent type of airoperated epicyclic gearbox, it could hardly be established that driving fatigue was materially lessened as against the use of a synchromesh box and friction clutch. In any case, added the speaker, the greatest physical effort always rested with the steering.
Double-decker for 13,500
A standard double-deck bus cost £5,000, and in the municipal sphere the maximum period for repayment was 12 years. Total interest payments in that period, at 5+ per cent., amounted to £1,732, so that the total cost, if spread over an assumed life of 15 years, was £452 per annum.
If some attempt were made to produce a vehicle at, say, £3,500 for a life of seven years, total costs were not impossible. At 51 per cent., interest amounted to £772, and the annual charge over seven years was £610.
Assessing those charges in an endeavour to approach the true annual difference in the two _ methods, Mr. Little said that . the expenditure of £1,200 on the heavy vehicle at and after the seventh year had the effect of reducing the difference in annual cost by 50 per cent.
The cheaper, light vehicle would show at once a handsome return in fuel consumption, and the faster turnover of vehicles would allow complete standardization in running depots to be more readily achieved. External washing by mechanical means was now almost universally accepted, but no completely automatic plant, capable of giving acceptable results without any manual labour, had yet been produced. Such a plant could, however, be made.
As an indication of the savings that could be effected with a truly mechanized plant, the speaker said that hand-brush washing could cost from 20-30 man-minutes. A " drivethrough " plant would give acceptable results at 4 man-minutes, No real success had attended efforts to produce something quicker than a hand brush for interior cleaning.
Effect of Non-standardization Lack of standardization had probably helped to perpetuate the engine drain plug and tin can, but something quicker and better was not difficult to imagine. Automatic lubricatois for chassis parts had reached a stage of high reliability. Rubber joints had not been universally' successful, but were being further; developed.
Although the automatic lubricator had done much to effect economies, it was still an additional component requiring maintenance. From the design angle, said Mr. Little, it should surely be the object to have bearings and joints that did not require lubrication, so that a chassis would not need inter-dock attention on this score.
Some engines were so overcooled that it was necessary either to preheat them or run them up for some time before Leaving the garage, in order to prevent them freezing during the first half-hour of service. That single item was probably the most troublesome of all in routine servicing. • What great advantages, he asked, would accrue from an air-cooled engine?
Part of the Engine No sign of development in that direction was apparent, so that improvements in the cooling system might be requested as an interim measure. The possibility of a system with less water content and a more efficient fan and fan-drive control had already been noted in the technical Press, and were it possible to mount the whole assembly as part of the engine, with all the plumbing in one unit, then a pressurized system which would retain an antifreeze solution should he possible.
Coupling this problem with the matter of weight, Mr. Little cited the underfloor-engine chassis as carrying about 2 cwt. of water and plumbing in its cooling system.
In matters which affected docking, some consideration should be given to jobs which seemed to defy properly organized sequence. Such items as brakes, clutches and springs were not entirely regular in their expectation of life. This was particularly so when the vehicles were used for city service. Efforts to resolve this had been made by using semi-automatic drives with a fluid coupling, and with compressed air as a servo medium.
The use of a fluid coupling and epicyclic gearbox had brought in its train the expense incurred in filling and topping-up the coupling, and until recently that cost much more than was incurred in the maintenance of a good straightforward clutch.
New seals had now been introduced. and these, together with the more efficient coupling now available, might make for a more acceptable unit.
As a result mainly of weight, but partly because of the limitations of vacuum servo systems in requiring frequent adjustment of shoe clearances, there was a call for improved brakes. Air brakes, said Mr. Little, seemed to provide the answer.
Initially, these proved to be an expensive answer, although design improvements and new facing materials had done something to restore confidence in the system.
Reduction in Weight
A much more satisfactory solution had proved to be reduction in vehicle weight within the range in which the well-proven vacuum system was satisfactory. Further, with light weight, an appreciable improvement in facing wear was evident, although it was too soon to give positive figures. With such equipment, the brakes could be brought within a predictable performance limit and within the scope of period-docking arrangements.
Springs were another problem in respect of regulated mileage procedure. The semi-elliptic spring was a simple multi-purpose device which was not unduly expensive, and systems so far devised to replace it had, apparently. more component parts needing maintenance.
Coil springs might bring improved riding, but they were not certain to bring reduced maintenance. Rubber had the great advantage that gradual deterioration could be seen, and replacements could be made during dock . periods without the trouble of out of cycle" repairs. For any new system, the greater use of rubber seemed to have the advantage from a purely maintenance angle.
Better Engine Performance
A particularly pleasing feature of present-day chassis was the improvement in engine performance. The engine, more than any other unit, used to dictate dock policy, but it now seemed clear that much greater success, from the maintenance angle, had been achieved by retaining the larger running units and reducing weight everywhere else.
Bodies should not and, in general. did not require any major attention during the first five or seven years of life. From the angle of carrying out body repairs following accident c8 damage, there was still prejudice in some quarters against the use of rivets. Experience had shown no difficulties on that score.
Whilst the application of blind riveting was one of the outstanding advances permitting the building of lighter structures, the speaker wondered whether the stressed-skin, solidriveted job available on some integral single-deckers was not a better proposition from the aspect of resistance to damage. Unfortunately, no doubledeck vehicle of that type had yet been tried.
Mr. Little added that a useful way of utilizing the proposed increase in overall length would be to fit bumpers front and rear. The savings in body repairs would be obvious, he said.
Dynamos and starters far exceeded in reliability the smaller electrical components such as switches, bell pushes and lamps. Whilstsuch parts were relatively cheap, the labour cost for their replacement was not.
In an analysis of defects which caused a total of 2,500 service calls, brakes topped the list with 20 per cent, failures. Next on the list came bodies-19.7 per cent.—closely followed by the electrical system with 19.5 per cent.
Engine defects were responsible for 15.6 per cent. of failures, of which the water and fuel systems were the chief single offenders.