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Summaries of Informative Papers Read at Earls Court Before Meetings of the Municipal Tramways and Transport Association, Associated Road Operators, Industrial Transport Association, Rubber Growers Association and Commercial Motor Users Association
Oil-engine Vibration Still Excessive
" WJE are certainly getting more trouble and less life
W from radiators than we did When the petrol engine was standard," said Mr. John F. Cameron, general Manager, Northampton Corporation TranSport, in his paper entitled " Oil Engines and Modern Chassis,' read before the Municipal Tramways and Transport Association Con-, ference, at Earls Court, last Friday. '
Radiator and body troubles attributable to the vibration of oil engines were, he stated, the causes of an unduly large number of vehicle changeovers in municipal fleets. He had compiled tables showing percentages of troubles experienced by 13 municipalities during 12 Months.
Mr. Cameron remarked that breakdowns in congested streets were matters with serious financial results, and there were, therefore, big problems in connection with municipal undertakings for manufacturers yet to solve. Vibration was excessive, especially at idling speeds. Change-overs of vehicles for body defects from this and other causes ranged from 2,2 to 22.22 per cent, of the totals.
Too Many Failures of Fuel Pipes.
There were too many failure's of fuel piper. Crankshafts were not altogether free from breakage. A, reasonable expectation for a 'crankshaft Would be: 200,000 miles. Whereas speCial bearing metals had -reduced bearing troubles, they had necessitated 'inOre frequent reconditioning of shafts, in some .cajes producing burning So that regrinding was UnpOSsible. Whilst lead-bronze bearings stood up to hard work, they sometimes increased oil consuniption. Furthermore, they were too costly. He was not satisfied with lubrication and thought that the correlation of oil consumption,' cylinder wear and piston-ring layout was worthy of the fullest attention. In .cOnneetion with injectors, he had changed 1,300 injectors in ninembnths from 38 vehicles.
Piston rings were a fruitful source of trouble, and roost inconsistent. Whilst one engine would run 110,000 miles without ring trouble, in another, after half that mileage, he would find the top land eaten away, some of the rings disappeared, and the remainder carboned up solid.
He had experienced trouble from leaking cylinder-head gaskets, and thought the rear of the block was starved.
Many difficulties were experienced' by maintenance staffs through bad accessibility. In this connection, he criticized the arrangement of auxiliaries, the amount of work necessary when pistons had to he :drawn, and the difficulty, in many cases, of adjusting water pumps. Whilst appreciating the " tremendous advantage " gained by hydraulic couplings and preselective gearboxes, he said theyresulted in an increased fuel consumption, amounting to about 1.59 m.p.g. Comparative figures for change-overs necessitated by orthodox-transmission troubles and preselective-gearbox faults were 9.68 per cent. and 19.42 per cent. respectively. He attributed this largely to drivers being unable to overcome the habit of using the pedal like an ordinary clutch control.
He quoted two favourable comments and one unfavourable comment on the needle-type of universal joint, and stated that the rubber type was giving good promise. A fault of the latter was that bolts sometimes worked loose. The metal type had been criticized on the ground of oil flinging. Although many brake troubles were experienced, they . were fewer than formerly. Exhausters for vacuum brakes were unsatisfactory. The build-up was not quick enough. Trials Of automatic adjusters were promising, an average figure of 25,000 miles was quoted for facing life. In his experience a design which resulted in one end of the facing wearing entirely away before the other was materially worn was unsatisfattery.
Brake temperatures up to 215 .degrees C. were not uncommon, with the result that tyre failure from this cause wasprevalent. Manufacturers should devote attention to drum diameter, clearance and ventilation. Spring failures were reflected in figures ranging from 0.23 per cent. to 5.89 per cent. Shock absorbers wese too variable and not sufficiently reliable. There was definitely scope -for suspension improvements. Where bad road conditions obtained there had been frame. breakages. Larger tyres (necessitated, he suggested, by inadequate springing) made steering heavy. If there were no alternative, steering gears required drastic revision.
Discussion Raises Interesting Points.
In ,the discussion which followed th'e 'reading of the paper, Mr. T. H. Parkinson. (Leeds) said that there was no possibility of increasing fares,but maintenance costs afforded scope .for effectinff economies. Gasket trouble, to which Mr: Cameron referred, was possibly due to loIs of water when cornering. The arrangement of overflow pipes
called for improvement. A loss of three-quarters of a gallon during a short morning run was common, and frequent topping up had reduced -his gasket• troubles by 75 per cent. He advocated the removal of all auxiliaries from under the bonnet, particularly the generator, which suffered from fuel creeping from the pump.
Fluid Flywheels and Wilson gearboxes were a big asset when 56 changes per hour had to be made. 'He had experienced some trouble with bands and drums. He agreed that exhausters were inadequate. •
Mr. H. 5. Troughton (South Shields) held that the troubles with oilers were little, if any, greater than with petrol chasSis, but stressed the importance of oil filtration, He doubted whether the Fluid Flywheel and Wilson gearbox caused an increase in fuel consumption. Furthermore, he was surprised at the higher maintenance costs referred to in connection with these units.
Mr. G. F. Craven (Halifax) paid tribute to the work of the Research Department of the Institution of Automobile Engineers. Ile also praised the work done by fuel and oil, companies. He suggested that supercharging oil engines might lead to valuable improvements.
' Mr. P.. V. Lamarque (I.A.E. Research Department) said that pipe-line breakag.ss were caused largely by internal vibration. This could he overcome by using composite tubes formed by drawing one over the other,.
Mr. T. Roland (Birmingham) thought it unsatisfactory
that injectors should need so much maintenance. Ills experience of cylinder-liner wear was 25,000 miles per 0.001 in. He agreed with the higher consumption figures u35 •
attributed to hydraulic clutches and preselective gearboxes. The maintenance of the Wilson box, however, was, in his experience, negligible, in comparison with the crashtype box, Reciprocating exhausters should disappear; the rotary type was satisfactory, but usually too sniall. It should be able to build up to 23 ins. to 24 ins, of vacuum in three-quarters of a minute.
Dr. P. Kremer (Hamburg) spoke of the " pancakes' engine, in connection with the construction of large singledeckers. During peak traffic in Germany, he said, it was impossible for the conductor to get round a double-decker. Mr. S. T. Patmore (General Electric Co., Ltd.) remarked that few realized that a one per cent, voltage drop caused four per cent, to five per cent, reduced illumination.
Mr. C. B. Nixon (Leyland Motors, Ltd.) thought that supercharging was of little value as a means for improving the oil engine.
Owing to shortage of time, Mr. Cameron expressed his desire and intention to continue the discussion in the pages of the technical Press.