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System Essential in Passenger-vehicle Maintenance
Page 85
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An Expert Describes Current Routine Methods, with Special Reference to Oil-engined Vehicles. Some Mileage Figures and a
Schedule of Equipment
AN outstanding problem of public-service-vehicle operation is that of provision for maintenance. The difficulty of most operators is to discover the happy medium between a hard-and-fast routine system, which, if it be not carefully planned, may prove extravagant, and the kind of haphazard " wait until it is needed" procedure which almost inevitably results, eventually, in expensive breakdowns.
Obviously, a regular routine is desirable. Its details, and particularly the intervals •between repetition of specified maintenance operations, can, in any given set of conditions, be decided only by trial and error. We have, however, been examining a number of such systems and the following brief notes indicate the average experience of operators : First, there is a firm rule on the need for a separate repair and maintenance depot. If there be several garages, it is advisable to arrange for maintenance to be carried out independently at a central depot. Where the system is so small that all the buses are lodged under one roof, those premises should incorporate the repair depot. Provision should, however, bss made at each garage for small running repairs.
Prevention—Not Cure.
It should not be forgotten that the main object of maintenance is prevention—not cure. Systematic examination and check, nightly attention to drivers' complaints, coupled with periodic minor and major overhauls at intervals determined in accordance with experience, comprise the broad outlines of a practicable scheme.
So far as minor running repairs are concerned, the driver's report should be the starting point for this part of the system. The driver should not omit reference to any defect which he has noticed and the repair staff should never overlook any complaint on a driver's report. Coupled with this system is the provision for a daily or nightly check of tyre pressure, inflation to a prescribed pressure and examination of the tyres themselves. This alone may result in a saving of upwards of 20 per cent. in expenditure on tyres.
As regards periodic attention, minor and major overhauls, it is now becoming recognized that, if conditions and the nature of the fleet permit, these operations should be linked up with the systerri of unit interchange. The term unit is meant to cover not merely larger components, such as engines and gearboxes, but also smaller items, including magnetos, injectors, batteries and brake shoes. With this fact in mind, a comprehensive and effective scheme will include :— An Effective Maintenance Scheme.
(a) A preliminary minor or " dock " overhaul, to take place at approximately every 5,900 miles. Magnetos or injectors are taken out and replaced, tappets are adjusted, brake facings examined and, as may be necessary, packing pieces inserted. The bodywork and paintworkshould be examined, minor repairs to the former executed and the paintwork touched up. (b) A second overhaul at 20,00025,000 miles. The latitude allowed here is to permit of some deviation from a too-strict interpretation of the mileage figure, so as to obviate interference with service rota. All mechanical parts are examined and the engine decarbonized. (c) at 100,000 miles a complete overhaul takes place. The engine and other main units are replaced: the body is repaired and repainted.
With new vehicles it is advisable, at the end of the first 12 months, or at the nearest dock overhaul to that period, that paintwork should be rubbed down and touched up, and a coat of varnish given. Subsequently, and apart from a thorough repaint at 100,000 miles, buses should be repainted in alternate years, concurrently with one of the chassis overhauls.
So far as petrol-engined vehicles are concerned, . the
general tendency is to regard a period of • 10,000 miles a that which should elapse between subsequent emptying an replenishment of crankcases. The oil is changed after a first 1,000 miles and subsequently at every 10,000 mile:
The following figures are of interest in the same conriss tion:—Brake facings need renewal at approximately 80,00( 40,000 miles, and front-axle king-pins and/or bushes a 80,000 miles. Opinions differ as to the limit of wear i .cylinders before reboring; about 0.007 in. meets the view of the majority.
Special Technique for Oilers.
Operators who have had long and wide experience wit oilers are evolving what might be called a technique of mail tenance particular to the type. The peculiar characteristh ofthe oil engine are apparent in the figures contained in it next paragraph. The difference as between oil and petis engines in respect of attention to lubricating oil is of ou standing importance. The provision of replacement uni is also involved in this scheme.
At 1,000 miles change the fuel filters; at 1,500 miles te and set the injectors; at 5,000 miles drain and clean sums and change the oil filters. Other 'maintenance operatics can follow the routine set out above.
There is a tendency in many quarters to prefer dr cleaning of buses to the use of water for that purpose. Th former system diminishes the tendency to rust and it savi time in the depot at night, because there is no need to shut vehicles to and from the " wash." The procedure is to f dry clean and then park for the night.
Care must be taken not to attempt the mating of ne. parts with old, For example, new gear wheels should t ordered and fitted in pairs. Such components as bearing; pistons and valves should be replaced in sets—not one a 'time. A cylinder rebore must be accompanied by thorough engine overhaul.
Necessary Equipment.
The following is a schedule of maintenance equipmer which has been found desirable for an establishment i which chassis overhauls and repairs are to be carried out i entirety;—A lathe, drilling machine, milling machine, grinc Mg machine, compressor, 10-ton press, magneto teste: plug tester, degreasing plant, oil-reclaiming plant, electri crack detector, valve-grinding and refacing equipment, it jector tester and oil-pump tester, high-pressure washing an greasing plant, brake-servicing equipment, jig attached t brake-servicing machine to enable worn drums to be true( boring bar for boring bearings in situ in crankcase, weldin plant, cylinder-boring and honing machine, battery charge: electric component, test bench and air bottles and means fc refilling thorn. The last-unused are now coming to be pis ferred for tyre inflation, Finally, there is a growing tendency to keep more detaile records of maintenance costs, arranged and classified so His the maintenance expense of individual vehicles can readil be. ascertained.