OPTIMUM MAINTENANCE
Page 59
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The Engineer's Target
Vehicle Upkeep Studied from the Theoretical and the Practical Aspects in a Paper Read to the I.R.T.E.
Scottish Centre INTERESTING comments on the whole subject of maintenance of commercial vehicles were made by Major W. H. Rothwell, M.I.Mech.E., M.I.R.T.E., in a paper read to the Scottish centre of the Institute of Road Transport Engineers, at Edinburgh. Major Rothwell is assistant chief engineer Of Young's Bus Service, Ltd., and Young's Express Deliveries, Ltd., Paisley.
Pointing out the importance of costing, he said that the road transport
engineer must have a sound working knowledge of elementary accounting, book-keeping and the collection and use of statistics.
Information required from the system of recording and costing was as follows:—
(a) Daily mileage and daily cumulative mileage, probably differentiating between loaded and light running.
(b) Consumption of fuel and lubricants.
(c) Charges for all materials supplied direct, with dates and details.
(d) All direct labour charges, preferably differentiated by trades.
(e) A record of all repairs and adjustments giving full details including date and names of tradesmen; (f) Condition of components inspected at -prearranged or " accidental" intervals.
(g) A record of all direct and indirect charges not already noted.
(h) Cost per day or hour and cost per mile per vehicle.
Performance Standards
It was essential to have crit:ria of performance to assess the behaviour of the complete vehicle or of components. Measurement of life in miles run was unsatisfactory, as no account of cost was taken; the only sound measure of performance was that of cost per unit distance. This was usually expressed on a basis of pence per mile or multiples of a mile.
The mechanical processes of measuring and assessing were often delegated as a foreman's duties, but they were best performed by a tradesman trained for the specific purpose. The employment of inspectors would mean better standards.
The rate of approach to the permissible limit of wear, Major Rothwell said, increased rapidly as the limiting condition was neared. In order, therefore, not to jeopardize recovery, this should be carried out when the wear is appreciably less than the maximum permissible.
On the subject of lubrication, he said that every attempt should be made to reduce to a minimum the grades of lubricant handled, and to ensure cleanliness . of the lubricant and its actual introduction at the point where it was needed. It was felt that the subject of oil reclamation had been almost criminally neglected by technicians.
Scrupulous attention to cleanliness on assembly, to Provision of efficient filters, to cleanliness of lubricant supplied, and to frequent oil changing and efficient reclaiming would effect astonishing economy by lengthening the effective life of components.
Preventing Corrosion Major Rothwell said that it was found that, in .many cases, corrosive wear was complementary to abrasion. In general, anti-corrosion precautions were apparently expensive and demanded the utmost care in application, but over extended service would be found to be a sound investment.
Fundamental explanation of fatigue of materials might be obscure, but experience had amassed much information which, if properly applied, allowed failures from fatigue to be reduced to a minimum. Every fracture, even of unimportant components, must be meticulously examined and a satisfactory explanation sought.
Training and control of labour constituted one of the most serious problems in road transport engineering. Flexibility in maintenance systems was essential to allow for constantly varying operating conditions, but no effort was too great to maintain an inflexible standard of good workmanship. This standard might be achieved only by unremitting endeavour to secure good discipline, good working conditions and understanding between labour and management.
Extending Technical Education No effort must be spared to i.--rease engineering knowledge. Opportunities of exchange of ideas and experiences should be developed to the utmost, and in this the Institute formed a potent factor in assisting the maintenance engineer. Education in road transport engineering was at present in a most unsatisfactory condition and a wonderful opportunity was presented for the Institute to bring order out of chaos and ensure a supply of properly qualified road transport engineers.
Large-scale operators usually had modern well-conducted systems of
stores control. Unfortunately, these were not always to be found with smaller operators. Admittedly, such systems were initially costly and demanded a constant expenditure for stores labour, but it had been proved time and time again that such expendi ture was justified hi the 'saying of tradesmen's (line; by reducing: loSs Of use of vehicles and plant, by controlling to a minimum the, amount of capital invested in spares and in 'having available spares w.hich are obtainable from makers or agents.only after, long delay. Another benefit of certaih systems of stores control "was the 'cross-check achieved of the maintenance recordkeeping system by recording the issue of spares to. specific vehicles. Further, the attention of the maintenance engineer might be drawn by the stores controller to what Might appear to be. excessive consumption of specific items. Full benefits of standardization could be achieved only by effieient stores control, and healthy co-operation between. workshop and stores staff would provide many means for enhancing efficiency.
The importance of costing had been stressed, and it would be appreciated that the stores control system was virtually an integral part of the costing system so far as material costs were concerned.
Case for Standardization No discourse on maintenance, be said, would be complete without refer ence to standirdilation. Aniong its advantages might be mentioned retitletion of -capital. invested in Spares and tools, facility for ,"cannibalization," or interchangeability, greater opportunity for development of overand under-sizing, opportunity of obtaining larger discounts by bulk purchasing, facility in labour specialization and in breaking down major maintenance operations to minor sub-operations, and facility in arranging flow of work.
Among the disadvantages were the loss of comparison between makes and types, greater vulnerability to change in the supply position, greater liability to be affected by epidemics of defects and a somewhat lower standard of flexibility in maintenance. .• It was hoped that, loose liners and chromium plating would solve the
problem of the early rebore. Loose liners Would permit change, of -liner without undue crankcase disturbance, and chromium plating should give an effective bore lifeof at least 140,000 miles. With the chromium-plated liners, piston .replacement might be necessary at 70,000. miles.. Use of special_ valves. and ,faced:seat inserts should pettnity,airaiitage.ltf -70,009 to be accomplished. before valv,e •• attention
became necessary. ,
These .mileages mould be normal accomplishments only if meticulous attention were paid to crankshaft grinding, boring of bearings, grinding of .bores, oil filtration, valve and seat refacing and, of course, cleaning and adjusting of injection. equipment. These remarks, he said, applied mainly to heavy vehicles: