PROFITABILITY FACTORS IN SI'
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PPING WORK • WHEN is intensive site work on sub-contract profitable to the haulier? It is a typical complaint that tipping-vehicle operation on major earthmoving projects bears little financial fruit; contractors often drive a hard bargain and some yield to the natural temptation to exploit the availability of cut-rate haulage. But to what extent is the haulier's profit dependent on the efficient use of the best type of vehicle and the distance of his base from the site?
Rates vary for the same type of work in different areas, local grouping by hauliers, or the lack of it, being frequently the most important factor with regard to profitability, but in many cases the rate is profitable or unprofitable according to the haulier's experience, the size of his fleet, his main source of income, his maintenance facilities and the loca tion of his depot or depots. • Commenting on the problems of site haulage by tipping vehicles, Mr. W. Harris, plant manager and a director of Dick Hampton (Earth Moving) Ltd., Itacknest, Alton, Hants, speaks from the vantage point of one who is responsible for the maintenance of 135 tractors and scraper units and 40 motor-scrapers (each of which may cost up to £20,000) and 15 excavators, a fleet of about 60 tipping vehicles being employed as required in conjunction with the larger machines. Site work includes motorway and other projects in various parts of the country, and the tippers are normally manned by local drivers on a shortterm basis.
Maintenance Methods Of first importance, the •tippers are maintained by the company's mechanics. On larger projects, site workshops are erected, providing covered space and facilities for a team of mechanics to maintain and carry out field repairs on all plant. On lesser contracts a maintenance engineer is often employed and regular contact is kept between site and the home base.
Mr. Harris emphasizes that profitable running is virtually impossible in the case of a small haulier if his workshops are not within reasonable distance of the site and if spare vehicles are not available. Moreover, he should _have
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sufficient control over his drivers to ensure that the3 co-ordinate their work with that of other sub-contractor to the best advantage.
The Dick Hampton tippers are of the 6-7-cu.-yd. typ4 based on 7-8-ton chassis and comprise 47 Bedfords an 12 Dodges, "off-the-shelf ", quantity-produced vehicle; being preferred to larger, more costly lorries because o their manceuvrability, ease of maintenance and relativell low repair costs; the casual labour often employed on thi; type of contract is in part responsible for a relatively hie incidence of damage and breakdown.
Strength and Scow Ends Chassis are strengthened by flitch-plating, and tht optional five-speed gearbox is used in the place of tin standard type on both chassis. Telehoist Telelever link type lifting gear or Edbro twin-ram underbody gear i fitted to the chassis, and scow-ended bodies are being increasingly employed to obviate repeated damage to tail board latches and so on. This adds considerably to th( cost of the assembly, however, mainly because of the mud higher cost of a gear providing the necessary tipping angh of 70° compared with a standard type capable of tipping to 55'. The use of front-of-body gears has been discon tinued because they were easily damaged when the tipper were being loaded by excavator.
Tribute is paid by Mr. Harris to the durability of tht suspension of the Bedford tippers, the high incidence ol spring failure being normally a major maintenanct problem. In common with the experience of all sift operators, tyre costs are greatly increased by frequen1 damage (much of which is caused by the lodgement ol stones between the covers of the rear wheels) and Mr Harris would welcome the opportunity to use large, singlt tyres in place of twin rears if British-built covers of thi! type were available at a reasonable cost.
Although some standard, fixed-sided steel bodies art employed, preference is given to bodies built by specialis] concerns because of their robust construction and heavy. duty floors. On account of the relatively short life ol bodies in comparison with chassis and engines, experiment: ire continually being carried out with modified types of )ody in search of longer life.
Jt is pointed out by Mr.. Harris that maintaining peak ..rigine output is particularly.important in site work because ass of power on the part of one machine may reduce the Narking capacity of other machines on the same "route ". [he sub-standard performance of injector equipment is the nost common cause of power loss, and injectors and njector pumps are, therefore,. normally tested whenever he vehicle is returned to the Blacknest workshops for iervicing or repair. A test shop is fully equipped with the atest types of Hartridge puma and injector test machines Ind units are reconditioned as required in the shop. Formerly the units were dispatched to a specialist company 'or testing and reconditioning, but this was wasteful economically because in some eases the fault was attributable to a different cause or to the malfunctioning of one or two injectors of the set. The availability of test equipment at the depot enables injectors and pumps to be selectively rejected according to performance,
The major on-site problem is created by continuous operation in high dust densities which normally necessitates daily servicing of the air. filters. Experiments are being made with Cooper Cyclopac air filters which combine a cyclone-type preeleaner with a cleanable. Duralife element, and it is anticipated that the use of these filters will enable the servicing period to be substantially increased because the element handles a very small proportion of the dust aspirated: The oil-bath filters of a number of Bedford TK tippers have been removed from the engine compartment to the cab, and this has enabled the servicing period to be increased in extreme conditions from 12 hr. to about a week. Cooper-King airblast types of.air filters will be fitted to a number of heavier earth-moving machines; • this unit is automatically cleaned by compressed air at • regular intervals, which eliminates the need for servicing.
Turbocharged Machines
Although turbocharging is applied to the power units of heavy earth-moving machines the company's experience of turbocharging is of potential interest to road-vehicle users. Turbocharged Caterpillar 235-b.h.p. and 320-b.h.p. engines are employed in Caterpillar tractors and despite their relatively high operating speed, they have a useful life before reconditioning is required at about 7,000 hr. Whilst turbocharging does not appear to affect the life of the pistons, liners or engine. bearings, the cost of maintaining the units is high. Trouble with turbocharger bearings is fairly common, which may in part be because of the difficulty of enforcing the maker's direction that the engine be idled for a 3-min. cooling-off period' before it is closed down, to avoid heat soak into the bearings.