ion Miles ion Tons
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by P. A. C. Brockington,
A.M.I.Mech.E.
IN the forefront of those who stress the practical importance of a transport manager having a status in the company compatible with the importance of transport to the industrial welfare of the country, Mr. E. A. Betteley, M.Inst.T., a director of Tarmac Roadstone, Ltd., Ettingsball, Wolverhampton, and general transport manager of the concern, can point to his own case as an outstanding example of such a policy. In close liaison with the managers of the 21 transport depots of the company, Mr. Betteley bases his decisions regarding vehicle types, operational requirements and maintenance on a full knowledge of all the practical factors involved, as well as the higher economics of costing.
Coated macadam and hot asphalt produced by the concern for road-making are manufactured, delivered and laid in one day and transport costs may amount to as much as 50 per cent. of the overall ex-works production costs. This is due to the large tonnages involved and the relatively low value of the material.
Material is delivered to the site at the required temperature in insulated tippers and a prolonged delay can result in solidification. This necessitates "digging out" after the vehicle has been returned to base, which is costly in terms of manual labour as well as wasted vehicle time. The vehicles feed Blaw Knox or Barber-Greene road-making machines and it is essential that deliveries are made to a strict time-table. Vehicle operations are, therefore, a fundamental part of the production processes with regard to timing as well as the actual means of transporting the material. Despite continuous rough usage, a vehicle serviceability ratio of nearly 99 per cent. has been achieved.
Increase Gross-load Ratings As chairman of the Midland Division of the Traders' Road Transport Association. Mr. Betteley has taken an active part in making official representations to the Minister of Transport to increase the maximum-gross-load rating of eight-wheelers and the maximum rear-axle load of fourwheelers. Mr. Betteley points out that the typical eight-wheeler" would be the "ideal tool" for many types of basic-rnaterials traffic because of its robust construction and favourable' all-round performance, if the gross-weight limit were raised to 28.tons, and that this would not impair the safety of the vehicle on the road.
In the case of the four-Wheelers employed by the company, the increase in legal gross rating from 12 tons to J4 tons has not given a comparable increase in carrying capacity, because of the limitation imposed by the maximum allowable rear-axle loading of 9 tons. An increase to 10 tons would provide valuable latitudewith regard to
824 weight distribution on a typical chassis and would allow the payload to be increased proportionately.
In the year ended March, 1961, the number of commercial vehicles in the group exceeded 560 lorries of 7-ton to 15-ton capacity (the remaining 5-tonners are being progressively replaced by heavier types) and the total distance covered was well over 10m. miles. The weight of materials carried was more than 24m. tons.
The choice of Thames Trader 6D-engined chassis with a wheelbase of 111 ft. as the standard four-wheel tipper in the fleet is of special interest as it represents a tribute to the sturdy_ characteristics of the whicle as well as an example of deriving the maximum benefit from a careful study
or weight distribution and tipping-gear problems. An
overhang of 2 ft. 2 in. is necessary for feeding the roadmaking machines and this has been obtained with the minimum sacrifice of payload. Maximum gross weight of the vehicle is 13+ tons and the normal payload carried is approximately 9 tons. Body length is 12 ft. 6 in. and the load on the front axle is 4 tons 4 Cwt.. when the weight on the rear axle approaches 9 tons. The vehicle is equipped with 9.00 by 20 tyres.
No concession is made to weight skimping in achieving this favourable payload. An all-steel welded body is employed, and an Anthony Hoist S.T.7 single-ram underbody slant-type lifting gear is used in conjunction with a relatively heavy sub-frame. The slant-type lifting gear is preferred to other types for this application as the initial high thrust of the ram stresses the main frame mernhers longitudinally and bending stresses are reduced. The angle of tip required is 45-50 degrees. Stability when tipping is specially necessary because the material is in a semi-solid condition. and this delays discharge until the body has been tipped to an angle of some 20-30 degrees. It is pertinent that fixed-sided double-skinned bodies are employed, which offer a high resistance to torsional deflection.
Sides and tail boards of the macadam-carrying bodies are insulated with Stillite slag-wool material, and similar insulation is also applied to the floors of the bodies employed for transporting hot asphalt as well as the remaining panels. Produced in rolls of 1-in, material, two layers of Stillite • are compressed to the required total thickness of If in. and afford notably efficient insulation. All loads are sheeted.
In a general comment on tipping vehicles, Mr. J. V. Davis. transport manager of the Central Division, pays tribute to the characteristics of tipper chassis currently produced by the majority of manufacturers, additional stiffening being normally unnecessary.
Special attention is given to the care of tyres, and exceptional mileages are obtained. Goodyear covers are fitted to the majority of vehicles and on average a mileage of 44,000 is exceeded before they are removed for re-grooving in the workshops
to a depth recommended by the makers. Re-grooving enables a further 10,000-12,000 miles to be Covered on the original tread, and the tyres are then remoulded by the makers. This extends their usual life by as much as 30,000 miles, the average total life of-a cover being in the region of 70,000 miles.
Three-piece wheels are included in the specification of all tipper vehicles and their use is regarded as an important operational requirement, particularly in respect of bead and wall life. The saving in both cases is attributed to firm location of the tyre on the wheel.
Heavy vehicles in the fleet include 20 eight-wheeled tippers, with a preponderance of A.E.C. Mammoth Majors and smaller numbers of Guy Invincible and Foden lorries. Light six-wheelers are also employed and comprise Thames Traders, with Boys extension and trailing third axles, and Dodge vehicles with York trailing third axles. Such vehicles are becoming increasingly popular because they enable legal gross weight limits to be exploited to the full. Although these vehicles are not built to the standard of the heavier and far more costly eight-wheelers, they give satisfactory service and overall running costs are relatively low.
Other makes of six-wheeler in the fleet include Albion Reivers and a Guy Warrior, which are also fitted with insulated bodies. The Dodge vehicles are equipped with Eaton 18,800 two-speed rear axles and results so far indicate that they will reduce fuel consumption and improve engine life. A.E.C. and Guy eight-wheelers are fitted with Pilot U6 twin-ram vertical-thrust lifting gears and 14-cu.-yd. bodies, whilst Homalloy or Duramin light-alloy bodies with steel sub-frames are fitted to the Fodens. Aluminium subframes are not considered satisfactory for tipping vehicles.
Of particular note, the Albion Reiver features independent drive to each rear axle and also hub-reduction gears, which are fully approved in principle by Tarmac technicians on the score that their use is favourable to the life of the main transmission components.
Incidentally, the synchromesh gearbox fitted to Thames Traders is not altogether liked at Tarmac Roadstone, Ltd., as it enables top gear to be re-engaged at any road speed when the vehicle is coasting and engine r.p.m. to be increased temporarily, to an excessive maximum, which can cause damage to certain mechanical parts. Coasting at high speed would be 'discouraged by the use of a gearbox of the crash or tonstankrnesh type.
The company are at the moment experimenting with five-speed gearboxes. A constant-mesh five-speed gearbox would be ,a welcome feature on the four-wheelers because, apart from the safeguard it would provide with regard to engine over-revving, this type would, it is considered, enable engine speeds to be more 'accurately matched to vehicle loading. A Thames Trader converted six-wheeler has been experimentally equipped With a David Brown five-speed constant-mesh gearbox, but assessing its benefits has not been possible in the limited time it has been in service.
Vehicle renewal policy relative to the 7-tonners is based on replacement inthe sixth year, depreciation being based on a five-year period, heavier vehicles normally having a considerably longer life. Although the average annual mileage of 35,000 for the Thames four-wheelers is low by frunkingvehicle standards,, it represents arduous working in practice: The -average' length of a run is 25-35 miles, and a typical working day may involve More than three trips. The time spent in loading and discharge is a sub
stantial proportion of the total. , Fuel consumptions ,of the Thames Traders vary between 13 m.p.g. and 164 m.p.g.; according to route characteristics and traffic conditions. In'the six-Whe'eler class, the Traders a26 average 12 m.p.g., whilst the average of the Dodge and Reiver tippers is approximately 10+ m.p.g.
Being used experimentally are two Commer articulated outfits and two Commer tippers, all fitted with the T.S.3 engine. To date, these vehicles have performed well, the first one having covered approximately 90,000 miles. Average fuel consumption is in the region of 17 m.p.g. for the tippers and 14 m.p.g. for the artics.
Platform type 10-12-ton semi-trailers are operated for an associated company for the transport of concrete products, the tractor units being either B.M.C. or Commer, and there are also several articulated Scan mell tankers for the carriage of tar. Scammell automatic couplings are fitted to the platform trailers ta facilitate the quick interchange of tractors, whilst all the tankers are fitted with a fifth-wheel coupling.
Stabilizers on all Trailers
Adrolic stabilizers are fitted to all the trailer outfits and offer a number of advantages. Apart from the control of jack-knifing when the vehicle is braked on a slippery surface, they improve stabil4 during normal travel and act as coupling dampers on inferior road surfaces. Drivers report favourably on their use, particularly if the outfit is equipped with mechanical-linkage brakes.
It is considered that the most advanced form of articulated-outfit braking is the York type incorporating a separate servo-operated system for the trailer, controlled by a lever in the cab. One of these trailers is in service, and it has been fully demonstrated that the ability of the driver to apply the trailer brakes before the tractor brakes promotes stability. The driver quickly learns to vary the lag between trailer and tractor braking to the best advantage according to the type of road surface, camber and so on.
Tractor and trailer brakes are regularly tested, and any fall-off of efficiency is immediately rectified. Brakes of all other vehicles are, of course, checked and adjusted regularly. The Tandem Hydrovac system of the latest Thames Traders is giving particularly good service.
Regular Servicing Essential Regular and thorough routine servicing of engine, axle, gearbox, brakes and steering is regarded as essential to reliable vehicle operation, but preventive maintenance as such is not considered necessary, given that all parts of the vehicle are carefully inspected at frequent intervals by a fully qualified mechanic. At the larger depots, greasing is performed by mechanics every 2,000 miles With the aid of a Tecalemit Majestic greasing battery, and at the smaller depots the chassis are greased by the. drivers under the supervision of the garage foreman. Engine, lubricating oil is changed at the same mileage intervals, a fully detergent S.A.E.20 oil being used throughout the fleet, simmer and winter.
Fuel injection pumps and nozzles are overhauled every 25,000-30,000 miles in fully equipped departments at Wolverhampton and Stockton-on-Tees, special attention being given to the wear of pump elements -and camshafts, the action of diaphragm-type governors and nozzle atomization. After fitting to the power unit, maximum engine speed is checked by tachometer and in no case is a speed above the rated r.p.m. allowed. The governor is normally reset to reduce the speed slightly below the rated r.p.m.
Stocks of spare engines and major components are maintained at the larger depots. The maximum mileage so far covered by a Thames Trader is about 100,000, and'the performance of the 6D engine gives promise that the vehicles will normally exceed 120,000 miles before reconditioning,is necessary. If an ,intermediate overhaul Of any of the engines is required, it is performed in the workshops.