AERG-ENGIN :CHNIQUES FOR LORRIES
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WHEN working on aircraft jet engines some eight years ago, Mr. K. W. Eaton, now fleet engineer of Guymers (Transport) Ltd., and of an associated company, the Barr Common Trading Co. Ltd., nr. Aldridge, Staffs, developed a keen appreciation of the value of advance lubrication techniques in the operation of power units, transmissions and auxiliary mechanisms. During the past three years, Mr. Eaton has, with the full co-operation of his directors, applied the concepts derived from his aeroengine experience to the 40 prime movers and 42 articulated trailers of the combined Guymers-Barr Common fleet with outstanding results in terms of running costs and serviceability.
Types of prime mover mainly comprise Leyland, Albion, B.M.C. and Thames, whilst trailers include B.T.C., York, Taskers and Kentucky, the average vehicle mileage being 60,000 to 70,000. A major part of the fleet is engaged on tramping runs covering the entire country, and the overall cost of a breakdown may be very high. . Reliability is, therefore, a first consideration, and using the most suitable lubricant for engines, transmissions, linkages and so on, has played an important part in reducing failures to a minimum and increasing the life of components between overhauls. Every type of overhaul and repair is performed in the workshops.
Increasing Durability Increasing the durability of transmission components was initially regarded as the most important exercise because of the relatively high incidence of transmission failures. Visual examination of the parts suggesting that improved lubrication could prolong their running life. After examining the claims made by Slip Products and Engineering Co. Ltd., for its lubricants, Mr. Eaton applied the appropriate grade to various assemblies, and highly favourable results were obtained. Current practice includes the use of Molyslip G for gearboxes and final-drive units (including two-speed axles and hubreduction gears), Molyslip grease for water pumps, steering boxes and clutch-withdrawal bearings, and Copaslip anti-seize compound to wheel studs, brake linkages and cylinder-head studs.
In the six months before Molyslip G was applied to tractiveunit differentials two and a half years ago, eight units required reconditioning at an average cost of £50 after each had covered about 40,000 miles, and in the intervening period there has been one failure. Formerly, Albion hub-reduction gears tended to run hot, which was cured by use of the oil supplement, and in two years replacements have comprised one new axle shaft and two sets of planet gears. One gearbox has been rebuilt in two and a half years, compared with a life, reported by other users of the same box, of about 10 months, and the treated lubricant facilitates gearchanging. Untreated two-speed axles averaged about 30,000 to 40,000 miles before reconditioning was required (failure apparently being due to excessive heat in every case) whilst treated axles have operated for a vehicle mileage of well over 120,000 miles without signs of deterioration.
Frequent brake-linkage seizure on tipping vehicles carrying highly corrosive ash has been virtually eliminated by using Copaslip grease, which is now applied to all linkages, and in
le case of wheel studs its use has eliminated fractures and rovides easy removal. The clutch-withdrawal bearings of 'active units engaged on particularly arduous work originally isted about four months, whilst treated bearings appear to have n indefinite life.
Supplied by Ernest Newton and Co. Ltd., Birmingham, Hypoid 90 base lubricant is used for all gearboxes and axles, part from worm drives for which a special worm oil is proided. Although a firm ruling cannot yet be given on the ffects of running engines with an oil supplement (Molyslip E), us lubricant will be used in all new engines, following the ampletion of around 90,000 miles in less than 20 months by ach of two Leyland Comets running with Molyslip in the oil. he cylinder heads will be removed for detailed examination fter 100,000 miles.
A single grade of high-detergency S.A.E. 30 oil, blended to le specification DEF-2101-B by Newton, is employed throughut the fleet and also in private cars. Servicing a new corniercial vehicle engine at 600-800 miles includes an oil change. Nell is considered of first importance, but subsequently the il-change interval is extended to around 10,000 miles, when le injectors are also serviced, Fuel-filter elements are replaced fter 4,000 miles.
Dunedin injection test equipment is employed and is particu
larly useful in adjusting injectors because it enables the setting to be checked with the units fitted to the engine and with the engine operating at its normal running temperature. It has been established that an injector, set at the standard cracking pressure of 45 atmospheres on conventional test equipment,
operates at a pressure of around 42 atmospheres in service, and that presetting at 48 atmospheres is necessary to obtain the rated cracking pressure in operation. Providing the correct effective pressure improves atomization, gives smoother running and reduces smoking tendencies.
A new set of standard piston rings is normally fitted to an engine after the vehicle has completed 100,000-120,000 miles, which is preceded by deglazing with a Hepworth and Grandage Glaze Buster, driven by an electric drill. This can be performed in a few minutes and is an indispensable operation in that it reduces the bedding-in period to the minimum. If the bores are not deglazed, fitting new rings may increase oil consumption as much as 1 gal. in 100 miles and the engine may not be completely run-in for some 10,000 miles. After deglazing, oil consumption, in a typical case, is about 1 pint in 150 miles.
Cylinder-bore Wear
Cylinder-bore wear of the larger engines after 100,000 miles averages about 0.001 in. and ridge removal is unnecessary. A reconditioned cylinder head is normally available and this enables the time required by two mechanics for a reringing job to be reduced from four days (60 man-hours) to three.
At 200,000 miles, a cylinder head is checked for flatness and scoring, and if necessary is machined. (say 0.002 in.) to obviate gasket trouble after refitting. It is usual to fit new pistons at this mileage and occasionally new liners. Some of the older Leyland Comets have covered more than 500,000 miles, liners and bearing shells having been replaced twice. According to Mr. Eaton, the crankshafts are still in "very good condition ". Fram oil filters of the throw-away cartridge type are preferred to the cloth type because the element can be changed in less than 30 min. The cartridge is renewed every 3,000 miles_ Fuel consumption of the Leyland Comet and Albion Reivers is around 10 m.p.g., whilst the 5.1-litre engines of the B.M.C. vehicles afford a consumption of about 18 m.p.g. Drivers are responsible for blanking-off radiators an appropriate amount
during the winter running. Newton anti-freeze is universally employed, radiators being flushed out and filled with fresh solution in the autumn.
Michelin X tyres are fitted to the majority of vehicles, firstly because of their improved wearing life and secondly because the maker offers a very efficient repair service. Moreover, the factory. remoulds are considered to be as good as new tyres (the average life of covers fitted to general haulage vehicles is 60,000 to 66,000 miles) and their use provides a saving of about. £8 per cover. The maximum life of a rebuilt textile cover is arounci 10,000 miles.
Textile tyres afford an advantage, however, in an experimental application to the trailing axle of six-wheeled rigids, the driving axle of which is. fitted with Michelin X tyres. Because the tread of the textile cover " skids " on the road surface more easily than the tread of the Michelin tyres, driving-wheel scrub is considerably reduced and this improves the steering characteristics of the vehicle.
Experiment Being Made An experiment is also being made with Carlan pressureequalizing valves fitted to the rear tyres of a Comet C53 trailing unit, which promise to improve the life of the covers by "an appreciable amount". After 6,000 miles, the tread wear is not measurable, whereas inner tyres that are not pressure balanced always show some wear. The inner tyres of twinned wheels (and of Four-in-Line axles) usually wear at a considerably h:gher rate than the outer tyres because of the effect of road camber, and it is hoped that pressure-balancing w!ll cure this trouble. Mr. Eaton claims that it also improves stability and gives better braking. Although the wear of the inner (unbalanced) tyres of B.T.C. Four-in-Line axles is relatively high, the oscillating axle increases overall tyre life by at least 100 per cent compared with the tyres of tandem axles. The fleet of 19 tractive units comprises 18 Leyland Comet: and Super Comets and one A,E.C., the last-named beini employed as a shunter. Of the eight four-wheel rigids of 2-tor to 9-ton capacity, four are Albions, two are B.M.C. and two art Thames. Seven Albion Reivers and five Leyland Comets make up the 12 six-wheeled rigids in the fleet, the remaininE commercial vehicle being a Scammell Scarab tractive unit witi a flat trailer and a van trailer (which are employed for loca delivery-and-collection work) and a 7-cwt. Thames garage. service van. Two additional works shunting tractors comprise a converted Thames lorry with shortened chassis and a Foden Pye Telecommunications two-way radio sets with an effective range of 25 miles are fitted 'to the shunting and collectior vehicles, the service van and the directors' private cars, and are controlled from the Barr Common depot.
The total of 24 trailers in the general haulage fleet comprise: four Yorks, nine Taskers, four B.T.C. (Four-in-Line), foul Kentucky, one Carrimore (semi-low-loader), one Scammell pole carrier, and one 45-ft. unit built in the workshops on B.T.0 running gear. The Yorks and Taskers include two tandem-axle trailers and have capacities up to 16 tons, platform length; varying between 22 ft. 6 in. and 27 ft. 6 in.
The 12 contract-fleet trailers of the Barr Common Tradirq Co. are of the all-steel tipping type and are employed in conjunction with four tractive units for the carriage of coal, coke pig iron, graded clinker, scrap iron and steel. Based on B.T.0 Four-in-Line gear, the trailers are of M and G manufacture and are equipped with Welford bodies and tipping gear. Al
are fitted with vacuum and air brakes. •
The trailers of both fleets have S.A.E. Fifth Wheel coupling and can be hauled by any of the tractive units in the combinec fleet. With the exception of four vehicles, all of these are fittec with Eaton two-speed axles, combined with five-speed gear, boxes, which are preferred to a six-speed overdrive box as the 10 available gears offer an improved performance.