SHORTCOMINGS OF VEHIC ON OVERSEAS SERVICE
Page 26
Page 27
Page 28
If you've noticed an error in this article please click here to report it so we can fix it.
Some Candid Criticisms, by a Ma inlet Major Chassis Components Operating Un Middle East. Comparison I gineer, of Vehicle Manufacturers and of rduouS Conditions Which Obtain in the ritish and American Units
GENERAL observations in the position of technical adviser and maintenance engineer made over a period of five years indicate that there is a lot to be desired in the design, maintenance and operational facilities of commercial vehicles suitable for service in the Middle East. Altogether, a traffic mileage of over 22,500,000, of which 3,750,000 were covered in less than a month, by no fewer . than 173 makes and types o'f vehicle, forms the basis of the following comments.
Probably no worse conditions could he found for these vehicles, which were in the bands of experienced army drivers and youthful Arabs, both of whom, in many cases, were imbued with the same ideas of quick delivery of the goods, and an even more hasty return to base—but for entirely different reasons.
Temperature variations were often as much as 120 deg F. in a period of 24 hours. Road conditions, could vary from tarmacadam to virgin sand, deeply rutted tracks, gravel or boulders, all in a distance of a few miles, In a journey of 22 miles, 1,300 ft. below sea-level could become 1,600 ft. above it. Sea-level could be replaced by 4,500 ft. above it in the same distance, and brilliant sunshine might, in a few hours, be replaced by torrential rain of the monsoon variety, rapidly transforming tracks into impassable mud. Civilian-operated vehicles were mainly of the 3-ton to 5-ton class, usually of American manufacture, but practic ally every European country, including Sweden, was represented. The heavier types, of 8-ton to 10-ton capacity, invariably powered by oil engines, were usually' of Italian origin, often four-wheelers, with a sprinkling of American six-wheelers, mostly articulated.
Passenger chassis were mainly of the 32-40-seater single.
deck variety, of American origin, with bodies locally manu-factured on the lines of the all-too-familiar utility range: they were invariably subjected to gross overloads.
British Makers Fail in Their Service Organization
The larger concerns were often to be found operating British vehicles, and at least one of our manufacturers maintained a sound service organization in the area. From 1942, onwards, it appeared that, due to lack of replacement assemblies, this admirable protagonist of our export trade would have to yield some ground to American competitors who were in a position to supply alternative units, particularly engines, which, with minor alterations, could be readily fitted.
W.D.-types operated in the area included all the models seen in the Services, emanating from the foremost manufacturers in the United Kingdom and North America.
Restrictions in the U.K.. which may be admirable from the point of' view of the road and licensing authorities, unfortunately do not produce a vehicle of maximum load. on minimum space which is suitable for these countries. Whilst British manufacturers provide an average of anything from 10 to 20 per cent, more body space, combined with a reduction of a similar amount in unladen weight, their products are sure to suffer from such a practice.
One manufacturer produces a 10-ton vehicle having a body length in the region of 20 ft., with an unladen weight of 7f tons, but a far more satisfactory vehicle, for export market requirements, is an American product of the same load capacity weighing 10i tons unladen, with a body space of barely 15 ft. It is true that the British vehicle may effect a saving in fuel, but in a country where this commodity is fairly cheap and easily obtained, 180 b.h.p. is of more assistance to the operator than a mere 120 b.h.p.
British and Italian engines, mostly favouring the more usual method of direct injection, proved to be very sound in operation. Troubles were restricted to the maintenance of fuel pumps and injectors, service facilities for which did
not seem to be provided to the extent necessary for easy unit replacement, so as to avoid unwelcome attention by inexperienced fitters. In the early stages, lack of adequate
testing apparatus for injector pumps caused a considerable amount of over injection, promoting a crop of piston failures and bearing troubles. Ample provision for filtration appears to cater, for the extraction of foreign matter from both induction and lubrication systems. In many cases, however, a considerable increase in the capacity of such filters would reduce the attention now necessary at very frequent intervals. particularly to the air cleaner, of which the oil-bath-type is easier to service than its felt counterpart, although thereis little to choose in effectiveness.
It is noteworthy that, in spite of the maintenance efficiency with which the Italian engineer is usually credited, very rarely was an oil engine of Italian make to be seen operating without' a healthy knock accompanied by columns of black smoke. In most cases, minor attention was found to improve performance to a more satisfactory standard.
American Oil Engines to the Fore
American-built oil engines predominated, and the various designs were the subject of much discussion and comment as to high standards of efficiency and ease of maintenance. A well-known proprietary unit, employing direct injection coupled with a low-pressure fuel system and mechanically operated injectors, was undoubtedly very satisfactory and appeared in a variety of chassis. An additional and optional refinement of a low-pressure boost assisted operations at high altitudes and, at 4,500 ft., no noticeable deterioration in performance 'wasexperienced.
• Heater plugs proved a weak point with one antechamber-head design and rarely stood up to the conditions imposed, although, in other respects, this engine was very sound. A two-stroke .engine, of clean lines, having four cylinders, mechanically operated injectors incorporating separate metering devices, and a reliable low-pressure supercharger for scavenging, which was easily convertible to run in either direction as an industrial engine, formed the power unit for• a four-wheeled 10-tonner. Unfortue
irately, this vehicle possessed an axle loading far in excess of that permitted in this country.
Good results, obtained under varying conditions with this engine, were offset by a tendency to burn off the tips of the injectors if the unit was permitted to idle at very low speeds. Moreover, overfilling the sump when Imperial gallons were confused with the U.S.A. gallons had a nasty habit of providing the supercharger with an excess of lubricating oil, with results to the 'pistons which will be obvious.
Doped Petrol Causes Trouble
Petrol units were usually of well-proved designs which had seen considerable service in pre-war years. However, as was to be expected, the high lead content of the fuel played havoc with the standard design of valve having a low nickel-chrome content, and no facilities were available for Stelliting to the extent necessary. Sodium-cooled valves and Stein-tad seats provided some assistance, or temporary immunization from trouble, but as the material position deteriorated, so the periods between " decokes " grew shorter, until the maximum possible mileage with the average British overheadevalve engine was not more than 4,000.
Side-valve engines fram this country appeared to have the advantage, although, being in the minority, accurate results under conditions prevailing in various localities were difficalt to obtain. Reports, however, indicated that a minimum of twice the aforementioned mileage could be obtained between top overhauls.
American-built engines did not suffer to the same extent, for reasons which are common knowledge, but, even in this case, results on the lines previously mentioned ‘vere observed. Side-valve units had a definite advantage, and results under the most arduous conditions indicated that with average care mileages of well over 20,000 could be obtained.
Poor though results were with leaded fuel of 80 octane, as used in the U.K., it is probable that the fuel which was obtained locally in the Middle East, and reported to have a T.E.L. content of up to 3 cc. per Imperial gallon, produced. conditions which, combined with the prevailing high temperatures, would have been disastrous but for, at times, the almost frantic work carried out under considerable difficulties by artificers who rarely bad the materials or correct tools to do the job. This was a state of affair which had been anticipated, and was continuously represented by those in charge.
Cooling modifications carried out by civilian operators indicated that manufacturers were not conversant with requirements in this direction. Common and easily effected modifications to radiators and header tanks, and an increase in the number of fan blades and in the speed of fans and water pumps, or even the provision of a larger water pump, were the rule rather than the exception. Whilst vehicles were apparently fairly satisfactory in the earlier stages of their life, they were in need of some • assistance when cooling efficiency dropped for obvious reasons.
Even this excuse could not be put forward for one W.I). model which, during the early stages, suffered from overheating to an alarming extent. I spite of •modification this vehicle was neverreally satisfactory while operating under load in high atmospheric temperatures or following winds.
'Apart from transfer-box and front-axle-drive troubles during the early stages of development of both British and American vehicles of this type, transmission failures were few. The oil seal and the occasional half-shaft failures were not frequent enough to embarrass transport availability.
Gearboxes and Universal Joints Give Satisfaction Propeller shafts, with needle-roller or rubber uniVersal joints, were substantially sound, although occasional loose flanges or excessive wear could be traced to poor main tenance. The practice of some manufacturers of fitting soft-metal dust-excluding flanges rendered flange retaining bolts liable to slacken off on a run of 100 miles. Other than a tendency to develop oil leaks, the average gearbox in service was found to be satisfactory, although mainshaft bearings naturally suffered from exposure to sand.
Transfer boxes of four-wheel-drive vehicles were, in the first instance': very troublesome. However, minor modifi cations to the American versions, such as increased end float on the intermediate shafts to counteract expansion due to the excessive heat generated, the provision of larger diameter bearings, and more sturdy box mountings, provided an assembly more serviceable than one manufactured in this country.
The basic trouble of the British machines appeared to be the mounting of an outrigger bearing-housing on the cover plate, rather than on the box. Holding-bolts of both cover plate and hearing housing provided the driver with a permanent task while the vehicle was under load running on sand.
Front-axle-drive design appeared to be satisfactory with the increase in diameter of the universal joint. A similar result, obtained by reducing the lock on some vehicles, was not, however, so satisfactory from the operator's point of view.
Whilst British-made axles were sound from the beginning, it was, however, found necessary to increase the diameter of an American-built constant-velocity joint from k ins. to 6 ins, before comparative results were obtained.
A particular advantage enjoyed by single-axle-drive vehicles of North American origin was provided by the employment, in many cases, of a successful proprietary two-speed rear axle having ratios of approximately 6.8 and 8.3 to 1, which refinement undoubtedly considerably increased engine and transmission life'. This axle, weighital little more than the single-ratio assembly fitted to tin standard pattern W.D. 3-tonner in civilian service as a 5-tonner, was so satisfactory in service that, apart from cover-plate removal for routine inspection, no reason was found to disturb such assemblies fitted to several thousand vehicles on maintenance charge at various times.
Suspension failures, naturally provided a major problem for all maintenance engineers. Difficulties would have been minimized by an increase in the number of leaves; an increased length of spring; shock-absorbing properties of rubber-mounted shackle pins as fitted to some lighter types of vehicle; rubber-blocked eyeless springs to avoid the shock transmitted through bracket and main leaf when a worn pin and bush are unavoidably retained in service; a substantial damper leaf or shock absorber; brackets rigidly mounted with h.t. steel bolts, to avoid some of the doubtful riveting Passed out from certain factories All these features would have materially assisted those unfortunate individuals whose job it was to rivet, weld, or otherwise marry up broken leaves, to enable an urgent load to be delivered.
Modification Causes Centre-bolt Failure Apart from the more standard versions of springs and mbuntirags, a few had been modified to provide the W.D.
specification vehicle with increased ground clearance at thecentre of the frame. This result was obtained by increasing
the depth of the hanger brackets and the camber of the spring, the latter modification being carried out without any corresponding increase in the dianteter of the U bolts The result was that centre-bolts failed, due to difficulty in pulling down a highly cambered spring fitted to a 4-5-ton load carrier usually in an unladen condition. The deeper hanger brackets resulted in a member which refused to support a shackle pin suspended some 6 ins, below the frame.
Brakes, facings, drums and brake-operating gear were very sound in practically all cases, and the consumption of facings fell far below the scale of spares provided. Protec tion against the ingress of foreign matter into drums and operating gear was satisfactory if properly maintained.
General application of a servo device on practically all vehicles of 3-ton capacity: and upwards, provided sound braking under any conditions, although one British manufacturer appears to have a faith—not shared by drivers— in a self-energizing shoe system on a 5-ton vehicle.
Electrically operated brakes, mainly fitted to some makes of trailer manufactured in America, are sound. Two methods of operation are employed—a separate hand con trol or a foot control adjustable with, and operated by, the foot brake of the prime-mover. In practice, the latter method provides for inexperienced drivers, whose failure or excessive zeal in operation of the hand control with a 4-5-ton load on a trailer of 2i-tons unladen weight, plays havoc with the fifth wheel mountings and pin.
However, a 25 amp. load on a 75-105 amp, battery on the prime-mover does not give a great margin of safety and, in-all fairness to the battery manufacturer, an increase in the capacity appears necessary in such cases.
Electrical equipment appears to have reached a high state of efficiency, but the wiring mountings and protective
aspects could be improved. A type of distributor giving good service over a number of .years in the U.K. gave considerable direct and indirct trouble due to a loose and
unprotected body mounting, in the side of the engine block. Dust and sand produced the necessary abrasive,, which, following a sloppy mounting, threw a load on the distributor shaft and bushes until the gap at the points varied from a few thous, to in. Sand which found its way into the solenoid and starter contacts of an American-milt compression-ignition unit, also provided much and varied trouble, from points fusing to mountings fracturing. Voltage-control regulators were generally satisfactory and fairly easy to adjust, although lack of testing plant rendered the task of checking the output of some -of the more ambitious American equipment a little difficult.
Tyres undoubtedly accounted for the greatest number of involuntary stops. With the trend towards single-tyre equipment of large diameter, in place of the reliable 32 by 6-in. and 34 by 7-in, covers, came a crop of troubles, relieved only by the gradual increase in the number of plys from eight to 12 in the case of the more common 10.50 by 16 cover.
This increase coincided with a deterioration in the quality of materials which, apparently, accounted for the failure of tyre manufacturers successfully to design, in the early stages of production, a 10.50 by 16 tyre which would stand up to the high temperature rises accompanying a rise in pressure of 33i per cent. The result was the all too common collapse of the right-hand rear tyre of the average 3-tonload carrier, although failures were not confined to this position.
Heat Promotes Type Pressure Rise Releasing the air did not materially assist, as it was found that the tyre invariably returned to its original high pressure during the heat of the day. This brought about a certain degree of under-inflation during the late evening, due to drivers failing to reinflate.
The equivalent increase in tyre size in the lighter classes of vehicle resulted in a fairly satisfactory tyre of 9.00 by 13 range. When fitted to vehicles not originally designed for such sizes, there was an excess loading on the axles due to off-set mounting, so that bearings, stub axles and threequarter-floating rear axles, in particular, suffered to a considerable extent
Lubrication was found to be of major importance, as was naturally expected, so, with frequent oil changes and the use of very light-grade oils, plus a heavy-grade oil for chassis lubrication, the life of component parts of the vehicles was considerably increased.
Even as light a grade of oil as that designed for Arctic climes could be used in the sump without any ill-effects on the engine, as was proved by a car of British manufacture which ran during the heat of an Egyptian summer on such a grade. The result was that consumption was light and no apparent increase of wear on the bores or bearings was experienced, although the oil pressure fell to a low level on long runs.
Service facilities for civilian vehicles were confined to a few manufacturers, mainly American and trench, the former, in all cases, maintaining a staff capable and anxious to assist in any possible capacity. This service was extended in full where American products were in service with the • W,D.—a post-war trade qualification which apparently escapes our own manufacturers, the visits of whose representatives were very infrequent and whose resident technical advisers were almost non-existent.