LITRES 'ULL 12 TONS
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THE Faden four-cylindered 2.72-litre engine is dwarfed by the F.E.4/8 8-ton chassis, not only in size but also in weight, yet its performance is exceptional. It weighs just over 81 cwt. without electrical equipment, but pulls a 12-ton load with remarkable ease and economy. Advantage is taken of the 3-ft. 91-in. length and 2-ft.. 5i-in. width of the engine to put it between -the seats of the cab and fit an additional seat over the bonnet, thus providing comfortable accommodation for a second loader.
The Foden forward -control light 8-tonner was introduced at Earls Court last yea'r and, apart from modifications to facilitate gear changing and the fitting of a transmission parking brake, it has been littL: altered before going into production. Its eingine is basically similar to the Foden six-cylindered two-stroke 'Unit, employing the Kadenacy system of combustionin which a Roots lowpressure supercharger delivers air to a chest and passes it through tangential ports into the cylinders.• Weight is saved by using a, light-alloy crankcase and cylinder-block casting with cast-iron wet liners. Being • a two-stroke unit, the output per litre is practically double that of a conventional British oil engine. With a governed speed of 2,000 r.p.m. the maximum output is 84 b.h.p. and 235 lb.-ft. torque is delivered at 1,500 r.p.nn. Many of the components are interchangeable with those of, the six-cylindered unit, because the bore and stroke and camshaft and. crankshaft journal diameters are similar. The crankshaft has five main journals,_ and the main and big-end bearings employ steel backed white-Metal-lined shells. .
A one-piece casting is used for the cylinder head and the overhead exhaust-valve gear is operated by pushrods and rockers. The iC.AV. fuel-injection' pump, complete with hydtaulic_ governor, fuel lift pump and built-in filter, is mounted as a unit on 'top of the blower, whichis attached to the near side of the engine. The exhaust manifold is• taken from the opposite side.
Whereas the fan is attached to the camshaft and driven at engine speed 'on -the .six-Cylindered unit, it is driven by the crankshaft on the "four," thus reducing the proB12 trusion of the tunnel at the front of the cab and providing additional footwell space for the central seat. A friction drive is incorporated for the fan. The radiator is placed forward and the oil-bath air cleaner for the engine is sited adjacent to the inverted T-shaped header tank.
Formerly a nine-speed gearbox was specified, but the production models can be supplied, with a four-, fiveor eight-speed unit. All are based on a normal fourspeed gearbox, the super-low ratio in the five-speed unit being a separate attachment, as is the two-speed auxiliary which is now controlled by a cut-out motor actuated by a single tumbler switch 'outrigged from the steering column.
Although the main gears are ,engaged by dogs, the auxiliary employs spring-loaded dogs,. providing a preselective action. When the steering-column switch is moved to energize the motor, the dog slides towards the position for engagement, but the change is not made until the load is reversed on the gear teeth or the clutch pedal is depressed. A 151-in.-diameter clutch is used and the gearbox, with auxiliary, unit, is attached to the engine. A single Silentbloc mounting is • employed at the front and at the rear the pads are attached through brackets to the clutch housing.
The transmission includes a Kirkstall hypoid final drive, with an integral pump, and the Hardy Spicer propeller shafts have a centre bearing pivoted on two rubber bushes to the frame. Fox lightweight springs, which are relieved on the lower side of the leaves, help to reduce weight.
The braking system embodies two-leading-shoe_units actuated by Lockheed hydraulic equipment, with assistance from a Foden engine-driven booster. Adequate frictional area is available in the 16f-in.-diameter drums. with 3-in.-wide shoes at the front. and 5-in at the rear;
The transmission brake, with the drum attached to the
tail end of the propeller shaft, is a recent development which is likely to be followed by other British manufacturers. The transmission drum is 13 in. in diameter, with two shoes mounted to give a servo action in both directions. The facings on these shoes are 111 in. long and 2i in. wide, providing a total 'frictional area of 57-1 sq. in. "
With a normal 18-ft. platform body the Foden 8-tonner has an unladen -weight• of 3+ tons, but the teak body fitted to the test vehicle, together with a full fuel tank and equipment, raised the tare weight to 3 tons 19+ cwt. Concrete blocks and iron castings, with timber battening, bi-:oughtthe vehicle weight to a leVel
12 tons and for part of the day there were three people in the cab. The axle position is well chosen 'for load distribution, about 4 tons being imposed on the front wheels. Although appearing new, the vehicle had over 50,000 miles to its credit, most of the mileage being covered in endurance tests in the Welsh hills by day and trunk operation 4106 tdad at night. Hand-brake development trials had also been made on the vehicle and, although specifically stated by a notice in the cab "to be used for parking or in an emergency only," the transnlission brake has been tried extensively with the vehicle in motion. It is not intended for .continuous braking on long hills.
The first of my tests was to make a fuel-consumption run over a 34.2-mile circuit which started and finished at the Sandbach works. The fuel tank was filled to overflowing and the radiator grille masked to reduce the opening to 10' in. wide by 7 in.—deep. Muffs are being made for the present production models.
I had expected to complete the circuit non-stop, but because of poor visibility and market-day activities, we were delayed at practically every village and town. Middlewich shopping centre was responsible for two stops, and then came a clear tun to Lostock, where a steady 30 m.p.h. was maintained, with a slight whine from the gearbox overdrive.
Compared with other Foden two-stroke-engined goods vehicles I have tried, the 8-tormer is quieter. The engine note, a combination of blower whine and injection and exhaust nOise, was modulated, and the customary roar from the silencer tail pipe was less noticeable. The well-built composite-construction cab with trimming comparable with that'• of• many mass-produced private cars, also helps to prevent noise reflection. Additional comfort was afforded by a Smiths heater, which is desirable because no warmth penetrates through the bonnet and little from the panel behind the radiator.
The radiator screening enabled the water temperature e14 to be raised rapidly to, 165' F., which in turn gave a satisfactory oil temperature' of about the same level, there being a difference of about 10° F. between the oil-cooler inlet and outlet. The cooler is incorporated in front of the normal water radiator and additional tubes can be added for operation in,warmer climates.
Between Lostock and Mere the road is wide and there were no hindrances, but the narrow _ A50 .road k was particUlarly congested, so that speed had to be reduced and several halts were necessary in Knutsford and Holmes Chapel. Parked traffic added difficulties to the progress of 'a 40-ton outfit at the • front a the traffic
stream. • •
Altogether 13 stops were made in the circuit, and the Foden did well to complete the course in 1 hr. 25 min., which, after deducting standing time, equalled, an average speed of 25.7 m.p.h. The amount of fuel used was 2.28 gal. giving a return of 15 m.p.g., which was exceptionally good, considering that stops averaged one to every 21miles, and that the engine was idling for 41 min. on the journey. I would have preferred to have made a second high-speed test to reproduce long-distance work overseas, but it was obvious that traffic conditions would not improve throughout the day.
A chance to make good use of the eight-speed gearbox occurred when driving from Sandbach to Mow Cop, there being inclines of varying gradients on the approach to the test hill. At first I occasionally provoked a protest • from the gearbox when attempting "' split changes," but, once accustomed to the control, I found the Foden a joy to drive. Normal half-changes in ratio are made without declutching. A start was made on a 1-in-6+ gradient, followed by an easy change to high first on 1 in 9. .
With the 6.5-to-1 ratio axle and the four-or eightspeed gearbox, a 1-in-6 incline is about the steepest that the Foden will climb, but the alternative axle ratio of
7.16 to 1, or the five-speed gearbox with super-low ratio, covers operations where freak hills, such as the brow of Mow Cop, are found. I optimistically attempted to change to second gear on the hill, which practically stalled the engine and necessitated another start from rest. The transmission. parking brake was particularly effective in preventing the lorry from running either forwards or backwards, holding it stationary without undue effort on a 1-in-6 incline.
I was so engrossed by the performance that Ifteglected to note the time taken• during the climb, and all too soon the 1-in-3i section.at the top of Mow Cop came in-sight. Water and oil temperatures both. reached a tnaximum of 185' F., and the oil-cooler millet 175° F., the grille still being covered, as in the consumption trial. An ambient reading of 55' F. was recorded.
, There are some sharp bends in the steep descent, and as the porting of the two-stroke engine affords less retardation than normal during, overrun,. I was prepared to change down to bottom gear.The Foden repreSentative suggested using third gear, because 'many brakefade tests had been conducted with the vehicle on Mow Cop, and they had shown no great loss of efficiency after descending at 20 m.p.h. This was proved when I 'applied the pedal with some vigour at the foot of the
and found adequate retardation to lock the rear wheels.
• The conditions were exceptionally poor for measuring
full braking efficiency, and tests on level ground caused extensive wheel locking. During attempts from 30 m.p.h. the tyre marks indicated that the rear wheels were stationary for 40 ft., so that the distances of 301 ft. from 20 m.p.h. and 64 ft. from 30 m.p.h would be much reduced on a good dry road. According to the manufacturer's tests on a dry road, the Foden can be stopped in 22 ft. from 20 m.p.h. and 43 ft. from 30 m.p.h. Tapley readings ranged from 50-69 per .cent. Hand-brake trials were made from 20 m.p.h., and the readings ranged from 25-32 per cent., according to the effort applied, the extra tooth on the ratchet making appreciable difference to the braking.
Acceleration tests were made in the main, ratios and direct drive in the auxiliary, the half-step sequence being found to be slightly slower. The Foden has reasonable acceleration, reaching 30 m.p.h. within 47 sec. of starting from rest. The torque range of the two-stroke engine is npt suitable for law-speed work, such as accelerating from 10 m.p.h. in top gear, and the provision of an easy-change gearbox would deter. any, driver from such laziness.
To end the day's work, the vehicle was put through its paces in competition style, taking bends at fair speed and reaching 45 m.p.h. on level ground. To afford good performance overseas, no change is made in the 9.0020-in. tyres, but the advocated gross vehicle weight is reduced to 10-} tons.