• Home
• Used vehicles
• Product news
• Dealer news
• Compliance
• Buying advice
• Archive

When Petro Fakes Precedence

By

John F. Moon,

A.M.I.R.T.E.

THERE are many operators in this country and overseas who still cannot successfully employ oilengined medium-capacity vehicles. The reasons are varied, but for those people whose choice is thus restricted to petrol vehicles, the British Motor •Corpora

tion offer their Series III range of Austin and Morris 3-ton and 5-ton chassis with a 4-litre power unit. A Morris normal-control 5-tonner, with this engine, was the subject of .a. recent road test and its general performance was up to the standard normally associated with this type of chassis.

Externally the new Morris is very different from its predecessors; the long front overhang, whilst not exactly handsome, has been designed so that most of the engine is outside the cab, with the result that there is only a small cowl obstructing .the passenger space. At the same time, the axle has had to be placed close to the cab to afford a reasonably correct load distribution, thus giving the vehicle its long snout.

The cab itself is a genuine three-seater, and is the widest normal-control cab built in this country, having a maximum interior width of 5 ft. 2 in. at the waist rail. It incorporates such refinements as a separate adjustable driving seat, twin opening windscreen panels, twin driving mirrors, a door-operated courtesy light and a very useful " oddments "• shelf

running the full width of the cab below the instrument panel. Rubber is used for the outer front-wing sections, which will help to reduce repair costs.

Internally, the Morris specification includes a new six-cylindered engine and gearbox, a redesigned frame and suspension, and Hydrovac-assisted hydraulic braking. The engine is similar to the old Austin Series IT 68 b.h.p. power unit but it now develops 87 b.h.p. at 3,000 r.p.m., with a: corresponding torque increase of 22 lb,-ft. . Whether this appreciable power increase from such a relatively small engine has been justified is a matter of doubt. Certainly the engine showed severe signs of overheating throughout the test and the sharp fall-off of the torque curve at 1,250 r.p.m. was reflected by the need for constant gear changing on undulating roads. Any lack of good torque characteristics could, however, be overcome by the addition of an Eaton twospeed axle, this being offered as an optional extra. The use of this axle, with ratios of 5.83 and 8.11 to 1, would undoubtedly produce a better performance on hills and probably improve the overall petrolconsumption rate. So far as overheating is . concerned, attempts are being made to reduce this tendency, but these seem to be principally along the lines of cutting out the effect rather than the cause.

I definitely did not like the first of these, though; this •is a crude metal-andlasbestos shield hanging between the engine and the cab scuttle. It is not very effective in reducing the cab interior heat, and during the tests even the floorboards became unduly hot because of the nearness of the exhaust pipe, which runs below the near side of the cab. Opening windscreens, however useful in hot weather, cannot cool hot feet, but scuttle vents might help.

The test vehicle was provided with a concrete-block payload of 5 tons 12+ cwt. which, with a driver and two passengers, brought the gross vehicle weight to 8i tons. This was ton above the recommended loading when fitted with 7.5020 in. (10 ply) tyres, but, although not a practice to be approved, I decided to test the Morris with this overload, as it is not unlikely that this would . often happen in service. Under such conditions 8.25-20 in. (12 ply) tyres would have been fitted, these being optional equipment.

Accompanied by Mr. Bob Berresford and Mr. John Neal. both of the Morris-Commercial proving department, I set off for Castle Bromwich for braking and acceleration tests. These tests were conducted under ideal conditions, and extreme accuracy was ensured by the use of a fifth wheel for speed recordings. I had rigged up the magazine of the brake-test equipment on the spare-wheel carrier and during the tests it was easy to see that the time lag in the braking system was only very small when making emergency stops.

This was because the distance between the chalk mark on the road and the start of the rear-wheel skid marks was, on each occasion, only slightly greater than the fixed distance between the magazine and the rear-axle

centre line. Braking was smooth and all the wheels locked in a straight line from both 20 m.p.h. and 30 m.p.h. The hand brake gave constant retardation rates of 38.5 per cent, when applied from 20 m.p.h. The lever is well positioned for emergencies.

Following these tests, I drove the 5-tonner to Warwick, which was the starting point of the fuel. consumption run. The heat in the cab was, fortunately, not so pronounced on the driver's side (although this would not be the case with a left-hand-drive vehicle). I was able to appreciate the good all-round vision, especially as regards the low bonnet line, although the front wings have a sharp fall-away and the near-side wing is not visible from the driving seat.

The steering was somewhat heavy on tight corners and there was a marked tendency towards wander which became worsc as the speed increased. It was, therefore difficult to relax completely, which can, in a way, be a good thing on a long journey.

The suspension would be improved by the use of dampers on the front axle—these are available as an extra—and this would possibly give better steering characteristics and reduce the transference of road shocks to the steering wheel. Another small point which attracted my attention was the position of the door interior handles. These are at the rear of the doors and are difficult to reach because the seat squabs partially obscure them. Only one windscreen wiper is fitted as standard, and this struck me as an unfortunate omission when we ran into heavy rain later in the day.

With Warwick as the starting point, a 12.6-mile run was made along the A41 road to the foot of Warm ington Hill. This route is undulating and second gear was required twice and third gear once. The distance was covered at an aVerage speed of 27.3 m.p.h. and the use of 10.65 pt. of petrol indicated a consumption rate of 9.46 m.p.g. A return run over the course, made later in the day, produced figures of 11.86 m.p.g. for an average speed of 28.9 m.p.h., giving overall average figures of 10.66 m.p.g. and 28.1 m.p.h., which are reasonable considering the severity of the route.

Sunrising Hill was used for engine-power and brakefade tests. This climb, on the Banbury—Stratford on Avon road, has a general gradient of 1 in 10, steeper sections up to 1 in 6+ occurring on the two bends. The El I I

ambient temperature during the ascent was 70° F. and the engine coolant temperature was recorded as 176° F. at the bottom of the hill: As soon as the first bend was reached, low gear was used and the total time in this ratio was I min. 18 sec., second gear being used for 1 min. 32 sec. during the hilt-climb. The radiator toptank temperature had risen to 201° F. by the end of the climb, but as the radiator is pressurized to 4 p.s.i. the boiling point is raised to 224° F., showing a margin of 23° F. on this climb. For use in hot climates, a six-Waded fan is fitted.

A satisfactory stop-start test was made on a 1-in-6-1section. It struck me that the engine was near its limit of power when pulling away on this gradient and, here again, for hilly working the use of the Eaton axle would be beneficial. Two descents of the mile-long hill were made with the gear in neutral and the brakes applied to restrict the speed to 25 m.p.h on the first occasion and 30 m.p.h. on the second, the engine being speeded up to provide the necessary braking boost.

Apart from rather • pronounced brake squeal, both descents were made without incident, and at the end of the second an emergency stop from 20 m.p.h. produced a Tapley meter reading of 43 per cent. Faint black marks were left on the road after this stop and the pedal travel had increased by I in. The drums were smoking badly, but the braking efficiency was not sufficiently impaired to warrant anxiety on long, downgrades.

On the second day of the test the payload was removed and further runs were conducted between B12 "

Warwick and Warrnington to ascertain the unladen performance of the vehicle. The average of the two unladen runs was 12.04 m.p.g. at the same average speed as the previous test. A combination of the two fuelconsumption figures gives a consumption rate of 11.35 m.p.g., which is what can be expected when operating with the vehicle laden in one direction only.

,During the unladen runs a certain amount of misfiring was noticeable, and I put this down to faulty ignition setting, which must be rather critical in a highly strung power unit such as this. This misfiring would undoubtedly raise the petrol-consumption rate and had it been correct, the second set of fuel figures should have been better.

Marious maintenance tests were done on the vehicle on its return to the Morris Commercial works, the first of these being to adjust the tappets. This task was complicated by the ,fact that it was difficult to align the starting handle with the crankshaft dog because of a badly fitting radiator fan cowl, and the time of 231 minutes taken to adjust the tappets includes about 4 minutes spent in negotiating this obstacle. It is not possible to attend to the tappets while standing on the ground because of the bulbous front end, and it was necessary to sit on the off-side front wing.

A standard tool kit had not been supplied with the test vehicle and all maintenance tasks were done with workshop tools. When adjusting the brakes a trolleytype jack was used, and this enabled both wheels of each axle to be jacked up simultaneously. Each brake unit has two adjusters and these are of the internal type, which are not easy to reach despite their advantage of being protected from road dirt. The total time spent adjusting the brakes was 21 minutes.

1 was further handicapped by the lack of a maintenance manual and thus wasted a certain amount of time during the battery inspection. I knew the battery was below the off side of the cab and, having seen a detachable panel at the off-side step decided that this was the way in. The panel, however, which took I I minutes to remove and replace, is used only when it is required to remove the battery, and I later discovered that there is a floor-trap under the driver's seat for battery inspection. Doing the job properly took 1 minutes.

Carburetter Cleaning

A Zenith 36 VIS downdraught carburetter is fined to the engine and cleaning out the five jets of this instrument took 8 minutes. The main and compensating jets are located at the bottom of the float chamber and these can be removed after detaching the float chamber by using the squared end of one of the float-chamber retaining bolts.

The fuses are located on the off side of the cab scuttle and one of these was changed in 20 sec. In the event of a fuse blowing on the road, a further 30 set. should be added to this time for opening and closing the bonnet. The six sparking plugs were removed, inspected and replaced in 411 minutes.

Level checks were then carried out. The engine oil level was ascertained in SO sec., slight difficulty being caused by the dipstick fouling the distributor head when it is pulled out. By crawling underneath the cab it was possible to cheek by feel the gearbox oil level in minutes, and the rear axle oil level was also verified in the same manner in 45 sec.

By rolling back the cab rubber floor-mat and opening a small trap, access is given to the master-cylinder reservoir, and starting from scratch, the reservoir level was checked in 2 minutes 7 seconds. This time includes replacing the trap and mat. The engine air cleaner is an A.C. oil-bath unit, and removing the cover and filter unit to see the oil level and then replacing occupied 35 sec.

Room for Maintenance

There is plenty of room on both sides of the engine for maintenance purposes and such items as the main .lubricating filter, distributor, starter motor and dynamo are unobstructed and allow free use of spanners and other took The only impediment to easy engine maintenance is the shape of the front end, which demands plenty of awkward stretch to reach low-down engine accessories, so much so that most of these items will obviously be reached by experienced fitters from underneath.

The Morris 5-ton petrol-engined long-wheelbase

• normal-control chassis, with standard timber drop-side body, is retailed at a total price of £969 10s. 5d., this price including £131 10s. 5d. purchase tax. As a chassis only, complete with scuttle, the price is £806 10s. 5d., the purchase tax being the same. Available extras include rear helper springs and .8.25-20 in. (12 ply) tyre equipment.