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UMIN7NV
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by Tony Wilding, MIMechE, MIRTE ONCE AGAIN the majority of vehicles tested by Commercial Motor in the past year have been psv or heavy goods types. Of the 19 vehicles that have been put through their paces by CM technical staff, 11 ere in these categories. Three have been four-wheelers for the maximum-gross weight or just below it, and there were three vans and two "special types"—an ambulance and a 4 X 4 cross-country vehicle.
Bad weather for most of the winter and the difficulty of getting vehicles from some manufacturers are the principal reasons for the relatively low number of tests carried out, certain marque names being notable by their absence. Nevertheless, some important vehicles have been reported upon and the continued use of extensive operational trials for heavier goods vehicles and psv has enabled assessments to be made based on experience obtained in simulated operating conditions.
The year saw the first test of a vehicle with Gardner 6LXB engine—an Atkinson 30-ton tractive unit—while throe new models introduced during the year have been made available, namely a Bedford CF van, a BMC Boxer and Scania LB 80 32-ton-gross tractive unit. The Dennis FD4 ambulance with Jaguar engine also appears in the list of tests together with the Citroen Ami van which is now available in Britain while in the psv field two fairly new Seddon chassis are the Pennine IV coach and RU bus. Lightest vehicle tested in the year was the Citroen Arni 8 Service van, a report of which was published only last week. Although quoted by the manufacturer as having a payload capacity of 7.25cwt, this figure includes the driver and the nominal payload that can be carried is 6cwt. Fuel consumption returns were especially impressive. And high standards of road-holding and suspension qualities enabled high average speeds to be attained in spite of the output of the 600cc flat-twin engine driving the front wheels being only 35 bhp. Steering was slightly heavy for a vehicle of its size but "delightful accuracy" under all conditions overcame any criticism. The Ami 8 needed to have its toad located as far forward as possible to get the best handling characteristics and was then comfortable to drive. On a long-distance run, partly laden, the vehicle put up high average speeds and on a motorway check returned an average of 60 mph and a fuel consumption of 42.3 mpg.
Morris Minor
The Austin 8cvit van tested in the year will be better known as the "Morris Minor van" which was originally introduced for 5cwt payloads in 1953. After a variety of mechanical changes and uprating first to 6ewt and more recently to 8cwt, the design was considered to be still perfectly acceptable for a commercial vehicle and equal to the competition put up by vehicles of the same capacity but with more modern lines. Excellent fuel consumption results, braking and acceleration figures were obtained and in this case also a long-distance run was completed. On a journey which includes 400 miles or so of motorways completed at near maximum speeds and just on 120 miles on other roads including the crossing of two major cities, the Austin returned an average speed of 38.2 mph at a consumption rate of 35.8 mpg. The ride was hard judged by current standards but it was not uncomfortable and the firmness and stability when cornering were appreciated.
From the road-test report of the Bedford CF it must have been quite clear that this new model from Vauxhall should prove a worthy successor to the long-standing CA range. The 18cwt version with 1.6 litre petrel engine was tested and as well as giving more-than-satisfactory general results, the vehicle was found to be exceptionally comfortable for the driver, to have good brakes and light and accurate steering, It was felt that there would have been an improvement in fuel consumption on the runs with stops if the four-speed synchromesh gearbox had been fitted instead of the three-speed unit. The gap in ratios between second and top was rather wide which meant that the vehicle had to be driven harder than desirable to obtain satisfactory average speeds on simulated town work. The CF had all the qualities required of a van of its type including well-designed seats, well-placed controls and easy access to the driving area and body.
There have been no vehicles in the 2-6-ton load capacity class tested during the year and in the next-higher section there is just one, the 13MC Boxer which was reported on in CM of April 17. This chassis in fact, only just got into this section with a payload of 9.25 tons. It was introduced last October to fill a gap in the range of goods chassis made by Leyland Motors (Scotland) Ltd—between the Laird 13 tons gross and the Mastiff 16-ton-gross four-wheeler. The model was one of the six trucks and artics put through a full 731-mile operational trial and on this and all the other tests the vehicle came out very well. It had reasonable fuel economy and adequate general performance and excellent brakes. Higher rear axle ratios-6.14/8.38 to 1 instead of the 6.5 /8.87 to I as in the test vehicle—would have given better results without making the operational trial with its 1 in 5 gradients much more difficult for the vehicle. Even on the steepest sections second gear with low axle ratio was adequate and it was almost possible to get away in 1st /high from a standstill on the 1 in 5 gradient of MIRA. Bad weather at the beginning of the southern leg on the operational trial must have affected the results adversely but fortunately the snow which fell did not cause any trouble apart from reducing visibility except for the first 40 miles or so when it lay on the road. All the figures compared reasonably well with those from similar vehicles tested by CM but with regard to brakes, shorter stopping distances have never been returned except by lighter chassis.
The Dennis Pax V test was a supplement to the operational trial of the same model carried out in 1968. This one had a two-speed axle as against the previous single-speed unit and the main purpose of the exercise was to assess the difference since the Eaton two-speed unit had been made the standard fitting. Briefly, the change gave a worthwhile improvement in average speed and fuel consumption over the arduous section of the long-distance operational-trial route and a marginal improvement in overall consumption also. The actual overall results were 10.8 mpg at
• 38.3 mph average speed as against 10.6mpg at 38.8 mph for the original test. Because the rest of the specification of the test vehicle followed that of the original test exactly, brake and acceleration tests were not carried out, those quoted in the charts being the returns on the original.vehicle. As with the BMC Boxer a higher set of rear axle ratios would have been practicable for the test and would have given better results; bottom /low was not needed on the run and as the high ratio in the two-speed wile was the same as in the single speed the test vehicle had the same maximum speed as its predecessor.
Relatively high gearing in the rear axle of the Mercury 16-ton-gross four-wheeler detracted to some extent from top gear performance of the vehicle but enabled the excellent average speed for the operational trial of 38.8 mph to be attained and with a worthwhile fuel economy represented by an overall fuel return of 11.2 mpg. A power output of 146 bhp in conjunction with a bottom gear ratio of 6.63 to 1 meant that the Mercury was able to complete the 1 in 5 gradients of the test route without trouble. Acceleration times on tests were satisfactory as were brake figures. But the Mercury did not show up too well from the driving angle for although the cab was comfortable and noise level reasonably low, the brake pedal was rather heavy and power assistance did not "come in" on the steering until half a turn had been completed. This, in conjunction with a tendency to wander, made driving the Mercury tiring. In considering the results and figures quoted with this article it should be pointed out that the Mercury was tested as a chassis and the payload (10 tons 19cwt is quoted) would have been less with a body; with a light-alloy body a payload of around 10.5 tons should have been possible.
Two of the vehicles tested in the next category—that for maximum-gross vehicles —had Gardner 6LXB engines. The test of the Atkinson was the first with this power unit and like the Foden eight-wheeler, fuel economy of a high order was a major finding on the test. The attic has ousted the eight-wheeler as the main British trunk vehicle but for applications such as tipping, the eight-wheeler is still holding its own as the most popular maximum-gross machine. It was as a tipper that the Foden was tested and as well as normal checks for acceleration, braking and fuel consumption, the vehicle was used on a site to simulate actual operation. Laden to a gross weight of 26 tons, the test vehicle gave consumptions of over 11 mpg both at. 40 mph running and at high speed on the motorway and on the operational trial which included loading and tipping the vehicle and negotiating unmade road the consumption was 9.8 mpg. With a 5.2 to 1 final drive ratio maximum speed was 58 mph but the ultra-low bottom gear of the Foden 12-speed gearbox enabled the fully laden eight-wheeler to climb a gradient of 1 in 3. Extra-strong power-assisted steering made the work of the driver easy when shunting on soft ground but this in conjunction with stiffness in the linkage made steering the eight-wheeler in a straight line on normal roads difficult. There was some deadness in the steering and as well as this braking was criticized. Braking distances were reasonable but there was felt to be excessive delay between application of the pedal and full brake effectiveness_
V-8 ermined attic
Lightest of the artics• tested in the year was the Ford DI000 which ran at 24 tons gross and was taken over the 731-mile trunk-route operational trial circuit. The chassis had a Perkins V8 engine which in conjunction with ratios in the Eaton two-speed axle of 6.14 and 8.38 to 1 made for a lively performance but again the route could have been completed satisfactorily with higher axle gearing. Brake results of the Ford were good and it was a pleasant vehicle to drive with a reasonably low level of noise in the cab, comfortable seats and light steering and controls. But the suspension was rather "bumpy" and a tendency to oversteer meant that the steering had to have close attention at times especially when making slight changes in direction at high speed.
I estimated in the Ford road test report that consumption would have been up to 10 per cent better with higher axle gearing and this was based on findings with the BMC Mastiff which had a Perkins V8 engine also. In this case there was higher gearing in the axle and in spite of a higher gross weight of 26 tons, the vehicle returned 7.9 mpg over the operational trial route. Light controls played a big part in reducing fatigue in driving the Mastiff tractive unit but one tended to over-correct the steering which made it somewhat "tender," particularly when driving at high speed. A very bumpy and bouncy ride when first tested was a cause for complaint in the report but on a subsequent run in the vehicle this criticism was seen to be overcome by modifications incorporated in by then current chassis. Satisfactory figures for acceleration and braking were obtained on the test vehicle but braking could have been improved if there had been less wheel locking on the semi-trailer. A light-weight Taskers design was employed and while this played its part in allowing a payload of over 18 tons to be carried it had single tyres which gave inadequate adhesion for the brake effort being applied.
Next in gross weight class came the Atkinson 30-ton-gross tractive unit with Gardner 6LXB engine. This test confirmed that reports of excellent fuel consumptions made for Gardner-engined vehicles have considerable substance. With 8.8 mpg over the operational route, consumption was more than 2 mpg better than comparable vehicles tested previously. And the test vehicle was in no way sluggish, returning an average of 33.7 mph-about the usual-although the transmission layout did not give a suffiCiently low bottom gear to allow gradients of 1 in 5 to be tackled. Because of this a short diversion from the normal route to avoid the two gradients of this severity was made. Hills of 1 in 6 were climbed satisfactorily so that the model should cope with normal conditions and the change of route would have made little difference, in my view, to the overall result. General results of the test were satisfactory but the seats were uncomfortable and front suspension harsh while the steering had a "sponginess" in it. Otherwise the Atkinson was a pleasant vehicle to drive with a reasonably quiet interior. There were signs that the effort being applied to the driving axle brakes Was less than the designers had intended and this was put down to the possible fault with the load-sensing circuit for these brakes.
Swedish competitor
Although it did not reach the economy standard set by the Gardner-engined Atkinson, the Scania LB80 tractive unit gave a very good account of itself. Consumption returns were 1 mpg better than any other 32-ton-gross artic previously. tested and a better average speed resulted from the operational trial. In addition to this the vehicle was extremely easy to handle, having a comfortable cab and a low level of engine noise. These facts should be borne in mind when inspecting the charts accompanying this article; the Scania was the highest-weight vehicle to be tested in the year. The aspect of the Scania most praised in the report was the steering, and except for a rather heavy engagement action when selecting the lower ratios in the synchromesh gearbox, the Scania was no more arduous to drive than a car. Acceleration times better than the average for 32-ton-gross artics were obtained but braking figures were a little below the average; there should even be an improvement in the latter respect with the bigger front brakes which were being fitted on production to the model at the time of the test.
The two vehicles in the "special types' section could not have been more different-a Dennis ambulance and Bedford/Boughton 4 x 4. The Dennis FD4 ambulance was one of the two prototypes built after the design had been developed to meet the requirements of the working party on ambulance training and equipment published in 1967. It was introduced at the 1968 Commercial Motor Show and is probably unique in being the first ambulance to be designed for this purpose right from the beginning. The Jaguar engine driving through a Borg Warner automatic transmission to the front wheels gave the FD4 a lively performance and with variable-rate coil springs having replaced the original rubber spring units, the ride was considered to be up to the standard needed for injured persons. An ambulance with a high-performance character requires easy handling and good braking and these were also found to be present in the Dennis design, although the power steering option would have been preferred for low-speed manoeuvring. Fuel consumption . is obviously one of the least important aspects of an ambulance but in spite of the 140 bhp engine the model was in no way thirsty. Between 12.5 and 18 mpg was returned according to the type of route covered.
An idea of the capabilities of the Bedford /Boughton Packhorse 4 x 4 vehicle to cope with the conditions for which it is designed was given in the road test. It climbed a 1 in 1.73 gradient carrying a load of over 2 tons and grossing almost 5.5 tons! The Reynolds Boughton conversion is of the Bedford J4 and the name Packhorse was considered to be very appropriate. And on the cross-country and alpine circuits of the FVRDE test ground at Bagshot Heath, the test vehicle made no complaints, was perfectly stable when driven hard round unmade roads and tracks and, in fact, proved to be virtually unstoppable. Fuel consumption when driven at up to 40 mph was acceptable at 12.3 mpg and impressive braking figures were obtained.
The list of six psv covered in this review includes a I6-seat bus, two full-size coaches and three conventional buses, two of the latter being double-deckers. The 16-seater was the Ford Transit with Strachans body. The model is based on the parcels van built in quantity for Ford by the bodybuilder and although the chassis is designed primarily for the transport of goods, the test vehicle gave a good account of itself in this special application. Fuel consumption varied between 9.6 mpg and 16.9 mpg according to the type of test carried out and the Transit was easy to handle, had more-than-adequate brakes and brisk performance. Noise level inside the body was acceptably low at all times and the heating equipment was well up to the job of keeping the saloon at a comfortable
temperature on the bitterly cold day that the test was carried out.
First of the coaches tested was the Ford R226 which had a Duple 53-seat body and this vehicle was put through the full operational trial circuit to Scotland and back. On the 731-mile journey fuel consumption averaged 11.8 mpg and the circuit was completed at an average speed of 44.1 mph. Braking, as confirmed by normal tests, was powerful and positive at all times; the inclusion of a Telma electric retarder in the specification of the vehicle resulted in the main brakes being used on relatively few occasions. But at medium speeds more attention than was considered desirable had to be paid to the steering to get the coach to go where it was required although at high speed the vehicle handled reasonably well. The Ford turbocharged engine in the test vehicle performed very well over the operational trial. On motorways, averages of over 65 mph could be maintained without exceeding the 70 mph limit and all the steep hills on the route were climbed in fine style.
The second coach was the Seddon Pennine IV tested this year with a Plaxton body having 51 seats. The vehicle was borrowed from Hanworth Acorn, the London Airport-based operator, for the test and in spite of engine output at 120 bhp being relatively low the model gave a good account of itself so far as performance was concerned. The test included an operational trial over part of a set service operated by Associated Motorways from Harwich to Cheltenham and the 181-mile run was completed at an average speed of 29.7 mph which included simulated pick-up and set down stops for an average fuel consumption of 13.4 mpg. A reason for the Perkins 6.354 engine being able to provide an adequate performance at a gross weight of 11 tons 10.5cwt was put down to the good selection of gearbox and two-speed axle ratios. Braking efficiencies were high and the vehicle was able to climb the 1 in 4 test gradient at MIRA. On the MIRA ride and handling sections it also performed well. When on the road there was little or no pitching in the vehicle even on bad surfaces and when cornered very fast, roll was limited to very few degrees. Noise level
inside the saloon was low and there were adequate heating and ventilation facilities.
The conventional single-deck bus tested was the Seddon RU rear-engined design which had a 63-passenger body. This model was also put through a form of operational trial, this time over a 23-mile route in the Midlands during which 31 .random stops were made at normal alighting points and stages. This route was covered at an average of 25.5 mph with a fuel consumption of 11.4 mpg which were roughly the same figures as obtained on a laden two-stops-per-mile test. The lowest consumption was, as to be expected, when stopping six times in each mile where the figure was 6.9 mpg but on non-stop running a consumption rate of 15.1 mpg when going at up to 40 mph was returned and 16.7 mpg was obtained when running up to 30 mph. These figures confirm the undoubted fuel economy of the Gardner 150 bhp engine but there was a complaint that the accelerator was heavy and the treadle badly placed. This made driving rather tiring. But the Seddon had easy steering and powerful brakes which gave extremely good figures. The noise level was remarkably low which tended to make performance deceiving and although one got the impression that progress was slow during acceleration tests, acceptable times were produced.
Turning to the double-deckers, a feature of the Leland Atlantean tested by CM was the fact that it had the automatic version of the Pneumocycfic gearbox. There was some trouble in the beginning with jerky engagement of first gear but after adjustment this was improved on and the system worked very well. The Atlantean also handled well from other aspects with light and easy power steering which had no vices, and good brakes. For a vehicle grossing just 15 tons, acceleration times were short and the fuel consumption returns were up to a required standard although gale-force winds on the second part of the test when part laden and unladen runs were made had a big effect on economy, lower figures than when fully laden being obtained.
The Bristol VRT had accommodation for four fewer passengers than the Leyland and was not as long so that gross weight was only just over 13.25 tons. This vehicle also performed nicely with a derated version of the Gardner 6LXB producing 165 bhp. Acceleration times were good and apart from heavy steering the vehicle was pleasant to drive; the Bristol had semi-automatic transmission. Short distances were needed to come to a stop on the brake tests but care had to be taken when applying the brakes to produce smooth intermediate retardations. A form of operational trial was carried out with the bus, the exercise consisting of an 11-mile route through Bristol stopping at random at Bristol City Omnibus Co request and stage signs. There were 23 stops in all and the run highlighted heavy steering, power-assistance being considered desirable for a bus of the type and weight. For the passengers there were exceptionally comfortable seats and a low noise level from the rear transverse engine.