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TOTTING UP THE TESTS

During the Past Two Years 54 Vehicles have been Road Tested : Results Show Slight All-round Gains, Particularly with Safety Features SINCE the last summary of road-test performance figures was given in The Commercial Motor on April 30, 1954, 54 vehicles have been submitted for assessment. These have ranged from the smallest 5-cwt. van at present made in Great Britain, the Reliant, to two of the largest tractor units made anywhere in the world, the Scammell Constructor and the Rotinoff Atlantic.

It has been possible, therefore, to keep a reasonably accurate check on vehicle manufacturing progress over the past two years, and whilst no 'revolutionary designs have appeared, solid development in design is apparent. Performance figures are, on the whole, improved when each class is compared with the classes reviewed in the previous summary, particularly as regards braking.

Several New Ranges Several completely new ranges have been introduced during the period covered by this survey. These include a petroland oil-engined range of 1-, 3and 5-tonners from the British Motor Corporation, and a fresh series from the Rootes Group. Progress by Rootes has been further marked by the more general adoption of the unconventional TS.3 two-stroke three-cylindered oil engine, which has shown itself to be equally suited to passenger and goods operation.

The tendency for manufacturers to design and build their own medium-capacity oil engines has continued; and figures are given in this article which show the performance of the B.M.C. 2.2-litre, 14-litre and 5.1-litre engines, the several versions of the Rootes TS.3 engine and the Standard 2.1-litre unit. The small B.M.C. oil engine has proved popular with operators of Austin and Morris 1-ton and 1k-ton vans, and, like the Standard engine, has been used extensively in taxicabs.

Braking performance has been improved principally by the more general adoption of vacuum servos on vehicles of 5-ton capacity, the extended use of air-pressure servo mechanisms on maximum-capacity chassis, and detail developments in all air-pressure systems, which have been dictated by the more strenuous demands found overseas.

During the period under review a new style of road test was instituted by The Commercial Motor, in which a series of maintenance tasks has been carried out on vehicles submitted for test. This has entailed a longer total testing time per vehicle which, in turn, has made it possible to carry out more extensive fuel-consumption tests on passenger and

delivery vehicles. The maintenance tests have shown that, whilst most vehicles are generally well laid out for normal servicing, some tasks are complicated by awkwardly placed body panels and traps. Certain vehicles, such as the Rowe Hillmaster underfloor-engined coach, have been designed solely for maintenance from underneath, for which a pit is essential.

Brake adjustments were not always as easy as they might have been. It was irritating on occasions to find that to reach internal brake adjusters it was necessary to remove the wheels. One chassis required four different sizes of spanner in order to adjust the complete set of brake units. Whilst there is much to be said for the internal brake adjuster in respect of protection from road dirt, the external type, by reason of its accessibility, encourages more frequent adjustment.

Weather Date Dry Dry Dry Dry Dry Dry Snow

Six chartsand six tables have been prepared to give results at a glance for the 54 tests under consideration. Weather plays an important part in a road test, particularly in respect of braking performance, and the general conditions under which each test was conducted are indicated in the tables accompanying the charts.

Referring to Chart I, it will be seen that the most economical vehicle tested was the little Reliant three-wheeler, which returned 51.6 m.p.g. when running over a test course between Sheldon and Meriden. This course, which is a five-mile stretch of undulating main road, is used whenever practicable for all light vans and the averages returned covering a run in each direction have been found to be representative.

The test of the Morris 1-ton petrol engined van was marred by extremely wintry conditions and by a slight overload. An overload was also being carried by the Standard 12-cwt. van, despite which it showed commendable economy when compared with similarly laden petrol-engined vehicles.

It is interesting to compare the fuel-consumption figur'es achieved by the Commer 15-cwt. pick-up tested in 1954, with those of the Commer 25-cwt. chassis and cab tested in 1955. The earlier of these two trials was conducted with the side-valve engine, which was displaced in November, 1955, by an overhead-valve unit. Despite an increase in gross vehicle weight of 181 cwt., the fuel return, as the figures show, was generally only 2 m.p.g. lower in the case of the larger vehicle, showing the new engine to be a sUbstantia1 improvement in efficiency.

One of the earlier tests of-this series concerned the Seddon 25-cwt. pick-up, powered by a Perkins P.3 oil engine. The laden non-stop figure of 48.9 m.p.g. was so good as to be thought faulty and a second run was made, with the same result. This figure has since been substantiated to the manufacturers by operators' reports.

Light delivery vans, taken generally, are almost as pleasant to drive as the private cars from which the majority of them is evolved. Attention could, however, be given in some cases to rearward visibility, especially in respect of adequate rear-vision mirrors, and ease of entry for the driver. Quickacting windows in the doors would encourage better hand signals.

Vehicles of 2-6-ton capacity are considered in Chart 2, from which it will be seen that the average bracket of consumption rates that can be expected from an oil-engined 3-tonner is from 27.5 m.p.g. to 31.1 m.p.g., whilst an average figure for an oilkengined 5-boner is in the region of 18.5 m.p.g., compared with 10.75 m.p.g. for a petrol-engined chassis of the same capaciIy.

Rain marred the braking results of the Albion Claymore 4-tonner and the Rutland Tucan 5-6-tonner. Nevertheless, the figures were well up to standard compared with those of other vehicles of thisecapacity. The Rutland 2-3-tonner was handicapped for braking tests by being straight off the production line, with the result that the facings were by no means fully bedded-in.

A TS.3 oil engine powered the Karrier Gamecock tested recently and produced an acceleration figure of 18.6 sec. up to 30 m.p.h. This is much better than the figures returned by an equivalent petrol-engined machine tested as a cesspool . and gully-emptier last year. The next highest figure of 19 sec., achieved by the Morris 3-ton oiler, is perhaps a little misleading, because, during this test, the vehicle was carrying only a 2-ton payload.

Swedish 6-ton Oiler

A foreigner appears in the midst of these tables in the shape of the Scania Vabis 6-tonner, which was tested in Sweden during 1954. This vehicle had a large oil engine, which resulted in a comparatively high fuel-consumption rate of 17 m.p.g., but the power is reflected in the rapid acceleration. In view of the high gross vehicle weight of 101 tons, the braking figure of 47.25 ft. is particularly good, the system used being a Lockheed hydraulic circuit with Bendlx Hydrovac servo. The performance of the Scania Vabis illustrates the typical line of thought of the Continental designers-a large engine to provide sustained high-speed running with reduced regard for economy, Two Swedish vehicles also figure in the 6-8-ton category (Chart 3). Here, again, in braking they are well ahead of equivalently loaded British vehicles, but their fuel economy is not so good. Two Mack 7-tanners are included in this category. The one marked "A" is the prototype 7-tonner built during the summer of 1954 and powered by a Perkins R6 oil engine, whilst the other vehicle is a production model with a Leyland Comet oil engine.

The fuel consumption rate of 20.8 m.p.g. returned by the earlier vehicle was achieved by the prolonged use of the overdrive top-gear ratio over a relatively fiat test route. The Rootes TS.3 engine, as fitted to the Commer 7-tanner, again showed itself to be one of the most economical medium-capacity oil engines built in this country and this economy is backed by an acceleration rate and hill-climbing ability which show that power is not in any way wanting.

Extreme economy was also yielded by the E.R.F. 4,4G 8-tonner, powered by a Gardner 4LW oil engine. As with other vehicles in the current E.R.F. range the 4.4G was notable for its high finish, particularly in the cab, which is stylish, comfortable and well laid out. , The braking figure returned by the Thornycroft Trident is interesting in showing what a substantial improvement in performance is possible with a vehicle weighing over 12 tons gross by the use of an air-pressure-hydraulic system. It is becoming increasingly apparent that maximum-load fourwheelers, which can now operate at 14 tons gross, are slightly heavy for a conventional vacuum-hydraulic system to cope with successfully, and it cannot be long before more vehicles of this type are equipped with either full airpressure or air-hydraulic systems.

Sixand eight-wheelers, both rigid and articulated, form the subject of Chart 4 and the smallest of these is a Trojan-Tasker 2-ton articulated outfit, which was designed to provide a large payload space for low-density commodities. Powered by a Perkins P.3 engine, it showed economy and this, combined with its manceuvrability, makes it a useful vehicle for the transport of bulky but light packages.

The figure of 9.3 m.p.g. given for the Guy six-wheeler was the result of a 100-mile run from Wolverhampton out into the hills of Shropshire and back. During this test a straight run over a shorter and less formidable route was made, on which occasion a consumption rate of 11 m.p.g. was achieved. The high figure resulting from the long run was influenced by the average speed of 22.6 m.p.h., which entailed driving at full throttle for almost the whole time. Similarly, the figure of 10.15 m.p.g. for the A.E.C. MercuryEagle articulated unit was the result of running 1,178 miles on trunk road work, maintaining an average speed of 22.2 m.p.h.

The Albion in the chart is the sixwheeled version of the Chieftain, powered by the Albion four-cylindered 85 b.h.p. oil engine. Despite the low power-to-weight ratio of this chassis, its performance Was most satisfactory, although a fair amount of gear work was necessary when in hilly country.

Good braking was an outstanding characteristic of the Dennis-Scamrnell spirit tanker, and during several emergency stops from 30 m.p.h. no trace of instability could be found.

The Leyland Comet-Scammell articulated 10-tonner tested was the prototype of a large order for British Road Services. It had the new Comet Mk. III oil engine, which develops 100 b.h.p. at 2,200 r.p.m., five-speed gearbox and singlespeed rear axle The outfit was notably light and easy to drive and its general overall performance no less satisfactory. When braking from 20 m.p.h, on a dry road the vehicle pulled up smoothly within its own length.

Rain and darkness put paid to any chance of getting satisfactory braking figures from the Sentinel six-wheeler, but it is reasonable to suppose that under more favourable condilions braking distances of well under 70 ft, would have been achieved, The Rutland six-wheeler included in this series was. a twin-steer chassis built specially for Spain and which, by dint of an overdrive-top gearbox and Eaton two-speed axle, was capable of over 70 m.p.h. It was learned from the

United States at the time that this figure stood as the unofficial world speed record for a 7-ton truck.

Chart 5 embraces special types of goods vehicle and included in this category is the Willys Jeep, which is now being imported into this country, but is expensive. Its 70 b.h.p. engine gave outstanding acceleration and its crosscountry performance proved to be no less impressive.

Good acceleration was also a feature of the Dennis ambulance powrecl by a Perkins P.4 engine (the report of which will be published next week), and the Rolls-Royceengined Thorny croft Nubian 6 x 6, which was tested as an air-crash-tender. The Rotinoff Atlantic tractor employs a Rolls-Royce supercharged oil engine, which makes it one of the speediest vehicles of its type on British roads, Reference to the fuel-consumption graph shows that its

performance has not resulted in extravagance. A normal undulating road was used for this test and the 103-ton-gross outfit covered the course at an average speed of 18 m.p.h.

All the vehicles in this category have good braking performances. One of the more spectacular of thesb was the crash stop from 20 m.p.h. made with the SeammellCrane, a trailer outfit running at almost 85-tons gross. The trailer used for this test embodied a new type of braking system developed by the Crane engineers, and showed that a unit of this size could be quite controllable from such relatively high speeds.

The Thornyeroft Nubian was brake-tested over a frosty road and prolonged skidding accounted for the 52-ft, stopping distance which was recorded. An exceptionally powerful braking system is fitted and in normal circumstances this braking distance would be substantially better. Despite a wet road the Willys Jeep made some rapid emergency stops. The transmission hand brake is notably efficient and can be used to produce a 0.49g. stop with fourwheel drive engaged.

Smooth and poWerful braking is a feature of the new Dennis ambulance, This vehicle is also endowed with

economy, power and manceuvrability.

Date Particular attention has been paid to the reduction of engine noise and Gregoire rear suspension is used to provide a 27.854 comfortable ride, whether fully laden

.

or unladen.

20:55 The Land-Rpver quoted in Chart 5

7,5.54 is the long-wheelbase pick-up version,

3.6.ss

22.4,55 which was tested in conjunction with

a Brockhouse 15-cwt. two-wheeled trailer. A thorough' cross-country trial culminated in a successful climb up a 1-in-4,1 gradient when running at 3 tons 34 cwt. gross.

Another Specialized vehicle, not dealt with in this chart but tested within the past 12 months, is the KarrierYorkshire gully-emptier, which was operated for three days in the Luton area, The test vehicle was a petrol-engined model and the gully-emptying equipment incorporated a Coventry .Victor twin-cylindered auxiliary engine for driving the vacuum and -hydraulic pumps. The use of this engine resulted in 'a great saving in fuel, and during one day's testing 'a figure of 1,200 lb. of sludge per gallon at 2.2 m.p.g. and 2,8 tn.p.h, over,all was returned. When making nine stops per mile during the gully-emptying tests, the vehicle engine was running at a consumption rate of 3.55 m.p.g.

Of the seven passenger vehicles tested and considered in Chart 6 perhaps the most outstanding was the Borgward Microbus. This vehicle is powered by a twin-cylinde red two stroke petrol injection engine of "0.688 litre, developing 293. .b.h.p. Petrol injeCtion each:4s it with remarkable economy and when tested with----a 15-cwt. payload, the nonstop fuelsetesumption rate was 40 m.p.g. When running Without load over the same course: it returned 87 m.p.g.

The popularity of Underfloor-engined designs for passenger vehicles is reflected by the-factthat the other six models tested were of this type, :TheCommer Avenger was an earIY production model rurpting -witha -derated TS3 engine developing 90 .b.h.p. This rating has, since .becn., increased to 105 b.h.p. and the higher-powered engine was installed in the Beadle coach tested in June i 1955.

.. .. The Rowe Hillmaster coach is an interesting design produced to meet an operator's own needs. It has a Meadows 4HDC 310 oil engine, which Combines economy with a lively performance. Hs quiet running is another of its desirable features.

A four-cylindered engine is used in the Albion Nimbus bus, which was introduced immediately before last year's Glasgow Show. The Nimbus, Which is derived from the Claymore goods chassis, has been 'designed for low-trafficdensity routes and feeder services, and its short overall length and good turning circle make it highly manceuvrable.

New hydraulic power braking and power-assisted steering systems figured in the specification of the Daimler Freeline export passenger chassis which, over a 164-mile run through the Malvern and Cotswold hills, returned a fuel-consumption rate of 10.24 m.p.g. at the high average speed of 24 m.p.h. The test vehicle was a 20-ft. 4-in.-wheelbase model with left-hand drive and was one of an order for Oslo. It was running at a gross weight of 13 tons 4 cwt., but despite its size and weight it was light and safe to drive.

A 645-mile run from London to Land's End at an average speed of 31 m.p.h. was the highlight of the A.E.C. Reliance coach-chassis test. The fuel-consumption rate during this run was 13.7 m.p.g. and during a later consumption test over a short level route, the chassis returned 19.1 m.p.g. at 26.6 m.p.h. The brake-test figure quoted for this chassis is the result of tests made immediately after the Land's End run and before the brakes had been adjusted 10 full efficiency. Better figures than 63 ft. should therefore be possible.