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Successful Debut of Four-cylinder DJ. Perkins

6th December 1963
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Page 62, 6th December 1963 — Successful Debut of Four-cylinder DJ. Perkins
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BY JOHN F. MOON, ROAD TEST: Commer Diesel-engined 4-tonner WHEN the Rootes Group announced a new series of mediumcapacity forward-control Commer and Karrier goods vehicles in February of this year, it was revealed at the same time that a four-cylinder version of the Perkins 6.354 six. cylinder direct-injection diesel engine was to be offered in certain chassis, although at that time the engine was not to be made generally available to other manufacturers. Since then, of course, the 4.236 four-cylinder engine has been placed on the open market, but a recent road test of a Commer 4-ton forward-control lorry provided the first opportunity of putting the performance of this neW engine to the test.

Running at slightly above Commer's recommended gross vehicle weight, the Perkins-powered 4-tormer returned a consumption rate of 2025. m.p.g. when cruising at about 30 m.p.h. and 19-2 m.p.g. hen observing a maximum iced of just over 40 m.p.h., .jd these are very accept )1e figures for, a vehicle irrying a full 4-ton pay ad. The acceleration and 11-climbingperformances ere lively, whilst the unit behaved smoothly and reasonaly quietly under all the test conditions, including the irect-drive acceleration runs made between 10 and ) m.p.h. In view of the fact that the 4.236 adds only £123 ■ the 4-tonner's price when compared with the standard iassis, which has a Rootes six-cylinder o.h.v. petrol engine, s. use in this vehicle becomes a very economical proposion-even more so if one is to assume that the 4.236 will as great a success as its six-cylinder elder brother, the .354.

Generally, the 1963 Commer CA-cabbed 4-tonner is a ..ry useful addition to the Rootes commercial-vehicle inge, and is well suited to both urban-delivery and iedium-distance operations, the cab offering advantages 6om both viewpoints. Unfortunately, the vehicle tested ad below-average braking performance caused by excesve wheel locking at front and rear, required above-average edal efforts to produce normal retardations, and had to a abandoned part-way through becausn of a complete raking-system failure, due to cracking of one of the ft-hand front wheel cylinders.

ebruary Description

The Commer 4-tonner was fully described at the time I its introduction in our February 8, 1963, issue. Apart -ow the alternatives of petrol and diesel engines (the andard Rootes petrol unit has a capacity of 4-139 titres. net power output of 100 b.h.p. at 3,600 r.p.m. and a )rque rating of 198 lb. ft. at 1,200 r.p.m.), there are no hassis-specification options, the only wheelbase available eing 11 ft. 9 in., for which Rootes-built dropside and latforrn bodies with an interior length of 15 ft. 6 in. and n interior width of 7 ft. are offered. In addition to being vailable complete with bodywork, the 4-ton model can be specified as a chassis and cab or a chassis and scuttle.

A new four-speed, constant-mesh gearbox has been developed for the 4-tonner, as hasP a new hypoid-bevel driving axle. Furthermore, compared with the 4-ton design which went out of production when the new model was introduced, the suspension is appreciably better by reason of the use of much longer springs, whilst the new cab is an obvious improvement. The use of the 4.236 engine has a particular advantage in the case of the 4-ton model in that the chassis price is £67 less than that of its predecessor, this being because the earlier model had a semi-horizontal version of the 6.354 engine, which was used in conjunction with a synchromesh gearbox. The earlier 4-tonner had 20-in, wheels too, of course.

Diesel v. Petrol

So far as the relative merits of the dieseland petrolengined versions of the 4-ton chassis are concerned, with the standard tyres and axle ratio (5-143 to 1 is standard, with the option of 5-833 to 1), the theoretical maximum bottom-gear gradient ability of the diesel model is 1 in 5, whilst that for the petrol is I in 4.25. In terms of theoretical maximum road speeds, the diesel's figure is 50 mph., and the petrol version is some 14 m.p.h. faster, whilst there is very little weight difference between the two models, the Perkins-engined chassis being a mere 28 lb. heavier than the petrol job.

The vehicle submitted to we for test had the factorybuilt dropside body and was in standard trim apart from its Michelin 7.50-16 " X " tyres, which had been fitted in place of the standard 7.50-16 (Nylon) equipment, there being no price difference between these two types of tyre. Non-standard cab fittings included a two-man passenger seat and heating and demisting unit, the respective prices of these being £3 and £18. Thus equipped, the 4-tonner had a kerb weight of 3 tons 3-5 cwt., and the imposed test load of gravel, three short steel bars and two concrete blocks totalled 3 tons 19-75 cwt., so that, with myself, two Commer engineers and test equipment aboard, the vehicle grossed 7 tons 7-75 cwt., the inter-axle distribution being such that each of the front tyres was carrying nearly 5-5 cwt. more than each of the rear tyres.

The weather during the first day's testing was stormy, with heavy rain and strong winds, so any chance of carrying out accurate brake tests, for instance, was obviously ruled out. Fuel-consumption figures were taken first, therefore, the " normal-road " runs being made along a gently undulating 6-mile out-and-return stretch of M. Good economy was shown during the three tests made on this circuit, the very small difference between the figures obtained at the 30 and 40 m.p.h. cruising speeds being significant and indicating that with this gearing and at this gross weight the 4.236 is consistently economical between these two maximum speeds. Similarly, when making two

stops per mile the economy was good for this class I vehicle: the average speed quoted in the data pan( incidentally, is based on the total time that the wheels we turning and does not include the eleven 15-second stol made during the test, the engine having been left idlir during each stop.

In view of the appalling weather and the widely he view among commercial-vehicle engineers that fue consumption figures are invariably going to be heavi, under wet conditions than they would be on a dry day, repeated one of these runs on the second day of the te to see what difference the weather would make to a consumption rate. I wasted my time, for not only was ti quantity of fuel used exactly the same as on the previa( day, but the total running time was identical also!

The fourth fuel figure detailed in the data panel obtained under continuous full-throttle conditions over 10-mile return stretch of MI motorway, and this result ah was acceptably good. Although not the most economic British 4-tonner, it is obvious (hat this Commer design

rable of a very consistent performance at reasonably low I cost, and this can be obtained while making full use the model's lively acceleration performance, which is -lieu'arty good through the gears and by no means ggish in direct drive, as the test figures show. During direct-drive acceleration tests it was noted that the ;ine and transmission were quite smooth from 10 m.p.h. wards, but it was almost possible to "feel the crankshaft iding when running at less than 10 m.p.h. in top gear. had intended to carry out part-load and unladen connption tests with this vehicle, but the brake failure )erienced during the course of subsequent brake ts made this impossible.

lefore the vehicle had -to be abandoned, however, .dient-performance checks were made on Bison Hill, a 5-mile slope with an average severity of 1 in 10.5. These ts were made in an ambient temperature of 11.5C. ..7°F.), and a 3-min. 42-sec. full-throttle ascent made .m a standstill caused the engine-coolant temperature rise from its normal value of 77°C. (170.6°F.) to only C. (174.2 F.). The climb was reasonably swift and at time did the road speed fall below 8 m.p.h. Bottom gear s engaged for .a total time of 40 sec., and no smoking s observed at the exhaust outlet.

.de Test

• made my usual fade-resistance test down Bison Hill neutral, having first checked the maximum deceleration lormance by Tapley meter on the wet road surface at top of the hill, the meter showing an efficiency of per cent under these conditions. It took 2 min. 25 sec. coast down the slope in neutral, and at the bottom a ond retardation check was made, and the meter indicated .t the maximum efficiency had fallen by 0-22 gr, whilst all wheels locked again. This efficiency reduction was are than I would have expected from a modern vehicle ining at this weight, but how much of the reduction s due to genuine fade and how much to varying degrees wheel locking is impossible to say: the fact that the eels locked at all after the descent indicates that there s plenty of braking left.

Returning up the hill, I stopped the Commer on the n-6.5 section, on which slope the handbrake was found be powerful enough to prevent backward motion. A lf-th rattle restart was then made in bottom gear, after lich the lorry was turned round and stopped on the ne section, but facing down the hill. Again the handIle held the 4-tonner, whilst only about quarter-throttle s needed to move away in reverse. Neither of these tarts was made completely smoothly, there being a Jain amount of definite engine judder for which the iuntings may have been responsible.

On the second day of the tests the weather changed mpletely, and all the roads in the Luton area were quite Following the repeat fuel-consumption run already 'erred to, maximum-pressure brake tests were carried out mi 20 and 30 m.p.h. and on each occasion the braking wer was such as to lock all the wheels once slight system ; had been overcome. This excessive locking made for Dtracted stopping distances, of course, and would Jbably have led to instability had the roads been wet.

1 think the trouble must be put down to very high line ..ssure, which in turn suggests servo unsuitability, for ; handbrake tests produced only average Tapley-meter idings and there was no tendency for the rear wheels lock. Alternatively, of course, the latter could have been due just to handbrake-lever inefficiency. I am not able to state with certainty what exactly was the matter with the braking system: I can, however, affirm that it wasn't very good, and the position was made worse by the very high pedal effort needed to pcoduce relatively modes) decelerations under normal traffic conditions, the effort required being such as to suggest that the servo was not working at all.

And finally, when making further maximum-effort stops on a rough concrete road in an endeavour to reduce the sliding distance, one of the left-hand front wheel cylinders came adrift, causing a-hydraulic-fluid leak and a resulting complete absence of footb rake performance.

Apart from this trouble, this latest Commer dieselengined 4-tonner is quite a satisfactory vehicle. The steering is well balanced at normal speeds, although far too heavy at walking pace, and the castor-effect is good. The suspension gives a very good ride indeed, being smooth and with almost complete absence from pitching, roll and disturbance of the steering.

Smooth and Quiet The Perkins engine I found to be generally smooth and quiet for a four-cylinder unit, and very little vibration got through to the cab. The new gearbox is good also, but the change-speed lever is rather a long way back relative to the driving seat and the lever travel between bottom and second is somewhat excessive, which makes quick changing between these two ratios a bit difficult sometimes. The ratios are well spaced, giving speeds of 9, 18, 32 and 50 m.p.h.

I have already commented favourably about the latest Commer forward-control cab, my most recent references to this design having been in the Commer 7-tonner test report which was published in our August 16, 1963, issue. The tab has many advantages from the angle of driver and passenger comfort, whilst the finish is above average also. Criticisms that I made in August included the absence of at least one sun visor as standard and erratic windscreenwiper performance: a visor is still not fitted, whilst the tendency for the wiper blades to lift above the top of the screen was present also: As •with the six-cylinder 7-tonner, engine accessibility with the 4-ton model is good, there being ample removable and hinged traps in the floor of the cab to give clear access to all parts of the engine.

The Commer 4-tonner as tested has a list price of £1,071 in chassis-cab form, the Rootes-built dropside body costing a further £135. The chassis-scuttle version of this chassis is listed at £966, whilst in all cases petrol-engined models are £123 less. Quoted optional extras in addition to the twin passenger seat and heater already mentioned include Cromard cylinder liners at £12 extra and a 30-gal. fuel tank at £3 extra.

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