NEW A.E.C. REGAL MARK II 32-SEATER
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puts up a first-class performance Exacting Route and Searching Tests Prove New Chassis to be a Fine Example of Modern High quality Passengervehicle Design and Reveal Excellent All-round Characteristics in Latest A.E.C. 61litre Oil 0 NE essential of a modern coach is that it should afford its passengers as high a degree of comfort as possible. It must also be economical to operate, capable of running at a reasonably high average speed, inoffensive to other road users, etc., and, of course, equipped in a manner entirely consistent with safety Under present-day traffic conditions.
With progress in design, the standards by which these qualities are judged naturally become higher, and, accordingly, the manufacturers' task grows gradually more difficult. All the more credit is, therefore, due to the leaders in the field whose responsibility it is, presumably, to set the standards.
Having this thought in mind, we embarked upon a test of the latest passenger-vehicle product of the A.E.C. concern—the Regal Mark II bus or coach chassis, which was introduced at the Commercial Show last November. Our expectations were in no way disappointed, for there is hardly a point in its make-up that can fairly be criticized, whilst there are numerous features that evoke high praise.
For demonstration and test purposes, the machine was equipped with a Harrington 32-seater coach body. Although concerned at the moment with the chassis rather than the body, we must remark that the latter seemed well chosen as comple
B28 mentary in the demonstration of the good qualities of the former.
Laden with the equivalent of 32 passengers in 1-cwt. weights, the vehicle was first subjected to a consumption test. It was equipped with a calibrated test tank ; thus an accurate indication of the fuel consumed was afforded. The route chosen was of more than average difficulty, so that the consumption rate we obtained may be regarded as
on the heavy side, and can be employed with safety as a basis for calculations.
Our course lay from the Southall end of the Greenford Road, via Harrow,, Pinner and Northwood to Batchworth Heath, on the Rickmansworth Road, and back. This involves the ascent of the considerable acclivity on which Harrow is situated, on both the outward and the return runs, whilst there is a stiff climb up to the turning point. It also necessitates the negotiation of considerable traffic. Despite the delays thus incurred, however, we averaged the creditable speed of 24 m.p.h. for the journey.
The course was exactly 23.8 miles long, and, in traversing it, 7.4 litres (1.625 gallon) of fuel were consumed. This gives a return of 14.6 m.p.g., which may be regarded as satisfactory in view of the severity of the test, occasioned by the arduous nature of the route.
It should be recorded moreover, that on the return run we made a stop and restart test on the ascent into Harrow—estimated to be about 1 in 7. This was accomplished in first gear with complete ease, the hand brake functioning perfectly and the machine moving away from rest smoothly and without any indication of undue effort.
On Sudbury Hill, entering Harrow from the south-east, we made seine observations which are of consider
able interest. In judging the per formance of the machine it should be noted that the 5.75 to 1 rear-axle ratio was used, which is slightly lower than standard.
Approaching the gradient at 24 m.p.h., we dropped into third gear when our speed had fallen to 20 m.p.h. As the slope stiffened, the speedometer needle backed slowly until, when we had rounded the first bend, it stood at 11 m.p.h.
This denotes the power unit to possess excellent "hanging-on" qualities, and we believe the climb could actually have been completed without recourse to a lower ratio, but the driver rightly elected to employ second gear, with the result that we accelerated steadily from that point, changing up as the speed rose and reaching the summit at 23 m.p.h. in top gear.
Those who are familiar with this hill will appreciate the significance of this performance.
An engine which possesses slowB29 pulling characteristics may be at a disadvantage when quick acceleration is demanded, but we had already detected indications of liveliness that pointed to the two qualities having been combined in this latest A.E.C.Ricardo power unit. The figures we obtained in our next test confirmed our earlier impressions. The powerto-weight ratio is, of course, high (0.641 b.h.p. per cwt.) and the gear ratios slightly on the low side, but even allowing for these factors velocity is gained with a marked rapidity.
Before the governor cuts •cmt. at 2,000 r.p.m. .40. m.p.h. is attainable in " top " and 25 m.p.h. in third gear. Perhaps the former road Speed is slightly low for fast coach work, but for this purpose the higher ratio is available.
For high maximum as well as average speeds, good retardation is indispensable, and the brakes of this new coach are really excellent. An accompanying graph gives the stopping distances and times, and whilst these are impressive, and prove that, in this respect, the chassis fulfils the condition relating to road safety, .the manner in which they function, to to comply with the passenger-comfort condition, is even more so. When fully applied at, for example, 33 m.p.h. the vehicle comes to rest without shock or jerk, the retardation suggesting great rigidity of the mechanism and particularly of the provision for torque reaction. It is worth recording, in this connection, that the facings are of a thickness that should ensure long life. • This is a detail representative of the care that has been devoted to the design of the whole chassis, and is a good instance of how money invested in first cost means money saved later in maintenance expendi ture. ' • Our graph shows that a slight advantage is gained by employing the hand brake, in addition to the foot brake, especially at the lower speeds, as is usually the case, because of the slight time lag practically unavoidable with servo systems. Wheel skidding could just be provoked by this method, which is a sure indication that the efficacy of the service brake is the highest practicable for normal conditions. , Whilst the hand brake is entirely satisfactory, the position of the lever seemed to be just short of the ideal for a good pull.
Before leaving the subject of brakes, we must make reference to the interesting system of raising a vacuum. Instead of employing an exhauster, engine suction is utilized, as on a petrol unit. The lead to the vacuum tank is connected to the induction pipe, and the last-named is provided with a throttle valve, which closes it to atmosphere automatically when the fuel is cut off. To prevent the undesirable consequences of entirely restricting the supply of air, however, a limited quantity is admitted when the valve is shut.
Returning to the question of passenger-comfort, noise, vibration and suspension merit consideration. The only time when "Diesel knock" was apparent within the saloon was on the occasion of the few initial explosions after engine speed fell, with the fuel cut off, from higher to minimum r.p.m.
Vibration is practically non-existent • throughout the range and the manner in which the coach glides over potholes and the like points to a suspension system of high efficiency. From the point of view of other road users, a main offence of oilengined coaches is the emission of smoke. During the whole of our day's test we only once detected visible exhaust fumes, and this was shortly after connecting up to the main fuel supply, after using the test tank. The phenomenon was accompanied by momentary misfiring, the result of admitting air to the system.
A modern and desirable tendency is to lighten the labours of the driver. It is well reflected in this new Regal. On a previous occasion we had reason to criticize an A.E.C. clutch that was unduly heavy to operate. There is no ground for complaint on this score now. No great muscular effort is demanded to , operate any control. All the gears are delightfully easy to select either up or down the scale. Especially quick changes from top gear to third gear, and vice versa, can be made without difficulty.
We found the machine most pleasing to handle, and would have genuinely enjoyed a longer spell at the wheel than time permitted.
Every chassis component incorporates interesting mechanical features—refinements in one form or another—but they are too numerous to mention in this report of performance. We must :ontent ourselves, therefore, by reminding our readers that although the price at which the machine is offered may appear high, in terms of value for money it is not only reasonable but competitive, for the Regal Mark II ranks among the finest passenger chassis obtainable.