SUNBEAM VAN SHOWS s NT EFFICIENCY ON TEST
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‘ EFINED as is the inocTn internal-combustion engine, and easy to drive as is the modern motorvan, to experience, to ,the full, smooth and silent motion and simplicity of control one must travel by electrical means. In the field of passenger transport, no one will dispute the sovereignty of the trolleybus in these respects, and they are even more apparent in the battery-electhe vehicle.
Admittedly, its progress is leisurely, but this serves to enhance the characteristic of refinement, and it is rather surprising' to find how much less difference than might be expected the low speed makes in the time taken for a round of moderate length.
This last fact is probably of the greater concern to the operator, also matters of consumption, range, hillclimbing and maintenance, but the silence of the electric is, nevertheless; not merely a luxury. It has commercial value, as has good appearance, whilst ease of control is reflected in freedom from accidents, regularity and dependability, and it much reduces the degree of skill necessary on the part of the driver. In other words, it is easier for a tradesman, for example, to obtain roundsmen if he uses electric vans, because the difficulty constituted by the man who is a good salesman and well qualified in other respects, but a poor driver, is largely overcome.
Last week, we subjected to test a Sunbeam 12-15-cwt. van, with a view to forming a first-hand opinion as to the practical capabilities of this means for achieving independence from liquid fuel. We were most favourably impressed_ Although we chose a hard course and included a long spell of stopping and starting in simulation of house-to house delivery, we consumed electricity at a low rate and satisfied ourselves that the range of the vehicle on one charge is wholly adequate for average requirements.
Furthermore, whilst a van in normal service is probably losing weight throughout its round, because goods are being delivered, the Sunbeam, while in our hands, carried the same load for the duration of the trial, and, in point of fact, its gross weight exceeded the recommended maximum by 31 Cwt.
Commencing our trial from the St. John's Wood Road depot of Rootes, Ltd., we headed northwards to the Hampstead hills. Along Wellington Road to Swiss Cottage, which is a gentle upward slope, we maintained a steady 12 m.p.h. Up Fitzjolm's Avenue—.a steep pull—the speedometer needle fell ba4 gradually to a minimum of 8 m.p.h. Then came the sharp incline up to Whitestone Pond on Hampstead Heath; the gradient is, lve believe, about 1 in 10. The Sunbeam, however, lost but little speed and cruised up at 5 m.p.h.
Just short of the top, where the gradient is not far off its steepest, we stopped to try the holding power of the brakes and to investigate restarting capabilities. With either the hand or foot controls, the vehicle could easily be held or its motion checked. As for the restart, no suggestion of difficulty or fuss was detectable.
Here is a good' instance of the small demands made upon the driver. No gentle letting-in of the clutch is called for, nor synchronized action with the brake lever; one simply puts the accelerator pedal hard down and simultaneously removes one's other foot from the brake
pedal. The contactor does the rest; it automatically brings the four contacts into operation electro-magnetically in sequence and at a predetermined speed, which cannot be exceeded. One normally starts and accelerates in this way, so no different technique is needed' when doing it up a hill.
Along Spaniards Road we carried out an acceleration test (in one direction), and paused at the Inn, from which the road takes its name, to take consumption readings (electrical l) for the outward journey.
There is an amp.-hr. meter on the dashboard, which records the number Of units of electricity taken out of the batteries, or .put into them. At the outset, the needle pointed to 7 amp.-hrs., that being the quantity that had been used since the vehicle had come off charge. There is a red mark on the dial at 240 amp.-hrs., this being the total capacity of the batteries. Thus, when the needle approaches the mark the driver knows his charge to be nearly expended.
This meter, at the Spaniards stop, indicated 52 amp.his. Therefore, we had used 45 units for the 3.6 miles covered up to then—heavy consumption. but uphill most of the way.
Along the undulating road to Highgate and back to the old Spaniards Toll Gate, we carried out our delivery. work test, stopping momentarily every tenth of a mile; the distance was 2.4 Miles and the time taken 20 minutes, which included a pause for photography. Roughly, 24 stops were made. This used up another 20 amp.-hrs.
Then, in the opposite direction, on the same stretch of road as before, we repeated the acceleration test and
after that, returned to headquarters by way of Haverstock Hill and Camden Town.
Descending Hampstead Hill, we made rough braking tests, which revealed ample retardation for a vehicle of this type, and down Haverstock Hill we tested the maximum speed, which proved to be about 30 m.p.h. Despite the short wheelbase, the Sunbeam was steady and seemed perfectly safe at this velocity. In view of the low speed at which it normally travels, we decided that no useful object would be served by carrying out a set of brake tests by measurement.
For the last section of the run (5.5 miles), the consumption was 30 amp.-hrs., the hill this time having been in our favour. For the total journey only 95 amp.-hrs. had been used, so 2i rounds, such as this, could easily be made on one charge. There is not much to complain about in that, and it must be borne in mind that all that is lost uphill is not regained downhill, so the range would be bigger in level districts. Our average consumption for the trip works out at 8.25 amp.-hrs. per mile, whilst for the delivery work section it was only a little higher—. 8,35 amp.-hrs.
An outstanding feature of the Sunbeam is its small turning circle, and this, combined with its short wheelbase and ease of control, renders it at a marked advantage in thick traffic, or in districts where the streets are narrow and the corners sharp.
In connection with house-to-house service, the simplicity of setting the machine in motion is of immense value—just hard down with the foot and away you go. A glance at the accompanying graph—the mean of our two runs, shows, furthermore, how quickly the -vehicle acquires its speed. Although its maximum on the level is only about 15 m.p.h., it does not waste much time in getting off the mark.
The question of range is, of course, involved with battery capacity. A choice of five sizes is offered-128, 160, 192, 224 and 240 amp.-hrs. Various makes of battery also are available—Britannia, D.P., Exide, Tudor and Young. Indeed, any reputable make is offered by the Sunbeam company. The machine tested was equipped with Young accumulators of 240-units capacity. According to the make and size of battery, the price varies, of course.
Access to the batteries for topping-up the electrolyte may be gained through floorboard doors, or by drawing them out on runners. To put the batteries on charge, a plug on a lead from the charging A26 board is inserted in a socket on the dashboard under the meter. On the latter, visible through a slot in the dial, there is a small disc which slowly rotates in one direction for charging and in the other for discharging. On plugging in, the attendant can verify that charging is in progress by observing that the disc is turning the appropriate way, which is clearly marked with arrows.
Reverting to the electric control, there are essentially two circuits—main and relay. In the latter are the accelerator switch gear, a master control giving "off,"" forward " and " reverse," a 10-amp. fuse and a detachable plug, which can be pulled out and pocketed by the driver to prevent unauthorized movement of the vehicle when left unattended.
The relay circuit operates the electro-magnets, which, in turn, actuate the four main contacts. All of these are of the self-cleaning type. As they contact together, there is a" rubbing of the faces, so that the metal is kept free from deposit likely to cause sparking or bad connection. Only the first contact tends to arc, and that only when broken. It is, therefore, enclosed in an asbestos flash trap. The life of a contact is said to be at least 10,000 miles, and they can be replaced easily at a cost of about 7d. each.
There is also a fuse in the main circuit, mounted acssibly on the dash. It can be renewed in about half a minute, a spare being part of the vehicle's standard equipment. It carries a maximum of 80 amps. and it is extremely rare for it to blow. The resistances are under the driver's seat.
All electric equipment is of B.T.H. make and has been developed from this company's well-known trolleybus apparatus. The motor is mounted, roughly, in the centre of the chassis, and transmits through a Hardy-Spicer shaft to a double-reduction spiral-bevel rear axle. All wheels have Bendix brakes and are shod, as standard, with Dunlop 5.25-16 tyres. The charging apparatus installed at the Rootes depot, which is typical of a first-class unit, comprises a Westinghouse metal rectifier. Its function is to reduce the mains current to 60 volts and to convert a.c. to d.c.