Chassisless Construction in a Prototype Electric
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First Details of the New A.C.M., which Combines Low Weight with Many Unusual and Practical Features Making for High Efficiency and Ease of Manufacture.
THE Ministries of War Transport and Supply •are displaying considerable interest in the batteryelectric vehicle, and about a year ago permission was given for the manufacture of a few prototypes. One of the first of these, a 1-tonner, as representative of a range for 15-cwt., 1-ton and 30-cwt. loads, was, shown last Monday to officials of the Mihis tries concerned, large users and others interested.
The new vehicle is known as the A.C.M Electric, and is built by A. C. Morrison (Engineers), Ltd., 10, -New Street, Leicester. It constitutes almost a 'complete answer to those critics, including ourselves, who have strongly advised eliminating the principle of designing battery-electrics as mere
modifications of vehicles constructed for propulsion by engines.
A well-known operator once said that his idea of a commercial vehicle was a box on wheels. In the electric vehicle' this conception can be carried into effect far more easily than with most other types; so, also, can the idea of chassis-cum-body construction, which is that adopted in the A.C.M.
One of our illustrations Shows clearly the framework which, it is interesting to note, is of chromemolybdenum steel, giving lightness combined with strength. It is in three main sections--a dropped centre part to carrythe two batteries, and ends bolted on.
The front axle is a standard 'car type, whilst the rear is a strong tube at the ends of which are mounted units, each comprising a single-helical internal • ring gear with its pinion and driving motor These motors vary only in length according to the power required in each model.
The springing throughout is by quarter-elliptics with their eyes in rubberbearings, braking and driving Stresses being taken by a rubber, Cushioned torque -rod mounted over each spring.
The four-wheel .brakes, which are of the Cirling type, • tiave Lockheed hydraulic operation.
The same controller is standardized for all models; it is equipped with a hydraulic, delay action, the driver merely, pressing a pedal, when the controller changes automatically, allowing a half-second delay per speed, of which there are 11. A rapid make and break prevents arcing. Reverting to the driving motors, the provision of two obviates the need for a differential, but, in addition, their design provides a special differential action, in that the flux is interchanged between them so that, whip turning, the inner motor takes less power than the outer and spinning is discouraged. They have series-parallel ccuitrol.
Ariother. . interesting feature is the great saving of weight -permitted by using split poles with aluminium yokes. It is claimed that the average efficiency of these motors is as high as 84 per cent. compared with a normal of about 76
per cent. Peak efficiencies in both • cases are, of course, higher. The average was taken over a loading equal to a road with a 10 per cent. upgrade to-a similar down grade.
Charging is through a Standard Telephone rectifier. No amp.-hour meter is fitted, but the state of the battery charge is indicated when a push button is depressed.
Jacking is usually somewhat difficult on a low-built vehicle of this type and, where required, a built-in system can be provided at an extra charge.
Dunlop •EIectruk tyres designed for 50 lb. air pressure are fitted.
The bodywork is also most modern, the panels being of plywood bonded to sheet steel at one side. This_ steel is turned over for 1 in. all around, thus sealing the plywood. Each panel is riveted to the steel body frame, and the joint sealed with plastic synthetic rubber. . The same construction is used for wings and scuttle. It must be emphasized, however, that this is not stressed-skin construction, and the sides may be open in special types of body.
It is obvious that in any battdyelectric chassis it is of major-importance to reduce the unladen weight, as every , 10 lb. of vehicle requires about4 lb. of battery to propel it. Any saving is in a Way cumalative, because the lower the vehicle weight the less the battery weight required for an equivalent load, whilst the tyres can be smaller and .the springs lighter. Unladen, this 1-ton vehicle weighs 224 cwt, ready for the road. achieve 60 miles per charge on a straight run, without stops, on normal roads.
The control of this vehicle is extremely' simple, there-being only two pedals, that already mentioned, and the .other for the brake, whilst to the left of the driver's seat and mounted en'the seat training is a -.handle which has reverse, neutral and forward positions. A hand brake of the pull-out
type is mounted on the dash to the left of the steering column.
Normally, each battery rests on the floor of its compartment, hnt as the door is swung down an eccentrically pivoted roller at each side lifts the battery, which can then be slid out over these rollers and others.
The batteries are, of course, the heaviest components of an electric vehicle, and to prevent them from exerting any bending moment on the framework they virtually rest direct en, the springs, through the medium of transverse channels.
At present, the final drive is geared to give a top speed of 20-22 m.p.h.
Some operators consider 18 m.p.h. ample, and it is possible that an alteration will be made to meet their requirements, It is, of course, difficult to fix prices, but it is believed that the 1-tonner will
be sold, -retail, at about £400 with battery and .body, whilst a suitable charging plant 'would cost £35.
As an example of how weight reduction has been effected, we may mention that the weight of the driving-axle assembly with its motors is about the same as that of a normal rear axle.
The standard battery fitted is the Exide, but others may be employed, according to users' needs.
Should the driver, whilst forgetting to switch on, depress the controller pedal and then use., the switch, an inter-locking device will prevent any trouble which might otherwise occur as a result. The prototype did not
actually have this safeguard fitted, but it will be added -to the production vehicles.
' It is estimated that, with stops, a
vehicle of this type will be able to 1 achieve 40-50 miles per day on one charge without boosting. If this proves to-be correct in practice, it will be a greatly appreciated advance.
With battery-electric vehicles the export side is often neglected. Actually, there should be many places abroad, particularly in well-paved towns and cities, where this type of vehicle should prove extremely useful. There is an additional factor—electric power is often more easily available and is cheaper than liquid fuel. It is, therefore, interesting to note that the A.C.M. is so constructed, as regards its body.
and general features, that it can be shipped in an unassembled condition and will thus occupy but little shipping space; it will also require only 50 manhours to assemble abroad.
Such improved features as greater mileage per charge, easy maintenance, and accessibility should give welldesigned vehicles in this class a fairly large market overseas.