The Crompton Battery Bus.
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We Make a Further Test of This Machine at Chelmsford.
'One hears that Crompton's of Chelmsford have a new electric vehicle ready." So our readers will have noted in the issue of this journal for the 23rd November, 1911. On the 8th April, 1909, still further back, we were enabled to publish an exclusive illustrated article concerning the first example of the Crompton battery-propelled chassis for industrial purposes. We then inspected this ingenious combination, when it was submitted to the L.G.O.C., at what were, at that time, that concern's branch depot at Albany Street.
Mr. H. Burge, who, in February of this year, read a paper descriptive, of the system before the Institution of Electrical Engineers, has continued to maintain his efforts to bring the system to perfection. As a matter of fact, at a comparatively recent date a motorbus, equipped with the latest arrangements, has passed the necessary Scotland Yard tests with flying colours, and the machine has now, for some little while past, been quite ready to be placed in regular London service. Crompton and Co., Ltd., however, is a manufacturing company with a world-wide reputation for the construction of electrical equipment and components of all kinds ; it has no interest, and contemplates taking none, in connection with the practical operation of motorbuses in public service. This is undoubtedly a wise decision, but, of course, the company is looking forward to the completion of
negotiations which will enable a properly-constituted operating concern to put its machines on the streets.
As at any time business arrangements may be completed which will enable these cars to be put into service on a large scale, we have thought it useful to ascertain for our readers particulars of the latest constructional developments of the Crompton system. For that purpose, therefore, we sought Mr. Burge, who, as we have written, has been particularly identified with the company's motor-vehicle experiments. Mr. Hodgson, the company's manager, has kindly devoted considerable time to the discussion of the scheme with a representative of this journal.
We reproduce several photographs herewith, and these will serve to demonstrate the lines upon which developments in connection with this chassis have taken place during the past months. The tests have been regularly conducted near Chelmsford.
The principle of the Crornpton scheme has always been to employ a suitable battery of the latest type of construction, and, by clever electrical scheming, to obviate many of the disadvantages which are readily admitted as inherent to the employment of battery-propelled chassis per se. There is no need on this occasion again to explain in detail the wiring of the system, as this was done in connection with our report of Mr. Burge's paper in our issue of the 29th February last. but, while referring our readers to that account., we would remind them that the wiring has been modified to a considerable extent since that date. We may, therefore, confine ourselves to recording that the latest type of machine again uses a motor generator, which is located between the battery and the motor or motors, and that, by this arrangement, it is possible automatically to limit the amount of current which may be drawn from the battery. The entire control is so arranged that it is effected without loss through series resistance, or on account of the regrouping of windings.
Very full advantage has been taken by the inventors of the possibility of regenerative action on the part of the electrical equipment. It is now possible, when stopping the vehicle, for the motor to regenerate, or, in other words, to "pump juice" back to the batteries, right down to the time when the vehicle is brought to rest, and this may be effected without the use of any mechanical brake.
We ourselves were more particularly concerned, on the occasion of our visit to Chelmsford last week, with the testing of the machine on the road for that class of control, which is so necessary for town use. Rapidity of acceleration and retardation must, in all modern systems, whether they be electrically or mechanically arranged, be effected without perceptible change-speed steps.
Uniformity of acceleration and retardation are, as
a matter of fact, so admirably attained on this new machine, that, in driving, it is almost impossible to gauge the actual gain or loss at any time in road speed. The control • is exceptionally sweet, and is effected solely by the use of a single small pedal. It is possible to depress or release this to its full travel instantaneously or. slowly at will without dire effects on the mechanism. In short, we may say that seldom have we driven a machine on which the control is so simple., and on which the driver is relieved so very well of the necessity for mental and physical concentration. We should say that the Crompton bus is foolproof to the full extent it is possible so to design a machine for public service.
It is interesting to note that a special shunt winding on the motor gives a speed-torque which is similar to that of an ordinary series-wound motor, but, at the same time, the full regenerative properties of the shunt-wound type of motor are retained.
Some criticism has been levelled at the Crompton bus with :regard to its ability to hold the vehicle electrically-braked on a gradient, but, taking full account both of the mechanical gear friction and of the road resistance, it has been found possible to hold the machine, solely by electrical means, on a gradient of 1 in 28, in the course of actnal experiments, so we are informed by the constructors.