• Home
• Used vehicles
• Product news
• Dealer news
• Compliance
• Buying advice
• Archive

PETROL-ELECTRIC POSSIBILITIES.

Some Criticisms of Orthodox Design —The Case for Electrical Transmission— Prospects, Principles and Prejudice—Will the Gearbox Eventually Disappear ?

AT A TIME like the present, when the motor industry, unfortunately, is in a state. closely approaching suspended animation, due to the chaotic state of world trade, there is, in some quarters, a tendency to disparage and to lose interest in, questions of design. .

Yet, if the industry is to make a sound recovery, the designer must lend a hand as well as the business man. Neither the industry as a whole, nor any individual concern, should neglect to explore all possible avenues of improvement, as it is only by sustained improvement that the British product will be kept ahead of its competitors, when the markets of the world reopen.

Contrary to some opinion, we hold the view that it is at periods such as this, when productive activity is reduced unavoidably, that designing activity should be increased four-fold. The war, which should have provided many designers with a breathing space in. which to proceed uninterruptedly with their investigations, was somewhat disappointing in its effects. We were presented with few surprises or new ideas when it was over. Little fresh soil was thrown np on the fields of mechanical road vehicle. achievement. That may not, perhaps, have been the fault of the designers.

Nevertheless, we think that the present is preeminently the time to reconsider problems of design and, for that reason, we make no excuse, for dealing, in this article, with the question of alternative methods of transmission.

Transmission Troubles.

There are few thinking persons who regard the gearbox as other than a necessary evil, either on a motorcar or on a motor lorry. Yet it must be admitted that, for a fundamentally unsatisfactory appliance, the gearbox has been brought to a very high state of development. Concentrated and continuous study of gearbox problems in all their aspects has resulted in the elimination of very many of the bad features of the system, though the fundamental drawbacks still remain and, apparently, must always be felt. The modern gearbox is the result of making the best of a bad job. .

Yet, in reconsidering this transmission question, a fact which. must not be overlooked, and which cannot he disregarded when examining the possibilities of alternative systems, is that the very prevalence of this form of construction renders its supersession a very difficult matter—whatever the virtues of an alternative may be.

Vested interests have inevitably grown up around gearbox transmission. Unit manufacturers, gear cutters, and machine tool makers are, naturally, all interested in the retention and perfection of the system.

Moreover, it has been so universally employed for very many years on such thousands of vehicles that it has become almost a tradition. Thousands of users, drivers and mechanics are familiar with no other system, have been, as it were, educated and trained CM gearbox transmission, and have become so accustomed to any defects it may possess as to ignore them.

The very fact that a certain amount of knack and dexterity are needed in the manipulation of the gears on the orthodox type of vehicle actually strengthens its position. It increases the opposition of the skilled man to any system which will render unnecessary some of the skill he has acquired.

Thus, the. position of the advocate of alternative B20

systems—such as petrol-electric systems—is, like that of all reformers, not very enviable. _

Successful Electrical Transmission.

Yet, in spite of this. strong predisposition in favour of gear transmission, certain electrical systems have made quite remarkable. headway. It is not the purpose of this article to enumerate them, nor to describe them minutely, but to consider, briefly, wherein the advantages of electrical transmission lie, what drawbacks it may possess, in comparison with purely mechanical transmission, and what the future prospects are likely to be. In doing so, it must be remembered that we are not dealing with something wbich may possibly become practicable at some time in the future, but with a system which has already, against ordinary commercial competition, been proved sufficiently attractive to many users to induce thorn to abandon the orthodox gearboxed machines We are faced with the fact that the petrol-electric vehicle has made very favourable progress in spite of the strongest opposition.

There are, of course, various types of electrical transmission, . and there are many possible arrangements by which power can be transmitted electrically from the engine to the road wheels, but, for the. purposes of this article, we pro-pose, to confine ourselves to the system ellich has been most successful commercially in this country. This is that in which the clutch and gearbox are eliminated, and their function performed by a combination of two electrical machines—a dynamo and motor.

The engine is directly coupled to the dynamo. This in turn is connected, electrically, to a reversible motor, which drives the cardan shaft of a chassis which, as regards rear axle construction, does not differ materially from orthodox practice. There is thus no directs. mechanical connection between the engine and the back axle. No batteries of any sort a-re needed, as the-necessary current is only generated as and when required.

The controls are very simple. The engine is controlled by an accelerator pedal of the usual pattern, and there are two small lev.ers, usually mounted on the steering column. One of these is not used while

i the vehicle s actually in motion. It has three positions: "Forward," " Neutral," and "Reverse," which terms explain its functions. The other lever is a " resistance " lever, and its purpose is to vary the strength of the dynamo field, and so to regulate the relative speed of the niotor and the engine and dynamo, under varying road conditions. Its function, really, is similar to that of the ignition control lever on an ordinary petrol vehicle, as, in using it, the driver relies on his sense of hearing to .get the maximum of power out of his engine without causing it to labour. This lever must be manipulated by the driver in conjunction with the accelerator or throttle pedal.

Having briefly outlined the construction and control of the machine, we may pass on to consider the advantages claimed for it.

Multiplicity of Virtues.

The advocates of this system say that it is superior in 'about half a dozen ways to the vehicle of orthodox construction. Smooth starting and running, which naturally result from the elimination of clutch and gears-, and the substitution of the known flexibility of electricaleinachines, save tyre wear.

The absence of mechanical connection between engine and axle isolates the former from road shocks communicated in ordinary types through the trans

mission mechanism. The electrical drive forms a sort of cushion.

Simplicity of control and silent running are naturally claimed and are demonstrable. Saving of petrol is also claimed, and a point is made of the fact that the engine always runs at its most advantageous speed.

Frictional losses are naturally reduced, owin t the elimination of the gearbox and its gears. The elastic electrical drive naturally eliminates the possibility of shocks and stresses which are occasioned in the orthodox vehicle by bad or careless driving. Additional to these advantages is claimed the important feature of greater safety. The electrical arrangement is a certain preventive of running backward on a hill, even if the vehicle is stopped and the brakes removed. It is, thus, quite impossible for a petrol-electric vehicle of this type to get out of control as may happen through a missed gear, or other cause, with the ordinary type of vehicle. This fact., combined with the smoothness of its running, makes it, so its advocates contend, ideal for the purposes of passenger transport. It must be said, in justice to the claimants, that it has achieved considerable popularity in this application.

There are other advantages to be obtained from a machine which carries what is, in effect, a miniature power station on it. It can be used, when stationary, to supply the necessary current for various purposes) such as electrical welding, driving fire pumps or other types of machine.

• What Captious Critics Say.

Having presented the case of the petrol-electric, let us now examine the arguments against. What do the opponents of this type of vehicle allege?

First of all, the word " electrical" frightens many people. It savours of the mysterious, it suggests complicated wiring, the possibility of elusive faults ; it implies the necessity for expert electrical knowledge on the part of those -who will he responsible for the running and maintenance of the vehicle. Frankly, the mere mention of the word puts many people off.

Now, the writer, with no more interest in this type of vehicle than that of a detached observer, would like to lay this electrical bogey once a-nd for all, if possible. Do the electrical scaremongers realize that every petrol-engined vehicle on the road depends for ignition upon an electrical machine of far greater delicacy than the robust machines of the petrolelectric trarrsmission ? Yet, everybody takes the magneto for granted and it inspires no nervousness on anybody's part!

Again, the line shafting of nearly every works and repair shop in the country is-driven by a very similar machine. Our tube trains run with unfailing regularity by this same motive power. Candidly, why should this unreasonable prejudice exist?

But the critic has other objections to raise as well; sometimes he will allege that, as a complete vehicle, the petrol-electric is heavier on account of the inevitable weight of the electrical machines. Here he is, perhaps, on firmer ground. Probably the dynamomotor combination does weigh a little more than the components it displaces. The petrol-electric people assert, however, that the reduction in the. weight of other parts made possible by the reduced stresses, and shock elimination, of the elastic form of drive, more than counterbalances the comparative heaviness of the electrical machines. As a complete vehicle, they maintain that the petrol-electric vehicle is as light as, or lighter than, the average petrol lorry.

Some Doubts and Difficulties. ..

There is another canard—it seems—in circulation about the petrol-electric vehicle. It is alleged to be comparatively slow on hills, and refuses to be hurried up them. The petrol-electric enthusiasts, however, have an answer ready. " Yes," they say, "that is true, as regards pre-war machines. The present-day machine is a very different proposition." Evolution and improvement, apparently, have taken place. Engines have been made more powerful. Electrical efficiency has been increased. The hill-climbing drawback—if such it was—exists no longer. Mention of electrical efficiency, however, raises another question--that of the relative efficiency as compared with orthodox design. In other words, are the electrical losses greater, or less, than ordinary mechanical gearbox losses?

The best test of this is themverall efficiency of the Vehicle as a whole—measured in terms of fuel consumption. It is only fair to say that some figures Which the writer has by him at the moment,supplied independently by persons who had no: idea that they would be used in such a way, show that the petrolelectric vehicle compares very favourably with other types in this respect. Some advocates of the system maintain that it actually shows a distinct saving in fuel over all other types.

The impartialt observer, therefore, is forced to marvel somewhat that petrol-electric systems have not attained a greater vogue. Criticismon nearly every point can apparently be confounded. Probably the greatest hindrance to the progress of the system is this extraordinary prejudice against -things electrical in the minds of-so Inany people. It is, of course, like most prejudices, based on ignorance. Nevertheless, it will take time to overcome. If these notes .will help.to remove some of it, so much the better.

Some Final Concluions.

If there. is a valid objection to the system it probably relates to the method of control. The hand operation of the resistances whereby the strength of the dynamo field is regulated when the vehicle is in motion, is not ideal, because it involves aural attention, on the part of the driver, to the running condi tion of the engine. This objection is present, of course, on every orthodox vehicle in a much more accentuated form, as all drivers rely for gearchanging and ignition regulation upon their hearing (although, let it be here said, we -know more than one stone-deaf man who can manage petrol engines and cars as well as those with full use of the faculty of hearing). Comparatively, therefore, it is not a disadvantage, but it ia a feature which could be improved.

Automatic regulation, would make the system nearly ideal, and there is no doubt that,. before long, this automaticity willbe -achieved. When that hap pens, the petrol-electric vehicle should take a lot of beating. The writer has endeavoured to preserve an impartial attitude, and togive the arguments both for and against the system. But, in investigating its virtues and its alleged vices, one is sensible of a growing predilection in its favour.

After all; the gearbox is a makeshift sort of job,. Gear changing is always a nuisance, exeept to the enthusiast who uses his gear lever like a golf club, and experiences a similar satisfaction when he holes out in one ! But there is no need to provide the dexterous driver of a public-service vehicle with a change speed lever for amusement purposes. Them is., however, a great need that vehicles of this description and, indeed, all heavy vehicles, should be. made as fool-proof as possible. It is towards this end that the efforts of the esigners of petrol-electric systems are being directed. There is little doubt that they will Ultimately be successful, and that they have already achieved a. remarkable measure of success. .