ACCUMULATOR ELECTRIC TRACTION. THE ELECTRIC AUTOMOBILE
The use of the accumulator or storage battery in electric traction
affords a very good example of how a means of propulsion may fail in one
set of circumstances and contrive to succeed in another. Its history
serves to remind us that the problem of cheap transport is really a
group of problems, each one of which demands a particular solution.
The accumulator is a device for storing electrical energy in the form of chemical energy. Its action depends upon the effect of currents of electricity on lead plates in a bath of sulphuric acid. The passage of the current through the battery produces chemical changes which enable the battery to give out current when required. As the battery may remain 'charged' for several days, and may be discharged slowly or quickly, it provides a means of 'storing' electrical energy. In practice, and under favourable conditions, the efficiency of the storage battery is about 80 per cent. That is to say, there is a loss of about 20 per cent. in the process of conversion and re-conversion.
Great hopes were once entertained of accumulator traction on
tramways. The storage battery offered a means of escape from all the
difficulty and expense of carrying electric mains overhead or
underground. By fitting each car with a storage battery, it could be
made an independent self-contained locomotive, capable of running a
certain number of miles until the
battery was approaching exhaustion. By providing centres where the
batteries could be re-charged—or, to save time, replaced by batteries
previously charged—a continuous service could be maintained on a tramway
system.
The advantages of accumulator traction, apart from the saving in first cost, are the absence of obstruction and danger from overhead wires, and of the risk of a general stoppage of the service when the current at the generating station fails from any accidental cause. When accumulators are used, the conversion of a horse tramway to an electric tramway becomes a very simple matter. All that is required is to erect a generating station and provide each car with a storage battery and electrical equipment. This equipment, it may be mentioned, is substantially the same as with ordinary electric cars. The current flows from the accumulator through the controller and the motors back to the accumulator.
Many trials were made with this system in the early days of electric traction, but there are no survivals. The failures were due in part to weaknesses in the batteries and to the difficulty of handling them with proper care under the rough and ready conditions of tramway service. The main cause, however, was the inherent drawback of all locomotive systems—the fact that the tractor has to haul its own dead weight in addition to the weight of the car and passengers. Lead being one of the heaviest of metals, this dead weight was a very serious item on accumulator tramcars. It proved to be a fatal item when the attempt was made to run large cars on heavy gradients. The rush of current demanded in starting such cars up-hill was in itself too severe a tax on the delicate structure of the batteries. In practice, moreover, the necessity of bringing each car back to the depot for re-charging, after a limited journey, proved very troublesome. The more extensive the system and the more frequent the service, the more troublesome this necessity became. Even the most enthusiastic advocate of the storage battery was at last forced to admit that it was not applicable to a system of transport, which demanded comparatively high speeds with large cars on all gradients and over a range of several miles from the centre of power.
After the admitted failure of accumulator tramways, the storage battery was for some time used only on river launches and small private vehicles. The conditions in both cases—and especially in the former—are very favourable to its operation. On a river launch the weight of the battery is not a serious item, as it serves to some extent in the place of ballast. Launches, moreover, are generally required for trips of a limited number of miles up and down the river from the boathouse or charging station of the owner. In contrast with the tramway, there is no demand for rapid acceleration at starting or for abnormal power at intervals. The batteries discharge slowly and fairly evenly, and are not subjected to serious vibration. The electrical equipment is extremely simple, as the motor is fixed on to the propeller shaft and operated by a controller on the deck close to the steering wheel.
However, if economy were the only consideration, it is doubtful whether the electric launch would have survived against the competition of steam and petrol launches. It has survived because the simplicity of the equipment, its silent running, and the absence of heat, smoke and fumes, make it the ideal thing for river work. The hire of an electric launch on the Thames costs more than that of a steam launch, but plenty of people are willing to pay the additional charge to avoid the drawbacks of steam propulsion on a small vessel.
Similar considerations underlie the extensive use of electric broughams in cities. Such vehicles are required only for travel within a restricted area and on streets where the gradients are seldom severe. Their carrying capacity is generally limited to two or four passengers, so that the batteries do not require to be unduly heavy. A maximum speed of 12 miles an hour is quite sufficient for city streets; and with careful treatment the batteries can be very economically used and will not deteriorate nearly so rapidly as they would under tramway conditions. Considerations of economy, on the other hand, do not weigh very heavily with the class of people who use private electric broughams. They are prepared to pay for the best available; and the electric brougham, with its noiselessness, its easy running, its absence of smell or other nuisance, is regarded as the ideal which other modes of city transport must do their best to approach.
In London a certain amount of business has been done for some years in hiring electric broughams for various periods on terms which include current, maintenance, garage facilities, driver's wages, and all other charges. The convenience of such an arrangement to the hirer need not be emphasised, since what is wanted in this case is a vehicle which is always ready at a telephone call. But the system has another important advantage, which bears upon the economic prospects of accumulator traction. By retaining the vehicles under its control the hiring company not only centralises the arrangements for storing and re-charging, but it is able to take care that the batteries are properly treated. Just as the success of the surface-contact system depends on minutiae of design, so the success of accumulator traction depends upon minutiae of treatment. Carelessness in driving the vehicles and in handling the batteries at the garage may transform a perfectly satisfactory mode of city transport into an extravagant nuisance. Consequently the success of this class of business depends upon an organisation which permits of constant supervision over every vehicle and every driver.
A good deal of ingenuity has been exercised upon the electrical equipment of broughams; and it is probable that further improvements will be made. In some cases the front axle is driven by the motor; in some cases the back axle. The earliest cars used toothed-wheel gearing in order to reduce the speed of the small fast-running motor. Improved types on this principle still exist, but there are some interesting forms in which the motors are placed right at the hub of the wheels and effect speed reduction and control by electrical means, without any intermediate gearing.
In addition to these improvements, the storage battery itself has made a distinct advance in design and construction. It is more efficient, more durable, and more reliable now than ever it was before. The closer attention given to its treatment tends in the same direction; and the result is that storage-battery makers and engineers have a very accurate knowledge of what the accumulator will do at a certain cost under certain conditions. The conditions being the variable factors in the problem, and being in large measure determinable by choice, it is rather remarkable that the engineers and financiers should have selected, at the outset, the very conditions which were least suited to the peculiarities of the accumulator.
The attempt to adapt battery traction to tramway work is a conspicuous case in point, but it is not perhaps so conspicuous in the public memory as the efforts to organise electric cab and electric omnibus services in London and elsewhere. These efforts have been made so often and failed so regularly that they have made it difficult to obtain capital for any form of electric battery propulsion.
The electric omnibus has many of the drawbacks of the storage-battery tramcar, but they are not so serious in the case of an urban service, adequately met by small cars running at moderate speeds on short routes with moderate gradients. It is possible that if recent metropolitan electric omnibus enterprises had been as happy in their finance as in their engineering, they would have succeeded well enough. But even in their engineering they had to meet great difficulties. They sought to protect themselves against excessive costs by entering into maintenance agreements with the makers of the batteries; and although the terms of these agreements were satisfactory enough, their validity depended on careful treatment of the batteries by the drivers of the cars—a matter which it is rather difficult to guarantee. Moreover, the number of omnibuses put on the road was so small that the garage costs and other standing charges were proportionally very heavy. With a larger fleet and with efficient organisation, much better results might have been achieved in spite of the inherent difficulties of the situation.
Although the electric cab has the advantage of being a smaller vehicle and therefore more adapted to economical propulsion by storage batteries, the conditions of the cab service are not at all favourable to the system. The essential feature of a cab is that it should be available anywhere, to go anywhere at a moment's notice. An accumulator-driven vehicle, on the other hand, is tied by an invisible cord to the charging station. Even if charging stations were multiplied enormously, the electric cab would have no real freedom of action, since several hours are required for the process of re-charging. We have only to compare the limitations of the electric cab with the freedom of the petrol cab (which can renew its supply of petrol in a minute or two at any motor depot) to realise that the roving commission is not at all suited to the former.
In 1899 a very bold effort was made to establish an electric cab service in London. To inaugurate the service a procession of the cabs was formed, but it excited more ridicule than serious interest. The clumsy appearance of the cabs was against them; and their behaviour was not satisfactory enough—as to speed and reliability—to overcome the first unfavourable impressions. They soon disappeared, to add another failure to the long list of disappointments in connection with accumulator traction.
The private electric automobile remains, however, because it has been organised under conditions which suit the peculiarities of the storage battery. Its survival, in conjunction with the failure of a similar means of transit for tramway, omnibus, and public cab services, has pointed to another direction in which the electric automobile should be a commercial possibility. That is, in connection with the local distribution of goods from large stores and other centres.
The United States have given a very distinct lead in this matter. In New York, Chicago, Washington, and other large cities the electric automobile for private use is highly developed and there is also an extensive service of electric vehicles ranging in size from a small parcels van to a large lorry capable of carrying loads up to several tons. No doubt the local cost of other means of transport has something to do with this American development, which has, moreover, been strongly supported by the companies which supply electricity to the public. But the fundamental reason lies in the special character of the service demanded.
The vans belonging to a large store all start from a certain point and return to it after journeys of limited range. Owing to the period occupied in loading up, and also to the pre-determined hours of most of the deliveries, there is no difficulty about affording the time required for re-charging the batteries, or in arranging each journey so that the vehicle returns before the batteries are exhausted. With a standardised fleet of vehicles, it is possible to remove the discharged batteries and replace them with charged ones in a few minutes. The whole arrangement, in fact, is like a private automobile garage, with the advantage that the probable demand can be forecast with a somewhat greater degree of certainty.
Steam and petrol-driven wagons run most economically on long steady journeys at fairly high speeds, and the electric automobile does not attempt to compete with them on these lines. But it offers competition within city limits for door-to-door delivery; and its prospects are particularly good for light parcel service, where the horse is still maintaining its position against the petrol vehicle. The advantages of the electric vehicle in neatness and noiselessness will certainly secure its success if the cost can be proved to be not appreciably greater than that of its rivals.
Apart from the necessity of careful organisation, the main essential of success in electric automobile work is a supply of cheap electricity. Owners of private electric launches have to pay anything from 8d. to 2s. 6d. per unit for re-charging their batteries, but these high prices are due to the intermittent character of the demand and also (in some cases) to the cost of providing machinery to supply current at special pressures for particular launches. An electric automobile garage, situated close to a public generating station and offering a larger and more regular demand, will of course obtain current much cheaper. And it is possible that arrangements may be made for supplying electricity to automobiles at a much lower rate even than that customary for general power demands. In the metropolitan borough of Marylebone, for instance, an electric garage may obtain current during the small hours of the night at 1/2d. per unit, which is half the standard rate for power purposes. This low price is offered because there is otherwise practically no demand at all for electricity during these hours. If, therefore, a garage arranges—and the arrangement is quite feasible—to charge its batteries overnight, the power bill may be divided by two.
The electric automobile has been used to some extent as a touring car, but although journeys up to 100 miles have been performed on a single charge, the time occupied in re-charging, and the difficulty of finding convenient charging stations, are fatal to any development in this field.
The accumulator is a device for storing electrical energy in the form of chemical energy. Its action depends upon the effect of currents of electricity on lead plates in a bath of sulphuric acid. The passage of the current through the battery produces chemical changes which enable the battery to give out current when required. As the battery may remain 'charged' for several days, and may be discharged slowly or quickly, it provides a means of 'storing' electrical energy. In practice, and under favourable conditions, the efficiency of the storage battery is about 80 per cent. That is to say, there is a loss of about 20 per cent. in the process of conversion and re-conversion.
Fig. 8. A modern electric automobile.—The electric
battery is placed under the front half of the car, and the motors drive
the back axle through chains. (British Electric Automobile Co., Ltd.)
The advantages of accumulator traction, apart from the saving in first cost, are the absence of obstruction and danger from overhead wires, and of the risk of a general stoppage of the service when the current at the generating station fails from any accidental cause. When accumulators are used, the conversion of a horse tramway to an electric tramway becomes a very simple matter. All that is required is to erect a generating station and provide each car with a storage battery and electrical equipment. This equipment, it may be mentioned, is substantially the same as with ordinary electric cars. The current flows from the accumulator through the controller and the motors back to the accumulator.
Many trials were made with this system in the early days of electric traction, but there are no survivals. The failures were due in part to weaknesses in the batteries and to the difficulty of handling them with proper care under the rough and ready conditions of tramway service. The main cause, however, was the inherent drawback of all locomotive systems—the fact that the tractor has to haul its own dead weight in addition to the weight of the car and passengers. Lead being one of the heaviest of metals, this dead weight was a very serious item on accumulator tramcars. It proved to be a fatal item when the attempt was made to run large cars on heavy gradients. The rush of current demanded in starting such cars up-hill was in itself too severe a tax on the delicate structure of the batteries. In practice, moreover, the necessity of bringing each car back to the depot for re-charging, after a limited journey, proved very troublesome. The more extensive the system and the more frequent the service, the more troublesome this necessity became. Even the most enthusiastic advocate of the storage battery was at last forced to admit that it was not applicable to a system of transport, which demanded comparatively high speeds with large cars on all gradients and over a range of several miles from the centre of power.
After the admitted failure of accumulator tramways, the storage battery was for some time used only on river launches and small private vehicles. The conditions in both cases—and especially in the former—are very favourable to its operation. On a river launch the weight of the battery is not a serious item, as it serves to some extent in the place of ballast. Launches, moreover, are generally required for trips of a limited number of miles up and down the river from the boathouse or charging station of the owner. In contrast with the tramway, there is no demand for rapid acceleration at starting or for abnormal power at intervals. The batteries discharge slowly and fairly evenly, and are not subjected to serious vibration. The electrical equipment is extremely simple, as the motor is fixed on to the propeller shaft and operated by a controller on the deck close to the steering wheel.
However, if economy were the only consideration, it is doubtful whether the electric launch would have survived against the competition of steam and petrol launches. It has survived because the simplicity of the equipment, its silent running, and the absence of heat, smoke and fumes, make it the ideal thing for river work. The hire of an electric launch on the Thames costs more than that of a steam launch, but plenty of people are willing to pay the additional charge to avoid the drawbacks of steam propulsion on a small vessel.
Similar considerations underlie the extensive use of electric broughams in cities. Such vehicles are required only for travel within a restricted area and on streets where the gradients are seldom severe. Their carrying capacity is generally limited to two or four passengers, so that the batteries do not require to be unduly heavy. A maximum speed of 12 miles an hour is quite sufficient for city streets; and with careful treatment the batteries can be very economically used and will not deteriorate nearly so rapidly as they would under tramway conditions. Considerations of economy, on the other hand, do not weigh very heavily with the class of people who use private electric broughams. They are prepared to pay for the best available; and the electric brougham, with its noiselessness, its easy running, its absence of smell or other nuisance, is regarded as the ideal which other modes of city transport must do their best to approach.
In London a certain amount of business has been done for some years in hiring electric broughams for various periods on terms which include current, maintenance, garage facilities, driver's wages, and all other charges. The convenience of such an arrangement to the hirer need not be emphasised, since what is wanted in this case is a vehicle which is always ready at a telephone call. But the system has another important advantage, which bears upon the economic prospects of accumulator traction. By retaining the vehicles under its control the hiring company not only centralises the arrangements for storing and re-charging, but it is able to take care that the batteries are properly treated. Just as the success of the surface-contact system depends on minutiae of design, so the success of accumulator traction depends upon minutiae of treatment. Carelessness in driving the vehicles and in handling the batteries at the garage may transform a perfectly satisfactory mode of city transport into an extravagant nuisance. Consequently the success of this class of business depends upon an organisation which permits of constant supervision over every vehicle and every driver.
A good deal of ingenuity has been exercised upon the electrical equipment of broughams; and it is probable that further improvements will be made. In some cases the front axle is driven by the motor; in some cases the back axle. The earliest cars used toothed-wheel gearing in order to reduce the speed of the small fast-running motor. Improved types on this principle still exist, but there are some interesting forms in which the motors are placed right at the hub of the wheels and effect speed reduction and control by electrical means, without any intermediate gearing.
In addition to these improvements, the storage battery itself has made a distinct advance in design and construction. It is more efficient, more durable, and more reliable now than ever it was before. The closer attention given to its treatment tends in the same direction; and the result is that storage-battery makers and engineers have a very accurate knowledge of what the accumulator will do at a certain cost under certain conditions. The conditions being the variable factors in the problem, and being in large measure determinable by choice, it is rather remarkable that the engineers and financiers should have selected, at the outset, the very conditions which were least suited to the peculiarities of the accumulator.
The attempt to adapt battery traction to tramway work is a conspicuous case in point, but it is not perhaps so conspicuous in the public memory as the efforts to organise electric cab and electric omnibus services in London and elsewhere. These efforts have been made so often and failed so regularly that they have made it difficult to obtain capital for any form of electric battery propulsion.
The electric omnibus has many of the drawbacks of the storage-battery tramcar, but they are not so serious in the case of an urban service, adequately met by small cars running at moderate speeds on short routes with moderate gradients. It is possible that if recent metropolitan electric omnibus enterprises had been as happy in their finance as in their engineering, they would have succeeded well enough. But even in their engineering they had to meet great difficulties. They sought to protect themselves against excessive costs by entering into maintenance agreements with the makers of the batteries; and although the terms of these agreements were satisfactory enough, their validity depended on careful treatment of the batteries by the drivers of the cars—a matter which it is rather difficult to guarantee. Moreover, the number of omnibuses put on the road was so small that the garage costs and other standing charges were proportionally very heavy. With a larger fleet and with efficient organisation, much better results might have been achieved in spite of the inherent difficulties of the situation.
Although the electric cab has the advantage of being a smaller vehicle and therefore more adapted to economical propulsion by storage batteries, the conditions of the cab service are not at all favourable to the system. The essential feature of a cab is that it should be available anywhere, to go anywhere at a moment's notice. An accumulator-driven vehicle, on the other hand, is tied by an invisible cord to the charging station. Even if charging stations were multiplied enormously, the electric cab would have no real freedom of action, since several hours are required for the process of re-charging. We have only to compare the limitations of the electric cab with the freedom of the petrol cab (which can renew its supply of petrol in a minute or two at any motor depot) to realise that the roving commission is not at all suited to the former.
In 1899 a very bold effort was made to establish an electric cab service in London. To inaugurate the service a procession of the cabs was formed, but it excited more ridicule than serious interest. The clumsy appearance of the cabs was against them; and their behaviour was not satisfactory enough—as to speed and reliability—to overcome the first unfavourable impressions. They soon disappeared, to add another failure to the long list of disappointments in connection with accumulator traction.
The private electric automobile remains, however, because it has been organised under conditions which suit the peculiarities of the storage battery. Its survival, in conjunction with the failure of a similar means of transit for tramway, omnibus, and public cab services, has pointed to another direction in which the electric automobile should be a commercial possibility. That is, in connection with the local distribution of goods from large stores and other centres.
The United States have given a very distinct lead in this matter. In New York, Chicago, Washington, and other large cities the electric automobile for private use is highly developed and there is also an extensive service of electric vehicles ranging in size from a small parcels van to a large lorry capable of carrying loads up to several tons. No doubt the local cost of other means of transport has something to do with this American development, which has, moreover, been strongly supported by the companies which supply electricity to the public. But the fundamental reason lies in the special character of the service demanded.
The vans belonging to a large store all start from a certain point and return to it after journeys of limited range. Owing to the period occupied in loading up, and also to the pre-determined hours of most of the deliveries, there is no difficulty about affording the time required for re-charging the batteries, or in arranging each journey so that the vehicle returns before the batteries are exhausted. With a standardised fleet of vehicles, it is possible to remove the discharged batteries and replace them with charged ones in a few minutes. The whole arrangement, in fact, is like a private automobile garage, with the advantage that the probable demand can be forecast with a somewhat greater degree of certainty.
Steam and petrol-driven wagons run most economically on long steady journeys at fairly high speeds, and the electric automobile does not attempt to compete with them on these lines. But it offers competition within city limits for door-to-door delivery; and its prospects are particularly good for light parcel service, where the horse is still maintaining its position against the petrol vehicle. The advantages of the electric vehicle in neatness and noiselessness will certainly secure its success if the cost can be proved to be not appreciably greater than that of its rivals.
Apart from the necessity of careful organisation, the main essential of success in electric automobile work is a supply of cheap electricity. Owners of private electric launches have to pay anything from 8d. to 2s. 6d. per unit for re-charging their batteries, but these high prices are due to the intermittent character of the demand and also (in some cases) to the cost of providing machinery to supply current at special pressures for particular launches. An electric automobile garage, situated close to a public generating station and offering a larger and more regular demand, will of course obtain current much cheaper. And it is possible that arrangements may be made for supplying electricity to automobiles at a much lower rate even than that customary for general power demands. In the metropolitan borough of Marylebone, for instance, an electric garage may obtain current during the small hours of the night at 1/2d. per unit, which is half the standard rate for power purposes. This low price is offered because there is otherwise practically no demand at all for electricity during these hours. If, therefore, a garage arranges—and the arrangement is quite feasible—to charge its batteries overnight, the power bill may be divided by two.
The electric automobile has been used to some extent as a touring car, but although journeys up to 100 miles have been performed on a single charge, the time occupied in re-charging, and the difficulty of finding convenient charging stations, are fatal to any development in this field.
ADAM GOWANS WHYTE, B.Sc.
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