THE ELECTRIC TROLLEY-BUS.
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The Advantages that are Claimed for this Substitute for the Rail-bound Tramcar. The Economies of its Operation.
Ely Frank Ayton, M.I.C.E., M.Inst.T.
AT the present time there are no fewer than 21 areas in which electric trolley-buses are used in connection with the passenger services, namely, Ashton-under-Lyne, Birmingham, Bradford, Chesterfield, Darlington, Doncaster, Grimsby, Hastings, Ipswich, Keighley, Maidstone, Mexborough, Nottingham, Oldham, Rotherham, St. Helens, Southend-on-Sea, Tees-side, West Hartlepool, Woiverhanapton and York.
That so many towns have adopted this form of mechanical transport for passenger services is clear evidence that there are important advantages connected with it. Some of the municipal authorities eoncerned were already operating petrol motorbuses before acquiring trolley-buses and practically all are, or were, running electric tramways; in the case of Chesterfield, Darlington, Hastings (a companyowned undertaking), Ipswich; Keighley and Wolverhampton the electric tramways have been, or are being, entirely superseded by trolley-buses. In a number of these towns the trolley-bus fleet continues to be added to, and a recent statement published from Nottingham is to the effect that "the Nottingham Tramways Committee have decided upon an extension of the trolley-omnibus system. It appears that an examination of the capital and revenue of the undertaking has shown that the margin of profit on the trolleyomnibuses exceeds that of the tramways and that the former are giving higher returns than petrol omnibuses."
The modern type of trolley-bus, with a well-sprung chassis on giant pneumatic tyres, is, without question, one of tha most comfortable of all public-transport vehicles in which to travel. It gets ender way and gathers speed with a rapidity and smoothness unequalled by any other type. The absence of• smell and the almost Oiient running are characteristics of no small importance at the present time when public feeling is being roused against the noise of motor traffic in our streets.
Why Many Towns are Running Trolley-buses.
These advantages alone would be sufficient to secure the adoption of the trolley-bus in many eases, but when, allied to them, are found those of lower operating costs and a longer assured life for the vehicle, the reason why so many towns are now running trolley-buses and ninny others are considering their employment, is not difficult to understand. Actual experience with this form of passenger conveyance cannot fail to convince the student of transport that there is a field and future for it, a conclusion which is supported by the fact that the use of the trolley-bus is making definite headway, not only in this country, but on the Continent and in other parts of the world.
• The late Mr. Alfred Baker, who was general manager of the Birmingham Corporation Tramways Department, was a recognized authority on passenger-transport matters, an expert whose advice was frequently sought by other local authorities. He and his near neighbour, Mr. Silvers, the general manager and engineer of the Wolverhampton Corporation Tramways Department, were in the unique position of having actual experience in operating all three modern forms of road passenger transit, i.e., electric trams, electric trolley-buses and petrol buses. He summed up the case as between the two latter forms very, succinctly in a report to the Ipswich Corporation in 1925, in which the following statement occurred:—
"The strongest feature in. favour of the petrol motor omnibus is its mobility. It can, if neeessary, be taken off one route and put upon another. When this has been conceded all has been said in its favour as compared with a trolley-omnibus, and even this is discounted by the fact that public-service vehicles must, of necessity, adhere to a defined and regular route. „ Prom the point of view of cheapness of running, ease and comfort of riding, no vehicle gives better results than a modern well-designed trolley omnibus, (This statement must be qualified as regards cheapness of running by tramcars carrying 70 or 80 passengers in our large cities, on routes having a great density of traffic, such as do not exist in Ipswiche.. . •
" I have no hesitation, therefore, in advising that it would be wise policy to abandon the present system of tramways and, in place thereof, to substitute an. up-to-date system of trolley-omnibuses. I advise this not only from financial considerations, but from the point of view of the comfort and convenience of the travelling public. The trolley-onmibus system is reliable in service, more silent than either tramway or motor-omnibuses, whilst the absence of gearbox renders acceleration and deceleration almost perfect,with an entire absence of jerks, as is common with motor omnibuses.
" With regard to operating expenses, the cost of running motor omnibuses is heavier than either tramcars or trolley vehicles, and / am certain, from my own experience, that the working costs would exceed those of trolley vehicles by at least 2d. per mile."
Mention has already been made of the celerity with which the trolley-bus gets under way, that is to say, its high rate cf acceleration. In this particular characteristic it has no equal iu its class. That it should so excel in this feature is only to be expected when this essential difference between a petrol motorbus and a trolley-bus is considered, eamely, that, whilst the torque that can be exerted at the driving-wheel tyres of the.former is strictly limited by the capacity of the bus engine, the trolley-bus can draw upon the capacity of a power station; and the amount of power that may be put into the motor is only limited by the setting of the automatic circuit breakers on the vehicle. As the motor will, for short periods, safely tflke, more than twice its normal rating inpnt, it can be readily appreciated that the reserve of powee in the trolley-bus is very much greater than in the petrol motorbus.
The High Average Speed of the Trolley-bus.
This power of rapid acceleration is of great importance for ease and quickness of manoeuvring in traffic. and in maintaining a speedy service. That the trolley-bus excels in this respect is well brought out in the following' comparison published in the report for the year ended March 31st, 1928, of Mr. C. Owen Silvers, M.Instle, the general manager and engineer of the Wolverhampton Corporation Transport Department:—
Trolley Motor vehicles. omnibuses. Tramears.
Average speed in
miles per hour ... 9.103 8.122 -7.481
The results of the speedier service given by the trolley-bus and the effect in attracting more passengers are well exemplified in the first year's working of the Darlington system, after a complete change over from electric trams te trolley-buses. The receipts for the year totalled 139,964, an increase of no less than £7,131 over the previous year, or over 22 per cent. This result is typical of what happens in the generality of cases where this speedy, quiet and smoothrunning type of vehicle replaces the tramcar.
Mechanical Simplicity an Advantage.
One important feature of the trolley-bus should not be forgotten, namely, the simplicity of its mechanism. The electric motor with its one moving part, the armature, contrasts with the multiplicity of moving parts of a petrol engine—indeed, one may say that, if, in the case of a motorbus, everything but the back and front axles, springs, propeller shaft, etc., which are common to all power-propelled road vehicles, and the lighting dynamo are eliminated, what remains, with the addition of a controller and trolley. gear, is comparable with what is found on a -trolley-hne chassis. There is absent all the complexity of. the multi-cylinder engine magneto, gearbox, etc. Thie simplicity and the ruggedness of construction which the latter makes possible explains why the upkeep expenses of the trolley-bus are lower and why it requires less frequent overhaul, enabling it to he kept on the road for longer periods than the motorbus. The use of the trolley-bus system in substitution for trams carries with it the further advantage that the transport department still continues to be a good customer to the electric supply undertaking. Statements have been circulated that some electric supply undertakings would be glad to be rid of the traction load, but, having regard to the fact that a traction supply usually has a very good load factor, i.e., between 65 per cent, and 75 per cent., which is considerably better than the ordinary industrial power supply load factor, it is hardly likely that the supply authority would look with favour upon any scheme which would eliminate the demand for the current for traction purposes. The writer found, the other day, that, in the particular instance of a town where a fleet of 36 trolley-buses is being operated, the
load factor of the traction supply averages 74 per cent.
The Matter of Shortage of Generating Plant.'
During the last year or so more than one electric supply undertaking has found itself short of generating plant and, in consequence, in a difficult Situation for maintaining continuity of, suPply. This condition of affairs has been due to the postponement of the ordering of new plant, owing to uncertainty concerning the arrangements which would be made in the different areas under_ the national electricity scheme. It is quite likely that, in such trying circumstances, the manager of an electric supply station would wish that he could utilize the traction supply plant for his ordinary supply. There call be.no question, however, that, generally speaking, the traction supply is looked upon as a valuable part of the load of an electric power station, by reason of the
high load factor. • In the ease of a new route or transport system where no electric tramway exists, it becomes necessary to provide complete overhead equipment, including street standards, overhead wires, as well as electric feeder cables, whereas, in the case of substituting trolley-buses for trams, the existing overhead trolley wire equipment can be easily adapted, with comparatively small expense to the new system. In such circumstances, it will depend upon the amount of traffic which may reasonably be expected as to whether or not the trolley-bus is a better proposition than the motorbus.
With regard to the type of vehicle, the choice lies between the single-deck saloon and the double-decker _(with or without top cover in. the case of the latter), between the fourwheeler end the six-wheeler and, in connection with the electrical equipment, between the single motor and the double or twin motor, the latter utilizing the series-parallel system of control.
Traffic conditions will enter into the question as to the most suitable type of body. It used to be urged by the defenders of the tramcar that, for heavy traffic, no mo-torbus could compete with the former in regard to carrying capacity, but now that motorbuses, including trolley-buses, are built to carry upwards of 60 passengers, and this with vehicles employing all the additional convenience and comfort of the top-covered type, the tramcar is on the point of
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being robbed of this particular advantage. Whilst there are particularly favourable features in the double-deck' type of trolley-bus and exceedingly good results are being obtained in certain towns where they are in use, there is something to be said for the quick loading and unloading features of the single-deck saloon, particularly when it is arranged with a wide central entrance. On a three-mile route in a north-east coast town, where 32-seater central-entrance trolley-saloon buses are used, it has been found possible in rush hours to dispatch vehicles, loaded with an average of 50 passengers each, at the rate of one bus every minute and, operating 18 buses, to handle on bank holidays between 25,000 and 26,000 passengers during the evening rush. , -Where it is a question of securing the greatest possible seating capacity, the use of the six-wheeler is a necessity. Electric tiolleY-busei on six-wheel chassis are in use at Doncaster, Hastings, Maidstone, and Wolverhampton. It is possible .to build .a•six-wbeeler. that will turn within . the diameter allowed by the Ministry of' Transport, i.e., a minimum of 52 ft. and 'n maximum of 60 ft., so that no difficulty is involved in arranging turning circles of the usual size at termini.
The Single Motor Generally Favoured.
In regard to" the electrical equipment, it may be said that most of the vehicles in service to-day are fitted with singlemotor _equipment: This is certainly the simplest arrangement and one which gives reasonable economy in eleetrical energy consumption. When, however, there is frequent starting and stopping due to traffic conditions in congested thoroughfares, or the district is a hilly one and much starting has to be done on gradients, there is something to be said foe the double or twin motor equipment arranged for seriesparallel control. Against this advantage, which is reflected in somewhat lower consumption of electrical energy arising from lessened rheostatic losses (i.e., loss of electrical energy by conversion into heatiblu the starting resistances), must be set the greater weight of such .equipment when compared with the single motor arrangement. Having regard to the limitation of the loaded weight of a six-wheel bus to 12 tons, which is imposed by the Ministry of Transport regulations, it necessarily means a small sacrifice of seating capacity when a double or twin motor equipment has to be provided. It is usual, in the case of large double-deck vehicles, to provide a motor or motors capable of developing 60 to 65 b.h.p. on the one hour rating of the British engineering standards specification for traction motors, whereas 50 b.h.p. On the same rating is considered ample for the single-deck saloon.
As to speed, these trolley-vehicles of the modern type are built to run up to 28 m.p.h. on the level, and so wonderful are their hill-climbing powers that, fully loaded, actual tests have shown 15 to 16 m.p.h. on a steepish gradient of 1 in 11i. These features, combined with their characteristics of quick acceleration, make it possible for a more uniformly rapid service to be provided by electric trolley-buses in urban areas than would be possible by the use of motorbuses or electric tramcars.