EXPERIENCE WITH
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LONDON'S
SIX-WHEEL BUSES.
Thoroughly Practicable and Satisfactory Vehicles. More Economical than Fourwheel Buses.
By George J. Shave (Operating Manager and Chief Engineer, London General Omnibus Company, Ltd.).
A PPARENTLY opinion is divided as to the useful
ness or otherwise of the six-wheel vehicle for passenger transport—and with particular reference to the vehicle of the full length at present allowed, viz. 30 ft. It is considered unnecessary to introduce six wheels on a vehicle under 27 ft. in length, unless it is• with the object of using a much smaller wheel to allow of a low-loading or one-step-in platform. In giving a resum6 of our practical experience with the use of the six-wheel vehicles in London, I have the feeling that it may help to settle one or two points on which there is considerable difference of opinion.
The first six-wheel bus operated by the L.G.O.C. was placed on the streets of London early in June, 1927, and, subsequently, the licensed fleet of six-wheel buses was augmented to the present total of 11; 12 vehiclea the last of which will shortly be placed in service— was the number originally decided upon, as forming a nucleus capable of furnishing some reliable data as to the practicability and economy of maintenance of this class of vehicle from the engineering standpoint, and the earning capacity and general serviceability of the larger type of bus from the operating point of view. Some considerable experience has now been gained with the vehicles in respect of all these factors and, as the result, it has been possible to form a fairly definite estimate of the potentialities as well as of the
limitations of the vehicles as a class In particular reference to the traffic problems of the metropolis.
It may be stated at the outset that, from an engineering point of view, the six-wheel bus of the type adopted has proved itself to be a practicable and satisfactory proposition. The six-cyliudered power units, of which both poppet and sleeve types have been employed, have, in conjunction with the special design of 4-speed gearbox, proved themselves fully capable of meeting the demands made upon them under the rather exacting conditions imposed by town operation. In pursuance of an essential policy of keeping to the forefront of contemporary progress and to meet the ever-insistent demands for improved acceleration, silent running and economy of fuel consumption, several special designs of engine are, at the present time, being developed expressly for use in the sixwheel vehicles. The special type of twin rear axle incorporated in the LS vehicles, which em bodied a third differential between the two axles and a novel form of suspension, has • proved entirely satisfactory from all points of view. The pneumatic tyres with which all the vehicles are equipped have given quite satisfactory service and comparatively little trouble arising from punctures has been experienced. Their size is N ins. by 8 ins.
The immunity of the sixwheel vehicle from skidding or "side slipping "—an important characteristic in favour of the multi-rear-wheel axle—is demonstrated by the fact that no instance of skidding trouble has been reported throughout the tests. The vehicles, furthermore, prove to be easy of control, despite their greater length and weight, and any doubts which might, perhaps, quite reasonably, ha.ve existed, on the score of manoeuvrability in traffic, have been entirely dispelled by actual service experience.
With regard to economy of maintenance and operation of the vehicles, it was to be expected that, by reason of larger dimensions and added complica
tion, the expenses in respect of fuel, lubricant, cleaning and general maintenance would be greater than for the smaller, vehicles." It has been found, however, that taking all these items into consideration, the "all-in " running cost of the 72-passenger vehicle, including driver's and conductor's wages, does not work out at much more than One-third greater than the corresponding running. cost of the smaller vehicle, which carries little more than half the number of passengers. From the point of View of general operating costs, therefore, provided that reasonable advantage can be taken of the increased seating capacity in respect of revenue, it is Clear that the six-wheel vehicle presents a more economical proposition than its smaller fourwheeled prototypes.
The Sphere of the Six-wheeler.
In considering the possible applications of the six. wheel bus, it is first of all necessary to take into account the several points of difference in dimensions between this and the more familiar four-Wheel types of vehicle at present generating' in and round London, since certain of these differences clearly, introduce factors, inherent with the type, ,which at °nee limit the scope of Usefulness of the larger Vehicle. A comparison of the E.G.O.C. LS type double-deck, sixwheel bus with the 'well-known K, S and NS type double-deck vehicles is as follows:—
LS NS Seating capacity... 72 52 54 46.
ft. in, ft. in. ft. in. ft. in. Overall length ... 29 11 25 0 24 8 22 7
The first limitation to the usefulness of the sixwheeler is, of course, the comparatively large area covered when negotiating a corner. When turning on full lock, the diameter of the circle described by the six-wheel vehicle is not greatly in excess of that of the largest of the four-wheelers, hut it must be realized that, whereas this indicates that the width of the roadway required to enable the six-wheeler to perform a complete circle may not he very much greater than that required by the smaller vehicle, the overall length of the bus determines the " sweep " which must be made when negotiating a side turning or when drawing out from behind a stationary vehicle. In this regard, the additional 5 ft. in length of the sixwheeler sets a definite limit in respect of width of roadway which it can traverse without creating a temporary obstruction liable to lead to congestion of other traffic.
In congested areas it is really undesirable for any vehicle to require more than its own half of the roadway in which to turn from one street to another, otherwise on-coming vehicles must be hindered and the flow of traffic checked. In the heart of the City, and within an area of, roughly, three miles radius of the Mansion House, the width of the streets and congested character of the traffic are such as to raider the long six-wheel vehicle definitely unsuitable. Any advantage that might be expected to accrue in respect of reduction in number of vehicles by merit of the larger carrying capacity of the vehicle would be considerably outweighed by the hindrance to traffic, which would inevitably result from the operation of the more unwieldy vehicle within this area.
Greater Difficulty of Fare Collection.
A second factor which tends to restrict the universal employment of the six-wheeler lies in respect of fare collection. Experience shows that on "short haul" routes, that is to say, routes whereon a preponderance of passengers travel over comparatively short distances only, it is not possible to ensure that all the fares are collected. It is estimated that on such routes where heavy loadings are experienced, the conductor is not capable of collecting fares from more than 50 passengers, i.e. 78 per cent. of the total capacity (allowance being made for five standing passengers). In addition to this direct revenue loss, more frequent stops have to be made in consequence of the larger number of passengers desiring to board and alight at different points along the route, so that the average journey-speed tends to be reduced.
The majority of bus services operating in and across London fall either within the "short haul" or "congested area" categories, so that the utility of the six-wheel bus is very much restricted over an area covering the greater part of central London. In fact, it appears evident that, for services operating under the conditions specified, the six-wheel bus is, with few exceptions, both unnecessary and undesirable, and that this traffic can be Catered for more expeditiouSlY and more economically by the existing means of transport.
It follows from the foregoing that the maximum utility is to be obtained from the six-wheeler on the "long haul" type of route which does not intersect the highly congeSted Metropolitan area. Even here, however, consideration naturally has to be given to the fact that, on these routes, considerable fluctuations of loading are experienced and, in many cases, advantage of the full capacity of the vehicles is only taken during " peak " periods of about two hours' duration in the morning and two hours' duration in the evening, the loading during the remainder of the day falling to about half capacity.
On such routes advantage can be, and is often, taken of the spread-over system, whereby a certain number of vehicles are taken off the road during the slack periods and reinstated for the "peak " periods. This practice, however, can only conveniently be resorted to _when the normal headway, or service interval, is reasonably short, otherwise the opening up of the headways resulting from the withdrawal of vehicles during ;the slack periods may cause undue inconvenience to the travelling public.
This same limitation must be taken inte account when considering the substitution of the smaller vehicle by the larger one, and so it follows that, in practice, the six-wheel vehicle can only be employed economically and provide the convenience reasonably demanded by the travelling public on services where 027
comparatively slow headways are worked to during the " peak " period. Whereas it is not possible to lay down a definite limit applicable to all cases, it is considered that the large vehicle could only be advantageously employed on services where the headway does not exceed five minutes.
Consileration of the routes which the foregoing reasoning indicates to be practicable and economical for the six-wheel vehicle, shows that the conditions are met by the city and suburban routes which radiate from the environs of the city, the majority of which are at present served by the tramways. Such routes deal with heavy, peak-load traffic, fall within the "long haul" category and do not pass through the heavily congested and narrow streets, such as have to be negotiated by the cross-city services.
The Six-wheeler will Displace the Tramcar.
The advantages of the six-wheel bus over the tramway car for this class of work are manifold and obvious. The tramcar suffers from the inherent disadvantage of being restricted to a single line which is almost invariably located in the most unfortunate position in the roadway, both from the point of view of traffic congestion and danger to the public when mounting and dismounting. The failure of the power supply, the breakdown of one of the cars, or of any other vehicle which may become disabled on the track, causes entire disruption of traffic.
Furthermore, in many cases, the development of facilities in the outlying districts has resulted in large volumes of tram traffic converging upon a single artery on the fringe of the city, in consequence of which traffic flow is considerably retarded and congestion aggravated. In the case of the more mobile bus, alternative routes of entry to the city termini can be provided. Another obvious advantage of the bus as compared with the tramcar is that, by merit of its flexibility, it can easily be diverted to deal with cases of emergency or to meet the temporary demands of any special traffic flow. At week-ends or bank holidays in the summer season the larger-type vehicles, released from the business traffic, could be profitably employed on country routes where heavy traffic exists.
In conclusion, therefore, the results so far obtained from the operation of the experimental six-wheel buses in London traffic have shown that, whereas the usefulness of the large vehicle is restricted in so far as city operation is concerned, the potentialities of this type of conveyance for efficiently serving the radiating traffic of London are considerable and, when the time arrives, as inevitably it will arrive, for the tramway services to be replaced by a more efficient and more economical means of transport, there is little doubt that the large-capacity six-wheel bus will be found to prove the most attractive substitute.
I do seriously suggest to those concerned in operating tramways systems that the trackless trolley is a clumsy and uneconomical expedient in the gradual change over to a more mobile form of transportation, and that the six-wheel vehicle is the type which should be very carefully considered when it is essential to abandon the rail track of the tramway system. It would be preferable then to make an entire change—to depart entirely from the rail vehicle with its central station and to adopt the self-contained mobile unit.