• THE MUNICIPAL OMNIBUS BODY.
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A Consideration of the Types of Bus Bodywork and Interior Fitting that will Appeal to the Tramways Manager.
MUNICIPAL authorities, whether owning a tramway system or not, have always been regarded as potential buyers of buses. Hitherto the official attitude has been that the bus forms a valuable means of linking up the tramway with neighbouring towns and villages, for setting up alternative routes or increasing the existing network and, at the same time, incurring less capital expenditure than would result had new permanent way and overhead wiring to be installed.
More recently the high cost of maintenance, especially of the track, has led the corporation tramways manager, the highway committee and others responsible to regard the bus, not merely as An accessory to the tram service, but worthy of eonSideration as being a more economical means of providing passenger transport. Furthermore; the public, where both rail and road transport are available, are now showing a decided preference for the bus, because of the greater degree of comfort and attractiveness of the petrol vehicle, which also has the advantage that loading and unloading are done at the sides and not in the middle of the road. Another advantage which the bus offers is that smaller units can be adopted than is feasible with tramcars.
The tramway manager and engineer, when contemplating the purchase of a fleet of buses, being familiar with the general design and construction of a tramcar body and its bearing on the comfort and convenience of the passenger, will naturally look for similar features in the bus body. It will, therefore, be advantageous to compare the bodywOrk of these two leading varieties of public-service vehicles, and to show that the flexibility and independent running of the bus are not gained at the expense of other important qualities.
Characteristic Features of the Tramcar.
The typical tramcar of to-day has longitudinal seats inside, giving a spacious centre gangway and a crosswise roof-seating arrangement, many cars being fitted with top covers. Being a rail vehicle and running on the crown of the road, there are no difficulties in the way of making it a high-capacity vehicle. The longitudinal type of seating is, favoured because provision
has to be made at diagonally opposite ends for the provision of sand-boxes. The lower saloon, so designed, need not be as wide as the roof with its crosswise seats. It is only a matter of a few inches, but the difference is just enough to prevent the lower saloon from being converted to tile same arrangement of seats as is adopted with the modern bus, be it a single or doubledecker. Should an existing tram be converted to cross wise seating, then a compromise is effected by utilizing double seats on the near side and single seats on the off side, with long seats over the sand-boxes.
The Reversible Type of Body.
A characteristic which the bus does not possess is that of operation in either direction. This, however, is a feature which would not have been introduced except to avoid the necessity of reversing the car at a terminus. The long seat is eminently suitable in this connection, but where crosswise seats are introduced they must be designed with a pivoted back, and the top of the seating or cushion must be fiat. The great advantage of the reversible type of body is that it has a doorway and steps at each end, anti, with a double-decker, a staircase as well. This feature saves much time at the terminus, as the passengers getting on do not obstruct those who are leaving the vehicle. The double entrances are also useful in emergencies.
The Bus has Less Headroom and Less Weight.
• As' the bus has to operate upon every kind of road rurface, and is continually travelling on the camber of the highway, general compactness of design is studied more closely than with a rail vehicle. There is practically no difference in the overall -width of a doubledeck bus and tram, but with the latter vehicle it will often be found that there is more headroom both in the Upper saloon and lower saloon. A bus has seldom more than 5 ft. 11 ins, headroom, whereas 6 ft. 2 ins. and 6 ft. 3 ins, is not unusual with a tramcar. The tram has a larger platform, as it has to support not only the staircase, but provide accommodation for the driver in• either direction. The double-ended design of body, with its large platforms and ample headroom, necessitates a more rigid and stronger framework than is required for a bus, and, although some attention has been paid of late to the reduction of weight, the tram is still a comparatively heavy vehicle. It is of interest to note that a fairly modern 60-seated double-saloon tramcar weighs about 91 tons, of which over 51 tons is body weight alone.
Constructional Materials of the Tram Body.
Briefly, the materials used in construction are an underframe of pressed and rolled steel, the more important members of the body framework consisting of the best teak with pitch-pine longitudinals, only the parts of lesser importance being of ash. Solid mahogany panels are favoured for the lower saloon and sheet steel for the upper one, the latter material being utilized to act as a cantilever in supporting those portions above the end canopies.
The Bus Body Specification.
Bearing these facts in mind, the bodybuilder who receives a specification in connection with a tender for bus bodies for a municipality must expect to find that particular stress is laid on the right selection and quality of material, and that the details given will be more numerous and definite than are often received from other quarters. The tramways engineer, especially he who already has had a fleet of buses under his supervision for some time, will be conversant with the general practice of the bus builder. Here and there it may be found that the latest methods of weight saving and the use of sheet-metal rather than forgings for reinforcing the more
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important joints of the body will not find ready acceptance. The bodybuilder can, howev r, meet the situation by tendering to the specificatioi submitted and alternatively to his own construction design.
The Chassis.
The frame of the modern passenger b s chassis is built several inches lower than was the cu tom a year or two ago. The rear part is cranked do 'n both for the single and double-decker, so that only one step is required to reach the hind platform, or it may be brought down low enough so that the pa senger can mount directly on to the platform. As the diameter of the road wheels has not been reduced in p ()portion to the lowering of the chassis, not only is t e height of the wheel arch increased, but the framei elf has to be cranked upwards at the hind-axle posi on.
The Crosswise Seat of the Lower Saloon.
The universal adoption of crosswise s ts for the lower saloon has a direct effect on the get eral design of the body and especially on the bottom framework. The sides of the body, when viewed from t e end, must not depart much from the vertical. In 0th' words, the turnunder must be restricted so that there is .sufficient room for the feet of the passengers sitting against the sides. For the same reason the body mu .t be wider at the waist and bottom than one having ongitudinal seats. This means that, whether the body be a single or double-decker, it must not lie less than 7 ft. I in. over the side pillars at the Waist line. Long seats must be introduced to cover effectively the wheel arch, and with the modernchassis this will also include the cranked-up portion of the chassis.
As the vehicle has to run on the camber of the road, it is an advantage if the sides Slope inwards towards the cant rail, a similar design being utilized for the superstructure if a covered top be used.
Bus Entrances.
The single-deck type of bus. is built with four varieties of near-side entrance: (I) Front ; (2) rear ; (3) combined front and rear; (4) middle. The front entrance is suitable for small and medium-sized buses, as it is particularly fitted for one-man operation. The emergency door should be capable of being easily opened from either inside or outside. A convenient step is provided by hinging the back seat in the gangway directly to the floor, so that when the door is opened it can be completely reversed outside and below the floor. If this combined seat and step is not provided, then a permanent one should be fitted at the rear in an accessible position. The rear entrance is favoured by those who consider it a safe pattern; keeping the passenger away from the wheels, whilst from the constructional point of view neither the driving-seat bulkhead nor the back framing is pierced by a doorway. The combined backand-front-entrance type is suitable for busy localities, and -can also be adapted for one-man operation. The middle entrance is usually wide enough so that it forms a combined entrance and exit. It is most suitable for the larger type of single-decker.
The Bus Bottom Frame.
The bus body is wider across the bottom than the chassis frame, this difference having been increased since long seats were discarded. Due precautions are necessary in order to provide a safe support for the overhang on each side. . The chief members of the bottom frame are, therefore, the cross-bearers. These will be about 3 ins, deep and stiffened by a flitch plate. The ends of these cross-bearers are checked out to receive the bottom side. This is only made thick enough to provide a bottom fixing for the side pillars. It is not regarded as a part of the framework, which is rigid enough in itself to resist the stresses set up by any temporary deformation of the chassis owing to the inequalities of the road, as it is interrupted by the wheelarch bar, and the greater the radius of this the less its inherent strength.
The Transverse Unit.
The bus body is designed so that its greatest strength lies in each transverse unit. For this reason the side pillars are arranged opposite the ends of the crossbearers, allowing the junction to be reinforced by a bracket plate bolted to the side faces of both the pillar and the bearer. At the top of the pillar a similar bracket joins it to the hoopstick.•
Seats.
The crosswise or garden seat has undergone various detailed improvements since it has been introduced into the lower saloon and provided with a cushion. A wooden framework with a cross pattern of leg on the gangway side, and supported on a seat sail on the other, is now going out of use. The wooden framework is used because it is a convenient material to handle in factories largely devoted to woodworking. The cross-pattern leg is being discarded because, being cut out of the solid and curved in shape, it is apt_ to be short grained, and, in any case, requires reinforcement with a light flitch plate. A. straight-pattern leg is now usually preferred. It cuts into less timber, and, although requiring metal reinforcement, the lower seat structure can be made more rigid by the use of a strut.
Much attention has been devoted recently to the garden seat which has a seat board supported on legs of flat iron, which, when once bent to shape and drilled, require no further work on them. For the support of the seat back spring steel Is used. The backrest is made up on a board, which provides a top fixing for the plywood panel filing in the back. This plywood and the steel supports are rounded inwards at the bottom so as to give extra knee-room for the passenger sitting behind. The steel back supports have the advantage that a certain liveliness is imparted to the seat which should be allowed full play by supporting the seat directly from the floor at each side and not on the gangway side only.