AN IMPORTANT ORDER FOR TROLLEY-BUSES.
Page 9
Page 10
Page 11
If you've noticed an error in this article please click here to report it so we can fix it.
A British Maker to Supply One Hundred Chassis and Equipment for Service in Shanghai. Provision for 150 Passengers.
WHEN immediately after the war it became apparent that the cost of replacing worn tramway track had become prohibitive, we foresaw the commencement of a distinct era for the trolley-bus. It was unreasonable to suppose that municipally owned power stations would continue to be run merely for supplying the small amount of power required in any locality during the daytime and the supply of lighting current at night-time, throwing away the load which is imposed on a power station by an electric tramway system and replacing the tramways by motorbuses.
It is, of course, perfectly well understood that a fleet of motorbuses is quite capable of doing the work of a tramway, the only real advantage offered by the latter being its capability of better dealing, by means of large-capacity vehicles, with the peak-hour loads.
It was also evident that the housing problem would only be met by the creation or developrrient of estates on the outskirts or towns calling for an infrequent service of public passenger vehicles, and that the motorbus would not deal so economically with such sparse traffic as the trolley-bus would be capable of doing.
The tendency in the early days of the development of the trolley-bus was for the chassis to be constructed in the workshops of tramway undertakings, and we pointed out to British manufacturers that here was a type of chassis for the production of which they were peculiarly well equipped, and that they should take this new branch of industry strongly in hand so as to prevent it passing to another type of works which were by no means so well fitted to produce it.
Among the concerns which immediately took an interest in the new type of chassis was the Associated Equipment Co., Ltd., of Walthamstow, whose great experience in the manufacture of bus chassis was second to none, and, as proof of the value of this interest, they have just completed the first stage of an order for 100 trolley-buses built to the special requirements of passenger traffic in Shanghai, the specification for the chassis having been laid down by Mr. Donald McColl, general manager of the Shanghai Electric Construction Co., Ltd.
The first batch of chassis has been finished, and a complete test has been made of one set of equipment at Ipswich, the test being repeated on Thursday last at Walthamstow in the presence of a number of members of the Press and representatives of industry.
The trolley-bus chassis and the fourwheeled trailer chassis are being made by the Associated Equipment Co., Ltd., whilst, with regard to the electrical equipment, the motor is designed and manufactured by Bull Motors, Ltd., of Ipswich, and the controller and resistances are manufactured by the ElectraMechanical Brake Co., Ltd., of West Bromwich.
The tests which were carried out at Ipswich took place on a Sunday morning before the trams were operating and before any quantity of traffic was about, Mr. A. S. Black, engineer and manager of the Ipswich Corporation, very kindly giving facilities for the test' on some of the trolley-bus routes which have already been established in the town.
The tractors and trailers will be shipped to Shanghai and will there be fitted with bodies, so that, whilst we are able to describe the power plant, we are not in a position to deal with body design or equipment.
One very striking point about the trolley-bus chassis obtrudes immediately one sees the chassis, and that is the unusual amount of overhang in front of the front wheels. This is more than is generally adopted or considered acceptable in the case of a road vehicle ; but, as it shortens the wheelbase, a comparatively small turning circle is provided considering the total length of the vehicle. Advantage will be taken of this overhang to provide an ordinary tramway lifeguard when the vehicle is fitted up in Shanghai.
• The trolley-bus is driven by a single 50 h.p. Bull motor through a cardan shaft direct on the worm-driven rear axle. The controller is foot-operated and is of the ratchet type, each downward movement of the foot being the equivalent of one notch on the controller. We will deal, with this more fully later.
Taking the dimensions and weights of the tractor chassis, we find that the overall length of the frame is 22 ft. 81 ins., whilst the wheelbase is 10 ft. 8i ins. The track of the front wheels is 5 ft. 1i ins., and of the rear wheels 5 ft. 7tlins. The height of the frame loaded is 2 ft. 61 ins. from the ground, whilst the length behind the rear axle is 6 ft. The approximate weight of the chassis with motor and controller is 2 tons 13 cwt. 1 qr., of which 1 ton 2 cwt. is imposed upon the front wheels. Loaded with 3 tons • of passengers and body and with trolley gear (the total dead load being 2 tons 3 cwt.), the loaded axle weights would be as follow :—Front-axle weight, 2 tons. 18 cwt. 3 qrs.; rear-axle weight, 4 tons 17 Cwt. 2 qrs., making a total weight of 7 tone 16 cwt. 1 qr.
Dealing still further with the trolley-bus chassis, the sidemembers are straight and are made from 45-50-ton nickelsteel pressings 8 ins, deep, the flanges being 2/ ins, wide and the metal being I in. thick. The frame is fitted with suitable cross-members and motor-supporting brackets. The front axle is a nickel-steel stamping, with 31 per cent. nickelsteel swivel arms carrying the road wheels, which are made from steel castings and are mounted on taper roller bearings. The tyre size is 140 mm, wide, fitting on 720 mm. standard rims.
The drive to the rear axle is through a worm and worm 'wheel, the axle casing being made from steel_ castings with Vanadium-steel axle tubes pressed into place. The rear wheels run on taper roller bearings, and they also are steel castings equipped with twin tyres of the size mentioned, and with brake drums for internal-expanding shoes. The ratio of the worm gear is 81 to 1.
The steering gear is of the worm-and-wheel type, both worm and wheel being case-hardened.
The internal-expanding brakes operating on the rear wheels are controlled by lever or pedal, independently or jointly, whilst there is a foot-operated emergency transmission brake behind the meter.
The cardan shaft between the motor and the rear axle has a Spicer-type universal joint at each end, each joint being enclosed in a dnstproof and grease-tight case.
The motor has been specially designed for trackless tram duties, the makers, Bull Motors, Ltd., having had an experience which extends over a number of years. It is of the ventilated type, one hour' rated for 50 h.p. at 1,000 r.p.m., and is in accordance with the B.E.S.A. specification 173 of 1923.
Commutation is absolutely sparkless at any load up to 250 amps., with a field diversion of 33 per cent., whilst, apart from copper and insulation, steel is used for all revolving parts of the machine and also for the yoke and end brackets, Large roller bearings are fitted at each end, whilst there is a double-thrust race at the commutator end.
Provision is made for removing the armature, complete with the bearings and their housings in place on the shaft. This last-named is of large diameter, whilst all revolving parts are very carefully balanced before assembling, the whole armature being finally balanced when complete.
Adequate ventilation is _obtained through weatherproof inlets, paths being provided over the armature and through the core.
The speed curve of the motor is unusually good, the result being that the torque does not drop off rapidly at the higher speeds, and good acceleration is obtained without excessive diversion.
The controller, as we have stated, is foot-operated, and, having regard to the conditions in Shanghai, great importance is attached to the provision of control gear of a robust character with the most simple arrangement of connections. The advantage of foot operation is that the driver has his hands free for steering, sounding the alarm bell and operating the hand brake. There are certain disadvainages in taking an ordinary standard-type controller and placing it horizontally on the platform so that the control barrel, can be revolved by pressing the pedal. The objection to this is that, to return the pedal to the " off " position, a spring must he employed, that is to say, the pedal must be pushed outwards by the driver against spring pressure. The result is that, in overcoming the spring tension, it is almost impossible to notch the controller accurately when accelerating, so that contacts would very soon become badly burnt. As a result of a consideration of these disadvantages, there has been developed a controller in which the drum is operated by a pawl and ratchet, the pedal being pressed forward for a definite stroke for each notch of the controller. Thus, the contacts on the drums are always locked in their proper position under the fingers and do not become badly burnt, as so frequently happens when a spring is used to return the pedal to the " off " position.
The controller has six notches, five being plain resistance notches and the sixth a field shunting notch, giving an increase in speed due to one-third of the field current being shunted. To release the controller from any position the pedal is allowed to rise about 2 ins, above normal. The controller is then returned practically instantaneously to the " off " position. This arrangement of the pedal gives the " dead-man's" handle feature. On test it was found that the controller could be notched to the full " on " in• 5 sees. Even aeceleration is thus secured, and it is impossible with this system for a driver to abuse the motors or the transmission, whilst the result has been obtained without any complication of the contactor gear, and very little physical effort is required to apply the controller notch by notch. The working parts are of a substantial character, and special attention has been given to accessibility. That the controller is of ample capacity for its work is shown by the fact that it has been tested to 400 amps. at 500 volts, being approximately four times the full-load capacity of the motor. At this load the controller breaks the circuit without destructive arcing or other detrimental effect.
The E.M.B. Co.'s unbreakable jointless grid type of resistance has been adopted, and does not call for description here.
The trailer chassis follows in specification that of the trolley-bus, the dimensions, however, being as follow:— Frame-length overall, 18 ft.; wheelbase, 10 ft.; overhang behind rear axle, 4 ft. The frame height loaded and the wheel track are the same as in the rase of the trolley-bus.
The approximate weight of the chassis is 1 ton 10 cwt. 1 qr., of which 15 cwt. 2 qrs. is imposed on the front axle and 14 ewt. 3 qrs. on the rear axle. The approximate loaded weight of the trailer with 3i tons of passengers and body weighing n tons is 6 tons 15 cwt. 1 qr. In Shanghai the authorities reckon 20 passengers to the ton, so that the combined vehicle will be able to deal with a maximum load of 150 passengers. In the course of the tests a gross weight of 7 tons 11 cwt. 2 qrs. was imposed upon the tractor chassis, whilst on the trailer chassis a gross weight of 5 tons 15 cwt. 2 qrs. was imposed, making a total load of 13 tons 7 cwt.
In the course Of the acceleration tests it was proved that a speed of 14.4 M.p.h. was reached in 10 secs.. 182 m.p.h. in 15 sees. and -19.1 m.p.h. in 25 secs: Using the tractor only, a speed of 13.8 m.p.h. was reached in 6 secs., 17.6 m.p.h. in 10 sees., 19.5 m.p.h. in 15 secs. and 20.2 m.p.h. in 20 sees. As an instance of normal running, a route was taken totalling 1.56 miles in length. and nine stops of 10 sees. each were made on the way. The total time occupied was 9i mins., whilst the running time was 8 mins., the overall speed being 9.85 m.p.h, and the average speed during running time 11.7 m.p.h. The volts averaged about 450.