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National Debt to the TROLLEYBU r EQUIPMENT Maker Vital Importance
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of Proprietary Major Components in Trolleybus Production. Equipment Suppliers Largely Responsible for Success of Trolleybus Transport THE high cost of reconstructing tram track and the insistent public demand for greater comfort and speed in travel have resulted in a boom in the popularity of the trolleybus. This type of vehicle isnow in use all over the country and is doing much to make the public travel-minded. Bournemouth is but one of the towns in which trolleybus operation over a short period has brought astonishingly successful results.
The features of trolleybus transport which appeal so strongly to the public —its silence, smoothness, rapidity and safety—are largely due to the efforts of the equipment maker. To him is also due credit for low cost of working and maintenance—a matter of considerable importance to operators.
Weight of Motors Reduced.
Although laden weight has increased from about 8 tons for the original fourwheeled single-deckers to 131 tons in the case of modern six-wheeled doubledeckers, the weight of motors has been much reduced. Units of 80-90 h.p. are now produced weighing but 10f-111 cwt.. and showing improved commutation under more difficult conditions of operation.
The use of lightweight materials has enabled the weight of trolleys to be reduced from about 31 cwt. to 2f cwt. per bus. Wireless interference has been eliminated by the fitting of suitable devices, generally consisting of chokes inserted in the circuits of contactor coils and of auxiliary motors, together with screened wiring. In some cases,. special chokes in the main trolley circuit have been used Low-voltage lighting is now generally adopted, a charging generator or motor generator of about 1 kw. at 24 volts being employed.
Difficulties in connection with loss of effort in regenerative braking have been overcome by adding apparatus which causes rheostatic braking to follow on immediately after regeneration, without any further action on the part of the driver. .
Provision is now being made for the c58
propulsion of trolleybuses when disconnected from the main current supply. For this purpose, two 24-volt batteiies,. connected in parallel fort charging and in series for traction, are supplied.
Apart from the equipment of vehicles, considerable strides have been made in the development of efficient overhead apparatus. Where it is necessary to maintain a frequent tram service, while the overhead equipment is being converted to trolleybus working, considerable ingenuity is often required, and special measures have to be taken to ensure safety in the suspension of a considerable weight of cable. Much progress has been made in the design of overhead fittings, which have a greater bearing on efficient operation than might at first be imagined. '
B.T.H. electrical equipment, manufactured by the British ThomsonHouston Co., Ltd:, Rugby, is employed in Sunbeam trolleybuses, a make
which has recently achieved widespread popularity. The B.T.H. company produces a lightweight motor having a rated -speed of about 1;100 r.p.m. and, in conjunction with a 91-to-1 ratio and a 40-in, diameter wheel, affording a road speed of 30-35 m.p.h.
The control gear consists of a footoperated master controller, interlocked with a hand reverser and a set of electro-magnetic Contactors. 'A wire or strip resistance element, which is light in weight and resistant to vibration, is employed.
The English Electric Co., Lta., Stafford, collaborates with the Associated Equipment Co., Ltd., in the production of trolleybuses. All the equipment, except the trolleys and circuit breakers, is mounted on the chassis. The single self-ventilated motor is carried on four Floatex mountings supported from the chassis frame. In the A.E.C.-E.E.C. 761-type vehicle the motor is mounted outside the chassis. Power units ranging from 35 h.p. to 100 h.p. are available.
Controller Arrangement.
The controller for either the regenerative or the augmented series-field systems is of the foot-operated drum type, with which is interlocked a hand reverser. Only two types of contactor are used, both being electro-magnetic and equipped with powerful blow-outs.
The standard arrangement consists of two lightweight insulated trolleys mounted side by side on a common structure, and they can be supplied with any established type of wheel or slider head.
The General Electric Co., Ltd., Magnet House, Kingsway, London, W.C.2, which supplies the electrical apparatus for Leyland trolleybuses, has developed a series-parallel motor primarily for low-loading vehicles. The power units are mounted on each side of the chassis and .drive the two rear wheels on the respectiVe sides, thus obviating the need for a central differential.
A Simple Sykem.
To combat the tendency for drivers to omit using regeneration, the G.E.C. two-pedal system of regeneration has been evolved: One pedal applies power to the motors and the other controls both regeneration and the mechanical brake. The manufacturer has standardized three main types of motor suitable for 500-600-volt working, two being rated at 80 b.h.p. and the other at 40 b.h.p.
Windings are cooled by a " parallelflow " double fan mounted on the armature. The contactor is of the vertical plunger type with a compound operating arm. Two circuit breakers are installed. A wide range of equipment is manufactured by the Metropolitan-Vickers Electrical Co., Ltd., Trafford Park, Manchester, 17. Two of the motors are designated types 117 and 201 and are suitable for vehicles engaged on heavy city service. They are designed for operation either with compound-wound main field for regenerative control, or with. overwound series field for regulated held control.
Other items of equipment include shunt field resistances, radio-interference suppression coils, dectro-magnetic contactors and shunt-field contactors.
G. D. Peters and Co., Ltd., Windsor Works, Slough, is one of the prominent makers of trolleybus braking equipment, sponsoring the Girling-Consolidated air system. The mechanism is light in weight and the combination of the Girling system of shoe operation with Peters air-servo apparatus results in a highly efficient form of brake. The National Pneumatic-Peters system of door control is also popular for trolleybuses, its special feature being that if anything becomes trapped in the door, when it is closing, it immediately reopens.
Incidentally, . the Girling-Consolidated system is being used by Ransomes, Sims and Jefferies, Ltd., Orwell Works, Ipswich. This company has patented a design with which regenerative braking is obtainable not only on the controller pedal, but also on each depression of the service brake. This is followed automatically by rheostatic braking, where desired, whilst the air brakes are finally brought into use, simply by complete depression of the same pedal.
The company has also recently developed 4a new motor for combining with the air-compressor unit for the brakes, the complete motor and compres-s-or weighing only 116 lb.
Westinghouse Brake and Signal Co., Ltd., 82, York Road, London, Ni, needs no introduction as a maker of air brakes for trolleybuses. The pneumatic brake has the advantage that a reserve of power is available when the electric supply from the trolley wire is, for any reason, interrupted. The compressor is driven directly by an electric motor, which obtains its current from the trolley line. When the maximum air pressure is reached, an electric governor cuts off the current until the pressure falls to the predetermined minimum, when it cuts in.
Lighting Improvements.
So far as lighting is concerned, C.A.V.-Bosch, Ltd., Acton, London, W., has given much attention to the development of its low-voltage system, which is claimed to be silent and free from vibration. It embraces a singleshaft motor generator set, which meets all present-day requirements, including manreuvring by means of the batteries.
Among bearings for trolleybus use manufactured by Ransome and Marina Bearing Co., Ltd., Newark-on-Trent, are units for incorporation in motors and trolleybuses.
Apart from components for vehicles, there is a big field for the sale of auxiliary equipment, such as overhead fittings. British Insulated Cables, Ltd., Prescot, Lanes,, markets Rampend fittings for trolleybus lines, for which interesting claims are made.
Clough, Smith and Co., Ltd., 36, Victoria Street, London, S.W.1, is a concern which has had wide experience in the supply and, fitting of overhead systems, and has undertaken some difficult contracts, that carried out at Portsmouth being an example.