DEMONSTRATING A NEW TROLLEY-BUS.
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The Latest Garrett Passenger Vehicle Under Test. Features of its Design and Capabilities.
BY arrangement with the Ipswich Corporation a demonstration of the new Garrett trolley-bus was given on August 12th, partly over routes already cevered by vehicles of the railless type and partly by the conventional tramcar.
As a testing ground, the town is suited for the purpose by reason of its narrow and winding streets, a test hill, and the sound-intensifying properties of the town's thoroughfares. It is interesting to note that Ipswich was one of the first towns to adopt the railed horse tram, and it is likewise the pioneer of the trolley-bus. The vehicle in question is, of course, made at the Leiston works of Richard Garrett and Sons, Ltd., but the motor, a Bull, is an Ipswich product. The body of the demonstration bus is by C. H. Roe, Ltd., of Leeds, but coachwork of Suffolk origin is obtainable on the chassis.
A description of the latest product of the Garrett works was given in The Commercial Motor -dated July 14th, but it may be well to deal briefly with some of the more prominent features of the vehicle before passing on to its performance on the trial in question.
The leading dimensions are :—Wheelbase, 15 ft. 6 ins.; track, 6 ft. 4 ins.; overall width, 7 ft. 6 ins. ; but it should be noted that the wheelbase can be altered to snit any particular requirements. Thirty-seven seats are provided on the demonstration vehicle, but this also can be varied, as can the type of body—i.e., for one or two-man operation.
The chassis frame is a substantial job and can be supplied in three forms giving platform heights to meet various requirements. The strength of the chassis is vouched for by the fact that, on test, a load of 79 adults,and two children has been carried up a gradient of 1 in 30 at 18 m.p.h. The suspension is by semielliptic springs all round, which are
fitted with oilless shackle bushes, thus facilitating the work of maintenance.
Both axles are remarkably robust jobs, the products of the vehicle manufacturers. Au I-section steel stamping forms the front one, which provides centre,point steering. Drive and torque are taken through the springs, but the rear axle is of more than orl4inary proportions and the balls in the thrust bearings on the worm shaft are no less than
ins, in diameter; these are of Hoffmann make.
For so large a vehicle the steering is very light, being by worm and wheel mounted on ball bearings throughout. The column is inclined forwards at the top and the gear is mounted at the upper end, being out of the way of dust and mud. No doubt the centre-point steering has much to do with the easy motion of the wheel.
Steel disc wheels, mounted on roller bearings, carry Dunlap tyres, 160 mm. for 850 mm. rim at the front and 340 eam. for 850 mm. rim twin tyres at the rear. The brakes are both of the internal-expandingtype, working in 24-in, drums in the rear wheels. Each drum is 7 ins, wide, and Ferodo linings are used ; easy adjustment is provided for.
A short propeller shaft transmits the power from the motor to the rear axle through two Hardy flexible couplings, which are claimed to add resilience to the drive in addition to their duty of providing the required degree of angular flexibility. A point worthy of sppcial note is that ball bearings are used to centre the joints. thus taking the weight of the shaft and reducing the possibility of vibration.
Coming now to the motor—one of the most important parts of the vehicle— this is a 50 h.p. Bull unit, the armature of which revolves on roller bearings and is also equipped ' with a double-thrust bearing. Accessible greasers mounted on tubular extensions are provided, and the windings are stayed. The type of motor in question differs in minor details only from those ordered for the Shanghai trolley-buses. On the demonstration chassis, however, the motor runs -slightly faster—i.e., 1.385 revs, at a road speed of 15 m.p.h. and 2,000 revs. at 22 m.p.h. The armature can be removed without disturbing the bearings with the motor mounted in its cradle.
Turning to the oontrol system, simplicity is most marked, the left pedal used being an ordinary accelerator and the right one operates one pair of brakes. There are no levers in proximity to the steering wheel. The controller pedal has eight definite "notches" for forward speeds and a speedometer is mounted in full view of the driver.
The body fitted to the bus in question is of the side-entrance type, having double swing doors on the near side and an easily operated emergency door at the rear which is controlled from the interior only. Forward of the entrance, the ventilating windows open at the leading ends and those behind the
entrance in the reverse directioa, In addition there is a ventilator in the centre of the front of the body and air currents can be directed at will. The large windows are fixed, and many of the fittings and rails are of duralurnin. A further example of the endeavour to reduce weight may be mentioned, the brake shoes being of aluminium.
There are five interior roof lights and handrails, but no straps. The latter
would appear to be desirable additions, as short passengers find the rails rather too high to be comfortable. The backs of the seats are mounted on springs, giving a degree of flexibility which is rather more comfortable than the usual rigid squab. The extreme front and rear seats extend the full width of the body, but the remainder, and the seat opposite the entrance, hold two persons
each. • Starting from the centre of Ipswich, with about three-quarters of the seats occupied, the bus was driven over the Whearsted route and covered 1i miles in slightly under 10 minutes ; it must be remembered that the narrow streets and traffic conditions prohibited the use of the maximum speed or acceleration of which the vehicle was capable for more than a few yards at a time. Owing to the presence of workmen and an excavation job which was in progress it was not possible to turn the vehicle in one circle, but the space occupied in turning waa small for avehicle of 26 ft. overall length.
Several stretches of cobbles were traversed, but riding was comfortable in all circumstanCes. The unladen weight was about 5 tons. Silence, both' of motor and chassis parts, was of a high order and formed a marked contrast to the clattering and clanging of the trams.
On another route, owing to there not being two overhead wires, it was necessary to use a " skate " to provide a path for the current, but nevertheless an ascent of Bishops Hill, with its average gradient of 1 in 10, was accomplished at 32 m.p.h. A restart was made on a portion reputed to be 1 in 8 and a speed of 10 m.p.h, was attained in 8 secs. The working of the brakes was smooth but powerful, the foot brake, as a rule, only being employed. Acceleration was both sweet and rapid, 10 m.p.h. being reached on the level in 4 secs.
The coachwork proved to be free from rattles and drumming and entrance and exit were easy, the doors giving a clear opening of 4 ft. A minor improvement which appears desirable is the substitution of the centre wooden panel in the driver's partition by a glass one so that passengers may obtain a better view ahead to ascertain whether they are close to their destination.
On the whole, the performance was very creditable and was worthy of a company who have had a lengthy experience with the design ind construction of electrically propelled vehicles of several types.
Messrs. Garrett have tackled the problem of designing a trolley-bus from the electric road vehicle standpoint, of which it is a logical development, rather than from that of the modified tramcar. Throughout the chassis solidity and simplicity appear to have been governing factors, and these , ports should be reflected in sound service in users' hands.
It is interesting to recall that the makers have been established since 1770, and that they were responsible, for the "Steam Horse" in the early part of the 19th century. The manufacture of Garrett vehicles is carried out under one management and very few parts are made outside the works of the associated concerns. As trams are being rapidly replaced in various districts by trolley-buses, the latest activity of this Suffolk company bids fair to take a prominent part in their programme. '
Keighley, Bradford, Leeds and Ipswich authorities have had demonstrations of the Garrett bus, and, we gather, a favourable reception has been accorded to it in each place. Its maximum speed, about 22 m.p.h., ease of control and general manceuvrability render it suitable for operation in both open and congested areas.