Another Long Motorbus Trip and
Page 11
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On Wednesday of last week, at the invitation of Mr. Bernard Hopps, a representative of this journal accompanied the British Thomson-Houston petrol-electric bus during a considerable part of its journey from the makers' works at Rugby to the scene of the Herefordshire Automobile Club's hill-climbing contest at Frome's Hill. The report was too late for last week's issue. All necessary arrangements were made for the recording, throughout the journey, of the speeds attained, the petrol consumption, and the temperature of the commutators (after long runs on a give-and-take road, and again after a particularly long and trying hill-climb), the condition and weight of the vehicle having been ascertained, the tanks filled, and the reading of the cyclometer carefully noted, before leaving Rugby. The gross weight of the bus, on which there was a large quantity of stores and testing apparatus, was 5 tons 12cwt., and its running weight with the driver and four passengers would not be far short of 6 tons. The cyclometer was calibrated for a wheel fitted with a rubber tire in a partly-worn condition, i.e., with its diameter reduced by one inch through wear, but, as the tire was up to its original diarffeter, an addition of four per cent, to the cyclometer readings became necessary.
A start was made at 11 o'clock exactly, the cyclometer reading 4f)2.5 miles, to the accompaniment of dull weather and heavy roads. Not more than two miles had been travelled when the vehicle gently came to rest, and it was found that the petrol cock had, in some mysterious way, become closed. During the one-minute stop, this was made right, and the cock tightened up sufficiently to prevent a recurrence of the same trouble : with this single exception, there were no involuntarystops, the 30h.p. Wolseley-Siddeley engine, and the electrical transmission gear, running with a regularity and smoothness which would have been quite a revelation to anyone having experience only of the change-speed type of transmission. Although the writer closely watched the brushes on the generator while runring, for some time, sparking took place very seldom indeed, and the sparks were extremely minute.
It was intended to halt first at Stratford-on-Avon, and the route was via Dunchurch, Bubbenhall, Leamington, and Warwick, and we arrived just outside Stratford at 12.48 p.m. with the cyclometer reading 428.25 miles. Allowing for the 4 per cent, difference in the reading of the cyclometer, 26.75 miles had been traversed at an average speed of 14.8 miles an hour. During this part of the journey, the vehicle was timed over a mile of average road, without obstruction, finishing with a slight up-grade, and was found to have covered the distance in 3 minutes 10 seconds, or, at a speed of 19 miles an hour, the in-put at the motors during the run being 16 kilo-watts (100 amperes at 160 volts).
The petrol tank was now re-filled, and the amount put in was carefully noted and found to be 3.33 gallons : the consumption had, therefore, been at the rate of one gallon for every 8.1 miles, and this, considering the heavy state of the road during the early part of the journey, must be considered very satisfactory. The temperatures of the motor commutators were taken at the end of this part of the journey, and were as follow :-Near-side motor, 32.5 degrees Cent. (90.5 degrees Fahr.); off-side motor, 29.5 degrees Cent. (85 degrees Fahr.). The atmospheric temperature was 11.5 degrees Cent. (53 degrees Fahr.). After luncheon at the Shakespeare Hotel, the journey was resumed at 2.36 p.m., with the cyclometer reading 429 miles, and the petrol tank quite full. By this time, the roads had greatly improved, and, in fact, were beginning to show signs of being dusty. Cheerful sunshine tempted the passengers to the top deck, and all were immediately engaged in the exciting game of tree-dodging. Three traffic stops were made during the second portion of the journey-Stratford to Malvern, one ol them occurring at Bidford, where the horse attached to the "police trap" of the local superintendent of police exhibited resentment at the coming of the motorbus into that part of the country. Beyond these three stops, nothing occurred to mar the enjoyment of the run to Malvern Wells, via Bardon Hill, Bid' ford, Evesham, Pershore and Upton-on-Severn, and we arrived at the Hornold Arms Hotel, Malvern Wells, at .5.15 p.m., with the cyclometer reading 462.5 miles. Allowing for the three stops named, and which amounted to 3.5 minutes, the running time was 2 hours 29.5 minutes, and the average speed for the 33.84 miles (reckoning the 4 per oent. added to cyclometer reading) had been 13.6 miles an hour. The petrol consumption for this section of the journey totalled 4.875 gallons, giving ai average consumption of one gallon for each 6.9 miles. The higher consumption on this part of the journey is accounted for by the hilly nature of the last few miles of road : from Uptonon-Severn to the hotel the vehicle ascended about 500 feet.
After tea the journey was resumed, over the Malvern Hills, to Ledbury, where it had been decided to stay the night. Leaving the Hornold Arms Hotel at 6.21 p.m., with petrol tank again filled and cyclometer reading 462.5 miles, it was resolved to make the stiff climb through the Wyche cutting, and again to take the petrol consumption and motor temperatures at the hill-top. The vehicle climbed remarkably well, accelerating from time to time according to the varying gradient, and maintained an average speed of eight miles an hour. The petrol consumption along this exacting section averaged one gallon per 4.65 miles. The temperatures of the motor armatures at the top were :-Near-side motor, 41.5 degrees Cent. (106 degrees Fahr.); off-side motor, 34.5 degrees Cent. (94 degrees Fahr.). The atmospheric temperature was 6.75 degrees Cent. (44 degrees Fahr.). The temperatures of the commutators were thus well below those permissible, and commonly reached, on many tramway motors, in spite of the great length of the hill-about 1.33 mile. Most of the hill was climbed with the motors in parallel, and, indeed, it was only for two short periods on this hill that the series control was brought into operation. At no other time during the journey was this latter form of control employed. The average speed from Rugby to this point had been 14.28 miles an hour, and the average rate of petrol consumption was one gallon for every 7.10 miles. From the top of the Wyche cutting to Ledbury, being on a down-grade, it was not considered reasonable to take petrol consumption into account, but the holding power of the brakes was amply shown. The smoothness of running, freedom from mechanical or other troubles, absence of vibration, ease of control and extreme comfort were points which greatly impressed the writer. Our representative had the opportunity of travelling in the omnibus, during its ascent of Frome's Hill in the contest promoted by the Herefordshire Automobile Club, being, in fact, the only passenger, besides Mr. Bernard Hopps and the two members of his staff, who shared the driving seat with him. A passenger was required to bring the total weight to that stated in the entry, and Mr. Hopps arranged that the seat should be given to "THE COMMERCIAL MOTOR." The length of the portion of the hill used for the climb was 3,867 feet, with a total rise of 344.61 feet, giving an average gradient of 1 in 11.22, the steepest portion of the gradient being 1 in 6.37 for 25 yards, another 80 yards being but slightly easier in the slope. There was a favouring wind, but, sitting on the top of the omnibus, the effect experienced was simply an absence of draught and, as the vehicle occupied 9min. 54sec. in the ascent, the force of the wind could not have materially helped, otherwise the wind would have been noticed in the position in which our representative sat. The, omnibus went from start ' to finish without a falter. The pace varied according to the gradient, but the hum of the engine was continuous, showing that it was never "in trouble" throughout the climb. The quietness with which the vehicle travelled was very noticeable, whilst the absence of jerking and jolting was also marked. Its average speed up the hill exceeded 4/5 miles an hour.
In view of certain criticisms that the generator on motors might break down if subjected to damp weather, it is interesting to know that the vehicle was left outside without any protection from the rain of Wednesday night, without causing any ill-effect to the electrical equipment. This is owing to the thorough method, which the makers employ, in impregnating the windings, under vacuum, with a special compound ; moisture is thus prevented from reaching the windings.