95-seater the Double-decker qf the Future
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ADESIGN for a 35-ft. 95-seater with a horizontal rear engine was outlined by Mr. Clayton as the double-decker of the future. He estimated that its cost would not exceed that of existing models by more than £500. Of this sum. i100-£150 would be represented by a divided rear axle, which
would keep floor height and steps to a minimum, One accident to a passenger who slipped on a step. in a ,gangway necessitated by the use of a normal rear axle could cost more than £150..
The upper saloon,' which would not be regularly used, would seat 51 passengers in fairly austere accommodation. The lower saloon. would have 44 seats on a practically flat floor„ with seats back-toback over the rear wheel-arches. The straight staircase would be on the nearside and approached directly from the entrance ahead of the front wheels.
Semi-integral construction with a lightweight chassis frame was proposed. The wheelbase would be 19 ft. and the unladen weight was estimated as 9 torts, enabling a 10-litre engine to he employed.
Fewer Buses • Comparing the present position " of Liverpool Corporation's fleet with that which would follow the introduction of 95-seaters, Mr. Clayton said the existing 1,100 buses (averaging 57.51 seats each) could be reduced to 810, including engineering spares. He expected mileage to drop from the present annual figure of 42m. to ?;6m. (a -saving of 41m. miles at peaks and 11-m. miles at other .neriods).
The average annual mileage per bus would rise from 38,000 to 48,000, thus helping to spread overheads and reduce costs.
The cost per mile of maintenance and cleaning was expected to be 10 per cent. greater than at present. Despite an increase in fuel-consumption rate from 9.3 m.p.g. to 8 m.p.g., the total cost of fuel and renewals would be lower. An annual saving of at least £524,000, including £400,000 on wages, was visualized. Present costs would thus be cut by 10 per cent.
Mr. Clayton's design was based on the use of the lower deck as the main passenger compartment, with the upper saloon for peak traffic. The stairs would normally be barred and the upper deck would be regarded as an overload compartment. In fact, for the greater part of its time the vehicle would be operated as a single-decker.
The design was based on the belief that there must be a more positive .approach to the problem of attracting passengers, especially at off-peaks, and that the number of buses must be reduced to ease congestion. Mr. Clayton listed the following as important points for consideration:— To Attract Traffic (1) Higher seating capacity in the lower saloon, with a minimum of longitudinal seats. (2) Front entrance with drivercontrolled doors,(3) Maximum safety for passengers. (4) Easy entrance and exit with a flat floor. (5) Efficient saloon heater and ventilator. (6) Maximum time to be spent by conductors in collecting fares. (7) Quiet running by vehicles. (8) Pleasing colour snheme and tasteful fittings.
To reduce costs, maximum seating capacity was required at peak hours, greater attention must be paid to detail design to cut maintenance, and bodywork must be designed for interchangeability of parts and to facilitate repairs.
Basing his calculations on Liverpool Corporation's experionce, he said that the labour cost of chassis maintenance had decreased by 10 per cent. between 1952-53 and 1957-58, and material cost by 29 per cent. The overall combined reduction was 19 per cent. In the case of bodywork maintenance, the cost of materials remained stable, but labour costs had risen by 15 per cent., with an overall increase of 11 per cent.
£11,000 Saved
By using detergent lubricating oils, chromium-plated piston rings, and giving close attention to the surface finish of cylinder liners, nearly £11,000 was saved in 1957-58 on fuel and oil costs, apart from economies in maintenance. Costs of body maintenance had risen principally because of inadequate rust-proofing of some coachwork made immediately after the war, the introduction of the 8-ft.wide body, and "the so-called lightweight body of steel construction."
Comparing identical bodies mounted on different makes of chassis and operating under similar conditions, it had been observed that structural defects occurred in one body and not in another. This fact emphasized the need for the fullest co-operation between chassis manufacturers and bodybuilders.
Over a life of 18 years the cost of maintaining a bus, excluding overhead charges, tyres, cleaning and lubrication, was about three times the original price, and much greater thought should be given to the matter.
Sample figures taken in January and July last year showed that 38 per cent. of the chassis defects occurring on the road concerned brakes. Transmission defects amounted to 12 per cent., of which 9 per cent, were clutch troubles. Almost half the faults occurring on the road resulted from stopping and starting.
Long-term research should be conducted into the absorption of a large proportion of the energy generated by braking by means other than sliding friction. Inertia fly-wheels were being tried, but extensive problems would have to be overcome before they could be satisfactorily applied to double-deck buses, Another method of attack would be the development of the fluid-coupling principle for the absorption of energy, heat being carried away by fluid to a radiator. A small fluid coupling driven through a step-up ratio from the rear of the gearbox was suggested. If most of the energy generated by deceleration could be absorbed in this way, the size of friction brakes could be reduced and smaller wheels could be used, allowing wheel-arches to he made smaller.
A.C. generation, permitting high charging rates, coupled to a transistorized regulator would help to reduce electrical defects.
Unit Construction Unpopular
Mr. Clayton deprecated the unit construction of engine, clutch and gearbox. On a certain make of vehicle operated in Liverpool, the gearbox failed six times and the clutch 10 times for every engine failure. In the life of the engine the gearbox had to be taken down 16 times, instead of six, usually to obtain access to the clutch.
In practice, costs were further increased because when the gearbox was removed, the clutch was often refaced as a precautionary measure, although it would have served for a further period. Similarly, the gearbox was often given attention that was not essential when it .had to be taken down to reface the clutch.
He was not enamoured of the practice of mounting large numbers of units on a sub-frame.
At 1.iverpool, body maintenance represented 36 per cent. of total main
tenance costs. Last year 53 per cent. of the buses involved in collisions were damaged at the front end, and 29.3 per cent, at the rear. Mechanical damage could be rectified in two or three days, but body damage often took weeks to repair. Mr. Clayton suggested that front and rear sections of a body should be bolted onto the main structure.
Of accidents to passengers. about 51 per cent, occurred in boarding or alighting. Driver-operated doors were an important safety. feature. Injuries caused in sudden stops comprised the third largest category. Injuries to people falling on stairs still presented a serious problem. A straight staircase with a landing and rectangular treads was to be preferred to the spiral type with tapered treads. Steps inside the saloon should be avoided if possible.
The trend towards largerdouble-deckers was shown in figures. In 1956, 66 per cent, of the double-deckers built for the home market were 56-60-seaters, whereas last year the proportion dropped to 31 per cent. The percentage of 61-65-seaters in the two years had risen from 30.6 to 39.3. Even more significant was the rise in popularity of the 71-75-seater, which in 1956 represented 0.3 per cent. of output, and last year, 17.9 per cent.
Although body output over the past three years had been falling, the proportion of high-bridge and low-bridge types had remained remarkably constant.
More Front Entrances
A rear entrance was generally used in buses seating 65 or fewer passengers. Of the 66-70-seaters built last year, however, 40.9 per cent, had front entrances, and in the case of vehicles with more than 10 seats, the proportion of front entrances was 38.2 per cent.
A front-entrance bus with poweroperated doors took slightly longer to . load than a rear-entrance vehicle. In Liverpool, the average length of stop by a front-entrance bus was 8.6 seconds, and by a rear-entrance vehicle, 7.5 seconds. Limited observation suggested that loading times were slightly shorter with the front entrance forward of the wheels than with it behind the axle.
The prospect of larger vehicles and increasing traffic congestion raised problems of fuel consumption. Experience showed that as stops became more frequent,. the relative rise in fuel consumption declined per unit weight in crea se.
Consumption Not Progressive The fuel-consumption rate of a vehicle weighing 10 tons laden was 1 m.p.g. higher at three stops per mile than at two, but only 0.3 m.p.g. greater when making eight stops per mite instead of seven. Averaging four stops a mile, a bus with an average laden weight of 94, tons returned 9 m.p.g„ but under peak city conditions the consumption rate was only 6,4 m.p.g. Optimum gearbox and rear-axle ratios were essential if the lowest possible fuel consumption were to he achieved.
Mr. Clayton questioned whether weight should be reduced by relaxing standards of comfort and weakening the structure. rather than by extending the use of more costly light alloys. Under average operating conditions, with an annual mileage of 45,000 and an average consumption rate of 9 m.p.g., any saving in weight over 2.4 cwt. per £100 of additional cost would be of advantage to the operator. If the annual mileage were only 30,000 there must be a saving in weight of more than 3.6 'eWt. per £100.