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Why the LEGAL WEIGHT LIMIT OF THE DOUBLE-DECKER Should be Raised
Page 102
Page 103
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TT is difficult to conceive any good reason why, with the same type of vehicle, an extra weight of three tons for the carrying of goods should be allowed over the maximum weight allowed for the carrying of passengers, more especially as the overloading on goods vehicles is more difficult to control because it is less obvious.
Nevertheless, reasons there must be. Those reasons, I imagine, are bound up, more or less, with -three important points :—(a) The wear and tear on road surfaces arising from the weight of the vehicle; (b) the wear and tear on roads arising from the speed of the vehicle ; (c) the loss of life and limb through the uncontrolled speed of vehicles upon which no weight limitation is fixed.
Talere is a definite connection between weight limitation as imposed by Government regulations, permissible maximum road speeds such as it is now proposed to introduce, and the charge for road upkeep.
Anomalous Position of the Manufacturer.
Road construction is conceived, controlled and carried Out by a Government department. Motor manufacture and operation are mainly affairs of private enterprise. We are thus in an anomalous position. Those responsible for the construction and maintenance of the highways are prescribing, to a very highly developed and specialized branch of the engineering industry, the type of vehicle which it should employ, in the main interests of the roads on which they are to run.
A greater measure of co-operation would appear to be netessary. In the particular ease of the large fourwheeler it is within the knowledge of those connected with the commercial-vehicle industry that manufacturers were invited by the Ministry of Transport to state their constructional requirements as regards weight and overall length. It is also fairly generally known that a maximum weight of 10 tons fully laden was asked for, with a maximum weight on any one D24 axle not to exceed 6 tons. The industry had in mind as a maximum the doubledeck four-wheeled vehicle to carry up to 54 passengers. From an operating standpoint this vehicle represents to the community the most economically worked unit.
The manufacturers were informed by the then Minister of Transport that these weights could not be granted. In a sincere desire to help they agreed among themselves that a maximum -weight of tons would be technically and commercially possible without any undue violation of the safety margin.
This desire to help, it seems, was not appreciated, and it would appear that the M. of T. took the view that the makers were allowing themselves considerable latitude, as a Statutory Rule and Order of 1927 was afterwards issued prescribing a maximum laden weight of nine tons for the class of vehicle in question, with a limitation of 5i tons weight on any one axle.
No manufacturer in his senses, and certainly no operator who studies his business, would neglect to avail himself of any opportunity which presented itself of reducing the total unladen weight of his vehicle if it were possible to do so without incurring grave risks. The actual effect of the Statutory Rule has been to force the manufacturer to regard the total of nine tons as a minimum practicable instead of, as was intended, the maximum permissible.
• Sacrificing Seating Accommodation.
To produce to-day a vehicle within the weight limit can only be satisfactorily effected by a sacrifice of seating capacity, and this turns a vehicle into an uneconomic unit, with an additional disability of having to reduce seating capacity still further in order to provide more powerful lighting, more efficient braking, and greater comfort for passengers—to say nothing of the imposition by the Ministry of Transport of further public safeguards which might add to the weight of the vehicle as previously fixed.
It is an impossible situation that the maximum permitted weight should already have been reached, and in some cases exceeded, leaving no margin whatever for the development of the road vehicle so necessary in these days of progress. As the matter stands to-day no improvement which adds to the /weight can be effected without cutting down to unsafe limits the weight of the body or of the chassis, or, as indicated above, turning the vehicle into one of lower seating capacity.
It is difficult, in the absence of any particular formula of information as to the effect on road wear of an extra ton of weight, to imagine any sound argument for the retention of the nine-tons weight limit which is causing some manufacturers and operators such acute distress. It is still more difficult to conceive that the effect of an extra ton of weight, which would be such a useful help to us, would not be more than counterbalanced by the proposal to limit the permissible speeds of heavy fourwheelers—that is to say, in its effect on road-maintenance costs. Considering the matter from another aspect, the weight limitation imposes upon the manufacturer and the operator the following, to them, important limitations :— (a) The use of oil engines for passenger-carrying vehicles is, by reason of the weight limitation, definitely ruled out.
(b) Any new type of transmission which weighs much more than the present form (admitted to be the least satisfactory unit of the present-clay vehicle) could only be introduced by a redesign of the rest of the vehicle with the attendant danger of reducing safety factors too far.
(c) No vehicle can be produced and popularized in this country which is suitable for export to foreign markets where the roads and highways are not as favourable to the road vehicle as our own.
We are thus condemned to the use of petrol—a foreign product—because it permits the lightest form of engine, and to a type of vehicle which, whilst suitable for British roads, is not suitable for abroad.
Readers of The Commercial Motor may be interested to know sonic details of the struggle my company has had over the past two years in endeavouring to produce a 52-seater double-deck petrol-electric vehicle to come within the weight limit of nine tons. Working backwards from this given weight it was found first of all impossible, owing to the axle-weight limitations, to locate the electric motor in a special position which would have been very much in its favour. It was proposed to put the mritor in the unused space underneath the stairway. This was found perfectly feasible and practical in trials, but the back-axle weight limitation was slightly exceeded.
The Use of Lightweight Metals.
The dynamo and motor, which replace the gearbox, represented a handicap in the weight of something like 7i cwt. This weight had to be saved in other directions. A special study of light-weight metals was made and visits were paid by our engineers to the Continent in this pursuit. A matter of 5 cwt, was saved without any additional constructional risk—but at greater cost.
A calculated weight of the chassis left a matter of 37 cwt. which had to include the construction of a complete double-saloon body. This was accomplished also at great cost, and represents perhaps the finest piece of body-building work (not excluding metal ones) which has yet been accomplished in this or any other country.
The vehicle, when constructed, weighed a few pounds less than the maximum weight. It passed the London police, but had it been presented on a wet day it is quite possible that it would have been turned down.
The Braking Problem.
The next difficulty was that no amount of scheming would permit us to put on any other braking system than one which, although it fulfilled the Ministry of Transport regulations, was not powerful enough to satisfy either the prospective user or ourselves—this being due to smaller wheels• and smaller brake drums consequent on the requirement of a low floor line. The addition of a servo motor became necessary, and this proved to be the last straw.
Thus the petrol-electric system, as 'such, developed to bring it up to modern practice and to fulfill all regu lations, was defeated by a matter of 2 or 3 cwt. All further developments have to be hung up until the Ministry of Transport sees its way to remedy a state of affairs which is bearing unjustly upon manufacturers of orthodox vehicles and, to a still greater extent, upon ourselves. I think that the important point for manufacturers and operators is to find a remedy for their lack of representation or voice in the decisions of the Ministry of Transport on this important question of bus weight. It would not be difficult, I imagine, for the Minister to appoint an advisory committee with direct access to him in case of any disagreement with his departments on important principles. It is hard to conceive any difficulty arising in this connection so long as the Ministry has the help of such men as Sir Henry Maybury and Col. Bressey. The relation of regulated axle weights and area of surface contact of tyres at regulated vehicle speeds should not present any insoluble problems, and the information as to road requirements which such a committee could transmit to the industry would ensure the co-operation of manufacturers and operators.