HOW I THINK MY COACH COULD BE IMPROVED.
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Pneumatic Tyres. Low Centre of Gravity. Four-wheel Brakes Operated by Momentum of Vehicle. Hydraulic Brakes. Electrical Transmission. Electra-magnetic Braking. Underslung Chassis. No Multiple Doors. Tip-up Seats, Each with Windscreen,.
By CECIL V. CLARKE (1st Prize Winner).
ICONSIDER the majority of motor coaches on the road to-day are open to adverse criticism in respect to the performance of the following components,'and the design and arrangement of the following details :.—
Tyres, wheel construction, and suspension. Brakes.
Gear ratios.
Total unladen weight. Weight distribution when loaded and position of centre of gravity. Body construction.
It must be borne in mind, however, that the
. majority of these faults are die to the fact that nearly all motor coach chassis were originally designed for haulage work at speeds not in excess of 12 m.p.h. When used as =motor coaches they run at nearer 20 m.p.h. with an.over-run engine, and often a very topheavy load.
It is naturally the aim of motor coach manufacturens to make their vehicles attain, and in some respects beat, the road performance of the average modern motorcar.
The motor coach is already a more economical vehicle than the car, but it is still much slower than it need be' and is uncomfortable in comparison with,
even the cheapest cars. .
Few of the people who travel as passengers in solid tvred motor coaches appreciate how uncomfortable they really are. This is often because they have not had sufficient experience of private carmotori ng. In addition, they are out to enjoy themselves.at all costs and, consequently, are in an easily-pleased frame of mind.
I will nowtendeavour to show how I think the motor coach can be improved.
Chassis Improvements. .
First of all, it is absolutely essential for the vehicle to run on pneumatic tyres. Personally I do not consider the Giant pneumatic the best type, but prefer the medium-sized twin tyre for the rear, and the single similar tyre for the front wheels. This arrangement means that all wheels and tyres can be inter
changeable ; only one spare is needed, and the weight of a single wheel and tyre is such that it can be easily handled by one matt. Provision should be made for the inflation of these tyres by an engine-driven pump. The adoption of the pneumatic tyre enables a considerable weight reduction to be effected. Wheel, axle, and, consequently, unsprung weight can be materially reduced. Springs, spring brackets, and many other parts can be Safely made considerably lighter when they are insulated from excessive road vibration.
This weight reduction, and the lesser road resistance obtained by the use of pneumatic tyres will enable the maximum safe speed of the motor coach, and consequently its range, to be increased, provided, however, the weight distribution, brakes and gear ratios are correctly proportioned.
High Speeds and Braking.
I consider the speed of 30 m.p.h. on main roads per featly safe, provided the vehicle is equipped with a minimum of five speeds (if gear driven), a, considerably lower centre of gravity than that of the majority of motor coaches, and four-wheel brakes.
The four-wheel foot brake should be operated by the momentum of the vehicle, and not by any effort made by the driver. (I do not consider it possible to provide really effective .brakes operated by manual power for vehicles of this weight when travelling at over 12 'm.p.h.) The side brake, merely to hold the vehicle when at rest, would be manually operated. For coaches having the Orthodox clutch and gearbox transmission, I should favour hydraulic brakes, as they can be constructed with far fewer parts than the ordinary type actuated by rods and levers.
Alternative Transmission Systems ?
As an ideal, although I am afraid that at present the cost of manufacture would be rather prohibitive, I consider the electrical transmission as applied to the Crown magnetic car to be most. suitable for a vehicle of this type. Given a speed range from zero to E0 m.p.h., and an engine of about 40 h.p. nominal, and it should be possible to design an even move efficient electrical transmission than is possible with a car having a greater speed range. In addition, the system provides for ideal four-wheel electro-magnetic braking, i.e., one would have as much control over his vehicle as an electric tram driver. Also, there are the advantages of silence in operation and simplicity of control. For absence of all noise a sleevevalve engine would make the best combination with the electrical transmission. To obtain greater stability the chassis could well be underslung. This would also enable a nearly straight transmission line to be obtained. Seeing that the effect of road shocks becomes less as the dimensions of wheels, tracks:and wheelbases are increased, one can well argue that a well-designed pneumatic-tyred motor coach can be made to run more smoothly than a Rolls-Royce. This, I believe, is possible, but as yet I have not had the pleasure of riding in, or driving, one which did.
Ideas on Bodywork.
The usual type of body with multiple doors on each side, or even on one side, I do not consider at all satisfactory. Chassis will always distort when passing over or standing on uneven ground, and the consequent distortion of the body means rattling doors. One bad door is enough, but I have driven coaches
that' had a regular chorus of door chatterings! I consider the most suitable type of body to be 23-seater, inclusive of driver. There are no side doors except one on each side at the front. An emergency door can be provided in the centre of the back. The seats would be arranged in five rows behind the driver, four per row with a centre gangway. The seats to be. of the tip-up theatre stall type with arms. As the coach would travel at 30 m.p.h., a windscreen in front of every alternate row of seats would be essential. I am afraid the vehicle I have outlined is in the dim and distant future, but when it does appear–I shall endeavour to get a job driving one of them. The term. "poetry of motion" may then be applied to motor 'coaching.