FOR several years experiments have been carried out with a view to overcoming the noise and springing defects of the steel-tyred passenger train. Solid and pneumatic rubber-tyred wheels have been designed and tested on railway tracks ; satisfactory types of pneumatic-tyred wheels have been evolved and are in service on the Continent and have been introduced into Great Britain. Apart from the much quieter running of pneumatic-tyred rail coaches, there is better riding comfort, so that the benefits of this type of wheel are twofold.
The pneumatic type of rail wheel has not, however, been fitted to the ordinary coaches drawn by steam locomotives, but to petrol-engined rail-coaches of the single-unit pattern. Whether it will be applied to the former class of coach is, at the time of writing, not certain, but it would effect a big advance in railway comfort.
Early in 1932, following the results of tests made with pneumatic-tyred rail-coaches by the Micheline Company in France, a coach of this type was tested in England, between Bletchley and Oxford on the London Midland and Scottish Railway. The coach had ten pneumatic-tyred wheels, three in front and two behind, and was driven by a petrol engine of 27 h.p.
The special pneumatic tyres, fitted with metal flanges in order to keep the coach on the rails, were inflated to a pressure of 85 lb. per sq. in. Inside the tyre was a wooden hoop which allowed of deflation to the extent of 3/8 in. only, so that there was no possibility of the coach being derailed by deflated tyres. It is claimed that this type of tyre has an adhesion which is three times as great—due to the greater frictional coefficient of rubber—as that of a steel-tyred wheel.
A further advantage of the pneumatic-tyred wheel is that it prevents most of the rail track shocks from reaching the framework and body of the coach, so that the coach can be more lightly built.
The first Micheline rail-coach tried in Great Britain had a weight, empty, of 5 tons ; its seating capacity was twenty-four ; this works out at about 4 cwt. of deadweight per passenger carried.
A branch line steam train capable of carrying 160 passengers weighs, when empty, about 135 tons, giving 17 cwt. of deadweight per passenger, if full. If a train of this weight runs with only one-third of its maximum complement—as is normally done—the deadweight per passenger is 2-1/2 tons, about 12-1/2 times as much as for the pneumatic-tyred rail-coach.
This means a saving in fuel costs. The petrol consumption for the twenty-four seats coach was twelve to fourteen miles a gallon, about one penny a mile for twenty-four passengers ; this represents from one-fifth to one-tenth of the lowest steam locomotive train costs per mile.
Apart from this saving, the cost of a rail-coach of this type is considerably less than for the steam coach, the relative costs hearing a rough relation to the respective weights of the two.
The petrol or Diesel engined coach can be started whenever it is required, or a few minutes before the coach is to be moved, and stopped whenever the coach is stationary for more than a few minutes. There is no necessity, as with the steam-type, to start raising steam a few hours beforehand, or to keep steam up all day. There is no need for a fire-man or a skilled type of driver, as with the steam-engined coach, and the driving controls are simple.
The first Micheline rail-coach was capable of maximum speeds of about 70 m.p.h., and could travel, normally, at 60 m.p.h. It had a much better acceleration than the ordinary steam train, for it could attain a speed of 50 m.p.h. in 1,000 yds.: from this speed it could be brought to rest in 110 yds. without any shock or discomfort to the passengers.
The quiet operation of this rail-coach was such that passengers could talk, write, and walk about with almost the same ease as on an ordinary pathway ; the running was so smooth that there was no sensation of speed, even at 60 m.p.h.
Only five minutes were required to change a wheel in the rare event of a puncture; a special Klaxon horn in the driver's cabin gave an automatic warning whenever a tyre had lost 14 lb. per sq. in. of its pressure.
The original tyres were found satisfactory after over 20,000 miles of rail track use. Early in 1935 nine rail-cars of the original 24-seat pattern had covered nearly 1,000,000 miles in France and elsewhere.
After the encouraging results obtained with the coach, further research work was carried out and an improved coach introduced on the French railways in 1933. Most of these improvements are embodied in the latest type.
The original coach bore a strong resemblance to an elongated motor-coach of road design, but the improved coach is more on the lines of the orthodox rail pattern. It diners from the orthodox type, as it has a conning-tower which forms the driver's compartment.
The superior elevation obtained not only makes for increased safety, for it gives the driver an increased range of vision, but also enables him to drive the coach in either direction. The elevation of the driver allows more room for the engine and the radiator—for cooling the circulating water in the cylinder jackets. In this instance cooling of the radiator was effected by means of louvres placed in the extreme front, between the head-lights. The later model was fitted with an improved method of springing, by means of floating cross-beams and semi-elliptic springs placed outside the wheels.
The coach, with thirty-six seats, had two six-wheeled bogies, one at either end. The front bogie had three driving axles. these being coupled by means of chains and radius rods. The rear trailing bogie had three axles suspended on semi-elliptic springs. Each wheel had two independent brakes, making it possible to bring the coach to rest in 130 yards, on dry rails, from a speed of 50 m.p.h. ; if the rails were wet this distance was increased to 160 yards.
The coach, which was driven by a 140 h.p. petrol engine, had a maximum speed of well over 60 m.p.h. and a cruising speed of 50 m.p.h. It would attain the latter speed from rest in 70 seconds, or in a distance of about 1,100 yards. This coach was fitted with a four-speed transmission and would give these four speeds in either direction. The empty coach weighed 6-1/2 tons and, laden, 9-3/4 tons ; the former figure is equivalent to a dead load of 3-1/2 cwt. per passenger.
The petrol consumption for the loaded coach was 7-1/2 miles a gallon ; this works out at about 2d. a mile for carrying thirty-six persons in addition to the driver.
Early in 1935 fourteen of the thirty-six seater rail-cars had travelled over 800,000 miles on French railways. One car had run over 130,000 miles and two others, 110,000 miles each ; they were still in continuous service.
In 1934 the Micheline Company introduced the larger type of rail-coach with a seating capacity of fifty-six. Early in 1935 this model, but with minor improvements, was tested in Great Britain.
This rail-coach is about 54 ft. long and is provided with bogies at either end of the four-axles, eight-wheels pattern. The front driving bogie has two driving axles coupled by chains. The engine, which develops 200 h.p. at 3,000 r.p.m., is mounted on the body chassis. The central bogie pivot is so arranged that it carries no vertical load and therefore is free to carry out its designed work.
In the 1935 model, known as the Coventry Pneumatic Rail-car (fostered in Great Britain by Armstrong-Siddeley Ltd., Coventry), three of the four axles on the driving bogie are positively driven.
The suspension system in the 1934 model is by coiled steel compression springs and rubber ; in the Coventry Rail-car, semi-elliptic springs are used in place of the coil springs, this being in conformity with automobile practice.
The Coventry Pneumatic Rail-car is fitted with a twelve-cylinder petrol engine, developing 240 h.p. This is coupled to a self-changing gear-box giving four speeds in either direction. It accommodates fifty-six persons and has a compartment for luggage. It is equipped with heating apparatus and is lit by electricity. The coach has been designed to give as much window space as possible to enable the passengers to see the surrounding country. The car has a streamlined appearance and, as in the previous model, it has the driver's cabin in the roof to afford him a clear view all around ; he can therefore drive the rail-car in the reverse direction with ease.
The weight of the unloaded vehicle is about 8 tons 5 cwt. ; the useful load is about 5 tons, making 13 tons 5 cwt. in all. The power-to-weight ratio of this rail-car is a high one, so that it has a very good performance.
A very light construction is employed for the body ; this method is on account of the excellent shock-absorbing qualities of the 36-in. diameter pneumatic tyres employed.
The maximum speed of the rail-car is about 70 m.p.h., the cruising speed being between 55 and 60 m.p.h. The vehicle will reach a speed of 50 m.p.h. from rest in 56 seconds; this is equivalent to a distance of about 1,110 yards.
For braking, the Westinghouse compressed air system, with Lockhead hydraulic brakes acting independently on each bogie set of wheels is employed. The compressed air method is used to "boost" or assist the operation of the hydraulic brakes.
The normal braking is such that the vehicle when travelling at 50 m.p.h. can be brought to rest in 220 yards from the point of application of the brakes. In emergencies the brakes can be arranged to bring the rail-car to rest from a speed of 50 m.p.h. in a distance of 130 yards on dry rails ; on wet rails the braking is not quite so good, a distance of 165 yards being necessary.
On a route run by the French Nord Railway, a similar rail-car covered forty-one miles, making twenty-four stops, averaging for the whole distance a speed of 37 m.p.h.
In a demonstration run in England, a rail-car left Euston with a nearly full complement. On the outward journey it made stops at Willesden and Watford to demonstrate its accelerative and braking capacities. Leaving Euston, the climb to the first mile post up the Camden Bank, mostly at 1 in 70, was accomplished in 2 min. 16 sec., and the stop at Willesden Junction, 5-1/2 miles from the start, was effected in 7-1/4 min. After Willesden, a speed of 62 m.p.h. was attained within little over a mile of the start, and the 12 miles to Watford were covered in 13-1/4 min. At Watford the car was stopped dead in 9 sec. from a speed of over 55 m.p.h.
Proceeding to Leighton Buzzard, the 22-3/4 miles were covered in 25 min., start-to-stop, at an average speed of over 54 m.p.h., the highest speed attained being 67 m.p.h. The return journey was made without stop, the 40-1/4 miles being covered in 42-1/2 min. (57.8 m.p.h.) against a strong head wind. and with a slack for permanent way operations near Leighton. The highest speed attained on the return journey was 65 m.p.h. The running was remarkably smooth and quiet ; the braking performance was far beyond the capabilities of most other types of railway vehicle.
Two heavy services have been made possible by the introduction of this type of pneumatic rail-car on the Nord Railway of France.
There is a service on the Lille-Lens-Bethune route on which a rail-car covers 360 miles every day, during a period beginning at 6 a.m. and ending at 10.30 p.m. A second car in the same area covers 330 miles a day, from 7.30 a.m. to 11.30 p.m.
The rubber-tyred rail-car is eminently suitable for colonial purposes. Not only is it very much lighter in weight than its steam prototype, but it also occupies an appreciably smaller bulk, so that it can more readily be shipped by sea to its destination from the manufacturer's works in Europe.
From the driver's point of view the petrol or Diesel engine rail-car is more convenient and much cooler to drive than the steam-engine type with its firebox and boiler disadvantages. The Micheline pneumatic rail-car has already been used satisfactorily in some of the French colonies. Thus, the colonial models of this vehicle designed for metre and 3 ft. 6 in, gauges are in operation on the Congo Ocean and Madagascar railways, in the latter instance between the towns of Tamatave and Antananarivo—a distance of 230 miles. There are numerous gradients of l in 40 on this track, while some of the railway curves are of two and a quarter chains radius.
Hitherto, steam trains of similar capacity required fourteen hours in which to accomplish this journey of 230 miles. The Micheline rail-car takes only eight hours in which to cover the same distance.
The particular design of rail-car intended for colonial work has two sets of six wheels, one at either end. At the front end, under the driver's compartment, the front one of the three axles is a weight-carrying axle the other two being coupled driving axles. The three axles at the rear are purely load-carrying axles.
The rail-car is driven by means of a 27 h.p., four-cylinder petrol engine, the cooling water having a special condenser arrangement. The passenger compartment has eighteen scats, It is of heat-insulated construction and is afforded protection against the sun by means of louvres and awnings ; a special air ventilation system is also installed. There is also a compartment for taking about 6 cwt. of luggage.
The fully-laden weight is 7 tons 13 cwt. The cruising speed on the level is 50 m.p.h. while the maximum speed is 56 m.p.h.
In regard to the braking performance the vehicle can be stopped from a speed of 50 m.p.h. in 84 yards on dry rails and 130 yards on wet rails.