IF a broad view is taken of the transport conditions of most civilized countries having the usual road and railway facilities, it must be agreed that the road motor vehicle, whether it is used for passenger carrying or for goods conveyance, has some definite advantages over the rail vehicle. It is not limited to a single track between two fixed stations. The motor vehicle can carry its loads over a network of roads from door to door, without the necessity of transhipment. Further, its use is generally independent of any other ordinary road traffic, and it can start at any convenient time without affecting other road services.
The railway goods or passenger vehicle, on the other hand, must keep to its own track and also to a timetable arranged to keep the track clear at certain specified times only. Moreover, the railway station or goods depot is often a considerable distance from the destination of the passenger or goods, and some supplementary form of transport becomes necessary. With goods traffic, the usual procedure is to load the goods intended for transit on to a motor lorry, convey these to the railway depot, and unload them on to the railway trucks or vans. After reaching the nearest station or depot on the railway line the goods must be unloaded from the railroad on to another motor vehicle, conveyed along the roads to their destination and then unloaded once more This method of goods conveyance not only involves an appreciable loss of time in transit, but also necessitates two loadings and unloadings, with the added risk of damage during these processes; moreover, it necessarily adds to the cost of transport.
In view of these disadvantages it might be thought that to use the railway at all is a doubtful policy where small quantities of freight of, say, two to four tons are concerned, when the goods could be conveyed from door to door without employing the railway. The answer to this is that in partly developed districts, and in areas where the roads are either bad or are congested, it is very much quicker to send goods by rail. The speeds employed on railways are normally much higher than those on the roads. For long distance work, also, the advantages of rail transit are indisputable; moreover, the transit costs are lower.
In many undeveloped or partly developed countries there is generally a railway joining the main towns or industrial areas, and a network of roads leading to the railway stations and depots but there are few long distance main roads. And it is here that the railway scores over the road vehicle; for the latter cannot be used without suitable roads.
ON THE RAILS. Another view of a LNER road-
With a knowledge of these facts it is not surprising that transport engineers have considered the possibility of designing a new type of vehicle that will combine the advantages of each type while avoiding its drawbacks.
After a careful study of this problem, combined with a good deal of research work, a suitable vehicle, known as a “road-
Its particular application is on branch lines and, especially, on those branch lines where towns and villages lie some distance from the railway. Passengers or goods may be taken on at any convenient place, wherever there is a suitable road. New or partly developed districts lying some distance from the railway can thus benefit materially from the use of the road-
Apart from its advantages to the railway authorities, the road-
On the other hand, should a portion of the track be destroyed, or under repair, it is then possible to divert the road-
Perhaps the greatest advantage of the road-
From the point of view of the passenger service, the low tractive effort necessary to propel the vehicle on the rail results in much lower running costs, due to the reduced fuel consumption and absence of pneumatic tyre wear; this should involve lower passenger fares. Again, when on the railway track the road-
A NEAR VIEW of the Karrier type freight road-
THE RAIL WHEEL of a Karrier road-
From the point of view of the passenger’s comfort, the road-
The various advantages outlined above are embodied in the Karrier road-
The vehicle which ran experimentally on the LMS is fitted with a six-
The following is the method employed in this ingenious car for converting the wheels from the pneumatic road type to the steel-
Flanged rail wheels are fitted to the vehicle’s axles; on the outside of these are placed pneumatic-
The wheel changing operation is as follows. For road to rail transference, the “road-
The same principle holds good for both the front and rear wheels of the vehicle. The components are generally interchangeable on all four wheels. Two eccentrics per wheel are employed in this particular design, which enables as much lift to be obtained as is allowable by the wheel rim diameter. The operation of lifting a wheel of the necessary dimensions requires little manual effort. Further, when the road wheel is in a lifted position there is only one bearing in the mechanism which possesses any velocity relative to the main hub. In other words, all the road wheel mechanism remains stationary while the road wheel is out of action. The rear wheels are driven by a propeller shaft in the same way as an orthodox road vehicle, and the drive is cut off from the road wheels by disconnecting two pins which are utilized to secure the road wheels in an eccentric position to the slipper block structure. This structure -
It is impossible to insert these pins in the wrong position when raising the road wheels, as the horn block slipper covers up the driving pin hole which is not required and exposes the one into which the pin is to be inserted. The construction of the horn block slipper is unique. It has in its body an automatic lock which prevents the pins from becoming loose when any small vibration is experienced. While this object is satisfactorily achieved, the construction is such that with a minimum of effort, applied sharply, these pins may easily be withdrawn. A similar device is incorporated on the driving hub flange when the pins are inserted for road work. Very long pins ensure that the drive is distributed over wide centres, and their diameter is such as to render wear on the pin bearings highly improbable, on account of the small intensity of pressure to which they will be subjected. When the road wheels are driving, the rail wheels also are revolving, the connexion being made through the outer portion of the hub end which is keyed on a taper to form a connexion between the hub and the driving wheel. The wheel bearings are of the adjustable taper roller type. Another interesting feature is the adoption of the Lang-
As the vehicle runs up to the rail it is impossible to guarantee the position that the driving pins of the road wheel will occupy in relation to the holes in the slipper block. Provision is therefore made whereby the inner eccentric may be positioned in relation to the slipper block. Having established this position it then becomes necessary to ensure the correct relationship between the inner and outer eccentrics. For this reason two slots are provided in the inner eccentric into which the single plunger may operate. After the position of the inner eccentric is located the wheel may be swung round the periphery of that portion of the mechanism. And, when the outer eccentric has assumed its correct radial position in relation to the inner eccentric, the plunger, which has previously been withdrawn automatically from its original slot, now becomes engaged with a slot. This slot has been correctly positioned by its relation with the lower slipper-
The chassis of the road-
The tractive effort is ample, and permits the towing of other vehicles. The rear rail wheels are provided with sanding gear. Buffers are provided at both front and rear, special supports for these being anchored to the main chassis frame. There is also a spare wheel carrier fitted at the rear of the chassis. This is mounted on rollers, and it slides automatically to the ground upon release of the attachment fittings. Automatic lubrication is arranged for all the working members of the chassis.
A similar, but improved, road-
An improved device for bringing the road and rail wheels into operation is the Karrier “C” slot-
A COACH TYPE of road-
When travelling over the road, the two wheels are concentric and revolve as one, the drive being taken by two pins which pass through both outer and inner hubs.
When required for service on the rails the road wheel is lifted by means of the eccentric, pivoting about a fulcrum pin carried in a crank, the wheel being supported upon the rail wheel hub by means of a bush working in an oil bath. In its lifted position the road wheel is secured in a non-
The driving flange mounted on the outer hub performs the double duty of transmitting the drive and locking the fulcrum pin during the lifting of the road wheel. It bears a circle of holes so arranged that a special tool may be inserted to engage the fulcrum pin. A cam trigger in the eccentric at a point opposite to the fulcrum pin engages a slot in the driving flange and serves to prevent the collapse of the wheel when driving pins are withdrawn.
The operation of lifting each road wheel is as follows. The vehicle having been run by means of a built-
The Power Unit
The power unit is a 31-
The chassis is fitted with 12-
There is a financial advantage in using the road-
It will be appreciated, then, that the road-
It also seems possible that the “road-
THE CHASSIS of a road-
[From part 21, published 21 June 1935]
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