IMPORTANT DEVELOPME ROADRAIL TRANSPORT.
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The Stronach-Dutton System of Transp which Run on Tracks Alongside Jse of a Tractor, the Driving Wheels of lus Obtaining Increased Adhesion
IN OUR ISSUE dated September ,6th, 1921, we gave an illustrated description of the petrol tractors which were being manufactured for Roadrails, Ltd., by Guy Motors, Ltd., and subsequently we have, from time to time, referred
briefly amongst our news items to some of the de
velopments which have occurred in connection with the Stronach-Dutton Roadrail system. :Rapid pro
gress is now being made with this system, and we consider that the results achieved, and the great potentialities which exist, merit further publicity.
For those of our readers who are not well acquainted with the Roadrail system we will give brief particulars. It may be said that the development of a country follows the railway, although many people, without fully considering the .matter, may think otherwisei.e., that the railway follows development. It is, therefore, important that virgin country, where, of course, there are no good roads and which it is desired to open up, should be provided with railway facilities, but the present difficulties are the initial and Upkeep expenses of the heavy railway systems, particularly in country where it would _probably be some considerable time before the traffic carried would be sufficient to render ventures in railwa3rconstruction paying propositions Light railways have been suggested in order to meet the difficulty, but even these are expensive, costing from 28,000 to £12,000 per mile. The diffi. culty is that the railway track must be built strong enough adequately to bear the weight of the locomotives, qu;te apart from that of the trucks and goods carried, and, in order to obtain the adhesion between the driving wheels and rails which is essential to permit the transport of heavy loads, -the locomotives have to be very heavily constructed.
In order to overcome this difficulty and tio make it posB32 sible to utilize a track which need only be strong enough to carry the trucks, the originators of the Roadrail system make use of a tractor or locomotive which combines the advantages of the lorry and the railway locomotive, in that the front of the tractor is supported on the rails, whilst the driving wheels run on tracks either between or at the sides of the rails, these wheels being fited with rubber tyres and resembling the ordinary lorry wheel.
Owing to the high co-efficient of adhesion between the rubber-tyred wheels and the road, the necessary tractive force can be developed with a very light axle load, and, as the pecauville track can be employed, the total cost of laying the Roadrail track is from £1,000 to £2,000 per mile, and, as the tractors are capable of hauling substantial loads up gradients of one in twelve, the need for tunnels, banking and cutting is practically obviated and the track can be laid direct from point to point.
The tractors are constructed with rubber-tyred front wheels, the front axle being of the built-up type with a steel block at the centre, bored out on its under face for the reception of a ball-ended pin, which is carried on a four-wheeled bogie. If the tractor is being used for road work and it is desired to adapt it for used on the rails, the front wheels are run up a double ramp, the bogie pushed underneath the front axle, and the tractor run back until the axle is lowered on to the ball-pin ; the front wheels are in this mannner held free of the ground, and the tracter follows wherever the line leads. Curves with a radius of 35 ft. can easily be taken, so that, instead of crossing obstacles, the track may be carried round them without the necessity for a. large curve.
The tractors at present in use are of 50 h.p., being provided with two 25 hp. engines, the drive from each of which is taken through a standard clutch and short cardan shaft to a silent-chain reducing gear, which serves as a means for coupling them together. The reducing gear is provided with a dog clutch, so that the engines can be disconnected when necessary and can be started up individually. From the reducing gear a short cardan shaft conveys the drive to a four-speed-and-reverse gearbox situated amidships ; from this gearbox a short shaft takes the drive to the propeller shaft, enclosed in a tubular torque member, the final drive being through a double-reduction gear axle of the bevel-and-spur type.
In order to obtain the greatest possible adhesion _between the driving wheels and road, most of the weight is over the rear axle.
'Other forms of tractor are being developed, and The ball pin on the bogie fits into a socket in the front axle, and the bogie is easily removed or replaced by running the tractor up ramps.
• several steam machines with Sentinel type engines and boilers are now being constructed by 4Nni. Beardmore and Co., Ltd., whilst a lighter petrel tractor of 25 h.p., and which is practically a modification of the standard 2-tort (i-uY lorry, is being built by Guy Motors, Ltd.
Now we will deal with Road rail systems in active operation or in course of construction. The first track was laid in Johannesburg by the Union Government South African Railways. After two and a. half years' work the rubber tyres of the tractors were in good condition, being worn about, half an inch only all round. The tractor rode easily at 18 m.p.h. and took 0 ft. curves at 12 m.p.h.
As a result of successful
tests with a Roadrail track of 14 miles in Uganda, the remainder of a length of 50 miles is now being completed, and Sir Edward Northey, the Governor of British East Africa, recently stated that the cost would work out at under 21,200 per mile.
Three tractors are employed by the Spanish Government in the prosecution of its campaign in Spanish Morocco. These tractors have now been used for a considerable time and have proved of the utmost value for conveying stores and troops from the railhead to. the advance. base. In one case the track was cub by the Moors in the hope that the tractoi would be captured, but this merely left. the rails and took -to the road and thus evaded capture.
Apart from the use of the
110-adraii system in our Colonies and in foreign countries, there are signs. that big developments may occur regarding its use at home. In Scotland there is already one line in active operation and another in course of construction.
MacDonald, Greenlees. Wil liams (Distiflers), Ltd have for some time been experiencing great difficulty in connection with the transport of whisky between their Strona chie Distillery and Milnathort, in Kinross. Two steam tractors were employed on the work, but the roads were so cut up thatthey had become quagmires, and finally it sometimes took eight hours to perform the journey of five and a half miles, and in despair the company turned for help to Roadrails, Ltd. Three miles of Roadrail track were then laid and use made of two miles of . comparatively good road, -the tractors running first on the road and hauling road trailers, and then on the rails, when the trailers were unloaded by crane, the whisky being swung on to the rail trucks. As in winter much snow falls in-this district, a detachable chain track device has been developed ; this device can also be employed on the tractor when it is required to run over soft ground such as is found in cotton-growing districts.
A very important section of R.oadrail line has now been commenced in Sutherland, connecting Lairg with Inchard. The track will have a length of approximately 62 miles and is being built with the idea of developing this portion of the country, which is at present very inadequately served by a few carriers' vehicles. The new line will link up the nearest heavy railway with the coast, and it will carry passengers, mails and merchandise, whilst giving direct encouragement to the fishing industry, which, if it were not for the present difficulty of transport, would be one of the most important in the country, as from Banda Island to Kinlochbervie is one of the finest fishing grounds of the West.
Referring again to activities outside this country, a_ demonstration track has been laid outside
bourne in conjunction with the Melbourne Trust, which will take up representation for the whole of the country with the exception of Western Australia. In South Africa the British . South African Oo., on the recommendation of their consulting engineers, have purchased the exclusive licence to use the system. in Rhodesia, whilst in one important capital, the na-me of which we arc not yet at. liberty to divulge, some 55 miles of Roadrail track are being laid to cope with inter-suburban traffic, both passenger and goods.
Actual tests on a 14-mile track have shown that 450 tons of stores can be transported daily by three tractors in seven trips, the trucks, as a rule, returning empty, at a daily cost for fuel, oil and tyres of £14, which compares very favourably with other means of transport.
To appreciate the extraordinary mobility of the Roadrail tractor, those interested should visit the trial track which has been laid down at Wembley in the grounds which are being developed for the British Empire Exhibition._ The company were given B34 permission to lay the line -on condition that they did not cut down any trees, with the result that the track winds in and out of these, in a most remarkable manner. The track includes curves of 35 ft. radius and loops of 50. ft. and 75 ft. radius, and a gradient of 1 in 141 on the 50 ft. radius, which thus greatly increases the tractive effort required from the tractor.
We were recently afforded an opportunity for inspecting this track and for ridingon the trucks and tractor. We certainly found this most exciting. The tractor made light Of the steepest gradient hauling a load of 16 tons, comprising trucks and contents, add the way in which it dashed round the sharp curves, missing trees by inches, was positively awe-inspiring. It gave aremarkable demonstration • of the way in which the driving wheels of the tractor follow the bogie, to which, incidentally, is attached the tie-bar for hauling the trucks. The 50 h.p. tractor, although it looks a very hig machine, is quite simple to control, the controls being very much like those on an ordinary petrol lorry, the only additions being the separate clutches for the two engines and the dog clutch, which enables either engine to be used independently. The lastnamed feature is an important one, as, if through
any reason one engine is rendered hors de combat, the other engine can be employed until an opportunity arises for a, repair to be executed. Owing to the independent control of the engines, in starting up it is only nee,essary to conduct this operation with the one ; when this is running the other engine can he started from. it. Starting is facilitated by the use of B.T.H. magnetos fitted with impulse starters.
The overall gear ratios may be of interest. These are ; top gear 12.4 to 1, third gear 21.4 to 1, second gear 35.8 to 1, first gear 62.0 to 1, and reverse 68 to 1. The equivalent tractor speeds at a normal engine speed of 1,000 r.p.m. are 14.2 m.p.h., 8.2 4.9 m.p.h., 2.8 no..p.h., and reverse 2.5 m.p.h., and the drawbar pull on the lowest gear is 5,600 lb., i.e., approximately 21 tons.. The weights on front and rear wheels are 1 ton 17 ewt. and 3 tons 15 cwt. respectively. The rear wheels are fitted with 1,341 mm. by 120 mm. twin solid tyres.
The company, in bnilding small tractors, are doing so to meet the demands of people who desire tractors to haul 10 tons anywhere. Eventually it is hoped that the demand will be so large that a standardized tractor will be constructed at a low price, and we see no reason why these hopes should not be realized, for the system appears to present so many points of merit not found in the ordinary light railway that its future should be assured.