A TRACTOR-TRAILER FOR CONGESTED PLACES.
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A Design of Tractor which Secures a Short Wheelbase and so Improves Manoeuvrability.
WITH the call for greater efficiency in the transport of such goods as can be moved in large loads—from 8 tons to 12 tons—and for higher sustained speeds, efforts to secure the fullest advantages under the regulations as to the overall dimensions of a vehicle are continuous, and, accordingly, we were impressed recently with a demonstration of the value of shortening the wheelbase of the trailer portion of an articulated six-wheeler. The design of the experimental machine and of the tractor which has been the outcome of the experiments are the work of Mr. B. Whitby, of 412, Southbury Road, Ponders End, Middlesex. Mr. Whitby has had 23 years' experience in commercial motor construction, running, maintenance and repair, having occupied an important position at the Commer Car works at Luton, and having been engaged as a director of Redburn. Whit...1y, Ltd., of Enfield Highway, in the reconditioning of all types of commercial ,ehicle.
For certain haulage work that his concern was called upon to undertake, Mr. Whitby set to work to produce a tractor-trailer to carry loads of from 8 tons to 10 tons, and he took for the purpose a 3-ton Commer Car chassis and a Carrhnore trailer, and then considered the best disposition of the chassis components which would give the shortest tractor wheelbase, because the vehicle would be required to go into the docks and to wharves and warehouse yards, where space for manteuvring would be limited. In the vehicle shown in our illustration the wheelbase of the tractor is 6 ft. 7 ins., the body length is 22 ft. 6 ins., and the total overall length is 28 ft. 4 ins. On the maximum permitted overall length of 33 ft, a body 27 ft. 2 ins, in length is possible. There is, of course, the important alternative that should a user require a vehicle with a body only 18 ft. or 19 ft. long, a six-wheeler could be buil: that would be more easily manceuvrable than a 4-ton lorry.
It is interesting to study the conversion of the Commer chassis effected by Mr. Whitby. In the first place, the steering, gear-change and brake levers and the controls were taken right forward beside the engine, considerable ingenuity being shown in the provision of access to the engine and to the connection between the gear lever and gearbox. The rear axle was brought forward of, the countershaft and the chassis frame was shortened to a point just behind the differential on the countershaft. The driving chains thus drive forward. The fulcrum, however, falls behind the kingpin (which, of course, is situated over the rear axle), and to counteract the tendency of the front of the tractor to lift, the front springs are made short and stiff.
In the course of the demonstration made for our benefit the tractor-trailer was placed directly against the kerb, the front wheels were locked full over the moment they were free from contact with the kerb and the machine was then turned in a circle 26 ft. in diameter, on either lock. At one point the tractor is at an angle of about 80 degrees to the trailer, and if the cab had not been made large enough for a man to sleep in an even neuter angle could have been obtained. In a further test, a road 19 .ft„ 6 ins. from kerb to kerb was taken and the tractor-trailer placed again beside a kerb, the driver turned out and pulled out until the tractor. and trailer were about at right-angles to each other. Then he reversed to the extent of 4 ft. on the opposite lock and going forward again finished facing in the opposite direction. We saw a private car turning round at the same spot, and three reversal movements were necessary as against but one in the ease of the Whitby vehicle.
The vehicle described has already covered about 7,000 miles in active service, carrying loads up to 10 tons. It has been taken into congested places and has invariably surprised onlookers by its ability to get clear. At one particular
works a 4-tanner with a clever driver cannot get beneath a crane where loading has to take place under three or four reversals, but the Whitby vehicle can get into the same position without reversing. It has • been apparently " pocketed " in traffic, two or three feet behind some obstruction, and has extricated itself with perfect ease.
The converted tractor, however, is not favoured by Mr. Whitby, who has designed and patented a special chassis, which we show in diagram form. It will be seen that space
cannot be saved forward of the gearbox, except, of course, that the driver's position would be placed beside the engine. For instance, putting the front axle back whilst shortening the tractor wheelbase would not reduce overall length. Mr. Whitby's solution is to introduce a countershaft below the gearbox, the sliding gear wheel being doubled in length and engaging with a bull wheel on the countershaft, whence the power is transmitted through a propeller shaft, the radius of the torque tube being 3 ft—which is ample. There are two gear reductions, one on to the bull wheel and at the final drive.
Whore worm drive is favoured, shaft angularity is avoided by setting the bull wheel and countershaft at •the side of the gearbox and by employing an overhead worm, the worm wheel accordingly being t.) one side of the centre lineef the chassis. Either transmission arrangement utilizes space to the best advantage without overcrowding
the main units and leaves them ful;y accessible, while the angularity of the propeller shaft is reduced to a minimum.
The trailer being pivoted over the rear axle no part of the body ever projects outside of the normal line when a curve is taken, so that the driver does not have to worry about side overhang.
We understand that Mr. Whitby is willing to enter into negotiations for the use of his patent rights in this method of securing a short wheelbase to a tractor.