A TRACTOR-LORRY UNDER TEST.
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Notes on a Demonstration of Ransomes' Two-wheel Conversion Attachment, as Fitted to a Ransomes' Steam Wagon.
WE WERE present at an interesting series of tests carried out recently with the RanSomes' two-wheel trailer attachment, fitted to 4 steam wagon •of the same make, thus forming an articulated tractor-lorry with a carrying capacity of approximately double that of the ordinary wagon.
Before giving particulars of the tests and the conclusions which we drew from them we will summarize the main features of the machine. The attachment consists of a two-wheel trailer, which is connected to the end of the vehicle frame through the medium of a universal joint and stout coupling tube, which latter passes through the frame of the trailer, being located by two channel-steel crossmembers in which it can tarn, whilst its movement endway.s is restricted by two stout coil springs which cushion the bearing and drive.
On the frame of the lorry is a small turntable carrying a bolster, and a similar turntable, with bolster, is provided on the trailer, but in the latter case the turntable is carried on a saddle, which is free to slide on a longitudinal member, the length of the slide being limited by a stop. The body and its frame proper are carried on the two bolsters, and as both of the latter are free to swivel and tilt, distortion of the body owing to these twp movements is avoided, whilst, to assist in preventing torsional stresses, the buffers at the ends of each bolster are given one inch play.
With regard to the tests, we must saythat we were very favourably impressed with the capabilities of the machine..
To begin with, the wagon was run empty, except for 4 cwt. of fuel and a 150-gallon tank of water, on to the weighbridge, and the results were as follow :—
After this, the vehicle was driven into and out of a gateway, and then to a yard in the works, where a demonstration was given of what, happens when the
vehicle is reversed at full lock. This demonstration _removed from our minds any doubt as to the 'possible danger of accident which might occur through negligent driving. The trailer portion swung round to the maximum permitted by the stop on the slide already referred to, and there locked, the whole vehicle remaining stationary and the driving wheels merely skidding round idly when further motion backwards was at.. tempted. This proved that there is no risk of a.ny scissoring action, as can occur with the ordinary type of tractorlorry.
Next., various evolutions, such as backing into very narrow passages, were effected with the utmost ease, and then the vehicle proceeded to the Cliff Brewery to take on a load of beer After loading, the weighbridge was again brought into use with the follow
ing results:— Tne, cwt. qrs.
Front axle weight ... 3 17 2 Middle axle weight 7 12' 1 Rear axle weight ... 6 15 3 Total ... 18 5 2
Thus the useful load carried was 8 tons 16 cwt., but, it muSt be..pointed out that the trailer aecle was then overloaded to the extent of 5 cwt.., as the maximum conceded by the new regula tions is •61 -tons. After loading,' the vehicle was run along side streets and round right-angle turnings; eeyeral. of which caused relative lateral, movements betWeen the vehicle frame and trailer frame, thus showing the effect of. torsional stresses on the body. It was noted that until the moveMent was 'quite considerable it was all absorbed by the allowance provided by the buffers and spring flexion; only ciri -One occasion did -We notice a slight twisting of the body, and this was certainly: not more than, and 'possibly less than, that experienced with the body on the ordinary four-wheel -vehicle: What we considered n very .satisfactory test was that in which the-vehicle descended a hill with a gradient of 1 in 10, and half-Way down this turned
into a gateway just under 12 ft. wide arid at right angles to the road. -This feat was performed at the first attempt and without any need for reversing: •
We noticedthat steering with the Ran. somes' attachment is greatly -facilitated by the fact that the driver has to Watch only his driving -wlfeels•;' if • these • are clear lie knows that the trailer wheels will also clear.
One of the tests for which we had .Made a request; was that of running the vehicle river a' hog-back bridge: • Unfortunately, the onlybridges -available in the neighbourhOod -were not quite so severely humped as we desired,-but the tests gave verygood results as showing. the action of the two portions of the vehicle. With the wagon at one Sichanf• the crest and the trailer portiori at the other, the back of the wagon framenaturally tilts up. andtakes With it the' coupling pole, which at times rubs on a special plate provided on the bottom of the body. This is the only point about
the whole of the vehicle that struck us as not beiiig quite satisfactory, but we were informed that severe tests made with it had not caused any weakness awing to this particular movement, which in extreme cases would apparently not.do more than momentarily transfer more lead to the extreme rear of the wagon f rams.
The final test was that ef brake efficiency, which was demonstrated on an
incline of 1 in 11. The vehicle was rapidly brought to a standstill, first by means of the trailer brakes and then by means of the brakes on the driving wheels. Both sets of brakes appeared to be of equal efficiency, and there was no sign of tailwag, although, as-a matter of fact, we had hardly expected this as the roads were perfectly dry.
Taken all round, however, the tests were highly satisfactory, and we are of the opinion that the -Ransomes attachment is one that deserves every consideration.