An Auxiliary Gearbox for Addition Heavy Vehicles.
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ASCOTTISH engineer, . Andrew Binnie,' of Avon Motor Works, Avonbridge, Stirlingshire, has provisionally protected an auxiliary or intermediate gear for addition to existing heavy vehicles, thus doubling the ordinary number of ratios available.
It .would appear that it applies mainly to vehicles with the engine and gearbox mounted separately, as the provisional specification states that the auxiliary _box Is situated between the engine and the standard gearbox. Changing Of gears on the auxiliary box is effected by a double dog clutch sliding ona splined shaft,' a lever in the cali being connected to this clatch through a suitable spring-loaded fork-rod.
If the vehicle be climbing 4. gradient on second gear and is unable to take the c3S
third gear, but would be able to effect the climb on an intermediate ratio, the lever of the auxiliary gear is pushed into the low-gear notch, this operation merely compressing a spring on the fork rod. The actual change in the auxiliary earbox is then made automatically when the clutch is withdrawn to change into the third • gear of the main gearbox, so that both are changed simultaneously. •
The matter is of particular interest, as a short time ago an Albion threeton lorry equipped with this auxiliary gearbox was' entered for trial by the Royal Scottish Automobile Club, the specific reason for the entry being to obtain comparative figures of petrol consumption for the vehicle employing the standaed gearbox only and then utilizing the second tax. Up to the time of the trial-the veliicie had done nearly 17,000 miles with this auxiliary fitting.
The vehicle was a 32 h.p., built in 1921, and had an engine of 44 ins. bore and 5 his. stroke. On the first day the vehicle was ran unladen, weighing then '5 tons 7 cwts. 3 qrs. ; on the second day, with its load, it weighed 6 tons 8 cwts. 1 qr. The fuel employed was taken from the ordinary roadside sources and was of no particular brand.
The total distance travelled was 266 miles, half with the auxiliary gearbox in action and half with it out of action. The average speed in the former ease was 15.4 mph., and in the latter 14.7 mph,, and the routes -were normal undulating roads starting from, and finishing at, Glasgow. During the first day and not using the auxiliary gear, the petrol consumption. was 6 gallons 81, pints, equivalent to 8.77 m.p.g., or 29.73 ton-miles. With the auxiliary gear in use the consumption -wok 6 gallons 31 pints, equivalent to 8.81 m.p.g., or 29,87 ton-miles. These restilts were obtained with the vehicle unladen.
On the second day with the vehicle . laden, the corresponding figures were;— Petrol consumption, 8 gallons 6 pints, equivalent to 0.40 m.p.g. or 11.4 ton' miles. With the auxiliary gear in rise the results obtained were gallons 7 pints, equivalent to 7.17 m.p.g., or 40 ton-miles. These records show a difference of .45 per Cent. as regards petrol consumption, and .47 per cent, as regards ton-miles 'during the first day, On the second day the differences were much more appreciable, • being an increased m.p.g. of 9.9 per cent, and an iniprovereent of
9.78 per cent. as regards ton-miles, this being, of course, in favour of the auxiliary gear. • These figures show that the heavier the vehicle and its load the greater is the advantage of employing on auxiliary gear.
So far, the empioyment of supplementary gears has been mainly confined to such vehicles as the older-model Fords, which, of course, had only two speeds, and to rigid-frame six-wheelers which, designed as some of them are to travel either on road or across country, require particularly low ratios and what may be termed "between gears," when utilised for arduous service.