Nuffield Tractor
Page 42
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Now in Production
THE Nuffield universal tractor, of which details were first published in "The Commercial Motor," more than two years ago, has at last reached the production stage. Two models are, available, the M3, with a single front wheel, and the M4, Which has a front axle. They are similar in all other respects, and are made by Wolseley Motors, Ltd., Birmingham.
Basically, the tractor is of simple design, free from untried devices, and constructed with an ample margin of safety. The engine is a four-cy/indered' side-valve petrol-paraffin unit developing 42 b.h.p. at 2,000 r.p.m. Of similar internal dimensions to the new MorrisCommercial long-stroke petrol engine. it has a bore of 100 mm. and a stroke of 120 mm. (3.77 litres). There is a variable-speed governor, which operates over a range between 800 and 2,000 r.p.m., and incorporates a hydraulic damper to prevent hunting.
Renewable Dry Liners
Renewable dry cylinder liners and exhaust-valve seats are fitted. Special arrangements are made in the manifolding for efficient pre-heating of vaporizing-oil mixtures, and a manually adjustable hot spot gives two settings for pre-heating. Petrol, for starting purposes, by-passes the main carburetter float chamber, and is metered directly into an auxiliary carburetter. This simplifies the operation of changing from petrol to paraffin when starting from cold. Battery, starter motor and dynamo are grouped together on the off side of the engine, the battery being enclosed in a metal case. A 12-volt 75-amp.-hr. battery is provided, and the engine is equipped with magneto ignition. Oil filter, filler and dip-slick are grouped for easy maintenance.
A layshaft five-speed gearbox affords a range of road speeds from 2f-17 m.p.h. at 2,000 r.p.m. engine speed, when operating with the standard 9-in. or 11-in. by 36-in. tyres. The front track of the M4 model can be varied from 48 ins. to 76 ins. Each axle arm can be extended in steps of I in. over a range of 8 ins., and a further 6-in, adjustment is obtained by reversing the front-wheel centres. The rear track may be adjusted from 52 ins. to 88 ins.
Clamped sliding hubs permit variations from 52 ins. to 64 ins., and reversing the wheel centres affords another 12 ins, of adjustment. The hubs can be reversed to extend the track between 76 ins. and 88. ins. The wheelbase of the four-wheeled model is 78 ins., whilst the M3 wheelbase is 81 ins.
As a four-wheeled machine, the minimum ground clearance (under the front axle and final drive) is 18 ins. The main frame is 25 ins, above ground level.
Worm-and-nut mechanism is employed in the steering, and the turning circle, with the assistance of the independent steering brakes, is under 22 ft. for the M4 and 16 ft. for the threewheeler. Internal-expanding twoleading-shoe brake units are mounted on the differential shafts and are operated by independent pedals, which may be latched together for normal road driving.
Belt Pulley Operation
On the near side of the tractor is a belt pulley, which is provided with a separate clutch, the control of which is accessible from the driving position. With a pulley of 101-in, diameter, it gives a belt speed of 3,100 ft. per minute at 1,500 r.p.m. of the engine. The pulley can be dismantled for fitting alternative drives without disturbing the bearings or oil-seal adjustment.
Provision is made for the usual power take-off, and this is centrally located at the rear. At an engine speed of 1,400 r.p.rn. the power take-off shaft revolves at 532 r.p.m.
The drawbar is of the swinging pattern, reversible to give four posilions and provided with lateral stop pins. It remains in position when the tractor hydraulic lift is in use. As an alternative, the hydraulic power unit can be had with a power take-off shaft. and a comprehensive system comprising a hydraulic lift for tractor mounted implements, and two hydraulic powertappings controlled by independent levers. The M.4 tractor, complete with starter and drawbar, costs £495, whilst the M.3 model is priced at £487 10s. Lighting equipment and horn are available at a cost of £9. The hydraulic • power unit and linkage, with a power take-off, can be fitted for £60.