Many improvements in New David Brown 'Tractor
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War-iime Experience Embodied in Newseries Machine, Increased Draw-bar Pull with Modified Final drive Units
WHILST the production of David frown agricultural tractors has been vigorous during the war years," the company has found difficulty in meeting all demands. -The reason, of course, is that Tank gearboxes an I. steering units, and the manufacture of gears for aircraft together with components, have represented other of the company's contributions to the war effort. As a point of interest it may be mentioned that, at one of the critical periods of the war, David 13rown Tractors, Ltd., was the sole source of supply of gears for Spitfires.
There has also been •a big output of industrial-type tractors for use on airfields. both at home and overseas.
:The strenuous work which has been imposed on these machines, both in the agricultural industry and in the service of the R.A.F., has been a severe testing time, and the resultant experience has now been embodied in a new-series agricultural tractor identified by the symbol VAK/la.
As the company has produced nearly 10,000 tractors, most of which have been built and put to strenuous work on war-time service, it may safely be concluded that this latest model represents the maker's up-to-theminute ideas ori, tractor design,
Here are some of the new feattires
which have been incorporated in this model. The design of the radiator grille has been modified and this, whilst improving' the appearance of the machine, is of more substantial construction, The fitting of an improved vapoi-izing unit gives greater ecohoiny,
and still fUrther minimizes dilution of the oil in the sump. There is now an all-range governor, which is infinitely variable. w5thin predetermined limits, and the final drive in the rear axle has been modified, In addition, the wheelbase has been lengthened by 41 ins., a simplified cylinder-block drain has been fitted, and the fuel pump has now been dispensed with.
Dealing with these features in the order mentioned, the new radiator. grille is of all-steel construction and, due to the new position of the Irofit wheels.. it is afforded greater protection.
Regarding the vaporizing . unit, which is shown in one of the accompanying illustrations, the manifold is of one-piece construction, giving greater accessibility to the nuts which secure it to the filter head. The cowling of the inlet manifold against draught from the fan and the effects of side winds has been well con
sidered. Improved distribution of the mixture, increased power; and ' automatic regulation of the hot-spot temperature, have all been 'effected. The governor gives a fine degree of control over the ranges of engine speeds from 600 r.p.m. to 2,400 r.p.m. and its stability avoids the use of over-rich mixtures at partthrottle openings..
The change in the final-drive unite . of the rear axle is important in that . a new ratio of gears has been adopted, which gives, an approxiMatereduction of 5 per cent. in speed, with a corresponding increase in drawbar pull. Greater strength and increased life have been imparted _to the gears by a change in tooth shape.
These, neW gears can-be incorporated in existing David Brown tractors without the need for other modifications, but it is important that both off-side and near-side units
. should be changed at the same time.
• An increase in the wheelbase has been achieved by the simple expedient
of turninec' the front axle around, which
brings the wheel hubs 41 MS. farther forward, This Modification haS been found to be of major importance in that it gives improved weight distribtp tion, which is of particular value when using a three-furrow plough.
A detail perhaps, but one which operators will 'appreciate, is the new means provided, for draining the cylinder block. Previously, there Were two drain taps: now there is.-a single largewinged drai n sc rew With the dropping of the carburetter by 3 ins., a sufficient head of fuel is maintained under all canditions by gravity feed, and thus the fuel pump has been dispensed "With.
The oil-pressure relief valve is now incorporated in the oil pump and consists of a spring-loaded cylindrical plunger -controlling the flow of oil from a port communitating direct with the pressnre.chamber of
the pump.
Special attention has been devoted to• valve-rocker lubrication, and a felt washer and a retainer are fitted to each inlet valve to prevent an excess of oil passing down the stems.
The standard model VAK j la design of David Brown tractor, with steel wheels, is priced at £800, which is the same as for previous models without the improvements men
tioned. With power lift and inbuilt, manual width-control, the tractor costs £351. It is anticipated that, when pneumatic tyres become more readily available, the extra cost will not exceed £81) over the price of the alternative on steel Wheels. The tractor now available is a complete unit-principle row-crop machine,
offering distinct advantages. The maker is David Brown Tractors, Ltd., Meltharn, TIT. Huddersfield.