A FRENCH NARROW-GAUGE AGRIMOTOR.
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The Simple and Original Double Worm Drive and New Detachable Wheel Straking System of the Howald-Gerster Tractor.
GREAP INTEREST in the production of agricultural tractors is being shown by the
• agricultural department of the French Government, which is inviting both inventors and manufacturers to make known the types they have designed or are in a position to produce. A branch of the department 'interests itself in new designs, examines these with a view to their suitability for French conditions, and is doing everything possible to secure the adoption of the .best designs and to arrange that machines shall be built according to them.
One of the agricultural tractors in which the French AgriculturalDepartment is particularly interested, and which is now about to be produced, is the Howald light tractor for which S. Gerster, an engineer of high reputation in the French automobile industry, is largely responsible. This tractor has been specially designed for work on small farms and particularly among vines, where the maximum width must not exceed 39 ins. In view of the fact that France is the most important wine-producing country in Europe, it is rather surprising that more attention has not been paid to agricultural tractors having the necessary qualities to work in vineyards. In addition to a reduced width, it is essential that a tractor for small French holdings should have a, very short turning radius, and it should also-be capable of being used on hard roads without injury to itself or damage to the road surface.
The Howald machine is of the four-wheel type with power plant set almost amidships. This power plant comprises a four-cylinder monobloc motor of 62 mm. bore by 145 mm. stroke, having a two-bearing crankshaft and forced feed lubrication to main bearings And crank pins. The circulation of the cooling water is effected thermo-syphonically, with the radiator set behind the motor and: with a very big head of water above the cylinders. There is a belt-driven fan which sweeps the entire surface of the tubes. While there is nothing startlingly new in the motor; it is a plea,singly sinyile and substantial job, Back of the radiator is the petrol tank with a space between the two to allow heat to escape.
The gearbox isbolted up to the engine basechamber so as to form one unit with it ; it is of a very simple type, giving three speeds forward with a, single sliding ,set. The cone clutch, lined with thermold, is independent of the flywheel. One of the outstanding and patented features of the tractor is the final drive by worm and worm wheel to each of the rear wheels. It is passible (I) to drive on the two wheels, either with or without the use of a differential, (2) to drive on one wheel only, or (3) to drive one wheel aacEbraka on the other. The differ
ential is adopted in order to make the tractor suitable for road haulage. It is claimed that by means of the two independent drives the tractor can turn in a circle having a radius shorter than its own length, this latter being only 205 ins. This is considered a very important feature on small French farms, where every square inch of land is cultivated.
Between the propeller shaft and the worm shaft there is a spur reduction gear comprising a broadfaced driving pinion mounted on a castellated shaft, and meshing with two pinions fixed respectively on the left and right-hand worm shafts. When the driving pinion is in its central position, both worm shafts (Fig. 3, section A) are driven ; with. the sliding pinion pushed forward it meshes with the gear wheel on the left-hand shaft, and in consequence drives the lefthand road wheel only (Fig; 3, section
...13); and inversely, with the
sliding pinion pushed to t h e rear position the right-hand wheel is driven and the left-hand one is free (Fig. 3, section 0).
With a view further to assist
iiIi quick turning a brake drum is mounted on the e xt r e-mity of each worm shaft outside the housing, thus enabling the driver to leek the wheel which is not receiving power. The worms are carried beneath the worm wheels. A separate lever is provided for 4.—Double worm drive, showing the control of different vositions of the sliding gear. the slidin g pinion, for it is only necessary to transmit the power to a single wheel when making a sharp turn.
The operation of the sliding gear set follows the usual automobile practice. Ploughing is generally done on second gear, which gives a speed of 2.9 ft. a second or about 2 miles an hour ; first speed gives 1.96 ft. a second or 1.3 miles an hour ; and third speed gives 4.6 ft. a second or 3.1 miles an hour.
It is also intended that the tractor shall be serviceable on made roads as well as on soft ground, and for this reason the rear axle is suspended by means of a pair of semi-elliptic springs and a connecting rod which acts as a radius rod. The springs, which are attached to and below the axle and, at their ends, to brackets from the frame members, take care of the torque, while the drive is taken through the central connecting rod from the upper portion of the axle housing to the rear transverse frame member. The rear wheels are 43 ins. in diameter, with a width of 4.3 ins. The normal track of the machine is 38 ins. A patented type of quick-detachable strake is fitted. These consist of sets of three strakes united by curved lateral plates, these latter serving to hold the attachment to the rim of the wheels by means of flat, flexible springs. No bolts and nuts are used to attach the strakes to the wheels. The front wheels, which have a diameter of 23.5 ins. and a face width of 3.1 ins., are two in number, and are 'capable of being set to any desired width according to7the nature of the land on which work is being done.
The position of the driver's seat gives the operator control of the plough or other agricultural instrument used. The drawbar pull is 880 lb. The tractor can haul a two-furrow plough in normal ground and can plough to a depth of 6 ins. This corresponds to a tractive effort of 680 lb.
The power required at the drawbar is 3.7 h.p., and as' 6 hp. are available the margin is ample. During a 10 hours day,41lowing 10 per cent, for loss of time in filling tanks, oiling and making turns, the machine can plough as acres in heavy ground, and5.4 acres in light ground. Under war conditions it is estimated that the selling price of the tractor would be £340 and under peace conditions £180.