Innovations in the
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GARRETT PROGRAMME
First Details of the New A.G.E. Oil-engined Industrial Tractor, Six wheeled Steam Wagon with Pneumatic Tyres and a Trailing Axle, and the Blackstone engined 6-7-ton Lorry
THREE of the exhibits or Richard Garrett and Sons, Ltd.; Leiston Works, Suffolk, which will appear at Olympia in November, will constitute novelties. The A.G.E. oil-engined industrial tractor will be making its first public
appearance, likewise the six-wheeled steam wagon equipped with pneumatic tyres and having a trailing axle. The 6-7-ton lorry with a Blackstone oil engine was seen for the first time at this year's Royal Agricultural Show, but it will be introduced in November, in its latest form, to a wider public. Incidentally, the last-named vehicle has been subjected to strenuous long-distance testing, and the new model will embody such detail modifications as have been found advisable in the light of the experience gained.
,Dealing first with the oil-engined tractor, this can be equipped either with a four-cylindered Blackstone power unit or with an Invicta engine inade by Aveling and. Porter, Ltd., of Rochester. The tractor we c36 inspected was equipped with the former tyrie of engine, but the one to be shown at Olympia will probably hate the latter power unit.
This new industrial tractor is capable of handling loads of 15 tons or slightly over, and with a Blackstone engine has a drawbar rating of 20 h.p. It has a wheelbase of
7 ft. 4 ins., and weighs 3 tons 12 cwt. unladen. The rear wheels are shod with 42-in. by 9-in, pneumatics and the front wheels have 25-in. by 6-in. tyres.
A sprung front axle supports the main 'frame at one point at the forward end, whilst the rear wheels are unsprung, except for the flexibility' of the tyres.'
The frame is of the usual variety employed in tractors, forming a casing for the transmission, 'but, in this case, the engine passes through an aperture in the base of the frame, i.e., the frame is not also the crankcase Dealing with the Blackstoneengined model, the power output is some 40 b.h.p. at 1,000 r.p.m., the bore and stroke being 4 ins. and 6 ins. respectively, and the compression ratio is 14 to 1. The monobloc cylinder casting carries four separate liners, and the cylinder heads are in pairs. The injection system is, of course, the well-known Blackstone Spring type, obviating the need for a high-pressure pump. The crankshaft runs in three ball and roller bearings.
Starting is by means of an auxiliary .petrol engine which takes up the duty of crankshaft rotation from the starting handle and ceases work when the trip gear automatically disconnects it from the flywheel. The maximum speed of the engine is governed ; some 1,600 r.p.m. can be attained.
A single-plate clutch is located between. the engine and the threespeed gearbox with central control. The overall'forward ratios are 15.5, 255 and 29.8 to 1. A take-off can be obtained at right angles to the frame line. From the gearbox the drive passes through bevel pinions to the spar-pinion shaft which carries the drum of the hand brake—this is of the external-contracting variety. The pinion on the countershaft drives the final spur wheel mounted on the differential. Internal-expand
lag brakes in the rear wheels are pedal-operated. Turning to the second innovation, viz., the six-wheeled steam wagon with the trailing axle, we find that the specification follows closely that of the well-known type which has been in service for many years, as regards the engine, boiler, frame and the controls. The principal points of difference lie in the arrangement of the bogie, the wheels of which are shod with 40-in. by 8-in, twin pneumatics; the front wheels carry 12-in. by 20-in. low-pressure tyres.
Drive is by chain to the wheels on the forward axle of the bogie. The axle is, of course, of the dead type, whilst the third axle is of the trailing variety. They are both connected to the frame by means of a single, inverted, semi-elliptic spring on each side: The two axles are coupled by rods with the requisite articulating joints. The forward axle is located by radius rods, which permit chain-tension adjustment.
These radius rods and the coupling rods take the braking torque for the two axles. There are 16 internal-expanding shoes 'in the fotir drums of the wheels of the bogie. Half Of this number is controlled by the hand lever, half by pedal, and all 16 by the steam brake. The drums have channel-section bands sunk on to prevent distortion and "shrieking."
Dealing now with the oil-engined lorry, this has forward control, the driver sitting well clear of the Blackstone six-cylindered engine. The model is known as the Garrett GB6, and will carry a pay-load of 6-7 tons, according to the body.
The engine develops some 60 b.h.p. at 1,000 r.p.m. Its governed Speed is somewhat in excess of this. In this case, also, the spring-injection system is employed, and starting is by a 24-volt equipment. This voltage applies to the entire electrical installation.
The frame, which has a height of 3 ft. Oi in. When''loaded, is generously proportioned and has an interesting cross-member amidships, which not only gives great strength, but can be slid backwards, after removing the fixing bolti, to facilitate gearbox removal.
The transmission system includes a single-plate clutch, fonr-speed.-andreverse, unit-mounted gearbox with a silent third speed, which is something of a novelty for a heavy-duty lorry ; it is an advantageous feature in that generous use of the gears is advisable with oil engines of the governed, medium-speed type.
The steering embodies a Manes set. Braking is effected through the four wheels so far as the service set is concerned, whilst the hand brake operates in only the rear-wheel drums. The system is uncompensated, in accordance with modern practice. Final drive is by an overhead worm axle, connected to the frame by semi-elliptic springs, taking driving and torque stresses.
All road wheels are shod with 40-in. by 8-in. pneumatics. The leading dimensions are as follow :— Wheelbase, 15 ft. 3 ins.; overall length (with drop-side body), 23 ft. 2 ins. ; body space, 16 ft. 71 ins.; internal body width, 7 ft. The fuel tank holds 30 gallons.