A STURDY OILER FOR MEDIUM LOADS
Page 50
Page 51
Page 52
If you've noticed an error in this article please click here to report it so we can fix it.
Road Test No. 124
Further Evidence of the Fuel Economy of Oilengined Vehicles Obtained in a Test of T.S. Motors Gardner-driven 4 tonner, a Capable Performer
THE oil engine is now achieving a considerable advance into the medium-capacity and lighter goods-vehicle classes, and our road-test series will now be including several machines of about four tons pay-load capacity. Later, no doubt, we shall be publishing performance reports on new oil-engined models in the light-lorry category, as well as on rigid and articulated six-wheelers for loads of four to six tons.
One of the first chassis makers to be ready with a medibm-capacity oiler is T.S. Motors, Ltd., Maidstone, and we have taken an early opportunity to test the company's new product, namely, the type-134LC3 4-tonner. This is a straightforward and robust chassis and has a well-tried oil engine, the Gardner 4LWmodel, which gives 68 b.h.p. at its governed speed of 1,700 r.p.m.
An advantage which this engine has is that it can easily be started from cold by hand, so that, if required, an economy may be made on electrical equipment. The method usually adopted is to decompress all but one cylinder, position the crankshaft ;just after the compression stroke of that cylinder, and then swing the starting handle, so that the momentum obtained is sufficient to carry the fourth piston over top dead centre. This method is practically infallible, as we have demonstrated time and time again.
As on previous tests of this kind, we noticed a considerable emission of exhaust smoke during the first minute of running. After a mile of travel under load, this had practically disappeared, and thereafter smoke was visible only after periods of idling. A clever feature is the fitting of a metal outer casing to form a i-in. air jacket around the silencer. This keeps up the temperature of the gases and reduces the density of any smoke emitted.
The frame of this forward-control chassis is arched slightly to make provision for underslung rear springs, the result being that a floor height of 3 ft. 10 ins, is obtained. The worm final drive is underslung. With a wheel base of 12 ft. 8 ins., the standard body has a length of 17 ft. 1 in., and we were pleased to find that the turningcircle diameter is only about 48 ft.
Certain features of accessibility call for mention. The power unit is carried (separately from the gearbox) between two shaped channels forming a sub-frame with support between the first and second channel-section crossmembers, the latter being arched downward. The engine may, without difficulty, be moved forward after taking off the radiator, and it is possible to withdraw it sideways.
The gearbox is so mounted that it may be lowered, whilst, of course, the differential and worm gear can be dropped by releasing the tie rod and removing the base of the casing. The fuel tank rests upon two extended cross-members, which form a cradle below the frame, so that it can be removed by lifting it sideways.
The controls are light and conveniently placed, the gear and brake levers being on the left and the accelerator pedal lying between the clutch and brake pedals. The instrument board, etc., are mounted on a bulkhead plate forming part of the chassis, so that body removal involves a minimum of wiring disturbance. Remote control of the gearbox is obtained through three rods. Examination of the accompanying acceleration graph will give some idea of the power available when the 4LW engine is pulling a 9-ton load, through the medium of a 6.3-to-1 final drive and 38-in, 133r 7-in. tyres ; the acceleration, in fact, is more than adequate, and, in this regard, it may be mentioned that the Gardner system of governing the fuel-injection quantity gives easy and secure control over the engine.
It is possible to travel on a level road on top gear at 5 m.p.h., and to accelerate unostentatiouSly. Under load, when a gradient is tackled, top gear may be retained at speeds down to 15 m.p.h. without labouring the engine.
We conducted a timed ascent of Hollingbourne Hill, near Maidstone, which is 1,300 yds. long, the gradient rising in the first 500 yds. from 1 in 19 to about 1 in 13, the steepest section, about 500 yds. long, averaging 1 in 9, with a maximum of 1 in 7. Having started in second gear and changed to third, this gear was held until the speed dropped to 10 m.p.h., and a change from second to first was made at 6 m.p.h., the steepest section being climbed steadily at 7 m.p.h. As a result of the climb, the cooling water temperature rose from 122 degrees F. to 158 degrees F., indicating a distinctly coolTunning engine. Except for tropical service, a fan is not fitted.
On the level we satisfied ourselves that there was no unpleasant engine vibration at any speed in the range, and the same may be said for the transmission, the smoothness of the drive being finally demonstrated by placing the hand on the gearbox and on the rear-axle casing, when travelling at about 30 m.p.h.
The brake equipment of this chassis is rather interesting. A Williams and James exhauster, mounted at the front of the power unit and driven by chain, maintains a predetermined negative pressure in a vacuum reservoir fixed to the near-side frame-member, a lead being taken thence to the Dewandre vacuum cylinder mounted on the off-side. This pulls upon an arched, solid cross-shaft carried in spherical bearings and having rod connections to the front-brake and the outer rear-brake cam levers. The hand lever pulls on a separate cross-shaft mounted in plain bearings.
The foot-brake gives good results, as an accompanying graph shows, so that application of foot and hand brakes together at .speeds above 25 m.p.h. causes unnecessary locking of the rear wheels and should be avoided. The hand brake, w.hich acts on smaller drums mounted within the foot-brake drums, proves to be capable of holding the loaded machine, whether facing uphill or down, on a gradient of 1 in 7, so that it provides a useful extra brake.
Care was taken to ascertain how many full brake applications could be made after stopping the engine and therefore rendering the exhauster ineffective. Five good applications, each sufficient to hold the vehicle on a 1-in-7 slope, proved to be the capacity of the vacuum reservoir, and a good point revealed itself in that, with no more vacuum available, it was quite easy to bold the vehicle on this incline, using the foot brake without Dewandre assistance. In no conditions were we able to detect any brake squeaking.
The loaded chassis is stable at speed and when cornering, the suspension being excellent. The springs are set as nearly as possible to the inner rear wheels, giving a wide supporting base for the frame, so that undue rolling tendency is eliminated. The same may be said as regards pitching, no suspicion of which was detected, even on quite rough surfaces. The steering is fairly light, gives no trouble when manceuvring the vehicle at slow speeds and allows a nicety of selfcentring action.
Our last test of the day, namely, fuel consumption, gave the most striking results. On a 14-mile outand-home journey along the Maidstone-London road, consumption proved to be at the rate of 18.98 m.p.g., which gives a reading of no less than 169.87 gross ton-miles per gallon. The route chosen was not so hilly as many of the English trunk roads, but even if an allowance be made for this the economy in fuel cost is noted as the outstanding feature of this new model.