A Medium-capacity
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SIX-WHEELER OF MERIT
Carrying a 3-ton Load, the TW4-0 type Garner Shows its Ability to Maintain a Good Average Speed in Hilly Country at an Economical Rate of Fuel Use
ONE of the most interesting newcomers to the mediumcapacity six-wheeler category is the Garner, which can be obtained in a wide variety of wheelbases and with engines having four cylinders or six. Despite the number of types which is offered to suit the varying needs of a large class of industrial user, the chassis prices are distinctly moderate.
This end has not been attained by any cheeseparing of the specification, but by designing for simplicity, which is so often the keynote of mechanical merit and facilitates inexpensive production. The vehicle contains concrete evidence of ample forethought in the layout. For example, the wheels of the bogie are permitted articulation amounting to an axle-height variation of 5 ins., and the suspension system embodies certain novel features which ensure that, within the limit mentioned—which is more generous than is provided in many designs— the driving wheels on the intermediate axle must retain their adhesion, so that the chassis can be manoeuvred up steep ramps without loss of traction.
Another feature which is not only practical but unique is the pair of pivoted units, each comprising a portion of the cab floor, together with a part of the cab side. The removal of three studs and the loosening of a wheel-type nut allows the hinged structure to swing outwards and forwards, so that a mechanic can gain access to the near side of the engine or to the off side—according to which of the structures is moved— in a manner which is considerably
easier than obtains with the average normal-control vehicle. There is no need for a man to kneel doubled up in the cab or to stand on the ground and lean right across the cab floor, in order to gain access to the carburetter, etc.
The actual chassis handed over to us for test carried a standard Garner cab and a platform body, the former being mounted on its special sub-frame, which permits rapid removal of the cab and allows thorough under-bonnet ventilation. The vehicle had covered some 5,000 miles and was laden with three tons of ballast ; the itemized weights are given in an accompanying panel and show that the vehicle was fully laden. The plate on the dash specifies that the gross weight should not exceed 6 tons 6 cwt. Each of the three axles carries approximately one-third of the gross burden. During the preliminary run from Birmingham on to the open road we found that the general control was easy, and that the absence of any brake-assisting mechanism did not cause the need for the use of any physical effort beyond that which is reasonable. The gears were easily changed, and the fact that both the clutch and brake pedals could be adjusted for reach is a point which shows the forethought put into the general design. The clutch required very little pressure to release.
The chassis, which was of the type having a 12-ft. 9-in. wheelbase and a two-piece propeller shaft, was equipped with a standard final-drive ratio of 6.5 to 1. The gradation of the overall ratios, as shown in the accompanying panel, was found to be well suited to the output and torque characteristics of the fourcylindered engine. When a downward change was demanded the next lower gear sufficed for long periods. There was no trace of that annoying state of affairs, as sometimes happens, in which one change merely leads to another.
The lowest gear is amply sufficient to permit a restart with a full load on a gradient of 1 in 6, and the clutch takes up its burden without noise and without juddering. This was proved on Sunrising Hill.
The most severe climbing test was on this particular hill, which has a gradient of 1 in 61 at the steepest point and a general slope of 1 in 10. The average speed for this hill worked out at 7.54 m.p.h. from a standing start, close to the sideturning below the foot of the hill. The indirect gears were in use for .45 mile, first gear being used from the hair-pin bend up to the crest of the rise (.25 mile).
One of the genuinely striking features of this climb was the behaviour of the cooling system. Owing to the atmospheric temperature previous running had been accomplished with blanking strips over half the radiator. Before climbing Sunrising we stopped and removed these strips and checked the temperature in the header tank ; it was 185 degrees F. Immediately the Garner breasted the rise we stopped and .again took the temperature. Despite nearly half a mile of work on the indirect gears the temperature had dropped to 168 degrees F. There are various factors accounting for this. The air speed of the fan rises from 100 ft per minute at about 250 r.p.m.
to 1,200 ft. per minute at a little over the peak of the power curve. Roughly speaking, at the maximum rate of revolution the c40 air speed is 12 times that which occurs at tick-over speed. At the same time, the water-pump output rises from zero to nearly 21 gallons per minute at the peak of the power curve. This cooling performance is reassuring.
The fuel-consumption rate worked out at 10.28 m.p.g. at an average
speed of 17.8 m.p.h. Measured quantities were used in a separate tank, and the course employed was a hilly one, calling for a fair percentage of use of the indirect gears, and, in addition, then, were five stops, so
that the vehicle was operating under far from easy conditions. This Shows its economy of operation, from the fuel-consumption viewpoint.
The Zenith 36 UY-type carburet
ter, which was untouched throughout the entire test, had a setting as follows :—Choke, 24; float needle, 3.0; main jet, 85; progression jet, 16; compensator jet, 140; slowrunning jet, 55; slow-running tube, 2.5; starting jet, 180; cap jet, 2.5.
As regards braking, it was found that either set independently gave
steady and safe braking, and that nothing was to be gained by the use of both brakes together, except at the maximum speed. Irregular road surfaces did not have an adverse effect upon the braking, by reason of the operating mechanism being correctly laid out in regard to the off-centre springs of each axle of the bogie.
The acceleration curves reveal a steady increase of speed, and the average of 17.8 m.p.h. during the fuel-consumption test, ' despite a cruising speed of never more than 24 m.p.h., indicates the consistency of performance.
From the driver's point of view the cab is kept at an equable and pleasant temperature, even for hotweather work, whilst the suspension of the forward end—always a somewhat difficult matter with a sixwheeler—was found to give riding free from any harshness. The steering was in every way good.
Unquestionably the design of the front , springs has had a great deal to do with the steering properties quite apart from the matter of easy riding qualities and general comfort. Even on a wavy road surface there was no tendency for synchronized spring movements to occur, and even under the worst conditions experienced during our test run we were unable to detect any bad effect upon the steering due to road irregularities.
As regards the suspension of the bogie we found that the chassis rode easily and without harshness. When reversing over obstructions the driving wheels at all times retained full contact with the surface, which means not only proper availability of the tractive effort but small tyre wear. When applying the brakes, either with the normal amount of force, or when pulling Up in the shortest possible distance, the effort was equally distributed.