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30th December 1938
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Exceptionally Good Braking, Rapid Acceleration and Satisfactory Fuel Consumption Among Outstanding Performance Features of COG 5 Double-deck Chassis with Gardner Engine, Fluid Flywheel and Wilson Preselective Epicyclic Gearbox AFTER a day's test of a Daimler COG5 double-deck chassis, we are certainly not inclined to dispute the maker's claim that its products represent the last word in modern passenger transport. A policy of the company appears to be that nothing is good enough but the best, and this principle is reflected in the machine upon which we now base our views.

That others think similarly is evidenced in many quarters, notably in Birmingham, where, when an order now being executed is completed, the corporation will have put into operation, since 1932, 800 Daimler buses, all but 10 of which are COG5 Gardner-engined models with Fluid Flywheels and Wilson gearboxes.

A close study of the chassis and its components, and a trial of the vehicle on the road, show that no effort has been spared to achieve the aim of producing a really first-class machine, whilst, from the accompanying condensed specification and the diagram on which the main dimensions are displayed, it may be seen that, in respect of weight, wheelbase and body space, the chassis compares well with others of its type.

Without doubt, the Gardner 51_,W is one of the most economical power units available, and the returns we obtained from our consumption tests are satisfactory, in view of their severity. Bearing in mind that our figures were recorded with a vehicle laden to the equivalent of a doubledeck bus carrying its full complement of passengers, one is prepared to accept the statement that operators are averaging 12 m.p.g. and, in some s32

cases, considerably more. Not onlyto the engine, however, should we ascribe the economical running; the gearbox and hydraulic coupling must be accorded their share.

The lower of our two consumption rates-9.14 m.p.g. —was obtained on a two-mile stretch of road, which included two hills and which was covered in both directions. A halt was made every fifth of a mile, during one Of which the vehicle was turned. The idea, of course, was to simulate actual service conditions in a busy town.

After coming to rest each time, the chassis was immediately restarted, but it is definitely of note that the average speed, taken from start to finish (12.41 p.m. to 12.58 p.m.), was just over 14 m.p.h.

This points to the efficiency of the Wilson box and Fluid Flywheel, for 0.2 mile is not a long distance in which to accelerate from a standing start up to 25 m.p.h. to 80 m.p.h. and come to rest again.

With regard to the quantity of fuel consumed, which was measured by employing a small tank, which was replenished, at the end of the test, up to the level at the start, the return is certainly satisfactory, because repeated rapid acceleration of 10i tons represents a great deal of work done. Moreover, on the hills mentioned prolonged running in the lower gears was necessitated.

After the completion of this trial, the consumption was observed for the running during the rest of the day. No attempt, however, was made to economize. The vehicle was stopped many times, reversed often, and taken up and down our test-hill on two occasions, stopping twice on the steepest part to by starting up the gradient in first gear and in reverse.

Before we returned to the works, furthermore, we carried out five acceleration and numerous braking tests. All these were done on the fuel in the test-tank, which was subsequently measured. Thus, the rate of 10.00 m.p.g. recorded may be regarded as representing an excellent performance. In addition, the improvement serves to emphasize the exacting nature of the earlier trial.

Stoneleigh Hill, which has a gradient of about 1 in 6, was used to investigate the climbing abilities of the Daimler, There is no possibility at rushing this acclivity, because it is approached by a sharp right-angle

corner, turning out of a narrow, walled road over a bridge. The ascent is about a quarter of a mile long, and the gradient fairly constant for the whole distance.

A non-stop climb was accomplished, with power to spare, in first gear, the minimum speed being about 10 m.p.h. The restart in reverse was made easily, but there was little reserve in hand when getting away from a standstill, up the 1-in-6 slope, in the lowest forward ratio. For service in hilly districts, the maker recommends the use of the Wilson five-speed box.

Immediately after this series of trials, carried out in the order named, our thermometer showed a water temperature of only 160 degrees F., the atmosphere being 50 degrees F.

There is little to report, in addition to the information contained in the accompanying acceleration graph and the remarks we have already made on this subject about the accelerative characteristics of the COG5.

To attain 30 m.p.h. in under 35 seconds with full load is creditable, whilst not only is the saving in gear-changing time, afforded by the epicyclic preselective box, of marked practical value but also the incentive it gives the driver to make full use of the gears constitutes a contributory factor to general all-round economical operation.

Now we come to the brakes, and here we find a real and pronounced advance. Starting with the foot brake and obtaining such remarkably good retardation results, we made repeated trials, to assure our selves that false readings were not

being taken. All who have conducted brake tests know how easily inaccuracies can occur.

Not until we had tried the hand brake did we dispel our doubts, for the comparative inferiority of this system was such as to afford conviction that our methods were correct and that the speedometer was giving a true indication.

Coming to rest from 30 m.p.h. in 36 ft. represents an efficiency of 84 per cent. We have never before experienced so high a figure with a machine of this class, and only twice can we recall improving upon it in any class. Full marks must be awarded to the Dewandre and Lockheed components, to the Daimler parts of the braking system, and to the Daimler application of the proprietary units.

Notable features of the mechanism are the use of two vacuum tanks, which, doubtless, contribute to the almost entire elimination of time-lag, and the neat manner in which the rear Lockheed cylinders are housed in lugs in one of the tubular crossmembers, an arrangement which keeps them well away from the heat of the brake drum.

Even with 'full application of the brakes there was no deviation of the vehicle from a straight course, nor locking of any wheel. As will be seen from the retardation graph, the Jiand brake is quite useful although overshadowed by the other system. It can be employed as a reliable service brake not just for parking, and, on the held the machine with ease.

Turning now to the " handling" of this Balmier, we have finaber favourable comments to make Much has been said and written about the efficiency of the conventional gearbox.,, about the " satisfaction " to the: driver of rrinkMg good changes. and s& forth, but. every time we come to drive a raieue with some " easy change " type, of gear we are impressed: afresh with the conviction that it will surely displace the

• crash" type eventually.

For bus work none can deny that asystem that relieves the driver of continual manual lallipur and a fairly considerable mental strain, represents a positive saving in operating costs. The ease with which the Wilson gears can be changed, and the manner in_ which the Fluid Flywheel dio.ea the job which the driver usually has to do with his left leg, Make traffic driving, stopping, and restarting a light task, and are bound to be reflected in the efficiency of the service.

Only one minor criticism has to be made. We found the gear-changing pedal unduly heavy when disengaging reverse. This, we understand, is merely a matter of adjustment. In all other circumstances only moderate

effort was required to make a change.

Not the least attraction of the preselective gear is the fact that the driver has both hands free. For signalling and steering this is an unquestionable asset. Even with steering gear as light as that of theBalmier the advantage is great. Moreover, the gain is, so to speak, cumulative, because the freedom of the hands permits a lower steering box ratio, so that an easy working mechanism can be even easier.

With suck controllability„ excellent braking, and quick acceleration, fast schedules can be maintained, with safety, whilst first-class design, highquality materials and components, and splendid workmanship, ensure reliability and minimize maiutenande delays and expense.

There are: also. economy infuelancf, good appearance to consider. Here, again, the Daimler meets requirements in no half-hearted manner. The success this make has achieved is well merited and there seems good reason: tee expect that it will continue to:propees, in the sphere of operation foe whidi i is so well suited.

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