TESTS JUSTIFY TWO-SPEED AXLES
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BY THE TECHNICAL EDITORS
THE proverb "time saved is money gained" is true in the operation of commercial vehicles, and our tests conducted with the Eaton two-speed axle indicate that operating costs may be reduced _ when employing vehicles equipped with this component. Results of the tests with the twospeed axle showed that journey time is reduced and less fuel is used over a given journey when compared with a chassis having a fixed-ratio axle.
Leyland Motors, Ltd., lent us two Comet chassis to conduct these trials, one having a standard axle ratio of 6.167 to 1 and the second equipped with an Eaton two-speed axle. Chassis weights, taken before the load was added, showed the twospeed-axle model to be almost 2 cwt. lighter. Part of the reason is that the standard Comet has a robust composite axle weighing 856 lb., whereas the Eaton axle has a welded pressed-steel case and weighs 733 lb.
Both chassis were loaded with art equal payload and carried a driver and observer. The fuel tanks were filled to a predetermined point in the filler neck before starting over a 351-mile hilly route, which began and finished at the Leyland works.
In the first test the standard Comet chassis set the pace as the controlling vehicle and the twospeed-axled model followed within a reasonable distance. The drivers were told to keep in close convoy, whilst the observers noted time, speed and gear changes.
Within 21 miles of leaving the works we were at the foot of Sheep Hill and both vehicles were forced to stop because of a road obstruction. When the road was clear the leading vehicle was forced to climb the gradient in bottom gear with the engine turning at governed speed.
Bottom-gear low-axle ratio was employed by the driver of the second vehicle and a subsequent change to second gear was made and held until the speed of the leading vehicle caused him to change down to the first-gear high-ratio. The Eaton-axled machine climbed the gradient in a half-ratio higher gear than the other chassis, which meant that engine revolutions were lower over a given distance and less fuel was used.
A saving in engine wear and fuel was again evidenced on a level stretch of road leading into Belmont. Whereas the engine of the standard Comet chassis was turning at 1,900 r.p.m. to maintain a road speed of 35 m.p.h., the Eaton-axled model required a mere 1,580 r.p.m. The incline between Belmont and Bolton was negotiated a half-gear higher by the " two-speed " vehicle.
Because of traffic-light delays, the convoy was broken in Bolton and the "straight "-axled chassis got a two-minute start up the incline out of the town. It did not take long for the second machine to make up the lost time to rejoin the convoy.
On Monserat Hill the inherent advantages of the two-speed axle could not be enjoyed, because, by unhappy coincidence, the speed of the leading vehicle and the gradient forced the driver of the second chassis down into a lower gear than that being used by the leader. This was the only occasion that the standard Comet was able to forge ahead.
The quantity of fuel required for replenishing the tanks at the end of the course was carefully measured and the results indicated that the two-speed axle afforded a more economical consumption. Given a more favourable course, the difference in consumption would be greater.
As the results show, the course was extremely arduous, because the average given consumption rate of a standard Comet is approximately 18-19 m.p.g., whereas, over the test course, the standard machine yielded a fuel return of only 12.75 m.p.g.
The second trial was made over the same circuit, with the Eatonaxled chassis taking the lead and the driver instructed not to exceed 35 m.p.h. at any time. The fixedratio Comet followed, making the best time possible. Its speed was restricted to 37 m.p.h.—the maximum allowed by the engine governor.
The two chassis maintained close convoy to Sheep Hill, where the leading machine forged ahead. The standard Comet was over a minute behind at the Manchester Road traffic lights. Unfortunately, the lights were against the leading vehicle and the second machine came abreast before they changed to green.
The leading vehicle gained time on all the inclines, and it was nine minutes ahead of schedule at the top of Belmont Hill. Three minutes' delay in Bolton reduced the lead, but Monserat Hill provided scope for increasing the headway.
Further delay was encountered by the slow-moving traffic in Chorley, and the Eaton-axled chassis finally arrived back at Leyland eight minutes ahead of the standard machine, which had a relatively traffic-free run. By a coincidence, the consumption rate for both machines was identical.
Because of the variations in traffic conditions, the results of these tests must not be accepted as a complete guide to the performance afforded by the two-speed axle, but should be taken as an indication of what might be expected in operation in a hilly area.
There is no doubt that, by using a two-speed axle, journey time can be reduced, especially where a number of long inclines is negotiated in a normal day's work. Because of the speed-limit restrictions for commercial vehicles in this country, there can theoretically be no great saving of time in fiat counties. This does not apply to overseas countries, where the extra 10 m.p.h. available with the two-speed axle would enable the operating time to be reduced according to the journey.
The tests prove that if an Eatonaxled chassis be operated to a schedule comparable with that of a standard machine, fuel will be saved. How great this economy might be depends on the operating territory. In areas, such as the route chosen for our trials, fuel saving would, perhaps, not be so marked as in other parts of the country.