A Reflection on the Use of Automatic Transmission by Suburb Buses
2009-07-20 Source：english.chinabuses.com
Summarize：Automatic transmission technology is an increasingly popular choice in the bus industry because its features, such as precise electronic control system and maximization of the overall lifespan of the drive unit, help improve fuel efficiency and create a comfortable and convenient driving experience. Then, to what extent has the automatic transmission changed the capacity of suburb buses? And how should urban buses leverage automatic transmission to improve fuel efficiency? With these questions in mind we visited Bus No. 917 of Beijing Bafangda Bus Company and interviewed both the fleet managers and the experienced drivers.
The ongoing development of urban transport brings more challenges to the operational efficiency and effectiveness of the public transport system. Detailed oriented management built on sophisticated technology for buses has become an industry norm.
Automatic transmission technology is an increasingly popular choice in the bus industry because its features, such as precise electronic control system and maximization of the overall lifespan of the drive unit, help improve fuel efficiency and create a comfortable and convenient driving experience. Then, to what extent has the automatic transmission changed the capacity of suburb buses? And how should urban buses leverage automatic transmission to improve fuel efficiency? With these questions in mind we visited Bus No. 917 of Beijing Bafangda Bus Company and interviewed both the fleet managers and the experienced drivers.
In mid April 2008, ten brand-new buses equipped with Allison Automatic Transmissions were put into service on Beijing Bafangda Bus Company’s Bus No. 917 route, which is operating daily between the city and the suburb from Liangxiang to Tianqiao. “Bafangda Group has nearly 4,000 vehicles, but only 10 of them operating on Bus No. 917 route are equipped with automatic transmissions. This pilot project caused initially scepticism. People wondered if an automatic transmission could really help save fuel, and if the maintenance cost was high or not,” recalled Dai Jingxiang, the fleet leader.
Buses 917 equipped with Allison Transmissions transporting safely and smoothly passengers
Bus No. 917 drives through urban areas, suburban areas, and on the expressway, covering about 92 Kilometres per round trip. It runs faster on the expressway and in suburban areas than in urban areas. At present, monthly fuel consumption of an automatic transmission equipped bus averages 29-30 L/100km, which is not much different from that of a bus equipped with manual transmission.
In effect, using Allison’s electronic control system, the highest shift can be set by simply calibrating the control module of the transmission. Each Allison transmission has the option of 4, 5, and 6 speed shifts, allowing maximum flexibility for each bus and maximizing driving efficiency.
Gao Yong, a driver serving Bus No. 917 with over 30 years of bus driving experience among which 10 years was spent in driving buses, was quite straight forward: “The bus is more user-friendly with automatic transmission. The system is particularly well suited to demanding stop-start urban bus routes because there is frequent traffic jams which lead to the use of a clutch. An automatic transmission does not cause any wear and tear of a cluth and creates a smoother ride for passengers. In those days of using manual transmissions, everyone would nod every time the bus gets started. Now the acceleration is much smoother.”
In order to test the association between the application result of automatic transmissions and driving habits, Dai Jingxiang, the fleet leader, who originally did technical maintenance, purposely arranged two groups of drivers: one group of highly skilled drivers and the other group of average skilled drivers. “Actually this is a small test designed by me. The result shows there is no big gap of fuel consumption between the two groups. But given different driving skills, the degree of wear and tear to the clutch is surely different.”
Driver Gao Yong thinks both driving habits and systematic training are important, according to his own experience. “The guidelines for starting and putting the bus into gear should be strictly followed. It will be very fuel consuming if the bus starts by one single step on the gas pedal. Moreover, since it is comfortable to drive a bus equipped with automatic transmission, many drivers driving manual transmission equipped buses took over the maintenance of automatic transmission equipped buses, which affected the final results of the test. “Last year, Allison provided training for us. We learned that all kinds of transmission meters have a diagnostic function allowing them to read from the gearshift mechanism the lifespan of fuel, filter elements, and clutch plates of various shift positions.”
It is said that the ten buses have run 90,000-120,000 km since they were put in operation more than one year ago. However, the clutch plates of those manual transmission equipped buses put into service at the same time had become thinner to the extent that the plates had to be replaced, having been costing many clutch materials and working hours in replace them. In comparison, through extending the life of the driveline, and because there is no time and costs demanded for replacing clutch plates, rate of vehicles in good condition is improved, and thus promoting operational efficiency and lessening the number of back-up vehicles. As a result, the total investment input from the company has be reduced.
The fleet leader Dai Jingxiang summarized: “The clutch plates of those manual transmission equipped vehicles put into service are all worn out and need to be changed after running for over 100,000 km, otherwise, the company will suffer great loss and delay of work. However, the vehicles equipped with Allison automatic transmissions are still in good shape, requiring only regular maintenance and checkups. Although an automatic transmission’s initial cost is higher, it is user friendly and cost saving in the long run. Moreover, an automatic transmission can help ease the labor intensity of drivers, improve safety of vehicles, and provide a smoother ride to passengers.”
In real operation, however, the conflict between technology and safety hampers the showcase of the best result by automatic transmissions. In accordance with shift schedule, it is most fuel efficient when a bus runs at 75-80 km per hour. But domestic traffic control usually draws a line at 70 km per hour. Therefore, the maximum fuel efficiency associated with an automatic transmission can not be fully reflected. Driver Gao Yong has much experience with this: “Set at 70 km per hour, and the speed escalates by each shift. However, it will trigger the alarm at 65 km per hour according to the setting for safety, and the gear will pop off when your reaction is a bit slow.”
Proven by the results of the one-year pilot project at Bus No. 917 route of Beijing Bafangda Bus Company, the electronic control system of an automatic transmission can select the appropriate shift schedule, depending on road conditions and vehicle speed, so as to achieve best driving performance. If fuel consumption remains the same for an automatic transmission equipped vehicle and a manual transmission equipped vehicle, automatic transmission can substantially reduce the wear and tear of the driveline, thus reducing maintenance costs and improving fuel efficiency. Nonetheless, when considering traffic conditions and safety work, it seems as though the best of automatic transmission is still waiting to be unveiled.
About Allison Transmission, Inc.
Allison Transmission, Inc. (Allison) is the premier global provider of commercial duty automatic transmissions and hybrid propulsion systems. Allison products are specified by over 250 of the world’s leading vehicle manufacturers and are used in many market sectors including bus, refuse, fire, construction, distribution, military and specialty applications. Founded in 1915, the Allison business is headquartered in Indianapolis, Indiana, U.S.A. and employs approximately 2,700 people. Regional headquarters with dedicated support staff are located in China, The Netherlands, Brazil, India and Japan. With a global presence in 80 countries, Allison has over 1,500 distributor and dealer locations. More information about Allison is available at www.allisontransmission.com.
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