Capital Equipment News January 2018

COMMERCIAL VEHICLES

Full automatic transmissions are hard to beat when it comes to start/stop applications such as city buses and refuse compactors.

shifts gears by hydraulically locking and unlocking the system of gears and does not depend on a clutch to change gears in the vehicle,” explains Swanepoel. Prince further explains that all the gearing in a full automatic transmission is done through planetary gear sets. “Each gear set in the transmission comprises a ring gear, planetary gears and a sun gear. You have the sun gear in the middle of the whole set up and then you have three/four/five planetary gears spinning around the sun gear. On the outside of this set up, then you have a ring gear,” explains Prince, adding that an automatic transmission uses a wet disk clutch in order to shift from one gear to the other. “The fundamental difference between a full automatic and an AMT is that a full automatic transmission uses a torque converter, which uses oil as the initial mechanism to transmit power from the engine to the transmission, as opposed to a conventional clutch,” says Prince, adding that a torque converter is a progressive way of applying power from the engine to the wheels. Early automatic concerns Early attempts to develop and introduce automatic and automated transmissions in heavy-duty trucks were met with less- than-acceptable results. “There was a perception back in the days that automated/ full automatic gear changing systems were less robust, more complicated to fix, more expensive to maintain and less fuel efficient,” says Taftman.

From a market point of view, Swanepoel says in the older days drivers were devoted to manual transmission, and even referred to it as a point of pride as they had control over the vehicle and its performance. This made the shift from manual transmissions to AMTs/ATs very slow. He also adds that the premium price that comes with the advanced technology of AMTs and ATs also contributed to the slow uptake. The limited range of gears in AMTs/ATs also made it difficult for immediate adoption due to performance requirements. From an R&D and OEM point of view, Swanepoel says general delays in getting the calibration, shift scheduling, sensing, actuation and electronics of the AMTs/ATs correctly to optimise the performance of the drivetrain made it difficult for consumers to immediately adapt to the new concept of transmissions. Selesnick agrees, saying that the first gearboxes had issues with performance and reliability. “With the lack of technology this made it difficult to get the optimal performance from the engine to the gearbox,” he says. Over the years, further improvements have since been made to enhance the systems’ performance. “Training and awareness continue to play a huge role in the acceptance of these technologies. People nowunderstand that optimised settings of the automatic/ AMT transmissions enhance better driving, comfort and overall performance of the vehicles,” says Swanepoel. “If one looks at today’s automated gear

changing systems, they are just as robust and reliable as any manual gearbox. In the majority of cases, they are even more efficient than a manual gearbox as the electronic control unit (ECU) changes gears in an optimised way, taking many different variables into consideration, such as road speed, engine speed, engine load factor and topography,” says Taftman. Major benefits The biggest advantage of a completely manual transmission is that it is just the cheapest to purchase, though it may not necessarily be cost-effective to run, argues Prince. “The argument can also be made that manual is the transmission that gives you the most control of the vehicle,” says Prince, adding that, however, this is debatable depending on how good the driver is. “A manual transmission with an outstanding driver can probably give you 90-95% of the performance of an AMT, but truth of the matter is that humans are never at their best always,” says Prince. When it comes to AMT, Prince reasons that probably the biggest reason for the migration to automated manual transmission on heavy trucks is that it gives better fuel consumption than manual transmissions. “If you are talking about extra heavy commercial vehicles, fuel can account for anything from 35% to 60% of your total operating costs. So, an AMT is a natural progression towards controlling the larger part of your operating costs,” says Prince.

CAPITAL EQUIPMENT NEWS JANUARY 2018 14