LuK RepSet SmarTac extends uptime dramatically for trucks and buses
2/2/17 / LuK
Pushing the boundaries of wear and tear
When it comes to fleet operations, it is all about getting the numbers right. What costs are my vehicles causing per mile or per transported ton? And how can these costs be kept as low as possible so that my company not only remains competitive, but is also a step ahead?
Fleet operation costs are mainly influenced by service and repairs that occur during the vehicles’ lifetime. These include the usual repairs due to wear and tear, like replacing the clutch system in the drivetrain. The point in time when a clutch system’s technology has reached the end of its life cycle, however, it often depends on many contributing factors. The general rule among experts: With long-haul trucks, a clutch will last up to one million miles. Trucks and buses driven regionally and locally require a new clutch after a maximum of 600,000 miles. These numbers, however, only apply to optimal operating conditions. Under certain circumstances, the service life of a clutch system will shorten dramatically, especially if challenging operating conditions prevail, such as at construction sites or in city traffic.
Besides repair costs, it is primarily the downtime caused by repairs that is decisive for carriers and fleet owners. The easier a repair solution is to install, the sooner the vehicle can be on the road again.
About 50 percent extended service life
For the Automotive Aftermarket, Schaeffler offers its LuK RepSet SmarTAC as a clutch repair solution for commercial vehicles. This system not only makes repairs easy, it is also a technical solution that extends service life and allows carriers and fleet managers additional planning capacities for vehicle operation. However, a prerequisite for this is that the vehicles are already equipped with a TAC clutch.
Ensuring less downtime and longer mileage for customers is the goal of Schaeffler’s entire product portfolio. These requirements took top priority during the development of the new LuK RepSet SmarTAC, along with ensuring high product quality and driving comfort. One development partner is Mercedes-Benz, who has been employing the travel-controlled, self-adjusting clutch system as original equipment in their ANTOS and ATEGO truck models since 2014. The LuK RepSet SmarTAC has been available to the aftermarket since 2015.
The LuK RepSet SmarTAC repair solution comes with a clutch disc, clutch pressure plate, and conventional release bearing. TAC stands for “travel adjusted clutch”, which describes a travel-controlled, automatically self-adjusting clutch. Gradual wear of the friction linings of the clutch disc functions automatically to trigger the adjustment mechanism. In contrast to force-controlled, self-adjusting products from competitors, with the TAC system readjustment is performed according to need in predefined, mechanically limited adjustment steps. This allows the clutch’s attributes to be completely utilized for easier driving over its entire operating life – from the first start of the engine to the clutch’s final wear limit.
As precise as a Swiss timepiece
Responsible for this is a special adjustment mechanism mounted directly on the pressure plate. Every time the clutch is engaged or disengaged, the system recognizes the wear of the clutch friction linings by measuring the travel between the pressure plate and the flywheel. This change in axial travel is then transformed into radial movement by the adjustment mechanism using a pinion. The diaphragm spring, which is connected directly to the leaf spring, acts directly on the pinion – this, in turn, is connected to the spindle of the adjustment mechanism. Every change in travel (i.e. wear) causes the leaf spring to turn the pinion and the spindle a step further. The rotation of the spindle causes the ramp ring to move, which creates axial height compensation (i.e. wear compensation). In this way, the diaphragm spring is moved back to its original position in terms of actuation height and measured force, like the new state of a clutch.
The adjustment process is carried out with the precision of a Swiss timepiece. Over the pinion, drive pawl, and spindle, the TAC is adjusted in steps of 2/1000 millimetres. The travel adjustment control mechanism works almost continuously. The TAC automatically corrects wear of the clutch lining of 0.2 millimetres after each 100 clutch actuations. Moreover, when combined with the latest generation of clutch friction linings, the LuK HD 30 PLUS, its service interval is extended by up to 50 percent.
Wear reserves doubled
And speaking of wear: The LuK RepSet SmarTAC system also offers a minimum wear area of around six millimetres when ordered with the new clutch disc friction linings, the LuK HD 30 PLUS. This offers nearly twice as much wear reserve as conventional clutch systems – after all, friction lining is seen as the key component of every clutch system. Its quality is largely responsible for service life, power transmission, and shift comfort.
Under real-world conditions, Schaeffler estimates that LuK HD 30 PLUS friction linings deliver a minimum of 30 percent more durability compared to conventional linings. This means reduced downtimes and improved profitability for the operator. This product is characterized by its extreme durability, burst resistance, and high thermal resistance. These attributes ensure – over the entire service life of the lining – a soft drive-off and shift feel, along with high-precision controllability when carrying out parking manoeuvres. The linings of the LuK HD 30 PLUS is available in all current diameter sizes.
Developers used a special manufacturing process to combine desired attributes, like extreme robustness and long service life, with higher comfort in a single lining. In contrast to conventional friction linings, the LuK HD 30 PLUS is made of two different layers. The back of the lining is extremely temperature resistant, while the friction side achieves high levels of shift comfort, despite low wear attributes, and delivers optimal power transmission. In comparison tests, LuK HD 30 PLUS linings achieved twice the burst speed of comparable competitor products. Despite its extreme durability and its unique comfort attributes, this friction lining from Schaeffler meets the highest environmental specifications. There are no solvents used in the production process, and all materials used are free from asbestos, lead, cadmium, mercury, and chromium VI.