SACHS develops dual-mass flywheels for different areas of application and is the only brand that offers bus dual-mass flywheels in OE quality for the aftermarket.
Find all products in the online product catalog.
SACHS develops dual-mass flywheels for different areas of application and is the only brand that offers bus dual-mass flywheels in OE quality for the aftermarket.
Find all products in the online product catalog.
Coaches and city buses must run reliably and economically while simultaneously offering drivers as well as passengers the highest level of travel comfort. It is precisely such comfort that is made difficult by the down-speeding of the engines: They can be operated at extremely low speeds and generate increasingly high torques. At the same time, components are weighing less and less to save fuel.
These and other technical optimizations increase noise and reduce natural damping. This is where the SACHS dual-mass flywheel comes in. It is specifically designed to reduce engine vibrations in all speed ranges, thus offering optimal comfort.
The SACHS dual-mass flywheel ensures the highest shifting and ride comfort; the version designed for coaches and city buses transfers the engine torque to the clutch disk and the clutch pressure plate. In the process, it isolates the driveline from the vibrations generated in the engine. Reducing the vibrations in the bus effectively prevents rattling and humming noises.
The dual-mass flywheel is so effective that 80% of all buses are already being equipped with it.
The SACHS dual-mass flywheel for coaches and city buses is designed to considerably reduce torsional vibrations. In fact, SACHS engineers designed it specifically to meet vehicle manufacturer requirements.
The following diagrams show the improved vibration characteristics when using a SACHS dual-mass flywheel. (a: engine vibrations, b: transmission vibrations, X: damping)
Compared to rigid or simple flywheels, the DMF effectively reduces torsional and engine vibrations for increased ride comfort. That is why dual-mass flywheels are not only installed in buses, but also in other vehicles. SACHS also offers, for example, a high-quality DMF for passenger cars and transporters. Until recently, it is mostly rigid or simple flywheels that have so far been used in trucks, but thanks to the high-quality truck DMF from SACHS, dual-mass flywheels are also being used increasingly in this segment.
As a drive component in the bus, the SACHS DMF offers various advantages:
The DMF transmits the engine torque to the clutch pressure plate and the clutch disk. Its primary purpose is to isolate the torsional vibrations generated in the engine, preventing them from passing into the driveline. The DMF is therefore one of the important drive components in coaches and city buses.
The dual-mass flywheel consists of a primary flywheel, secondary flywheel, rotating plain bearing and coupling coil springs.
The current engine technology places higher and higher demands on clutch systems and the entire driveline. Consumption-optimized engines already generate high torque at low speeds. The usable engine speed range is additionally reduced towards the idling speed level to enable fuel-efficient and low-emission driving. This increases the combustion engine’s rotational irregularities. For the driveline, driver and passengers, this means increased vibrations, increased noise and reduced comfort. The SACHS bus DMF steps in here to powerfully isolate the vibrations, which helps protect the driveline against harmful vibration and ensures low-noise and comfortable driving.
The SACHS dual-mass flywheel is installed between engine and transmission, together with the clutch pressure plate and the clutch disk. The axial installation space requirement for a DMF with clutch corresponds to that of a twin plate clutch so that it can usually be integrated into an existing driveline configuration.
The dual-mass flywheel function effectively reduces noise. The flywheel is divided into a primary and a secondary mass. A highly-efficient, grease-filled spring damping system functions between both of the masses. This means the resonance speed of the dual-mass flywheel is below the idling speed of the engine, which is different from a conventional clutch disk that has a torsional vibration damper. Effective compression springs with a multi-stage characteristic curve design ensure optimal vibration isolation in the bus.
The SACHS bus DMF offers numerous benefits, such as optimal vibration isolation across the entire speed range, customized modification to the vehicle design, effective noise reduction, smooth setting-off behavior, great shifting and ride comfort, protection of the transmission, excellent start-stop behavior, long service life, reduced installation space requirements and efficiency through reduction of fuel consumption because vehicles can be operated at lower rpm levels.
A DMF can only be tested on a special test bench for dual-mass flywheels. The repair shop can perform only a visual inspection, which, however, – like the tests on the test bench – just provides a snapshot. Assessing such an inspection requires a great deal of expertise.
Inspect the dual-mass flywheel each time the clutch is replaced. If the clutch has already been replaced once, then also replace the dual-mass flywheel.