Freewheel clutch (overrunning clutch) for different automobiles
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Steady engine and gear: the flywheel
The flywheel is an energy storage device, charged by rotation and providing torque on demand. This is very important for engines as they would otherwise develop strong vibrations. As engines are becoming smaller and more powerful, the flywheel's construction needed an update. Nowadays, the dual-mass flywheel is becoming gradually standard. This has certain advantages as well as higher costs.
Taming the power line
Its construction condems the piston engine to shaking and rattling. It starts with an explosion pushing a piston straight ahead. This linear movement is caught via two joints by a con rod and the crankshaft. Subsequently, the linear motion is converted into rotational motion. This rotation is ultimately transferred to the clutch and from there to the gearbox. One-cylinder four-stroke engines cannot function without a flywheel. These engines must generate sufficient power in one stroke to enable the following three power strokes. Radial engines with many cylinders, on the other hand, can do without a flywheel. Over the last few years, car engines have become a great deal more powerful, reaching higher performance with fewer cylinders. Generating over 100 HP with a three-cylinder engine with barely 1 litre cylinder capacity has now become standard. Problem are the vibrations it causes, which could lead to destructive resonance. This could cause serious damage to engine and transmission. Before the great increase in performance, the integrated flywheel in the clutch plate was sufficient for a steady engine running. For the engines of today this will no longer do. They require a flywheel that stores the rotation energy and additionally separates the engine's vibrations from the gearbox in a reliable manner. This is why the dual-mass flywheel was developed. The dual-mass flywheel is a separate component, no longer integrated in the clutch plate. Today it is seperately listed and sold.
Dual-mass flywheel: function
The two halves of the dual-mass flyhwheel are connected by a bearing including a damper. One half is responsible for the engine, the other for the gearbox. Thanks to the dual-mass flywheel and its integrated damping, the transmission of vibrancy is prevented. The dual-mass flywheel is located behind the clutch plate.
The problem of the dual-mass flywheel is the integrated damping. It is in fact a permanent grease lubrication which cannot be replaced. Through overheating and ageing the grease can become mouldy and lose its lubricating quality. Both halves of the flywheel collide without damping. The driver notices this by knocking noises when shifting gear. The damage spreads quickly, ultimately affecting the gearbox and the engine.
Dual-mass flywheel replacement
Replacing dual a mass flywheel is just as complicated as replacing a clutch. Both procedures are very similar. The life span of the flywheel corresponds to ca. 150.000 km. When the clutch plate needs replacement after 120.000 km, it makes sense to replace the dual mass flywheel as well, saving yourself a great deal of work and ending up with a fully functional new clutch. A disadvantage of the dual-mass flywheel is its price. It starts at 250 EUR (± £220). More realistic are prices of 500 – 600 EUR (± £440 - £530) for a high-quality long-life spare part. Rather than saving on the material, a DIY'er should save time: if the flywheel has to be disassembled, it makes sense to replace the clutch along with it. However, it is important always to replace the clutch as a set. All accessory parts such as gaskets and bearing should be renewed as well. This guarantees a fully reliable clutch for the next 120.000 km.
Safety comes first
A dual-mass flywheel replacement requires disassembly of the gearbox. This can only be done from underneath the car. In order to safely work under the car, it must be secured. The accessory trade offers special car stands for this, enabling safely working under a car without the need for a lifting platform.