A lot of construction machines equipped with combustion engines have a centrifugal clutch. This small element plays a great role in the operation of this type of equipment. Its operation is based on simple principles of physics and allows for comfortable operation of the device. For instance, jack hammers, compaction plates and rammers, handheld power cutters and saws can be equipped with the centrifugal clutch. So, how does a centrifugal clutch work and what is it made of?
WHAT IS A CLUTCH FOR?
Clutches, as structural elements of machines – including vehicles, are used to transmit torque from the drive shaft to the driven shaft. To put it simply, thanks to the clutch, it is possible to transfer smoothly the mechanical energy generated by the engine to individual working elements of a specific device.
Car drivers who have experienced the failure of this key element can confirm a high need for applying clutches. Construction equipment operators would face a similar difficulty because working tools such as a chisel or a compactor foot would be started along with the starting of the engine. The clutch also functions as a kind of shock absorber and provides protection against too high torque that could damage the driveline.
CENTRIFUGAL CLUTCH – WORKING PRINCIPLE
The centrifugal clutch works in a rather characteristic way. It is activated when a certain rotational speed is exceeded. It means that it does not transmit torque when the engine is idling (in neutral, without load). The engine speed must be increased to start the working tool. Then, the centrifugal force counteracts the force of the springs which pull back the friction elements of the clutch and it leads to the starting of the clutch.
It has a huge advantage. The use of a centrifugal clutch allows, for instance, for the free preheating of the engine and reaching working temperature before using the main working tool (without the need of previous switching). The principle of operation of this type of clutch also affects the operator's safety. Why? Because when the speed is reduced, the drive and the working tool disengage, for example, a chain on a chainsaw stops turning.
THE STRUCTURE OF A CENTRIFUGAL CLUTCH
The structure of the centrifugal clutch is quite simple, therefore it is quite a durable element of the drive system. It mainly consists of weights, drivers and springs. Increasing rotational speed causes increasing pressure on faster and faster spinning weights. If the centrifugal force is greater than the force of the springs, the weights will move and contact the friction elements (clutch engages). Similarly, if the engine speed decreases, the springs will start to pull the friction elements until their disconnection (switching off the clutch).
PROPER USE OF THE CENTRIFUGAL CLUTCH
Despite the simple and durable structure, this type of clutch is not indestructible. For this reason, it is absolutely necessary to follow the recommendations received from the manufacturer and written in the instruction for use of the given equipment. It is also worth holding to the general rules that apply to all devices with a centrifugal clutch. They will help extend the life of this component and thus reduce service costs.
HOW TO CARE FOR A CENTRIFUGAL CLUTCH IN CONSTRUCTION MACHINES?
- Take care of proper lubrication of the moving parts of the device, so that the resistance and wear of the clutch is reduced. In addition, cold grease, e.g. in the impact mechanism of demolition hammers, can cause the slipping of the centrifugal clutch. Therefore, before starting work with these devices, it is necessary to warm up the engine at low speed.
- Switch between the idle speed and the working speed of the equipment as quickly as possible. Slow increasing or decreasing revolutions adversely affects the components of the clutch and shortens its life.
- Depending on the recommendations of the manufacturer of the equipment, a given model of the device should (in operating mode) be used only with full gas – of course, after previous warming up of the engine. Continuous operation at lower revolutions can damage the centrifugal clutch. This recommendation concerns, for instance, selected single direction vibratory plate compactors and vibratory rammers (tampers).