You are hereLiebherr Group: Products & Services for Argentina
Starting with 5-axle models, we plan to install the new clutch module gradually in all our three to five-axle mobile cranes. However, since thousands of mobile cranes with a dry clutch are still in action, since 1999 in the ZF-AS-Tronic gearbox and since 2017 in the ZF-TraXon gearbox, in this edition we explain how you can also drive a crane with a dry clutch without causing a great deal of wear. These tips are provided by our experts, Peter Pflug from our Testing and Engine Application Department, and Jörg Schlegel, a trainer at our Ehingen training centre.
Peter Pflug: Our tip “Press the accelerator and protect your clutch” initially seems to be a contradiction in terms, but what you have to know is that the clutch closing process depends on the drive resistance and the accelerator setting. You should therefore always start a normal trip quickly with plenty of accelerator so that the clutch does not suffer wear for any length of time.
Jörg Schlegel: These are automated manual gearboxes. The gearshift is controlled automatically which means that a clutch pedal is not required. The gearbox control system is also responsible for closing the clutch. The more drive power that is required, the more the accelerator pedal has to be pressed to achieve the appropriate coupling moment at which the clutch no longer slips. Various factors play a role in this – the gradient, the weight of the vehicle, the driving resistance, the selected gear and the driving mode, in other words on-road driving, offroad gear or manoeuvring mode.
You can influence the closing process of the clutch by pressing the accelerator.
Peter Pflug: The high gear ratio of the distributor gear is active for on-road driving, whilst the low one is active for off-road gear. If off-road gear is active, the second gear is automatically selected. This means on our 5-axle cranes, for example, when the clutch is closed, the crane has a minimum speed of 1.2 km/h. If an even lower speed is required, you should switch to manoeuvring mode. You have to proactively engage first gear. This enables you to travel at a minimum speed of 0.6 km/h when the clutch is closed.
Our tips enable you to save money and downtime.
Jörg Schlegel: Actually, you should not just use the offroad gear for driving off-road – it should also be used if you have to manoeuvre the crane for a lengthy period of time. The low ratio protects the clutch. It is essential that you ensure that the clutch is completely closed. You can check the monitoring lamp in the display unit to ensure that this is the case. If it is lit, the clutch is not fully closed. In that case, you have to press the accelerator a little further.
You need manoeuvring mode if you wish to drive even more slowly. This is the case, for example, if you have to position the crane precisely or you have to manoeuvre it out of a gap. The monitoring lamp will be permanently lit in manoeuvring mode to warn the driver not to remain in this mode for an excessive period of time.
Peter Pflug: Other situations in which there is a risk of increased clutch wear include traffic jams or stop and go traffic, particularly on gradients. We have two tips to help you with this: Switch from automatic mode to manual mode and engage a low road gear or even an off-road gear so that the clutch closes completely at a low speed. And reduce the number of starts to make by keeping a variable distance from the vehicle in front so that you can react to what is happening ahead.
Jörg Schlegel: If the clutch does become very heated, the symbol “CL” (clutch load) will appear on the display below the rev counter. If this happens, you should definitely allow the clutch to cool because if you subject it to any more stress, the clutch will suffer an extremely high level of wear. To do so, select neutral and leave the engine running. If you use our tips, they will enable you to drive the crane comfortably and with low wear, even if it has a gearbox with a dry clutch. Have a good trip!
This article was published in the UpLoad magazine 02 | 2022.