A slewing ring, also known as a slewing bearing is a rotational rolling-element bearing that typically supports a heavy but slow-turning or slow-oscillating load, often a horizontal platform such as a conventional crane, a swing yarder, or the wind-facing platform of a horizontal-axis windmill. You might be thinking but how is it different to other rolling-element bearings, but don’t worry we have you covered.
What’s so great about slewing rings?
They are relatively thin and are often made in diameters of a metre or more, so they can be rather large! As an example, the slewing rings on the Falkirk Wheel are 4 metres diameter and fit over a 3.5 metre axle, so that’s one very important engineering element right there!
Slewing bearings often use two rows of rolling elements as well as three race elements, such as an inner ring and two outer ring halves that clamp together, whilst the gear teeth integrate with the inner or outer race, and then are used to drive! Lubrication is of course very important, but also very difficult because they rotate continuously, ad need a good amount. Fortunately, a hydrostatic bearing with pumped oil flow may be used. Slewing rings probably don’t get the recognition they deserve, well until they break! They are serving a very important duty and that’s why they do often come at quite a high price, depending on the vehicle. The slewing rings on an excavator such as a Hitachi or Mitsubishi will be very different in design, so it’s important to make sure you know the exact type you need, before wasting a lot of money on the right model. Slewing rings will continue to be very important for construction equipment, because they’re incredibly solid and built to last.
Further reading on slewing rings
Let’s face it, Selecting the appropriate slewing ring can be a challenge, particularly if there are stringent technical, reliability or economic factors to consider. In these cases, for example, you’d need to look for a supplier who can provide advanced calculations and bespoke solutions, whilst perhaps even a supplier who delivers simulations utilizing state-of-the-art analyse methods. Depending on their design, slewing rings have the following features:
• High load carrying capacity
• High stiffness for rigid bearing application
• Low friction
• Long service life
• Surface protection and corrosion resistance
• Integration of additional features, including:
• Driving mechanism
• Control devices
• Lubrication systems
• Monitoring systems
• Sealing cassettes
We hope this gives you plenty of useful information to work with, but if you’re unsure on the slewing ring or bearing you need for your particular requirements, we may even be able to provide some guidance for you, so don’t hesitate to send us a message. If there’s any one thing to take away from this article, it’s that slewing rings comprise an inner ring and an outer ring, one of which usually incorporates a gear. That’s the core of this innovative engineering creation!