Compact and corrosion-free: plain bearings in a new type of Segway wheelchair

Problem

The supports are designed to deploy within 100 milliseconds in an emergency situation, such as when the tyres lose traction or the battery runs out of power. When that happens, the bearing points are exposed to up to 5,000 revolutions per minute. Finding bearings that can withstand such a load and are compact enough for small installation spaces was a challenge for the design engineers. The bearings are used outdoors and off-road, so they also have to withstand impacts, direct sunlight, snow, rain, dirt, and temperatures ranging from -10 to +50°C. And since every extra gram reduces battery range, the bearings need to be as light as possible.

This ruled out conventional metal ball bearings, especially because of their size.

Solution

iglidur P plain bearings proved to be the perfect solution. These are compact – 1 millimetre wall thickness with 12 millimetres inner diameter – but still handle loads of up to 50MPa. So they can resist the ground impact when the supports extend quickly. Like all igus bearings, they have solid lubricants embedded in them, so no additional lubrication is needed. No sand, dust, or dirt can adhere and clog or damage the bearing. Even rain and snow pose no threat to the corrosion-free plastic material. This makes the bearings very durable and maintenance-free. Hoss Mobility was so impressed that it also used them in the cushioned seat, the back shell, and the removable armrests. These applications, too, require minimal maintenance and maximum service life with small size and weight.

Wheelchair rear view; the extendable safety support containing iglidur P plain bearings is in the centre.

In an emergency, the support extends in just 100 milliseconds to prevent the wheelchair from tipping over. The bearing locations can be seen clearly here in the prototype.