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


Off paved roads and paths, many wheelchairs reach their limits: small front wheels sink into soft ground, and large ones increase turning radius, reducing agility. Hoss Mobility GmbH has developed a balance wheelchair that works like a Segway and needs no front wheels. Supports are used to ensure that it does not tip over even without a power supply. In these and other bearing points, the developers use iglidur P plastic plain bearings.

Profile

  • What was needed: bearings for the extendable safety supports, later for the seat, back shell, and armrests as well
  • Requirements: robust at high rotation speeds and shock loads, resistant to different weather conditions, lightweight, small dimensions
  • Industry: medical technology, mobility and rehabilitation equipment, wheelchairs
  • Success for the customer: plain bearings made of iglidur P material with compact installation size, weather resistance, and extreme impact resistance for the outdoor all-rounder in the igus bearing product range. The bearings allow the safety supports to move reliably over the long term without the risk of corrosion and without lubrication or maintenance
iglidur plain bearings in the Hoss Mobility wheelchair

iglidur P

The dimensionally stable all-round bearing for outdoors with very good coefficients of friction
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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 Wheelchair rear view; the extendable safety support containing iglidur P plain bearings is in the centre.
Hoss wheelchair with iglidur plain bearings in the safety support 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.