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Dimensionally stable in humidity

Polymer plain bearings in mountain bikes with spring-loaded rear wheels

Profile

  • What was needed: Bearing for rear suspension of mountain bikes
  • Manufacturing process: Plastic injection moulding
  • Requirements: Suitable for heavy duty and enormous lateral forces, very high dimensional stability in moisture
  • Material: iglidur® J
  • Industry: Bicycle industry
  • Success for the customer: Very durable plain bearings with predictable service life; secure seating in the bearing, even with very heavy loads and large lateral forces, without the need for additional lubricants

The  

Selection of the articulation points and kinematics

In the field of Bergamont's full suspension mountain bikes, "ConTrail MGN" is one of the top models. At the dropouts of the rear suspension, lightweight iglidur polymer plain bearings from igus are used for heavy duty applications. When designing a rear suspension, the definition of the pivot points plays a very important role. Thomas Marquardt: "We have a clear understanding of how a bike should run and carry out extensive testing during development." This not only applies to the placement of the pivot points and to the kinematics, but also to the selection of the bearing points. At all bearing points Bergamont originally used its "Fullys" ball bearings. For the first time, the "Contrail MGN" has deviated from this principle. "At the two front pivot points," says Marquardt, "that is, when connecting the rocker to the frame, we use deep groove ball bearings because the bearings here make a relatively large pivoting movement. On the rear joint, in the rear axle, this time we have departed from the old method and use a plain bearing. “

Larger contact area, nothing wobbles

There are good reasons for the designer, of which the most important is the lateral stiffness. A plain bearing offers a much larger contact surface than a roller bearing. "Even with very heavy loads and large lateral forces, nothing wobbles," explains Marquardt.  
 
At the same time, the iglidur plain bearings are also able to cope very well with the high pressure load that occurs at this bearing point. "The pressure is also distributed very well over the larger area. " Bergamont was assisted by igus in the tests on the plain bearing in the rear suspension joint. It was also about the selection of the optimal plain bearing material. René Achnitz, Global Product Manager, iglidur plain bearings: "In the first trials, we used the all-rounder material iglidur G, but then we found out that iglidur J was more suitable." “

At the rear joint, in the rear axle, the bicycle designers have taken a new path and use iglidur bearings.  

Plain bearings: Select the ideal material

That the tests first started with iglidur G, was obvious. This universal material for very economical plain bearings can be used for the widest range of applications. However, iglidur J offers a higher dimensional stability in moisture, and this parameter was also considered in the bike design.  
 
Naturally, the wheels often run through watercourses and puddles, and they are often cleaned after use with the garden hose or even with a high-pressure cleaner. Thomas Marquardt: "These loads also do not bother the polymer plain bearings." “

iglidur plain bearings in puddle  

Dealers and bikers fully satisfied

The self-lubricating iglidur polymer plain bearings can be expected to have a long,  calculable service life. However, the sales department had to first convince the specialist dealers. Thomas Marquardt: "Several years ago, we used plain bearings made of other materials and were too small in size." Therefore, there was now need for information and training. " With the current solution, however, the dealers are fully satisfied, as the feedback from the bike owners are consistently positive. The torsional rigidity of the wheel was very good and the suspension responded very quickly" reports Marquardt.  
 
This certainly also contributes to the very careful design of the bearing point. In bike production, the plain bearings are pressed into the rocker with slight pressure. In addition, a metal sleeve is inserted into the bearing, which forms the end stop for tightening the screws. So the bearings remain rotatable in any case after assembly work of the bike owner.   

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