Lightweight victory with plastic bearings in racing

Two-wheel motorsport has a whole range of different vehicle classes; down to single-cylinder machines. The limited engine power of these bikes is not a disadvantage, if the weight – namely, the mass to be accelerated – is also reduced considerably. Here, plastic bearings make an important contribution.

At Krämer Motorcycles (KMC), the Supermono racing bike has won the title in the single-cylinder championship, and is doing well in the current Super Twin season. The HKR-EVO2 bike has a top speed of 140mph. In the recent Tandragee 100 road race in Northern Ireland, Shaun Anderson achieved an average speed of 100.485mph, reportedly becoming the first and only racer to surpass the 100mph mark on a single-cylinder motorcycle.

Although the company is still relatively young, a lot of development work has gone into the machine. It began in 2009 as a private project of three friends, Christof Henco, Markus Krämer and Nico Rothe to develop their own motorcycle purely for motorsport purposes. This led to the founding of Krämer Motorcycles in 2014 by Markus Krämer, who previously worked as a development engineer at KTM. Accordingly, the decision for the central component was not difficult: the single-cylinder engine KTM 690 LC4 served as a drive unit from the beginning. Around this was built the rest of the bike, partly with standard parts and partly with self-developed components.

The chrome-molybdenum steel tubular frame weighs just 6.5kg; a third of the weight of the standard frame used on a KTM series machine. The tail boom made of XPE plastic is another highlight of the racing machine built in Töging. Seat and tank are joined together here, which also saves a lot of weight.

“One of our design principles is to combine multiple functions in one part and thus reduce the component count and thereby the mass to be moved,” explained Markus Krämer, CEO of KMC.

KMC looks at each and every component and tries to come up with in-house developments that meet their own requirements instead of using standard products. Weight reduction is of prime importance. Since the maximum power of a single-cylinder engine is limited, the only way to secure a speed advantage is to reduce its mass.

The latest development is the new link system for the rear swinging arm, which connects the rear wheel to the frame via a damper. The shaft of the previous link system comprised of nine metal parts, which had to be laboriously assembled and lubricated. The new design, on the other hand, only needs two press-fit lubrication-free plastic bearings and can be operated maintenance-free. Another advantage is that the weight is reduced by about a third: from 535 to 355g. Finally, the price of the components, including the iglidur Q flange bearings, is significantly lower than that of the previous design.

From igus, two igubal rod ends transfer the power in the foot brake. The footrest system uses iglidur J plain bearings, and the deflection shaft of the gear shift system is also connected with an iglidur plain bearing. Krämer also uses iglidur J plain bearings for shift and brake levers.

Conventional 80-horsepower machines are regarded as underpowered, the HKR-EVO2 weighing only 125kg cuts a good figure with this drive against much more powerful, but heavier motorcycles in the field. Strong braking deceleration and precise track guiding despite high cornering speeds with extreme riding positions bring the racing machine forward, especially on stretches with tight bends.