To outline these tasks was the objective of a workshop of the German Association for Materials Research and Testing (DVM).
The workshop was held in Darmstadt at the local Fraunhofer Institute for Structural Durability and System Reliability LBF.
Due to his activity as a bicycle expert Dirk Zedler regularly faces claims from the practice and has gained an idea of the product groups that are particularly responsible for losses. Zedler not only deals with claims where people get injured, but also with minor claims which nevertheless can be the origin of important amounts of loss. This applies e.g. to the case where a battery is mounted asymmetrically. If the kick-stand will not make up for this shortcoming, the bicycle will topple over and the battery housing will be damaged by scratches.
Batteries which are mounted at usual bottle holder eyelets, can tear out and the battery can fall down. Saddle fixing screws are often only designed to bear pressure, but no tensile forces. If the user lifts his e-bike at the saddle to bring it into the cellar, it is only the saddle that holds the heavy weight of the bicycle and this can make the saddle tear.
In addition, Zedler would be eager to know the behaviour of a battery in a crash test. Collisions between cars and e-bikes are situations one always has to think about. Fuel tanks of cars are also mounted in a protected way.
In general, e-bikes are faster and heavier; furthermore, they are used by inexperienced riders on mountain roads. That means higher operating loads and more braking. Fatigue cracks are more likely to happen. Zedler also calls for caution in the case of low step through frames and holes and bolts in the frame. Moreover, he is no friend of front motors.
On the other side, in the case of mid-mounted motors it’s often the chains which fail. They must be riveted properly, i.e. the job of a workshop in the case of a refitting. From Zedler’s point of view some of the components built on regular trekking bikes have often already reached the limits of their load bearing capacity and should not be used on e-bikes. He recommends using all facts known about loads on professional road and mountain bikes to design safe components for e-bikes, also in the case of the frame stiffness.
With regard to the motor control it must be ensured that the bicycle does not yet start when the user is in the process of mounting the bike. Zedler refers to the habits in particular of elderly people to place the foot on the pedal when mounting the bicycle. In bends riders have already fallen, when the propulsion generated by the motor didn’t stop, although the rider had stopped pedalling.
An absolute “No-go“ is in Zedler’s opinion a speed pedelec without suspension: To ride at 50 kmh (30 mph) over a manhole cover is much more serious than with a road bike due to the unsprung masses acting on the bike.
In traffic there are also situations where Zedler sees risks. Many pedestrians cross the roads “by ear”. And the speed of e-bikes is underestimated. The daytime running light can therefore improve the perception.
