Steinbeis-Team develops a universal test rig for bicycle wheels
The wheels are the most important part of a bicycle and require extensive testing, not only to determine service life and load limits, but also to make optimizations. The challenge is to replicate real-world scenarios as accurately as possible under laboratory conditions.The Steinbeis Innovation Center for Sustainable Lightweight Construction, E&M Industrial Engineering, and PI ROPE took on this task and developed an innovative test rig as part of a project funded by the Federal Ministry for Economic Affairs and Climate Action.
The aim of this project was to develop a novel test rig and testing procedures capable of performing service life, drive, and brake tests, as well as static strength and lateral stiffness tests. In addition to revisiting existing processes, which are based on prevailing standards, the focus lay in simulating realistic levels of load transfer.
A new concept was developed for testing these parameters under laboratory conditions based on several field tests conducted under different scenarios. Joining forces with E&M made it possible to go through testing sequences on a prototype rig, which thanks to its modular structure is suitable for a broad spectrum of wheel assembly testing conditions. The result was a true-to-life, cost-effective, and time-saving testing alternative for wheel assemblies, which now allows the entire service life of wheels to be tested in less than four days.
More functions – better results
Until now, wheel assembly testing was based on DIN EN ISO 4210-7. However, the assumed load levels and test sequences of this standard do not accurately reflect actual loads placed on wheels. It was necessary to completely rethink the peaks in load, the types of load, load duration, and variations in load. The results of extensive field testing allowed the project partners to determine a significantly broader spectrum of load scenarios than those used at that time under the DIN standard. During validation, there were significantly better degrees of overlap with the kind of load levels that actually occur.
Compared to the requirements laid down under the norm, the test bed is fitted with significantly more functions. These make it possible to apply more stress to wheels and the load levels are thus more realistic. In addition to standard impact testing, it is also possible to subject wheels to lateral forces during endurance testing.
The functions offered by the test bed include the following innovative test modules:
- Endurance testing (service life simulation) by running the wheel subjected to a normal force over bumps
- Individually programmable lateral impacting during endurance testing using an additional lateral force module.
- Drive testing of rear wheels: This involves securing a wheel set on the circumference and subjecting the drive unit to fluctuating stress in the form of maximum torque.
- Brake testing: Wheels are secured on the circumference and again load is applied to the hub. This also involves subjecting the hub to fluctuating stress in the form of torque and applying realistic braking forces to the wheel assembly.
- Hub testing: This allows a testing process to be offered to hub manufacturers. Again, hubs can be secured and individual functional components can be tested for durability by applying stress in the form of fluctuating torque.
Based on a number of experiments, improvements are currently being made to the test bed to prepare it for serial production.