FOERSTER
Application notes
Bottom bracket shaft test for e-bike torque sensors

Bottom bracket shaft test for e-bike torque sensors

Defective bottom bracket shafts can impair the measurement accuracy of e-bike torque sensors. Magneto-inductive structure and crack testing with MAGNATEST D reliably inspects the shafts.

The challenge

In magnetostrictive torque sensor applications, the bottom bracket shaft becomes both mechanical force transmitter and functional sensor. Its magnetic properties directly influence measurement accuracy. Alloy composition, hardening depth, residual magnetism and structural defects such as microcracks or inhomogeneities can impair sensitivity. High-volume production therefore requires comprehensive verification of mechanical and magnetic properties.

The solution

FOERSTER has developed a multi-stage test cell for production environments. The process includes component identification, demagnetization with EMAG, residual field C-scan, magneto-inductive microstructure testing using MAGNATEST D with dual fork probe, surface scanning for defects, and optical inspection. The modular setup can be integrated inline or operated as a stand-alone system.

The result

The solution ensures early detection of material mix-ups, incorrect hardening depth, residual magnetic fields and structural defects. Automated OK/NOK sorting guarantees traceable quality control in serial production. Flexible configuration allows adaptation to specific customer requirements and supports reliable performance of torque sensor shafts in e-bike applications.

The illustrated test cell comprises: (1) component identification and marking, (2) demagnetization with EMAG, (3) residual magnetic field C-scan, (4) magneto-inductive microstructure testing with MAGNATEST D, (5) surface scanning for structural defects, (6) optical inspection of geometry and cleanliness, and (7) automated OK/NOK sorting.