Have you seen this TMM Torque Sensor

[cirrus18]

Anybody know if these sensors are available as a retrofit? Could be a good project for someone with the necessary electronic know-how to develop a DIY product.

TMM sensor unit http://www.idbike.com/tmm-powermanagement.htm

The TMM4 sensor is the newest development of IDbike, and can be used for measuring the crank torque of the cyclist. Because of the high precision this sensor can be applied in elecrtic bicycles as well in power measurement systems.

At this time IDbike has started up production, sensors are available now.

[moderator edit to fix link]

 

[LockH]

TMM Sensor recently noted as a reference to a paper submitted to the 3rd International Conference on Materials Engineering, Manufacturing Technology and Control (ICMEMTC) in 2016.

Design and Implementation of Torque Sensing System of Intelligent E-bike:
http://docplayer.net/37527771-Desig...que-sensing-system-of-intelligent-e-bike.html

Conclusion
In this paper, a newly E-bike torque sensing system is designed and implemented. In this new system, the wireless power supply, the strain gauge sensor and the wireless digital communication are combined, and the compensation capability of the microprocessor is utilized. Due to the complex operation environment of the E-bike, the torque acquisition module is hidden in the axle to avoid the influence of the water and dust. The test results indicate that the system works well with high stability and accuracy. On the other hand, it satisfies the application requirement and provides a technical selection for the development and improvement of the E-bike.

... and re Idbike:
[youtube]gjonXtoF4t4[/youtube]

 

[spinningmagnets]

The Juiced Riders "Ocean Current" E-Cruiser has the torque-sensor in the drop-out, so...since I haven't seen any others yet, I wonder if the Juiced line is converting over to the TMM unit?