As mentioned last post, I got fed-up of waiting for the motor bracket to arrive and switched my attention to the next revision of the project. But, before I get too far ahead, I thought it may be worth revisiting the goals and progress of the v1 build…
The original aim was to modify a basic magnetic resistance trainer (with manual control) into a computer controlled ergotrainer for less than £50.
The handlebar adjustment lever was replaced by a micro and a hobby servo motor, while the computer control was achieved by adding support for a new trainer type to Golden Cheetah. The minimum cost was approximately £10 for the motor, and £20 for the microcontroller board. Probably another £15 went into the enclosure & switches to make the handlebar controller, power supply components, and a metal bracket & enclosure for the motor assembly.
Good news then – I ended up nominally under budget. Although of course there were other parts bought, experimented with, and discarded along the way (as I suspect is the case with any hobby project), so the actual spend would have been a bit over.
So, did I succeed in the original aim? Definitely maybe!
For my use case, absolutely – power based workouts for less than fifty quid, but there’s a catch…
I already own a power-meter, and it’s been absolutely necessary to use the real-time power data as an additional input – to trim the resistance to match the requested load.
Despite various calibration attempts, I’ve not been able to get sufficient accuracy without this element of closed loop control. So, while I’d say it’s been a success – it still doesn’t quite feel like the £50 ergotrainer I imagined at the start.
Which is where v2 comes in… In this new version, I’ll be ditching the whole cable & sliding permanent magnet assembly, and using electromagnets to control the resistance directly. My hope is that I can make this new design sufficiently accurate to be usable without a separate power meter.