Would have liked to wait for the right bike to show up at the recycling centre, but time was slipping by. So I bought a lighter chain wheel to replace the one used to test the concept.
Might be placebo, the power of suggestion, or perhaps I’m getting fitter… but I was able to pedal so hard that the alternator generated 17.9 volts. A new personal best! 🙂
If you want the details, this pic shows the chain wheel specs.