The "Low Tech Magazine" has a guide to building a DIY bike generator https://solar.lowtechmagazine.com/2022/03/how-to-build-a-practical-household-bike-generator

The "Low Tech Magazine" has a guide to building a DIY bike generator https://solar.lowtechmagazine.com/2022/03/how-to-build-a-practical-household-bike-generator/ https://solar.lowtechmagazine.com/2022/03/how-to-build-a-pra... Unfortunately even with the bike it seems like you really need to find one machine that can be repurposed, a rowing machine seems a bit of a stretch.