Originally Posted by
noglider
What are you hoping to accomplish? A few people use dynamos on their bikes to charge their electronics, but it doesn't seem worth the expense unless you're going to ride many days with a lot of time away from a power outlet. I use an Anker external battery to keep my phone charged while I'm on the bike. I'm at a power outlet every night.
I'm just thinking about this as a design exercise. Given that current solutions for charging larger devices (a phone, battery pack, etc) are expensive and less than ideal due to the issues already outlined (wide range of operating rpm, relatively low power output available, considerations for existing lighting systems, etc), what would a more ideal solution look like? I had the thought that a separate generator, driven by a front chainring, would alleviate most of these issues. It would largely operate within a small rpm range, could be sized for more output power than dynohubs, and wouldn't need to share its output with lighting systems.
The main problems I see are: difficulty of mounting (it would have to mesh with the smallest chainring, on the unused portion towards the rear of the ring), the small amount of available space, and weatherproofing.