There are dynamos you put into the front wheel. I think they are more efficient than the ones you are Talking about (exterior). https://hollandbikeshop.com/en-

There are dynamos you put into the front wheel. I think they are more efficient than the ones you are Talking about (exterior). https://hollandbikeshop.com/en-gb/bicycle-wheels/front-hub/dynamo-hub/shimano-dh-c3003-hub-dynamo-6v-3w-36-hole-silver/ https://hollandbikeshop.com/en-gb/bicycle-wheels/front-hub/d...