Originally Posted by
chucky
Think about it, why isn't a bottle dynamo as efficient as a hub dynamo in use? There's nothing magical going on inside the hub; it's the tradeoff between designing an efficient engagement mechanism and one that offers complete decoupling. You can't half both, although an electrically decoupled design like a SON offers the best tradeoff.
Actually, the discontinued LightSpin bottle dynamo was slightly more efficient than the SON, according to a German cycle magazine. Most bottle dynamos are designed to a price.