Originally Posted by
bobn
I am curious if anyone has experimented with the drag factor of a bottle generator. I'm not trying to be agumentative because you have the final say as to what you do. And that's fine with me.
Try spinning the wheel without the bottle gen. and time the rotations to stop. Then put on the lights with the bottle gen engaged and time the rotations again. I would do it but don't have one hooked up. Just curious as to the outcome.
I don't yet have a generator to test, but I accidentally did a similar test today. Last night I opened up my 3 speed hub to put a little more oil in. I overtightened it when I put it back together and noticed that when I spun the wheel it wouldn't spin freely like it had prior to my messing with it. Giving the pedals a couple of turns and then stopping sent the wheel spinning maybe one more rotation whereas before it had spun fairly freely. I was tired of messing with it, so today I rode it that way. I could definitely feel the drag, especially when coasting, but, other then worrying about what I was doing to my bearings, it didn't impede my ability to get home. I'll be fixing it before taking it out again, but I didn't find it to take longer than normal to get home, I just had to pedal a little more often. I'm not going to intentionally introduce drag for no reason, but when it's there, I think it improves my cadence.
If you're really worried about drag, it seems like a bottle dynamo is a good compromise. Unlike hub dynamos, you can remove all drag from a bottle dynamo when you're not using it, although when you are using it, I believe the drag is a little more. I believe I did see a study where someone compared many aspects of various generators, including bottle dynamos and hubs, and drag was included in that study, I think, but I can't find it right now. I've read too much dynamo info in the past 24 hours and can't remember which link is which.