Talk:Bottle dynamo

Hello, I'm looking for information on how to use a bottle generator to recharge a laptop. If you have any information about this perhaps you can drop a quick note over on the discussion page for our wiki: http://wiki.laptop.org/go/Peripherals/Bicycle_Cassette

Thanks in advance, from http://wiki.laptop.org/go/User:Hbonwit  —Preceding unsigned comment added by 59.94.102.168 (talk) 12:05, 15 April 2008 (UTC)[reply]

Now I know wikipedians just love to insert <citation needed> everywhere, but this is getting ridiculous. The fact that the dynamo will slow down the bike, because it extracts energy and will inevitably have some drag is both very obvious and known by anyone who has ever ridden a bicycle with such a dynamo. When the dynamo is disengaged, it's not touching the wheel, so there is no extra drag. Talk about stating the obvious, and yet, somebody thinks we need a citation. The same goes for the slippage.

When I say milk can go sour, do you really need a citation? 77.250.213.154 (talk) 01:20, 24 March 2009 (UTC)[reply]

Well, a link to the article on Milk, possible to the section relating to its mode of spoilage might be appreciated, if nothing else. As would one to, e.g. the general page about electrical generators, and/or the laws of conservation of energy.

What I want to know is whether anyone has evidence that a hub dynamo - a device that offers no more frictional resistance than a regular hub, if properly made - offers any kind of additional drag, much less a meaningful amount of it, when the attached circuit is open/broken, IE there is and cannot be any load applied to the device's terminals. Surely it would be like the eddy current retarder on a truck or bus, it only slows the machine when the circuit is actually switched in and useful energy is being drawn from it (or in the case of the retarder, unwanted kinetic energy is being turned into heat). The article as it stands seems to puff bottle dynamos slightly with the suggestion that they're superior because you can move them away from the tyre. Never mind that the only bikes I've ever ridden with them had the dynamo in a fixed position, and they themselves only offered any notable resistance when the attached headlight was turned on. 193.63.174.211 (talk) 09:32, 9 May 2013 (UTC)[reply]

You can see the drag from a disconnected hub dynamo by spinning the wheel off the bike. Anything with magnets and metals nearby will produce some eddy current drag. It's noticeable, although it's dwarfed by the tyre's rolling resistance as soon as you change the system from "bike hub" to "bike on the road". Andy Dingley (talk) 09:38, 9 May 2013 (UTC)[reply]