Bottle vs. Hub Dynamos

[snailracer]

A decent bottle dynamo is 40% efficient; a good hub dynamo is 60% efficient. So for a 3W bulb light, a bottle will make you put in an extra 7.5W of pedalling power and a hub will cost an extra 5W.
Modern LED lights will draw more power than this (about 7W from a hub dynamo at 30kph).
Lights off drag from a good hub is about 0.5W at 20kph, 1W at 30kph. An ordinary front hub will give about 0.25W drag at 30kph
...

A cheap LED dynamo light draws 2W at just about any speed. On the one hand, this results in less light than the 7W you mention, on the other hand it is less work for the rider.

 

[mrfacetious]

Hi guys, thanks for the replies. I think I'm going to go for the bottle as I think, given the pros and cons, it's the one i'd prefer. I'll only really use it for long distance rides, not my day-to-day circuit, as my primary aim in getting one was to buy a USB charger to attach to it, to give my phone some juice as it plays me music/tells me how lost i am.

 

[Spokesmann]

Use a number of old Miller bottle dynos - still work well!

This is my 12v version, I dont use it that much as it take about 10mph off my speed its got that much resistance!!

 

[bivvy]

I hope people don't mind me bringing this thread up. I'd love to know how mrfacetious got on with the bottle dynamo that was chosen. Did it do the job well?

 

[MichaelW2]

My touring bike has a Nordlicht 2000 bottle dynamo bolted to a braze-on rear mount. With any bottle dynamo, solid , well-aligned mounting is key.
My commuter bike has a High-end Shimano dynohub (with disc rotor). It is fit and forget, totally reliable.

The only issue with dynohubs is bearing maintence. Shimano ones are very tricky to service and few places will attempt it. Son are much better.
For touring, where lighting is only needed for the occasional foggy mountain or pub evening into town, bottle dynamos are probably best. For all day, every day availability, through UK winters, you cant beat dynohubs.

 

[palinurus]

I hope people don't mind me bringing this thread up. I'd love to know how mrfacetious got on with the bottle dynamo that was chosen. Did it do the job well?

He's not logged in for over two years! nonetheless I'd like to know how he got on too.

 

[uclown2002]

Holy Thread Resurrection!!