Originally Posted by
Alan K
I am curious about the modern dynamo as to much perceptible drag they cause. I remember the old style dynamos that used to work by spinning against the side of the rear wheel tire. I thought they were awful and removed it off my bicycle within a few weeks. Of course, this was pre- LED era so the bulbs didn’t produce much light for all that drag.
When you say "modern dynamo", they have not changed much in over a decade.
This article is one of many I read before I built up my first dynohub wheel over a decade ago. There is a graph with drag with lights on and off.
https://www.cyclinguk.org/sites/defa...ub-dynamos.pdf
I can't feel any drag when I am riding with lights on, so I usually just leave them on in daytime unless I am charging up batteries instead.
I mainly bought my first dynohub for bike touring to use for battery charging. On my last two tours, I was fully self sufficient on electric power from my hub. But my phone is typically off. I am very careful on my GPS to keep the backlight off or at a minimum. When charging batteries, my lights are off. I often use a AAA powered flasher in the rear during daytime.
If I am off the bike, lift my front wheel and give it a spin by hand, it will slow down much quicker if the light is on compared to off, so I know there is drag, but it is quite minor. That said, if you are a racer, you might not get on the podium if you had your lights on.
You did not say why you are interested in a dynohub. If it is for lighting, they are great. A very good recent article on that is here:
https://bikepacking.com/plan/dynamo-...harging-guide/
If you are interested, I described how I wired up my rando bike here:
Wiring up a dyno powered lighting system with USB charger
For battery charging, I used to use the Sinewave Revolution, but I switched last year to the Cycle2Charge V3 USB charger, it puts out a bit more power, but a downside is that if stops putting out any power below about 6.5 or 7 mph.