canyoneagle

So, I searched the forums and couldn't find anything in alignment with my question. I've posted it here rather than in the "mechanics" section because I feel I may actually find more dynamo users here.

I'm converting my Norco to dynamo power (using Supernova E3 and taillight), and have purchased a front wheel with a Shimano Alfine dynamo.

I spun the wheel, right out of the box, and noticed ALOT of drag, with a notchy feel, as if the wheel bearing cones are way too tight.
I know that I should expect some drag, and perhaps a little clicking, but wanted some feedback from other Alfine dynamo users before I started tweaking the bearing cones.

Thanks in advance!

DogBoy

I have a shimano dyno and notice the notchy feeling you mention out of the box. Put it on the bike and tighten it down and much of that goes away. When riding I don't notice it at all, and I can't tell the difference between the light being on or off and I get to full-bright at like 4 mph. I use the Lumotec IQ Cyo R and the Dtoplight tail. DO NOT ADJUST THE BEARINGS unless you really know what you are doing. PeterWhiteCycles sells these and knows what to do, you might ask them for guidance if you can't find any other sources. Harris Cyclery is another good source of info on these things.

BarracksSi

I can't tell the difference when the light is on and when it's off. I think there's a bigger difference in drag if I wear a bulky coat versus a slim-fitting cycling jacket, even though that's aero drag.

The leverage that the tire enjoys against the hub is pretty big, really. If you had the dynohub by itself -- not built into a wheel, that is -- and tried to turn its axle, you'd really feel those notches. But put it in a wheel with the tire & rim carrying their inertia far away from the hub, plus the weight of the bike and yourself, and it's hard to notice a difference.

When I bought a cheaper Shimano dynohub setup for my sister's bike, she absolutely loved it compared to the tire-driven dynamo she had been using.

canyoneagle

Thanks for the feedback.
I'm looking forward to being (mostly) battery free!
Part of this weekend's project is to install my new Nokians for our belated Winter here in the Salt Lake Valley.

Cheers!

fietsbob

Yup, Lunch is still not free, you feel magnetic drag as the spinning magnet goes from pole to pole
that the wire coils are wrapped around.
that is how the electric current is generated.

Built up in a wheel you will not find it significant, particularly when cold wet and dark.

canyoneagle

Yep, I knew to expect some drag. What I was wanting to gauge was how much is acceptable, and if there was a possibility that the notchiness might also be attributable to the bearings binding a bit.
Thanks!

fietsbob

If its not acceptable.. it really is up to you, as to what's acceptable..

Buy a Schmidt instead, the Brevet-Rando racers like the 20" wheel version in a 700c wheel
to lower the drag further, but the speed that you have to be moving is faster
to have the same power as the 28 version offers at lower speeds.

Arcanum

Alfine dynohub, Lumotec IQ Cyo and Toplight Line Plus lights here. More often than not, you won't notice the difference. If there are other things working against you and you're paying attention to your cycle computer, you might notice a small (1-2ish MPH) difference in speed when the lights are on.

The convenience, brightness, reliability, and peace of mind is more than worth it IMO.

Sirrus Rider

I have a Shimano 3n71 and a Cyo on one of my commuters. I only notice the drag when starting out, but once I'm rolling at a good clip it's hardly noticeable. Like others have said it's nice to have a bike that is "Grab and go" and not have to worry on whether or not the battery has to be topped off or unplugged from the charger by X time. That makes the setup worth the extra expense.

silver_ghost

If you thought the drag from the hub was bad, wait till you put on the studded tires! But as with your dynamo, the benefits outweigh the losses.

mechBgon

I have an Alfine dyno on a road-sport bike. I know the notchy feeling is a little disturbing at first, but it gives back almost as much as it takes (when the light is off). I sometimes feel a slight harmonic buzz through the fork at around 18mph, but it has negligible effect on riding speed at any speed. I'm still not 100% thrilled with the high weight-to-output ratio, but that's another story.

interested

It is very very likely that it isn't the bearings that are causing the drag. The "notchy" feeling stems from overcoming the magnet resistance. After passing the magnets*, they actually push almost as much as they resisted, so very little energy loss or drag is in fact produced that way. To put in another way, slowly rotating a hub generator doesn't give good information on how much drag it actually produce.

*the rotor wrapped in copper wires are stationary while the hub shell rotates, so it is a little more complex to describe in reality than that, but idea is the same.

The Shimano Alfine S501 (and 3N72, 3N80 etc, they are all electrically identical) only have a 2 watt drag at 30 km/h when the lights are off. A front hub normally has 0.5 watt drag. When the lights are on (B&M Cyo), it has a 7.5 watt drag at 30 km/h. A Supernova E3 will produce a somewhat higher drag because it produces more lumens.
But still, that is almost nothing. Even between different brand of racing tires the difference can be more than 20 watt in RR drag.

--
Regards

MileHighMark

It's unlikely that it's the bearings. I have a Shimano DH-3N80 hub, and as an experiment, loosened the bearings until there was noticeable side-to-side play (when the wheel was clamped in the fork). Gave the wheel a spin (by hand), and it still "pulsed" due to the magnets. To be honest, I really don't notice any more drag with the dynohub over the LX hub that it replaced (which had properly adjusted bearings).

canyoneagle

Excellent input, folks - you've more or less confirmed that everything's just hunky dory with the hub - I knew to expect some of the resistance/notchiness and wanted to have some confidence that the extent of notchiness was somewhat normal. I look forward to putting it into service!
The headlight and taillight should arrive later this week, but I will install the tires and front wheel to get things underway.