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Old 03-22-08, 02:06 PM   #1
Pedaleur
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Shimano Generator Hub -- Feels Notched

I just bought a Shimano 3N71 generator hub. When I turn the axle, it feel very "notched" or "clocked" (like the wheel button on my computer mouse, only much worse). I realize that there should be _some_ resistance, but shouldn't it be 'smooth' resistance? Or is this normal?
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Old 03-22-08, 02:41 PM   #2
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The bearing cones might not be adjusted properly. Make sure they are not too tight, and make sure they have grease in them. If the hub is brand new, the shop you bought it from should be willing to take a look at it for you.
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Old 03-22-08, 03:03 PM   #3
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Thanks. Unfortunately, I bought the hub mail order (but new). I have sent them an email, but I'm also looking for independent advice here.

My first thought was that the bearing were too tight -- way too tight -- but a quick turn with a cone wrench showed that wasn't the case.
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Old 03-22-08, 03:16 PM   #4
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Is this your first dynahub? If it's notchy it's probably OK. The following is from Peter White's website discussing the German SON dynahub:

When you hold the wheel or hub in your hand and turn the axle, you'll feel a lot of resistance. There are 26 poles and 26 magnets in the SON28 hub (fewer in the SON20). That creates 26 points around the hub shell that the axle wants to settle in, and a corresponding 26 points where the axle doesn't want to be. In the transitions between those points, the axle wants to turn in one direction or the other, to find the point where it wants to settle. As you ride, the hub turns relative to the axle, and 26 times in each rotation of the wheel, the hub wants to turn one way, and then the other, theoretically speeding you up and slowing you down, 26 times per rotation. At speed, the effects of these two forces almost completely cancel each other out, leaving you with extremely low drag overall. It's only when you don't have a lot of mass (your weight) and inertia (your speed) that the effect is to actually ****** the rotation of the hub axle. So there's no reason to be concerned about the way the axle feels when turned by hand.
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Old 03-22-08, 04:41 PM   #5
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Notchiness is normal for a dynohub.
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Old 03-22-08, 09:11 PM   #6
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Lace it to a wheel, and the wheel's inertia -- and much better leverage since it's so much bigger -- will pretty much take care of the notchiness.

That's really why a dynohub feels smoother and drags less than a tire-driven bottle generator. Think of trying to stop a spinning wheel with your hand. If you want to do it quickly & easily, you grab the tire & rim; trying to grab spokes at the hub is much more difficult.
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Old 03-22-08, 10:12 PM   #7
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I have four of them (two SONs and two 3N71, and I used to have a NX-30), so I know Ranman's quote is indeed correct. Don't worry, your hub is most likely in perfect shape.
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Old 03-22-08, 11:29 PM   #8
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Is this your first dynahub?
Heh. How'd you guess?

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If it's notchy it's probably OK. The following is from Peter White's website discussing the German SON dynahub:

<excellent quote snipped>
Exactly what I've been looking for. I did a lot of google searching to find such information, to no avail. I figured this was probably the case, but I also figured that I couldn't possibly be the first new generator hub owner to encounter this. Hence, my concern.

Thanks all. Looking forward to trying it out.
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Old 03-22-08, 11:44 PM   #9
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Where did you get it? I like to know the source.
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Old 03-23-08, 12:58 PM   #10
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Where did you get it? I like to know the source.
Online from Sweden (I live in Denmark): www.cyclecomponents.com

Useless if you live outside Europe, unless you like paying an extra 25% sales tax.
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Old 03-23-08, 02:16 PM   #11
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Online from Sweden (I live in Denmark): www.cyclecomponents.com

Useless if you live outside Europe, unless you like paying an extra 25% sales tax.
I checked out the price, it's 72 €, is the tax already included? VAT doesn't apply for outside Euro purchase, does it?

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Old 03-23-08, 03:29 PM   #12
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I don't see why they aren't shipped with an explanation in all languages saying that it's normal
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Old 03-23-08, 11:32 PM   #13
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I checked out the price, it's 72 €, is the tax already included? VAT doesn't apply for outside Euro purchase, does it?
That includes tax (in your shopping cart it tells you the total and how much is tax -- "Varav moms").

Theoretically, VAT doesn't apply outside Europe, but getting it refunded may or may not be possible. Shipping from them is a bit high (unless you order over ~$500, then it's free to many places).

They speak English, so you can write them an email to find out what it will really cost.
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Old 03-23-08, 11:34 PM   #14
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I don't see why they aren't shipped with an explanation in all languages saying that it's normal
Exactly. I figured if they were _all_ like this, there would be a note about it. Since there wasn't, they worrier in me took charge...I can't be the first.
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