SON hub dynamo

[Fergus Flanagan]

Just got my brand new 20in wheel with built in SON hub dynamo for my StreetMachine hmmmm! I have
noticed as I try to spin the wheel holding it in my hands it feels very very notchy and assume this
is the magnets, i didn't expect this, is this normal? Does it disappear with speed as it feels there
is alot of resistance when i spin it slowly. I was expecting it to spin quite freely at any speed
but until i mount it on the bike, I guess i won't really know if the notchiness or resistance
disappears. Has anyone else experienced this?

Fergus

--
::::: Only riders understand why dogs love to stick their heads out of car
windows. :::::

 

[Danny Colyer]

Fergus Flanagan wrote:
> Just got my brand new 20in wheel with built in SON hub dynamo for my StreetMachine hmmmm! I have
> noticed as I try to spin the wheel holding it in my hands it feels very very notchy and assume
> this is the magnets, i didn't expect this, is this normal?

It's fine. I recommend searching http://groups.google.com for a thread that I started last December
headed "Schmidt hub bearings".

> > > > > > Only riders understand why dogs love to stick their heads out of car windows. :::::

My wife almost fell off her bike in fright the weekend before last, when a dog with its head out the
window of a passing car barked in her ear
:-(

--
Danny Colyer (remove safety to reply) ( http://www.juggler.net/danny ) Recumbent cycle page:
http://www.speedy5.freeserve.co.uk/recumbents/ "He who dares not offend cannot be honest." -
Thomas Paine

 

[Mads Hilberg]

> Just got my brand new 20in wheel with built in SON hub dynamo for my StreetMachine hmmmm! I have
> noticed as I try to spin the wheel holding it
in
> my hands it feels very very notchy and assume this is the magnets, i
didn't
> expect this, is this normal? Does it disappear with speed as it feels
there
> is alot of resistance when i spin it slowly. I was expecting it to spin quite freely at any speed
> but until i mount it on the bike, I guess i
won't
> really know if the notchiness or resistance disappears. Has anyone else experienced this?

Taken from: http://www.peterwhitecycles.com/Schmidt-Lumotec.asp (scroll down to "My wheel
feels notchy")

>>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 hub. 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,
speeding you up and slowing you down, 26 times per rotation. The effect 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 retard the
rotation of the hub axle.<<

Mads

 

[Peter Clinch]

Fergus Flanagan wrote:
> Just got my brand new 20in wheel with built in SON hub dynamo for my StreetMachine hmmmm! I have
> noticed as I try to spin the wheel holding it in my hands it feels very very notchy and assume
> this is the magnets, i didn't expect this, is this normal? Does it disappear with speed as it
> feels there is alot of resistance when i spin it slowly.

Yes, yes (at about, oooh, ~1 km/h). I never notice it's there except when the road gets a bit
brighter in front of me. Don't worry, it's a superb piece of kit and I doubt you'll regret
getting it.

Pete.
--
Peter Clinch University of Dundee Tel 44 1382 660111 ext. 33637 Medical Physics, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK net [email protected]
http://www.dundee.ac.uk/~pjclinch/