Dyno Hub Question

So, my SP PD-8 dyno hub arrived, shipped from across town -- I could have ridden over to the store, but hey . . .

Anyway, holding it in my hand and spinning the axle, it feels like a hand coffee grinder with coffee in it -- or a large pepper mill. I expected some drag, but this thing has a lot of drag and a distinct indexed, grinding feel. Should a dyno hub have that much drag when it is not under load?

-- Jay Beattie.

On 10/1/2014 9:07 AM, jbeattie wrote:
So, my SP PD-8 dyno hub arrived, shipped from across town -- I could have ridden over to the store, but hey . . .

Anyway, holding it in my hand and spinning the axle, it feels like a hand coffee grinder with coffee in it -- or a large pepper mill. I expected some drag, but this thing has a lot of drag and a distinct indexed, grinding feel. Should a dyno hub have that much drag when it is not under load?

-- Jay Beattie.


Yes, normal.
You're breaking magnetic fields several (24 usually) times
per revolution. Besides having resistance to turning, it
does accelerate as it passes each pole you just don't notice
that as much. Once a rim and tire are on it, the effect is
less dramatic.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

On 10/1/2014 10:07 AM, jbeattie wrote:
So, my SP PD-8 dyno hub arrived, shipped from across town -- I could have ridden over to the store, but hey . . .

Anyway, holding it in my hand and spinning the axle, it feels like a hand coffee grinder with coffee in it --
or a large pepper mill. I expected some drag, but this thing has a lot
of drag and a distinct indexed,
grinding feel. Should a dyno hub have that much drag when it is not
under load?


Short answer: Yes. Don't worry about it.

Longer answer: I suppose it would be nicer if they didn't do that, and
the one or two makes with disengaging magnets may not do it. But
practically, it's not a concern.

As the hub rotates, the magnets in the hub resist being pulled into one
stable position (i.e. apply a negative torque), then pull the hub to the
next stable position (i.e. apply a positive torque). When twisting the
hub by hand, you _notice_ only the negative, even though the positive is
there as well; but when built into a wheel and rolling along, those
torques almost perfectly balance. It's not a measurable source of drag.

There may be a time you'll notice that "notchy" effect while riding. At
some speeds (depending on your hub and your bike frame) you may feel a
slight buzz in the handlebars, due (I think) to fork resonance with the
frequency of those "notches." It's never been a concern to me.

For Peter White's explanation, go to
http://www.peterwhitecycles.com/schmidt.asp
and scan down to "Schezbzflat! My hub feels notchy!"


--
- Frank Krygowski

On 2/10/2014 12:07 AM, jbeattie wrote:
So, my SP PD-8 dyno hub arrived, shipped from across town -- I could have ridden over to the store, but hey . . .

Anyway, holding it in my hand and spinning the axle, it feels like a hand coffee grinder with coffee in it -- or a large pepper mill. I expected some drag, but this thing has a lot of drag and a distinct indexed, grinding feel. Should a dyno hub have that much drag when it is not under load?

-- Jay Beattie.

Yup. My SON dynohub, supposedly the greatest thing ever feels exactly as
you describe when I try twisting the axle by fingers. Makers claim that
the drag is equivalent to two feet per mile of incline.
PH

On Wednesday, October 1, 2014 8:26:02 AM UTC-7, Peter Howard wrote:
On 2/10/2014 12:07 AM, jbeattie wrote:

So, my SP PD-8 dyno hub arrived, shipped from across town -- I could have ridden over to the store, but hey . . .



Anyway, holding it in my hand and spinning the axle, it feels like a hand coffee grinder with coffee in it -- or a large pepper mill. I expected some drag, but this thing has a lot of drag and a distinct indexed, grinding feel. Should a dyno hub have that much drag when it is not under load?



-- Jay Beattie.



Yup. My SON dynohub, supposedly the greatest thing ever feels exactly as

you describe when I try twisting the axle by fingers. Makers claim that

the drag is equivalent to two feet per mile of incline.

PH


Thanks to all. Based on the weight of the hub, it's certainly not going to be as light as my existing battery set-up (L&M Seca 1400 with Li-ion -- total weight of light and battery is about 485g), and it will certainly be a lot more expensive -- my light was off a sale table and under $100. Way more expensive if I go with the Supernova (which I can get $192 USD -- and probably will get, Lou) -- which produces less light than the L&M. And the hub obviously will produce more drag.

So, at the end of the day, I have to decide how much I value the fact that I don't have to recharge/recycle the battery. That's what this is all coming down to.

Recharging the L&M battery is not as convenient as my old NightRider Pro 750 which had a strap-on carriage that the battery slid in to. The battery on the L&M is small and has a strap, so I strap it to my stem -- and taking it off to recharge means dealing with the strap and getting it snug enough that the battery does not droop. It seems to me that the optimal light is one of the new big-lumen all in one units.

http://www.biketiresdirect.com/produ...FcRbfgodLz0AwQ

Crap, man, 800 lumens 121g -- $139. I am going to have to start riding all night to justify my dyno.

-- Jay Beattie.

P.S. re drag -- after a flat front tire melt-down last night (flat tire, bad spare tube, etc., etc.), I switched over to a sale table Bontrager nominal 25mm which is really like a 28mm. It's all weather with some tread pattern, but still a folding tire that is supposed to by sporty. What a pig! I feel like someone put Tubasti in my bearings.

drop it on the floor...it'll break it in.

jbeattie wrote:
On Wednesday, October 1, 2014 8:26:02 AM UTC-7, Peter Howard wrote:
On 2/10/2014 12:07 AM, jbeattie wrote:

So, my SP PD-8 dyno hub arrived, shipped from across town -- I
could have ridden over to the store, but hey . . . Anyway,
holding it in my hand and spinning the axle, it feels like a hand
coffee grinder with coffee in it -- or a large pepper mill. I
expected some drag, but this thing has a lot of drag and a
distinct indexed, grinding feel. Should a dyno hub have that much
drag when it is not under load? -- Jay Beattie.


Now you know why some folks prefer batteries :-)


Yup. My SON dynohub, supposedly the greatest thing ever feels
exactly as

you describe when I try twisting the axle by fingers. Makers claim
that

the drag is equivalent to two feet per mile of incline.

PH


Thanks to all. Based on the weight of the hub, it's certainly not
going to be as light as my existing battery set-up (L&M Seca 1400
with Li-ion -- total weight of light and battery is about 485g), and
it will certainly be a lot more expensive -- my light was off a sale
table and under $100. Way more expensive if I go with the Supernova
(which I can get $192 USD -- and probably will get, Lou) -- which
produces less light than the L&M. And the hub obviously will produce
more drag.

So, at the end of the day, I have to decide how much I value the fact
that I don't have to recharge/recycle the battery. That's what this
is all coming down to.

Recharging the L&M battery is not as convenient as my old NightRider
Pro 750 which had a strap-on carriage that the battery slid in to.
The battery on the L&M is small and has a strap, so I strap it to my
stem -- and taking it off to recharge means dealing with the strap
and getting it snug enough that the battery does not droop. It seems
to me that the optimal light is one of the new big-lumen all in one
units.

http://www.biketiresdirect.com/produ...FcRbfgodLz0AwQ


Sure about those 800 lumens? There can't be much more than a single
18650 Li-Ion cell in there and I wonder how they get 1.5h runtime out of
that with an 800 lumen LED.


Crap, man, 800 lumens 121g -- $139. I am going to have to start
riding all night to justify my dyno.

-- Jay Beattie.

P.S. re drag -- after a flat front tire melt-down last night (flat
tire, bad spare tube, etc., etc.), I switched over to a sale table
Bontrager nominal 25mm which is really like a 28mm. It's all weather
with some tread pattern, but still a folding tire that is supposed to
by sporty. What a pig! I feel like someone put Tubasti in my
bearings.


Since I switched to thickwall tubes and Gatorskins that (so far,
knocking on wood) hasn't happened to me anymore. On the MTB I use slime
tubes and no flats either. Although I managed to put a major gash in the
side of the rear tire, so even as it had another 20% of life left in the
tread it had to be replaced. Got a much cheaper Vee Rubber Flying on
there now and so far it holds up ok.

--
Regards, Joerg

http://www.analogconsultants.com/

jbeattie wrote:
So, my SP PD-8 dyno hub arrived, shipped from across town -- I could have
ridden over to the store, but hey . . .

Anyway, holding it in my hand and spinning the axle, it feels like a hand
coffee grinder with coffee in it -- or a large pepper mill. I expected
some drag, but this thing has a lot of drag and a distinct indexed,
grinding feel. Should a dyno hub have that much drag when it is not under load?

-- Jay Beattie.

Yes, it also scared the **** out of me first. You feel the resistance of
the poles. When you are over the 'top' it is 'downhill'. You also feel it
at the axle radius. Wait until you have completed your wheel.

--
Lou

jbeattie wrote:
On Wednesday, October 1, 2014 8:26:02 AM UTC-7, Peter Howard wrote:
On 2/10/2014 12:07 AM, jbeattie wrote:

So, my SP PD-8 dyno hub arrived, shipped from across town -- I could
have ridden over to the store, but hey . . .



Anyway, holding it in my hand and spinning the axle, it feels like a
hand coffee grinder with coffee in it -- or a large pepper mill. I
expected some drag, but this thing has a lot of drag and a distinct
indexed, grinding feel. Should a dyno hub have that much drag when it is not under load?



-- Jay Beattie.



Yup. My SON dynohub, supposedly the greatest thing ever feels exactly as

you describe when I try twisting the axle by fingers. Makers claim that

the drag is equivalent to two feet per mile of incline.

PH


Thanks to all. Based on the weight of the hub, it's certainly not going
to be as light as my existing battery set-up (L&M Seca 1400 with Li-ion
-- total weight of light and battery is about 485g), and it will
certainly be a lot more expensive -- my light was off a sale table and
under $100. Way more expensive if I go with the Supernova (which I can
get $192 USD -- and probably will get, Lou) -- which produces less light
than the L&M. And the hub obviously will produce more drag.

So, at the end of the day, I have to decide how much I value the fact
that I don't have to recharge/recycle the battery. That's what this is all coming down to.

Yes that is it and you can ride longer with as much light as in the
beginning. You gonna love it.
I'm preparing a road bike at the moment for winter evening riding. Swapped
the dynohub wheel from my tourer which I don't use in the winter and
ordered a Son Edelux II headlight because I don't want to blind other
people which I do at the moment with my Supernova E3 Pro headlight on my
other winterevening bike.


Recharging the L&M battery is not as convenient as my old NightRider Pro
750 which had a strap-on carriage that the battery slid in to. The
battery on the L&M is small and has a strap, so I strap it to my stem --
and taking it off to recharge means dealing with the strap and getting it
snug enough that the battery does not droop. It seems to me that the
optimal light is one of the new big-lumen all in one units.

http://www.biketiresdirect.com/produ...FcRbfgodLz0AwQ

Crap, man, 800 lumens 121g -- $139. I am going to have to start riding
all night to justify my dyno.

121 gr. Including batteries which last 3 hours at 300 lumen? The are lying.

--
Lou

On 10/1/2014 8:52 AM, jbeattie wrote:

Thanks to all. Based on the weight of the hub, it's certainly not going to be as light as my existing battery set-up (L&M Seca 1400 with Li-ion -- total weight of light and battery is about 485g), and it will certainly be a lot more expensive -- my light was off a sale table and under $100. Way more expensive if I go with the Supernova (which I can get $192 USD -- and probably will get, Lou) -- which produces less light than the L&M. And the hub obviously will produce more drag.

So, at the end of the day, I have to decide how much I value the fact that I don't have to recharge/recycle the battery. That's what this is all coming down to.

That is the value advantage of dynamo lights. Don't think about money
when you go the dynamo route, think about not having to worry about
batteries. I have dyno hubs on many bicycle in the fleet. There's
definitely a weight disadvantage and brightness disadvantage. But they
are good for riding on familiar roads that are not unlit. You wouldn't
want a dyno light as your only light on unlit roads and paths. I have
lights that are far better than a typical StVZO approved light. The only
one better than what I'm using, that I've seen, is the SuperNova E3 Triple.

You need to carry another light anyway with a dyno light in case you
need to do repairs, as well as to have a front strobe.

This morning on Caltrain there was one Bianchi Castro Valley with a
dynamo hub! I commented to the guy on it, and on his Shimano, non-LED
headlamp, and he thanked me for remininding him and proceeded to fix the
wiring from the light to the hub, something that he said is a frequent
source of trouble. Those connectors on the hub dynamos are pretty funky
and I wonder why they haven't done something similar to a Micro USB size
connector which can handle 500mA easily. Tin the stranded wire with
solder so it doesn't unravel. I also put a piece of heat shrink tubing
over the cable and connector.