generator lights for commuting how good are they?

[A Muzi]

> On 26 Jan 2007 17:35:19 -0800, [email protected] wrote:
>> The advantages of a good hub generator are usually lack of slippage,
>> and efficiency - at least, while the lights are on. (Some Shimanos are
>> draggy with lights off.)

Andrew Price wrote:
> How noticeable is that?

The only hard data we have is that at 15kph, an XT hub drags at 80g/cm,
a Sanyo Dynohub at 116g/cm with the lamp off and 150g/cm with the lamp
lit. (newer hubs seem if anything more free. Surely not more drag)

Spin an XT hub. Pretty free, eh? About double that, or -

short answer = 6v 2.4W is "not enough to notice when riding"

With a black plastic bag over the lamp and switch, I tried reaching
across to another rider's bike in daylight flipping the covered switch
as he tried to tell when the covered lamp was on or off. Can't tell
riding. My own bikes have no switch (just another corrosion magnet)
lamps always on.

You may confuse a rough feeling when spinning the axle in your fingers
with a real-world rim and tire moving the thing smoothly and briskly.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

 

[Larry Webber]

On Fri, 26 Jan 2007 17:35:19 -0800, frkrygow wrote:

>
>
> On Jan 26, 3:40 am, "Sirrus Rider" <[email protected]>
> wrote:
>> How do generator lights powered by Dynamo hubs like (SONs), Shimano Nexus,
>> Sturmy Archer (GH6 or Newer) measure up for commuting? How do they compare
>> to say Niterider evolution smart lights?
>
> Others have answered well. But I'll emphasize, it doesn't really have
> to be a hub generator. Almost all generators on the market put out
> similar electricity, whether hub units, bottle units or bottom bracket
> (roller) units. Yes, some are a little stronger or weaker, but in most
> cases the differences are fairly small.
>
> Exceptions: Among my generators "in storage" are an old, old Sanyo
> bottom bracket model, and a 1950s Sturmey Archer Dynohub. The Sanyo
> had fewer magnetic poles, so while it was OK at speed, it was dimmer at
> very low speeds. The Sturmey was built to a different, much weaker
> standard, putting out only 2 watts (IIRC). But again, those are
> exceptions.
>
> The advantages of a good hub generator are usually lack of slippage,
> and efficiency - at least, while the lights are on. (Some Shimanos are
> draggy with lights off.) OTOH, a separate bottle or roller generator
> has zero drag when it's off, not a lot of drag when it's on, and costs
> way, way less.
>
> Installation ease is a difference, too, depending who you are. Is it
> better or worse to have to build a hub into a wheel, compared to
> properly aligning a separate unit and getting the wiring right? Some
> people have trouble with the latter.
>
> BTW, an interesting compromise is the Aufa (nee FER) spoke drive
> generator. Kind of clunky looking, and a bit noisy, but no slippage,
> more efficient than most generators, and much less expensive than a hub
> unit. See
> http://www.aufa.de/index.php?subsite=products&category=2&filter=&detail=36
>
> Finally: Any worries about visibility when stopped are easy to fix.
> Use reflective tape, and add battery powered blinkies.
>
> - Frank Krygowski

Frank,

I have heard of these spoke generators but I am not clear on how these
work even after going to the URL you provided. Also, have you any
experience with "rim" dynamos where the dynamo wheel (rubber I presume)
rubs against the rim rather than the tire?

Larry Webber

 

[A Muzi]

>> "Sirrus Rider" <[email protected] wrote:
>>> How do generator lights powered by Dynamo hubs like (SONs), Shimano Nexus,
>>> Sturmy Archer (GH6 or Newer) measure up for commuting? How do they compare
>>> to say Niterider evolution smart lights?

> On Fri, 26 Jan 2007 17:35:19 -0800, frkrygow wrote:
>> Others have answered well. But I'll emphasize, it doesn't really have
>> to be a hub generator. Almost all generators on the market put out
>> similar electricity, whether hub units, bottle units or bottom bracket
>> (roller) units. Yes, some are a little stronger or weaker, but in most
>> cases the differences are fairly small.
-snip-
>> The advantages of a good hub generator are usually lack of slippage,
>> and efficiency - at least, while the lights are on. (Some Shimanos are
>> draggy with lights off.) OTOH, a separate bottle or roller generator
>> has zero drag when it's off, not a lot of drag when it's on, and costs
>> way, way less.
>>
>> Installation ease is a difference, too, depending who you are. Is it
>> better or worse to have to build a hub into a wheel, compared to
>> properly aligning a separate unit and getting the wiring right? Some
>> people have trouble with the latter.
>>
>> BTW, an interesting compromise is the Aufa (nee FER) spoke drive
>> generator. Kind of clunky looking, and a bit noisy, but no slippage,
>> more efficient than most generators, and much less expensive than a hub
>> unit. See
>> http://www.aufa.de/index.php?subsite=products&category=2&filter=&detail=36
>> Finally: Any worries about visibility when stopped are easy to fix.
>> Use reflective tape, and add battery powered blinkies.

Larry Webber wrote:
> I have heard of these spoke generators but I am not clear on how these
> work even after going to the URL you provided. Also, have you any
> experience with "rim" dynamos where the dynamo wheel (rubber I presume)
> rubs against the rim rather than the tire?

Any side-mount dynamo with a rubber pulley cover can be set up rim-drive
but they slip when wet or slushy. Sanyo had a nice rim drive with a big
(30mm?) pulley which ran well wet but I haven't seen those in a long
while.

I use a normal side-mount on tubulars to good effect even when wet. Rim
drive may be a little bit quieter but the loss of lights in the rain
bothered me.

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

 

[A Muzi]

-snip-
> On Fri, 26 Jan 2007 17:35:19 -0800, frkrygow wrote:
>> BTW, an interesting compromise is the Aufa (nee FER) spoke drive
>> generator. Kind of clunky looking, and a bit noisy, but no slippage,
>> more efficient than most generators, and much less expensive than a hub
>> unit. See
>> http://www.aufa.de/index.php?subsite=products&category=2&filter=&detail=36
-snip-

Larry Webber wrote:
> I have heard of these spoke generators but I am not clear on how these
> work even after going to the URL you provided. Also, have you any
> experience with "rim" dynamos where the dynamo wheel (rubber I presume)
> rubs against the rim rather than the tire?

The Aufa unit was supplied on the 1995 model Swiss Army Bike. It slips
over the axle, tabs engage spokes which turn a geared-up dynamo through
a belt. Generally dependable but a broken belt is hard to replace - hard
to find and hard to install.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

 

[Larry Webber]

On Sat, 27 Jan 2007 18:12:17 -0600, A Muzi wrote:

>
>>> "Sirrus Rider" <[email protected] wrote:
>>>> How do generator lights powered by Dynamo hubs like (SONs), Shimano Nexus,
>>>> Sturmy Archer (GH6 or Newer) measure up for commuting? How do they compare
>>>> to say Niterider evolution smart lights?
>
>> On Fri, 26 Jan 2007 17:35:19 -0800, frkrygow wrote:
>>> Others have answered well. But I'll emphasize, it doesn't really have
>>> to be a hub generator. Almost all generators on the market put out
>>> similar electricity, whether hub units, bottle units or bottom bracket
>>> (roller) units. Yes, some are a little stronger or weaker, but in most
>>> cases the differences are fairly small.
> -snip-
>>> The advantages of a good hub generator are usually lack of slippage,
>>> and efficiency - at least, while the lights are on. (Some Shimanos are
>>> draggy with lights off.) OTOH, a separate bottle or roller generator
>>> has zero drag when it's off, not a lot of drag when it's on, and costs
>>> way, way less.
>>>
>>> Installation ease is a difference, too, depending who you are. Is it
>>> better or worse to have to build a hub into a wheel, compared to
>>> properly aligning a separate unit and getting the wiring right? Some
>>> people have trouble with the latter.
>>>
>>> BTW, an interesting compromise is the Aufa (nee FER) spoke drive
>>> generator. Kind of clunky looking, and a bit noisy, but no slippage,
>>> more efficient than most generators, and much less expensive than a hub
>>> unit. See
>>> http://www.aufa.de/index.php?subsite=products&category=2&filter=&detail=36
>>> Finally: Any worries about visibility when stopped are easy to fix.
>>> Use reflective tape, and add battery powered blinkies.
>
> Larry Webber wrote:
>> I have heard of these spoke generators but I am not clear on how these
>> work even after going to the URL you provided. Also, have you any
>> experience with "rim" dynamos where the dynamo wheel (rubber I presume)
>> rubs against the rim rather than the tire?
>
> Any side-mount dynamo with a rubber pulley cover can be set up rim-drive
> but they slip when wet or slushy. Sanyo had a nice rim drive with a big
> (30mm?) pulley which ran well wet but I haven't seen those in a long
> while.
>
> I use a normal side-mount on tubulars to good effect even when wet. Rim
> drive may be a little bit quieter but the loss of lights in the rain
> bothered me.

Andrew,

Thanks for the information on both of these variants of dynamos.

 

[Clive George]

"Andrew Price" <[email protected]> wrote in message
news:[email protected]...
> On 26 Jan 2007 17:35:19 -0800, [email protected] wrote:
>
> [---]
>
>>The advantages of a good hub generator are usually lack of slippage,
>>and efficiency - at least, while the lights are on. (Some Shimanos are
>>draggy with lights off.)
>
> How noticeable is that?

I used the original Shimano hub, which was notoriously the worst for this,
for several years, and didn't really notice it.

cheers,
clive

 

[Chris M]

FWIW...

I use rechargeable lithium batteries and my favorite set of lights
uses 3 AAA for the front and 2 AAA (about 800 ma per battery) and I
tested them the other day and gave up after leaving them on for 10
hours. They are small enough to leave on and I can carry spares with
no burden whatsoever.

I had decided years ago to use rechargeable batteries throughout my
home so it was merely a case of adding the lights in to my battery
rotation. Maybe the situation is different if you have no existing
inventory of batteries and chargers, but at some point it makes a lot
of sense for anyone that uses remote controls for entertainment
systems, garage door openers, thermostats, some portable radio,
cassette and mp3 players (though the smaller mp3 players use
proprietary or semi-permanent batteries) and I probably forgot some
too. My point is that for any one thing, it is not worth it. When you
add up all of the devices, the amount some spend on batteries is crazy
given the alternatives.

Food for thought, it may not be worth it for you but consider your
total battery use before deciding. Given the added safety of having
lights stay on nice and bright even at stoplights can only add to your
safety. I imagine the generator noise can be distracting too, and
might mask the sounds that alert you to someone bearing down on
you...not likely I suppose but...

 

[Sirrus Rider]

Deciededly suburban to urban and back agian. I suppose I'm just thinking
ahead. My Niterider setup works great; however, my nagging concern is the
diminising time and returns of NIMH batteries. The feeling I have is I will
always have Niterider in my back pocket for the tune of $90 at least once a
year for a new battery or alternatively kludging together an alternative.
Plus one of the present downsides is always having to lug my charger around
to recharge my battery in the anticipation of a late-after-dark ride home.


John


"John" <[email protected]> wrote in message
news:[email protected]...
>
>
> On Jan 26, 3:40 am, "Sirrus Rider" <sirrus-
> [email protected]> wrote:
>> How do generator lights powered by Dynamo hubs like (SONs), Shimano
>> Nexus,
>> Sturmy Archer (GH6 or Newer) measure up for commuting? How do they
>> compare
>> to say Niterider evolution smart lights?
>>
>> John
>
> As many others have said, dynamo hubs are very nice and convient for
> commuting.
>
> Your choice of light is of great importance also. Bicycle Quarterly
> recently compared several dynamo-powered lights and has a good
> evaluation of each. Also, Peter White has an informative website on
> dynamo lights.
>
> For my commute, the E6 wasn't the best option. I commute through
> mostly main suburban roads, most of which are dimly lit. I chose the
> 1W Inoled and it's great for my commute as it provides full power at
> very slow speeds, has a stand-light, and provides enough spill to see
> enough to the sides as well as being more visable to traffic.
>
> What's your commute like? Distance, urban, streetlit?
>
> That answer will determine which is the best light for you.
>
> John McMurry
>
>

 

[[email protected]]

On Jan 27, 9:37 pm, "Chris M" <[email protected]> wrote:
> FWIW...
>
> I use rechargeable lithium batteries and my favorite set of lights
> uses 3 AAA for the front and 2 AAA (about 800 ma per battery) and I
> tested them the other day and gave up after leaving them on for 10
> hours. They are small enough to leave on and I can carry spares with
> no burden whatsoever.
>
> I had decided years ago to use rechargeable batteries throughout my
> home so it was merely a case of adding the lights in to my battery
> rotation. Maybe the situation is different if you have no existing
> inventory of batteries and chargers, but at some point it makes a lot
> of sense for anyone that uses remote controls for entertainment
> systems, garage door openers, thermostats, some portable radio,
> cassette and mp3 players (though the smaller mp3 players use
> proprietary or semi-permanent batteries) and I probably forgot some
> too. My point is that for any one thing, it is not worth it. When you
> add up all of the devices, the amount some spend on batteries is crazy
> given the alternatives.
>
> Food for thought, it may not be worth it for you but consider your
> total battery use before deciding. Given the added safety of having
> lights stay on nice and bright even at stoplights can only add to your
> safety. I imagine the generator noise can be distracting too, and
> might mask the sounds that alert you to someone bearing down on
> you...not likely I suppose but...

It's a personal choice. In our house, flashlights use rechargeables.
The entertainment remotes don't, and are usually considered bad
applications for rechargeables because rechargeable batteries
gradually go dead even doing nothing. Disposable alkalines cost so
little in that application that they're the way to go, in my opinion.

The problem with rechargeables in bike lights is that most people only
occasionally ride at night. If they charged up their AAs and put them
in the light, they might ride two weeks later, and get ten blocks from
home when they find the light dying, mostly from self-discharge. It's
less of an issue if you ride regularly, like commuting every day in
the dark - but it still becomes one of those "oh, damn" little chores,
to remember to recharge daily. That's the kind of chore I _know_ I'd
forget eventually.

The generator makes it a non-issue. It's always ready. And with an
alkaline-powered blinky taillight, being seen while stopped is not an
issue.

Works for me, anyway.

- Frank Krygowski

 

[[email protected]]

On Jan 27, 5:49 pm, A Muzi <[email protected]> wrote:
> > On 26 Jan 2007 17:35:19 -0800, [email protected] wrote:
> >> The advantages of a good hub generator are usually lack of slippage,
> >> and efficiency - at least, while the lights are on. (Some Shimanos are
> >> draggy with lights off.)
> Andrew Price wrote:
> > How noticeable is that?The only hard data we have is that at 15kph, an XT hub drags at 80g/cm,
> a Sanyo Dynohub at 116g/cm with the lamp off and 150g/cm with the lamp
> lit. (newer hubs seem if anything more free. Surely not more drag)
>
> Spin an XT hub. Pretty free, eh? About double that, or -
>
> short answer = 6v 2.4W is "not enough to notice when riding"
>
> With a black plastic bag over the lamp and switch, I tried reaching
> across to another rider's bike in daylight flipping the covered switch
> as he tried to tell when the covered lamp was on or off. Can't tell
> riding.

Regarding those measurement numbers - are the units supposed to be
grams _times_ centimeters, as a torque measurement?

(I'm assuming the numbers came from the manufacturer, not from your
own tests. Is that right?)

- Frank Krygowski

 

[[email protected]]

On Jan 27, 5:59 pm, Larry Webber <[email protected]> wrote:
> On Fri, 26 Jan 2007 17:35:19 -0800, frkrygow wrote:
>
> >
> > BTW, an interesting compromise is the Aufa (nee FER) spoke drive
> > generator. Kind of clunky looking, and a bit noisy, but no slippage,
> > more efficient than most generators, and much less expensive than a hub
> > unit. See
> >http://www.aufa.de/index.php?subsite=products&category=2&filter=&deta...
>iFrank,
>
> I have heard of these spoke generators but I am not clear on how these
> work even after going to the URL you provided.

To mount the generator, you remove your front wheel and its quick
release skewer. The metal part of the generator (the left part in the
photo at http://www.aufa.de/index.php?
subsite=products&category=2&filter=&detail=36) has a hole that slips
over your axle. You re-assemble the QR, then clamp the wheel back in
the fork. The big black lump in that photo with the word "aufa" is
behind the hub, under the front fender stays (at least, on my bike).

When the generator's off, your wheel spins normally with zero
resistance. To turn on the generator, that black plastic arrow-shaped
tab is flipped perpendicular to the picture, down into the spokes.
It's on a ring concentric with the axle, and causes that ring to
rotate. A two-stage toothed belt system spins the actual generator,
which lives in the "aufa" lump.

I first tried it on my commuting bike. It seemed noisy to me, and I
was sure it must be draggy. (I had a minor problem with my fork
bending it a bit.) But when I compared coasting speeds against my
usual bottom bracket generator, it was clearly more efficient.

Supposedly, early units had belt life problems. Mine came with spare
belts. I use this generator only occasionally, but it's never had a
problem.

> Also, have you any
> experience with "rim" dynamos where the dynamo wheel (rubber I presume)
> rubs against the rim rather than the tire?

Not personally, but I have a friend who has an AXA bottle unit set up
that way. I've been thinking about machining down a standard Union
(or Marwi) generator's wheel to take a thick O-ring as a drive wheel,
and giving that a try. From what I've read and been told by other
technical guys, the tire contact is actually a major source of energy
loss for bottle generators. ISTM the rim contact could help
efficiency, if it didn't slip.

- Frank Krygowski

 

[[email protected]]

On 28 Jan 2007 08:32:56 -0800, [email protected] wrote:

>
>
>On Jan 27, 5:49 pm, A Muzi <[email protected]> wrote:
>> > On 26 Jan 2007 17:35:19 -0800, [email protected] wrote:
>> >> The advantages of a good hub generator are usually lack of slippage,
>> >> and efficiency - at least, while the lights are on. (Some Shimanos are
>> >> draggy with lights off.)
>> Andrew Price wrote:
>> > How noticeable is that?The only hard data we have is that at 15kph, an XT hub drags at 80g/cm,
>> a Sanyo Dynohub at 116g/cm with the lamp off and 150g/cm with the lamp
>> lit. (newer hubs seem if anything more free. Surely not more drag)
>>
>> Spin an XT hub. Pretty free, eh? About double that, or -
>>
>> short answer = 6v 2.4W is "not enough to notice when riding"
>>
>> With a black plastic bag over the lamp and switch, I tried reaching
>> across to another rider's bike in daylight flipping the covered switch
>> as he tried to tell when the covered lamp was on or off. Can't tell
>> riding.
>
>Regarding those measurement numbers - are the units supposed to be
>grams _times_ centimeters, as a torque measurement?
>
>(I'm assuming the numbers came from the manufacturer, not from your
>own tests. Is that right?)
>
>- Frank Krygowski

Dear Frank,

http://www.myra-simon.com/bike/dynotest.html#drag

Cheers,

Carl Fogel

 

[Larry Webber]

On Sun, 28 Jan 2007 08:48:18 -0800, frkrygow wrote:

>
>
> On Jan 27, 5:59 pm, Larry Webber <[email protected]> wrote:
>> On Fri, 26 Jan 2007 17:35:19 -0800, frkrygow wrote:
>>
>> >
>> > BTW, an interesting compromise is the Aufa (nee FER) spoke drive
>> > generator. Kind of clunky looking, and a bit noisy, but no slippage,
>> > more efficient than most generators, and much less expensive than a hub
>> > unit. See
>> >http://www.aufa.de/index.php?subsite=products&category=2&filter=&deta...
>>iFrank,
>>
>> I have heard of these spoke generators but I am not clear on how these
>> work even after going to the URL you provided.
>
> To mount the generator, you remove your front wheel and its quick
> release skewer. The metal part of the generator (the left part in the
> photo at http://www.aufa.de/index.php?
> subsite=products&category=2&filter=&detail=36) has a hole that slips
> over your axle. You re-assemble the QR, then clamp the wheel back in
> the fork. The big black lump in that photo with the word "aufa" is
> behind the hub, under the front fender stays (at least, on my bike).
>
> When the generator's off, your wheel spins normally with zero
> resistance. To turn on the generator, that black plastic arrow-shaped
> tab is flipped perpendicular to the picture, down into the spokes.
> It's on a ring concentric with the axle, and causes that ring to
> rotate. A two-stage toothed belt system spins the actual generator,
> which lives in the "aufa" lump.
>
> I first tried it on my commuting bike. It seemed noisy to me, and I
> was sure it must be draggy. (I had a minor problem with my fork
> bending it a bit.) But when I compared coasting speeds against my
> usual bottom bracket generator, it was clearly more efficient.
>
> Supposedly, early units had belt life problems. Mine came with spare
> belts. I use this generator only occasionally, but it's never had a
> problem.
>
>> Also, have you any
>> experience with "rim" dynamos where the dynamo wheel (rubber I presume)
>> rubs against the rim rather than the tire?
>
> Not personally, but I have a friend who has an AXA bottle unit set up
> that way. I've been thinking about machining down a standard Union
> (or Marwi) generator's wheel to take a thick O-ring as a drive wheel,
> and giving that a try. From what I've read and been told by other
> technical guys, the tire contact is actually a major source of energy
> loss for bottle generators. ISTM the rim contact could help
> efficiency, if it didn't slip.
>
> - Frank Krygowski


Frank,

Thank you for the information on the spoke driven generator. I now
understand how this works.

If you do end up setting up a modified dynamo to
run off the rim I would be curious to hear how it works. Where I live
(Indianapolis, IN) rain is more of an issue than snow for me concerning
slippage. When we do get more than a couple of inches of snow I use an old
Trek mountain bike with LED battery lights or my Redline Monocog Flight
with the LED battery lights.

Larry

 

[[email protected]]

On Jan 27, 2:07 pm, Andrew Price <[email protected]> wrote:
> On 26 Jan 2007 17:35:19 -0800, [email protected] wrote:
>
> [---]
>
> >The advantages of a good hub generator are usually lack of slippage,
> >and efficiency - at least, while the lights are on. (Some Shimanos are
> >draggy with lights off.)

>How noticeable is that?

I have the Shimano DH-3N71 generator hub powering two Schmidt E6
lights. Is it noticeable when riding? No. But when spinning the
wheel by hand, it slows down very quickly. So you know it has a lot
of drag. Do you notice it while riding? No. But you still know the
drag is there. Overweight people probably don't notice they are 50,
100, 150, 200 pounds overweight as they go about their normal day.
Doesn't mean the excess weight is not causing physical harm to them
that will materialize later.

 

[Andrew Price]

On 28 Jan 2007 12:08:06 -0800, [email protected] wrote:

>I have the Shimano DH-3N71 generator hub powering two Schmidt E6
>lights. Is it noticeable when riding? No. But when spinning the
>wheel by hand, it slows down very quickly. So you know it has a lot
>of drag.

I take it that's when the lights are on - or is there also a
perceptible amount of drag when there is no load on the generator?

 

[Tim McNamara]

In article <[email protected]>,
[email protected] wrote:

> On Jan 27, 2:07 pm, Andrew Price <[email protected]> wrote:
> > On 26 Jan 2007 17:35:19 -0800, [email protected] wrote:
> >
> > [---]
> >
> > >The advantages of a good hub generator are usually lack of
> > >slippage, and efficiency - at least, while the lights are on.
> > >(Some Shimanos are draggy with lights off.)
>
> >How noticeable is that?
>
> I have the Shimano DH-3N71 generator hub powering two Schmidt E6
> lights. Is it noticeable when riding? No. But when spinning the
> wheel by hand, it slows down very quickly. So you know it has a lot
> of drag. Do you notice it while riding? No. But you still know the
> drag is there.

You mean that you mentally know the drag is there, even though you don;t
feel it per se when riding?

My Schmidt SON, which has a bit less drag than the best of the Shimano
hubs, results in no difference in terms of average speeds over long
distances. IIRC the drag is the equivalent of climbing one foot per
mile, which is imperceptible.

Back in the day when the options were pretty much a BB mounted generator
or a side mounted generator, the old French randonneurs mounted
flashlights on their bikes to minimize the use of the generator. They
would mail spare batteries ahead to the controles. I've never been sure
that the extra weight of the flashlights wasn't a bigger handicap over a
hilly course than just using the generator!

I think part of the perception of drag from generators that are
tire-driven is acoustic. You can hear the pitch go up and down with the
speed of the bike, and especially when climbing you are given constant
feedback of going slower. I think the rider tends to associate this
with the use of the generator and overestimates how much it slows him
down. A hub generator makes no sound audible by humans, at least (but
on one set of brevets I did note that a set of Rottweilers on one farm
only chased riders with Schmidt hubs, so I wonder if there is a sound
that is out of the range of human hearing but audible to dogs).

 

[Tim McNamara]

In article <[email protected]>,
Andrew Price <[email protected]> wrote:

> On 28 Jan 2007 12:08:06 -0800, [email protected] wrote:
>
> >I have the Shimano DH-3N71 generator hub powering two Schmidt E6
> >lights. Is it noticeable when riding? No. But when spinning the
> >wheel by hand, it slows down very quickly. So you know it has a lot
> >of drag.
>
> I take it that's when the lights are on - or is there also a
> perceptible amount of drag when there is no load on the generator?

The early iterations of the Shimano generator hubs actually had higher
drag when the lights were off! This was corrected.

There is a report from some 10 years back by Chris Juden that shows the
efficiency and drag of many generators. It was published in the CTC
magazine but is also out on the Web somewhere.

Ah, Google is my friend:

http://www.myra-simon.com/bike/dynotest.html

 

[A Muzi]

[email protected] wrote:
>>>> The advantages of a good hub generator are usually lack of slippage,
>>>> and efficiency - at least, while the lights are on. (Some Shimanos are
>>>> draggy with lights off.)

>> Andrew Price wrote:
>>> How noticeable is that?

> I <[email protected]> wrote:
>> The only hard data we have is that at 15kph, an XT hub drags at 80g/cm,
>> a Sanyo Dynohub at 116g/cm with the lamp off and 150g/cm with the lamp
>> lit. (newer hubs seem if anything more free. Surely not more drag)
>> Spin an XT hub. Pretty free, eh? About double that, or -
>> short answer = 6v 2.4W is "not enough to notice when riding"
>> With a black plastic bag over the lamp and switch, I tried reaching
>> across to another rider's bike in daylight flipping the covered switch
>> as he tried to tell when the covered lamp was on or off. Can't tell
>> riding.

[email protected] wrote:
> Regarding those measurement numbers - are the units supposed to be
> grams _times_ centimeters, as a torque measurement?
> (I'm assuming the numbers came from the manufacturer, not from your
> own tests. Is that right?)

Yes, from Sanyo.
Which would be, what, about 0.304 inch pounds off and 0.373 inch pounds
on?? Below anything on my torque wrench scales!
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

 

[[email protected]]

On Jan 28, 2:43 pm, Tim McNamara <[email protected]> wrote:
> In article <[email protected]>,
>
>
>
>
>
> [email protected] wrote:
> > On Jan 27, 2:07 pm, Andrew Price <[email protected]> wrote:
> > > On 26 Jan 2007 17:35:19 -0800, [email protected] wrote:
>
> > > [---]
>
> > > >The advantages of a good hub generator are usually lack of
> > > >slippage, and efficiency - at least, while the lights are on.
> > > >(Some Shimanos are draggy with lights off.)
>
> > >How noticeable is that?
>
> > I have the Shimano DH-3N71 generator hub powering two Schmidt E6
> > lights. Is it noticeable when riding? No. But when spinning the
> > wheel by hand, it slows down very quickly. So you know it has a lot
> > of drag. Do you notice it while riding? No. But you still know the
> > drag is there.


>You mean that you mentally know the drag is there, even though you don;t
> feel it per se when riding?

As I wrote above, "I have the Shimano DH-3N71 generator hub powering
two Schmidt E6 lights. Is it noticeable when riding? No. But when
spinning the wheel by hand, it slows down very quickly. So you know
it has a lot of drag. Do you notice it while riding? No. But you
still know the drag is there."

The drag does not disappear when you are riding. Its still there
whether you think you notice it or not. It consumes watts to overcome
the drag. The drag is physically present whether you feel it or not.

If someone filled your bike tubes with slime. Completely filled. 10
pounds or more of slime per wheel. But you did not mentally know this
because it was a joke. I bet you would have a physical diminishment
of your speed.

Whether you mentally perceive a real physical drag or not does not
diminish the real physical drag. Just like with the Shimano DH-3N71
hub. It has real physical drag. You must put out more power to go
the same speed as a normal front wheel, or put out the same power and
go slower because of the extra drag on the Shimano DH-3N71 hub.


>
> My Schmidt SON, which has a bit less drag than the best of the Shimano
> hubs, results in no difference in terms of average speeds over long
> distances. IIRC the drag is the equivalent of climbing one foot per
> mile, which is imperceptible.

I have the Shimano DH-3N71 generator hub. I have no comments on the
Schmidt hub other than its $120 more expensive than the Shimano and is
claimed to have less drag than the Shimano DH-3N71 hub. Based upon my
experience with the Shimano hub, I advise people to pay the extra $120
for the Schmidt.


>
> Back in the day when the options were pretty much a BB mounted generator
> or a side mounted generator, the old French randonneurs mounted
> flashlights on their bikes to minimize the use of the generator. They
> would mail spare batteries ahead to the controles. I've never been sure
> that the extra weight of the flashlights wasn't a bigger handicap over a
> hilly course than just using the generator!
>
> I think part of the perception of drag from generators that are
> tire-driven is acoustic. You can hear the pitch go up and down with the
> speed of the bike, and especially when climbing you are given constant
> feedback of going slower. I think the rider tends to associate this
> with the use of the generator and overestimates how much it slows him
> down. A hub generator makes no sound audible by humans, at least (but
> on one set of brevets I did note that a set of Rottweilers on one farm
> only chased riders with Schmidt hubs, so I wonder if there is a sound
> that is out of the range of human hearing but audible to dogs).- Hide quoted text -- Show quoted text -

 

[Tim McNamara]

In article <[email protected]>,
[email protected] wrote:

> On Jan 28, 2:43 pm, Tim McNamara <[email protected]> wrote:
> > In article <[email protected]>,
> >
> > [email protected] wrote:
> >
> > > I have the Shimano DH-3N71 generator hub powering two Schmidt E6
> > > lights. Is it noticeable when riding? No. But when spinning
> > > the wheel by hand, it slows down very quickly. So you know it
> > > has a lot of drag. Do you notice it while riding? No. But you
> > > still know the drag is there.
>
> >You mean that you mentally know the drag is there, even though you
> >don;t feel it per se when riding?
>
> As I wrote above, "I have the Shimano DH-3N71 generator hub powering
> two Schmidt E6 lights. Is it noticeable when riding? No. But when
> spinning the wheel by hand, it slows down very quickly. So you know
> it has a lot of drag. Do you notice it while riding? No. But you
> still know the drag is there."
>
> The drag does not disappear when you are riding. Its still there
> whether you think you notice it or not. It consumes watts to
> overcome the drag. The drag is physically present whether you feel
> it or not.

"You know the drag is still there" but you can't perceive it, so this
knowledge is cognitive not perception. Therefore the answer to my
question was "yes." Why the dissertation?

> If someone filled your bike tubes with slime. Completely filled. 10
> pounds or more of slime per wheel. But you did not mentally know
> this because it was a joke. I bet you would have a physical
> diminishment of your speed.

Possibly. Quite possibly not. There is not only the issue of
perceptibility ("least discernible difference" is the technical term),
there is also the issue of significance in measurability.

> Whether you mentally perceive a real physical drag or not does not
> diminish the real physical drag. Just like with the Shimano DH-3N71
> hub. It has real physical drag. You must put out more power to go
> the same speed as a normal front wheel, or put out the same power and
> go slower because of the extra drag on the Shimano DH-3N71 hub.

The question is (1) whether the drag is actually noticeable and (2)
whether it is significant. Does it actually slow you down? Is your
average speed slower over a long route at a similar level of subjective
exertion? I've never used that particular hub, so I don't know the
answers.