# Dynamo Hubs



## Bob the Wheelbuilder (Sep 21, 2003)

I'm just getting started with a hub dynamo powered light project for a fast touring (randoneering) road bike and despite reading lots of opinions, I'm still in the dark, so to speak, about what to do. So far I've read that:

The German made Schmidt SON seems to be considered the best money no object hub, with the highest efficiency and lowest drag when turned off. The model 20R is made for 20 inch wheels, but is probably puts out enough current for road riding at a reasonably fast speed, especially when using an LED light. It's the lightest hub and the one that uses the least amount of rider energy both when providing power and when turned off.

The old Shimano NX-30 had enough drag when off to disqualify it for a premium system, the newer Shimano DH-3N71 and Shimano Alfine DH-S500 are better, but not quite Schimdt quality. Shimano's newest hub, probably not yet available in the US (the DH-3N80) is considerably lighter and somewhat more efficient than any previous Shimano offering.

The focused-beam Schmidt E6 is an elegant solution to the low total light output of a Halogen bulb, but LED's are much more efficient, so the smart money seems to be with an LED system.

So if I'm on the right track, with the above, I'm looking for help answering the following questions:

1. Are the DH-3N71 and DH-S500 units identical in performance? I found an exploded diagram that indicated the dynamo guts were exchangeable, but not identical. I haven't been able to find a definite answer on the performance question. QBP lists both, and the price on the S500 is higher, any idea why?

2. How does the new DH-3N80 compare to the SON hubs? Sounds like they must now be very, very close in performance. 

3. One reference said the German DH-3N80 puts out 3 watts, but the version for the rest of the world only puts out 2.4 watts. Why the difference? Would it be worth it to get the German model? Will this hub even be sold in the US?

4. What about lights? Sounds to me like the LED lights are the only way to go for a dynamo system. The three commercial lights that sound best to me are the Lumotec Fly, the Schmidt eDelux and the Supernova E3. How do these compare to reasonable DIY lights in price and performance? As LED's seem to be improving so quickly, would it make more sense to use a cheaper light like the Schmidt E6 and wait for future even brighter LED's?

Here are some pages from a German dynamo review. If I'm reading the graphs correctly, it looks like the DH-3N80 is very close to the SON in performance. Can any German speakers translate the gist of the text? It came as a PDF, so babelfish can't translate it.

Sorry for the million questions, but I couldn't find one thread that had this info, so this may also be helpful to someone else in the future.

Thanks in advance.


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## poobardog (Mar 2, 2007)

Hi Bob
I've got a SON -haven't tried the Shimanos -so no comment on them -though watch for the weight on the cheaper models.

Definitely go for LED's -homebuilt. 
Ktronik built me a very simple circuit that runs 3 LEDs at approx 500mA in series and Martin has designed a more complicated more efficient driver.
You can read about them here
http://www.pilom.com/BicycleElectronics/DynamoCircuits.htm

http://www.candlepowerforums.com/vb/showthread.php?t=202121

Do a search also at CPF -heaps of info there.

I have the whole E6 setup -primary,secondary and the LED standlight -unfortunately the homebrew LEDs blew them away.

Cheers
Dom


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## Bob the Wheelbuilder (Sep 21, 2003)

poobardog said:


> Hi Bob
> I've got a SON -haven't tried the Shimanos -so no comment on them -though watch for the weight on the cheaper models.
> 
> Definitely go for LED's -homebuilt.
> ...


Thanks. Sounds like there is agreement the SON's are the best hubs.

I hope the DH-3N80 is available in the states soon. I'll probably try that first if I can get one, then it may end up on my commuter if I ever get the Schmidt.

About how much are the parts for Ktronik's design? Is there one source for all the parts or do you have to get the parts from several different places?


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## Calina (Apr 8, 2008)

Check these links, you might find them interesting,

http://www.candlepowerforums.com/vb/showthread.php?t=207165

http://cgi.ebay.co.uk/New-Airbike-light-system-with-SSC-P7-led-670-lumens_W0QQitemZ200250555296QQcmdZViewItem?hash=item200250555296&_trksid=p3286.m63.l1177

http://www.candlepowerforums.com/vb/showthread.php?t=169898


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## Katzenjammer (Jun 12, 2007)

The lower chart ("Antriebsleistung") appears to compare the power cost (measured in watts of work) for the different generators with the lights on (strong colors) or off (pale colors). So, the Shimano appears to be much the best at low speeds, and comparable to the Schmidt at high speed. The SRAM appears to be trailing the other two no matter what the speed, though (the "Fazit" section points out) their price point makes them worth a look if you usually ride at low speeds with your lights on.

I don't really have the time to distill the whole article, but the main point they make is that Shimano have made a big jump forward with their current products, putting them up there with Schmidt who have been til now the unquestioned leader.

Hope that helps.


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## poobardog (Mar 2, 2007)

Hi Bob
From what i've read -i think the Shimanos are getting there like Katz says and Ktronik is certainly happy with his.
I would have got a Shimano originally -just the SON looked very high quality when i bought it 3 years ago and i think the Shimano were having seal issues back then.

The parts can be got at a well stocked electronic shop like Jaycar (if you are in AUS) maybe Mouser or Digikey in the US, and cost peanuts. For Martins circuit it is a worldwide search for the parts LOL.










The parts on the left are from Ktronik -smaller than the parts i got from Jaycar and probably better quality.So you have to look at that if you need to fit them into a smaller space.

I haven't actually made a circuit yet as the one he made me is going strong with the higher rated caps than originally used.

Cheers
Dom


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## Surestick Malone (Jan 24, 2004)

Calina said:


> Check these links, you might find them interesting,
> 
> http://www.candlepowerforums.com/vb/showthread.php?t=207165
> 
> ...


I don't think the P7 is the best bet for a hub dynamo powered light due to its high current requirements.


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## pursuiter (May 28, 2008)

I went through the same hand wringing about which dyno hub and finally when ahead and purchased a DH-3N71. Nice and cheap, it is a QR front wheel, might get stolen. Minimal drag, Shimano quaility. People are pulling 12W out of it with no issues. I couldn't find any reason to spring 4X for a SON or wait for a slightly more expensive Shimano to finally make it to the furthest reaches of Shimano's market (US/Canada  ) . It appears you noticed the same thing I did, the Shimano internals sure look amazingly similar :thumbsup: 

Jenson has the DH-3N71 for less than $80....


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## Calina (Apr 8, 2008)

Surestick Malone said:


> I don't think the P7 is the best bet for a hub dynamo powered light due to its high current requirements.


Oops ! The first two links were supposed to answer an other thread :madman: . Sorry!


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## hoovermd (Dec 22, 2007)

I've got a SON and the E6 lamp.
Nice light, nice beam pattern.


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## SSBonty (Jan 30, 2004)

Do we know why the DH-3N80 hasn't been released with a centrelock disc mount yet? Is one on the cards? Otherwise it looks like it will have to be the SON for me...


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## dazzat3 (May 4, 2008)

Hi BTWB,

I have built a dyno LED system (with some guidance from Ktronik) using the shimano DH-3N80 and I am stoked with it performance "six SSC P4 running @ 950ma at 28 klms p/Hr". The beauty of it for me was that I never have to worry about charging or replacing a battery again and as a added bonus I got a set of training wheels as well as the light for only a little more than what a Trinewt or similar commercial light would have cost me. 

I run my light day and night on my commuter and I barely noticeable any drag or maybe I'm becoming a stronger rider...another bonus. 

The only down side...during group rides other riders want me to sit out front as my light light drowns theirs out & most of these guys have high end commercial lights. 

Go with the dyno hub that best suits your needs and wallet.

Get in contact with Andrew at Newcastle Avanti Plus "The Bicycle Center" he can order any Shimano product in for you....Why not take advantage current exchange rate USD > AUD.


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## znomit (Dec 27, 2007)

dazzat3 said:


> "six SSC P4 running @ 950ma at 28 klms p/Hr".


Dazzat you should get significantly less light at 35-40, is it noticeable/annoying? I looked at the boost curves and they seemed quite peaky.


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## Calina (Apr 8, 2008)

dazzat3 said:


> ,
> 
> I have built a dyno LED system (with some guidance from Ktronik) using the shimano DH-3N80 and I am stoked with it performance "six SSC P4 running @ 950ma at 28 klms p/Hr".


This is something I just don't understand. How is it possible to get more then 0.5A from a dynamo? What is the theory behind the magic?


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## Calina (Apr 8, 2008)

:???:


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## dazzat3 (May 4, 2008)

*No real noticable drop off*



znomit said:


> Dazzat you should get significantly less light at 35-40, is it noticeable/annoying? I looked at the boost curves and they seemed quite peaky.


Hi Znomit,

I really don't get any noticeable drop off even at 45/50. I should get a minimum of 570mA @ 54 km/h by Ktroniks figures below but I'm suspicious that the DH-3N80 and the 100uF bi-polar/4700uF cap combo is giving me more amperage (mA)....I can't explain it....It Just works.

It would nice to have the light aimed/tilted up a little higher for speeds of 45 plus...then I would get cars high beaming/flashing me all the time whilst commuting.

Speed V I P
4.0 km/h 7.69 V 3 mA 0.03 W
5.0 km/h 8.14 V 26 mA 0.21 W
7.0 km/h 8.47 V 50 mA 0.42 W
9.0 km/h 8.79 V 100 mA 0.88 W
12.0 km/h 9.16 V 170 mA 1.56 W
15.0 km/h 9.44 V 250 mA 2.36 W
18.0 km/h 9.75 V 350 mA 3.41 W
21.0 km/h 10.04 V 490 mA 4.92 W
23.0 km/h 10.24 V 610 mA 6.25 W
25.0 km/h 10.42 V 740 mA 7.71 W
26.0 km/h 10.50 V 820 mA 8.61 W
27.0 km/h 10.58 V 900 mA 9.52 W
27.5 km/h 10.62 V 910 mA 9.66 W
28.0 km/h 10.55 V 900 mA 9.50 W
30.0 km/h 10.34 V 740 mA 7.65 W
31.0 km/h 10.33 V 710 mA 7.33 W
37.0 km/h 10.14 V 630 mA 6.39 W
43.0 km/h 10.06 V 600 mA 6.04 W
54.0 km/h 10.00 V 570 mA 5.70 W


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## scuppy (Nov 10, 2007)

Here are a couple of ways to explain it:


The hub is an inductor. It phase shifts the current. A capacitor phase shifts it the other way, reducing reactance (dynamic resistance) dependant on frequency.

You probably know ohms law: I = E/R (E is V). For a reactive (dynamic) circuit, I = E/Z, where Z is the impedance. Impedance is a vector derived from resistance and reactance. When the frequency approaches resonance, reactance approaches zero so Z approaches R. If you google, you might find some graphs that show this, try 'LC circuit' or 'impedance vector'.

Adding a capacitor creates a 'tank circuit'. If you google, you will find a formula that you can use to determine the capacitor to use if you know the ocsillating frequency and inductance of the generator.


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## Calina (Apr 8, 2008)

scuppy said:


> Here are a couple of ways to explain it:
> 
> The hub is an inductor. It phase shifts the current. A capacitor phase shifts it the other way, reducing reactance (dynamic resistance) dependant on frequency.
> You probably know ohms law: I = E/R (E is V). For a reactive (dynamic) circuit, I = E/Z, where Z is the impedance. Impedance is a vector derived from resistance and reactance. When the frequency approaches resonance, reactance approaches zero so Z approaches R. If you google, you might find some graphs that show this, try 'LC circuit' or 'impedance vector'.
> Adding a capacitor creates a 'tank circuit'. If you google, you will find a formula that you can use to determine the capacitor to use if you know the ocsillating frequency and inductance of the generator.


That is a bit over my head but I can work it out.
Thank you! :thumbsup:

If I understand correctly, basically the capacitor lowers the resistance of the circuit.


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## znomit (Dec 27, 2007)

Calina said:


> [/LIST]
> If I understand correctly, basically the capacitor lowers the resistance of the circuit.


Only at one frequency. If you plot Dazzat3s numbers you'll see its quite peaky, so there is a tradeoff.


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## Bob the Wheelbuilder (Sep 21, 2003)

Found a US source for the DH-3N80: Harris Cyclery has them, mine should be here Christmas Eve.

Quality still doesn't have them, so I'm not sure where Harris is getting theirs.


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## Bob the Wheelbuilder (Sep 21, 2003)

I ended up getting two Shimano hubs, the light, expensive DH-3N80 from Harris Cyclery and the heavier and much cheaper DH-3D71 from Quality. I built the 80 into my randoneering wheel using bladed DT Aerolite spokes and a DT RR 1.2 rim. I used the 71 with an old WTB Speed Master so I can use it on a fixie commuter with a front rim brake and also occasionally use it with a disc on my 29er for off road epics. 

I have a 1 watt Planet Bike Blaze light on the fixie (it's plenty for commuting) and I'm probably getting a Busch and Muller IQ Cyo Sport or a Schmidt Edelux for the randoneering setup. Those two both have more powerful beams that have a horizontally ovalized shape that shines more efficiently on the road.

Off road, I'd ideally want a Supernova E3 or E3 Triple for their bright, round light patterns. The Blaze has an round beam and might be enough light for an occasional off road ride. Or I might get my hands dirty with a DIY light.

Quality now has a 36 hole DH-3D72 due to show up next month. It is supposed to have the lower rolling resistance of the DH-3N80. It's also disc compatible. I think the weight will be virtually the same as the 71 it replaces. I can't feel the drag of the hub with the light off or on. They are both a big step up from the decades old tire sidewall generators I had experience with.


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## mtnfiend (Feb 26, 2004)

Bob, Thanks for the update! I am thinking along similar lines as you. It sounds like you ended up with two sets of wheels in the end, when you originally wanted one wheel to light them all. Why did you end up with two? Was one too much of a compromise. 

I am thinking about getting the DH-3D71 and either the Salsa Delgado Cross or Stan 355 rim. I am looking for a dyno wheel for randoing, night rides in the winter, and 12/24 hour MTB events. 

I'm really not sure about what lights to get. I really like the E3 Triple but don't want to spend the money. I might end up with the single E3. Other recommendations are welcome. I'm looking for one light to light them all.


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## Bob the Wheelbuilder (Sep 21, 2003)

mtnfiend said:


> Bob, Thanks for the update! I am thinking along similar lines as you. It sounds like you ended up with two sets of wheels in the end, when you originally wanted one wheel to light them all. Why did you end up with two? Was one too much of a compromise.
> 
> I am thinking about getting the DH-3D71 and either the Salsa Delgado Cross or Stan 355 rim. I am looking for a dyno wheel for randoing, night rides in the winter, and 12/24 hour MTB events.
> 
> I'm really not sure about what lights to get. I really like the E3 Triple but don't want to spend the money. I might end up with the single E3. Other recommendations are welcome. I'm looking for one light to light them all.


I built the rando wheel for road use only. The DH-3N80 is a lot lighter and isn't disc capable. The symmetric build with a non-disc hub ends up being stronger.

I also wanted a second "beater" wheel I could use on a disc-braked 29er occasionally. I thought the Blaze light wouldn't be my final randoneering choice, but I wanted to give it a chance to see how it performed and now it has a home on the commuter. I think it will be very nice to not have to worry about the charge in my lights when deciding whether to commute on a given day.

You also have to understand I'm a wheel nut. Some of my bikes have two spare wheelsets.

If you have the time and skill, a homebrew light sounds like a good choice for off road racing. The road lights have some pretty sophisticated beam shaping that I don't think can be reproduced by hobbyists, so commercial lights are probably best for that application.


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## jimgskoop (Apr 13, 2006)

See this entry on my blog for some numbers comparing the DH-3N80 vs. the SON hubs...

http://sfcyclotouring.blogspot.com/2008/12/its-he-ere.html


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## unterhausen (Sep 28, 2008)

Jim, what do you think about your light?

I see you have made some other LED lights in the past. I gave in yesterday and bought the Cutter triple XPE because of the packaging. I have 3 XRE 20mm LEDs, and having a 2.5" housing just doesn't appeal that much. I'm going to use that one on my commuter, and have the XPE on my rando bike.


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## znomit (Dec 27, 2007)

Unter, the cutter XPE triple is ok. It doesn't seem to throw quite as well as their MR11 narrow but its fine to ride with, ok at 250mA and decent at 500mA. Only had one 70k ride with it but very happy. 
Mine is for my rando bike too, (for a 500km this weekend), less power draw than my 5 led light which should help with the 19hr 400km cutoff :eekster:


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## jimgskoop (Apr 13, 2006)

unterhausen said:


> Jim, what do you think about your light?


My Znomit-clone single Cree light works well -- I finally got to test it out with a bit of urban night riding. It only flickers a tiny bit initially when starting up from a dead stop -- something I was worried about actually. I can't detect the drag when the light is switched on, either. It is bright enough for urban commuting, but for higher-speed randonneuring events I'd want more light -- I'm thinking of building another similar light, but using 2 or 3 LEDs for more lumens -- or perhaps an MC-E. Overall it's satisfying that something this simple and low-cost to build (~$20 in parts) works as well as it does!

-Jim G


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## unterhausen (Sep 28, 2008)

znomit said:


> Mine is for my rando bike too, (for a 500km this weekend), less power draw than my 5 led light which should help with the 19hr 400km cutoff :eekster:


I take it that's not an ACP brevet? They give you 19 hours to do 300k


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## znomit (Dec 27, 2007)

unterhausen said:


> I take it that's not an ACP brevet? They give you 19 hours to do 300k


Yeah it was quite stupid, timed around the racers finishing when the organisers are around. Think they did 16hrs for the 500km.  
I managed 200 in 9hrs and called it quits due to general lack of pace (I think getting a flu shot the week before didn't help).
Light wise things went well. Ran on 250mA the whole way(my new handlebar bag was bumping the mode switch to the 250mA setting) so 300lm from the XPE triple, it was plenty, the roads were good and the moon was out, and I rarely got over 30kph.


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