Dynamos and LEDs

[greatwhite]

Shimano relaeased a new dynamo fron hub recently which weighs under 500g and spec level equal to XT/Ultegra. Now a normal front hub is about 150g and a battery can easily weigh 350g too. Also the conveinience of not having to mess around with battery charger before training rides appeals to me and with modern LED systems the Dynamo can provide ample light at low 'drag'/power draw. Anyone had experince with such a system? Can anyone add useful comments.

[Johan Bornman]

I've built a few front wheels for Randoneurs who ride all through the night and can't put up with limited battery time.

They tend to go for the German Nabeldynamo system which they rate as the best.  It's a fantastically well designed hub and claims to consume only about 20 watts or so in drag. Most randoneurs have abandoned batteries or, use it as a back-up when fixing punctures and the dynamo can't power the light.

I have no doubt that Shimano's hub will be good. My experience with these hubs is limited to building the wheel, kicking the tyres and spinning the wheel in my hand. It feels slightly notchy due to the dynamo. Special care needs to be taken with the rim you use. Large flange hubs and deep section rims break spokes. Therefore you have to use a box section rim but that's not an issue, or shouldn't be.

 

 

I think it is a good solution for commuters, randoneurs and Michael Knigh (aka kNight Rider).

 

 

[TheLegend]

 

 

I've built a few front wheels for Randoneurs who ride all through the night and can't put up with limited battery time.

They tend to go for the German Nabeldynamo system which they rate as the best.  It's a fantastically well designed hub and claims to consume only about 20 watts or so in drag. Most randoneurs have abandoned batteries or' date=' use it as a back-up when fixing punctures and the dynamo can't power the light.

 

 

[/quote']

 

Sorry, but it's Nabendynamo. What you wrote would be an umbilicus-dynamo and this still has to be invented! The hub-dynamos haven been there for quite a while now.

TheLegend2008-08-17 01:07:54

[Johan Bornman]

Sorry, but it's Nabendynamo. What you wrote would be an umbilicus-dynamo and this still has to be invented! The hub-dynamos haven been there for quite a while now.


Edited by TheLegend - Today at 9:07am

 

 

Oops, typo.

 

What is an umbilicus-dynamo? 

Have I been taken in by the marketing claims of only 20 watts?

 

 

[TheLegend]

 

Sorry' date=' but it's Nabendynamo. What you wrote would be an umbilicus-dynamo and this still has to be invented! The hub-dynamos haven been there for quite a while now.

 

Edited by TheLegend - Today at 9:07am

 

 

Oops, typo.

 

What is an umbilicus-dynamo? 

[/quote']

it's a rare thing: someone has to arouse/upset you so much that your umbilicus/navel starts rotating. theoretically this could be used to power a dynamo

 

[greatwhite]

They tend to go for the German Nabeldynamo system which they rate as the best. 

 

I had a look at those hubs - very nice' date=' but also very costly - the new 3N80 Shimano unit is both lighter and very close in terms of effiency, where the more basic shimano units have lower efficiency and significantly greater weight.

 

 

I have no doubt that Shimano's hub will be good. My experience with these hubs is limited to building the wheel, kicking the tyres and spinning the wheel in my hand. It feels slightly notchy due to the dynamo. Special care needs to be taken with the rim you use. Large flange hubs and deep section rims break spokes. Therefore you have to use a box section rim but that's not an issue, or shouldn't be. 

 

Any reason why radial spoking is not an option? I intend to use a PRO (shimano) R-50 rim (similar to a Mavic Open Pro in section, but a little heavier) because I have the rim lying around - that should be shallow enough surely

[Johan Bornman]

 

Any reason why radial spoking is not an option? I intend to use a PRO (shimano) R-50 rim (similar to a Mavic Open Pro in section' date=' but a little heavier) because I have the rim lying around - that should be shallow enough surely

[/quote']

 

Radial spoking certainly is an option. However, Shimano won't gaurantee their hubs when they've been radially spoked. Places too much tension on the flange and it tears away. I've seen it happen in extreme cases of over overtensioning and other abuse.

 

 

It is a pity, because the large diameter of the dyno hub causes spoke alignment problems at the rim, especially if the customer wants a deep section rim, and radial spoking would solve this problem instantly and elegantly.

 

I can't remember if Nabendynamo allows their hubs to be radially spoked or not.

 

Yet, a reasonably competent wheelbuilder can make radial work with no problems.

 

I have a Nabendynamo customer here on the hub. Perhaps if you start a Naben thread he'll chip in and give you better advice than I can in terms of experience, performance and allowed spoking. He'll still have the little manual that comes with the hub and it'll talk about spoking, no doubt.

 

Useless information: Naben is hub in German. Slightly related: hub is naaf in Afrikaans. The etymology appears to be linked.

 

 

Johan Bornman2008-08-22 06:58:32

[greatwhite]

Time to resurect this thread, the days are getting shorter - JB any more wheels built with such hubs and new experiences?

 

Any one else?

[droo]

I'd be keen to find out, being a builder of fine LED lights myself... If they are any good I'd certainly look at putting a system together with a regulator and a 10 minute backup for slow climbs and punctures. If anyone's got any pricing info I'd see if it would fit in my R&D budget (or if the local agent would be so kind as to loan me a front wheel... nudge nudge wink wink...)

[greatwhite]

Don't know if Coolheat have any. I suspect the demand is really small - South Africans are generally pretty poor at making themselves and the road ahead of them visible in low light conditions.

 

Bring one in from Germany - seem to be cheapest. The DH-3N80 which I am interested in will set you back over R1k at the current exchange rate, Shimano make a few cheaper units too as do Sram.

greatwhite2009-03-03 06:47:41

[droo]

Right, checked the technical specs and it looks like it could work (with a bit of fiddling...)

 

 

 

My question now is - would these hubs be strong enough for off-road use? I know they have rotor mounts, but...

[greatwhite]

Same shaft and bigger flanges than std shimano hubs - so why not (don't know how the guts will handle the knocks though)

[pbp2007]

Hmmm, looks like I missed the original post.

 

Apologies in advance for being too lazy to edit my rambling thoughts into a couple of punchy paragraphs.

 

I am the customer JB referred to. Apparently I was also Schmidt's first customer in Africa for the SON (Schmidts Originale Nabendynamo).

The details aren't to hand, but it could have cost about R2 500 for the hub and the Schmidt E6 light, plus another king's ransom minor charge from Yellow Saddle for building the wheel. I will have a look for the invoices this evening and confirm.

I use it permanently on my audax bike, which is also my commuter.

My SON is, I think, the 28. This reaches full output about 15 km/h. Lower-drag models are now available; their advantage is that they impose less drag in normal unlit riding, but reach maximum output at a higher speed. This is fine if you're a fast rider anyway. Plus, these days there's a big selection of suitable LED headlights that shine brighter at lower r/min anyway, so the low-drag units make even more sense.

 

I bought the dynamo setup because of Paris-Brest-Paris. In 2006 I was using two Cateye Super Spot 1W (supposedly) lights that I considered OK until I came screaming down Du Toits Kloof at 1 a.m. in pitch darkness and a howling south-easter - skidmark time. A couple of my fellow riders were using units with big batteries (Sigma and Nightlightning) but I was worried that I wouldn't be able to recharge them on PBP, hence my decision to go with the dynohub. I also liked the idea of generating the light through my own efforts.

 

How does it go?

If I'm riding home, like today, and it's getting dark, I never have to wonder if I recharged the battery or brought fresh ones. I simply click the switch and there's light.  (OK, you have to be moving, though lights are available with a standlight function that keeps them going for stop streets, etc.)

 

So it's no big deal to use the light as a daytime running light. Yes, there's a weight penalty, but I'm guessing that the better class of battery will weigh much the same. And yes, with the dynohub you can't quickly swap your lights from bike to bike. You also have to be careful that you don't rip out the wires when removing the wheel - just the sort of thing that will happen in the dark on a lonely country road. For such occasions, and for reading my audax cue sheet, I use a tiny light that clips to my helmet and runs off a CR302 cell. Oh, and there's always the faint possibility of pretzelling the wheel... but that's why I keep a small battery backup.

 

Drag is something that's not an issue in normal running. With the light on, initially there's a kind of buzz or tingle in the handlebars. According to the manufacturer, with light on, the drag is equivalent to about half a km/h in 10. Even in my worst moments on PBP I didn't feel the need to switch it off and use my battery backup instead, and at times I was barely clocking 10 km/h.

 

The SON hub is said to be good for 50 000 km between rebuilds. By the way, it can't be user-serviced. Some may see this as a challenge, but I'd rather not. It's on about 6 000 now.

 

As for the light itself, until recently the E6 was Schmidt's top-of-the-range light. Its 6V/3W halogen bulb is run over-volted and is rated for 100 hours; I always carry a spare. The current one is on about 90 hours and still does the job for me. The optics throw a trapezoidal beam - vaguely V-shaped - that looks odd at first. The good thing about it is that the beam puts the light in this tightly focused area, with sharp cutoffs at the side and top (oncoming traffic can see you without being blinded). On the negative side, this might lead to a kind of tunnel vision.

 

People using some of the more recent lights may consider the output of my setup laughably low. Fine; I can't argue with the numbers. But subjectively, I feel comfortable descending at speed even in absolute darkness.  I will say that, on PBP when the descents got twisty I also switched on my backup Super Spot because it gave me a wider beam. Basically, nobody could keep up with me on downhills because they simply couldn't see as well. On the flats, I usually had people queuing up behind me for the same reason. Trust me, it wasn't because of my pacemaking abilities.

 

A question has been asked about the use of this kind of hub offroad. If offroad means jeep track or similar, I don't see a problem. My SON is built like a tank. However, using this setup on singletrack would be a waste of time, even with the currently available super-LED head units. You'd just be going too slowly or your speed would be fluctuating too much. These things are designed mainly with road use in mind. That also means the light spread should be concentrated on the road surface; off-road, you'll probably want to see a much wider area around you and above you.

 

For short rides and randonnees up to 300 km a good battery light should be sufficient. However, the dynamo setup comes into its own when you have to start riding through the night and you're unsure of your backup.

 

 

 

 

 

 

 

[droo]

Will mail Shimano and ask them, don't feel like finding out for myself that they fail on big hits...

[droo]

Thanks PBP, my intention was to use a small battery or cap to power the light, and the dynamo to charge. But I don't have a computer on my MTB and therefore have no idea of the speeds I reach on singletrack. I have done a bit of homework and found a guy who uses a Schmidt for MTB night racing, but I think that for the meantime it's a bit out of my R&D "write-offable" budget if it doesn't work for me. Watch this space though, I may surprise myself yet...