Game Changing Dynamo Hub?
 

http://velo-orange.blogspot.com/2010...dyno-hubs.html

Apparently they will be selling a hub dynamo that has a "clutch" that you can disengage to remove any drag normally associated with a hub dynamo.

Personally, I don't have that delicate of a touch that I can notice the difference between my Shimano Deore hub and the Shimano 3n-71 dynamo hub that I now use. I don't know if this is much of a game changer for me but it might interest those that can feel the difference.

However, the Cree based dynamo light sounds interesting especially at the price level of $60. If it is at or above the output of a Cyo light then that could be very useful. I guess it really depends on how the light is focused and what the resulting beam will look like.

Be interesting to see if this one works reliably. Sachs had a similar decouplable drive dynamo mechanism that fit rear wheel hubs quite a few years ago and I have read mentions of others.

To me with the increased popularity of hub dynamos, with their much decreased drag compared to sidewall or bottom bracket dynamos, the necessity for a dynamo interruptable drive has decreased.

I've seen pictures. They look very bling... :thumb:

I'm more interested in this:
http://store.velo-orange.com/index.p...ynamo-hub.html

$50 Novatec dyno hub?

Looks a lot like the shimano 3N30 which you can get for 36US$. :D

It sounds like a good idea. I don't know if it's game-changing though. Have to see how it works out. The Son dynohubs don't have a lot of drag under no-load conditions.

Funny that he says he doesn't read forums any more, when he showed up here he didn't do too well for himself

As far as cheap dynohubs go, the Sanyo that Peter White sells for $50 seems like a good deal

I think the no-load disadvantage of new shimano nexus dynohubs was measured at 1-watt. I believe that watt includes the effect of the extra weight of the hub as well.

urban bike power output test

Most people who want the benefits of a dyno do not care about drag. If the game is the regular dynohub market, this does not change the game. If the game is the very small percentage of people who care about such things, perhaps this changes that game.

The 3N30 does not seem to be imported to the USA for retail; sales based on a quick Google search. Your linked to source in Germany notes a 30 Euro charge for shipment to the USA. The best buy here is probably the Sanyo QR dynamo hub which is $40 from Peter White Cycles with quick release or $37 without the QR skewer.

Really? It sounds remarkable silly to me. Get rid of pretty minimal drag by increasing mechanical complexity quite a lot? I'll have to wait until I see what the manufacturer thinks of the reliability, but I suspect it won't be much. They'll need to offer a warranty at least as long as Schmidt does, which is five years, to show they're confident they're making a good product.

Now, it's a good *marketing* idea, and most of what VO do are about marketing, so I'm sure they'll manage to sell it. Magical thinking sells lots of bicycle parts.

This is silly. Just because something like a SON isn't mechanically decoupled it doesn't mean it isn't decoupled. The physical world consists of more than just mechanics which pea minded cyclists can see with their eyes.

A SON disengages when you turn the lights off and that disengagement is just as real as any mechanical disengagement (which won't be 100.00% efficient either).

No, rotating magnets in a stator create drag, even when there's no load for the current to run through. Not rotating the magnets is an efficiency improvement. I don't think it's a big enough one to worry about, nor one that outweighs the increase in mechanical complexity.

Even my really cheap dynohub has such minuscule amounts of drag that I can't see the added weight/complexity being worth it.

I only swap my dynohub wheel out for the summer because of the weight ... the drag really is negligible.

The mechanical coupler will still need to rotate in order to maintain alignment...which will create drag (and probably more than a well made rotor). No matter where you draw the interface there will never be a perfect decoupling, might as well make it electrical.

I can think of half a dozen ways to do the engagement that have no moving part of the clutch rotating when disengaged, and which have zero drag. And that's without thinking hard; there are surely others. I still don't think it's a good idea, but not for the 'it doesn't work' reason. The point of a dynohub is simplicity and reliability. Adding moving parts rarely enhances either of those goals.

When riding with a bottle or bottom bracket dynamo, I was looking for ways to engage or disengage the dynamo without stopping. Stopping for the purpose was a pain at some level, that the dynohub eliminated. Of course the mechanical dynohub clutch could be equipped with some cable to activate it remotely, but I do not anticipate this level of sophistication with the first attempt. In the past, Union introduced a cable remote for one of their bottom bracket dynamos, but I am not sure how successful that remote was.

Peter White Cycles is offering a Sanyo BB dynamo which includes a operating and disengagement cable and lever that can be operated while riding.

Thanks, tatfiend, for the tip. With a Japanese trip coming up, I might try to get it there, hopefully for half of the Peter White's price and that mostly for collecting purposes. By now all critical bikes in my household are running dynohubs. A older Sanyo BB in my collection is without a remote.

I don't believe you. Just because you don't consider it part of the clutch it doesn't mean your mechanism won't add drag and it doesn't mean it will be reliable or efficient.

Using your same simplistic point of view there's no reason tossing a few magnets inside an otherwise rotating hubshell should add any drag...but it does because in order to make it reliable the generator mechanism needs it's own set of bearing surfaces, etc. Likewise for mechanical engagement: in order to have efficient engagement while "on" you need tight tolerances and secure fit which means you need planetary gears, bearings, etc which will drag even when the electrical part is mechanically disengaged.

Think about it, why isn't a bottle dynamo as efficient as a hub dynamo in use? There's nothing magical going on inside the hub; it's the tradeoff between designing an efficient engagement mechanism and one that offers complete decoupling. You can't half both, although an electrically decoupled design like a SON offers the best tradeoff.

Rotating magnets produce energy loss because they repeatedly change magnetization of the stator. This comes out as heat. In addition, moving magnets give rise to eddy currents that also yield heat. In a standard demonstration of the latter a cylindrical magnet is dropped down an alu tube where it comes to a virtual stop while neither significant mechanical losses are involved nor magnetization of the tube.

This, combined with the failure modes of a clutch mechanism, is why this will not be a game changer. It simply isn't worth it to deal with lower reliability for the small difference.

I have that hub on my REI Novara Transfer. Works as intended, never used any other dyno hubs to give a comparison. I'm sure it is heavier and not as efficient than the Bling Bling dyno hubs. Selling for $35 right now.

Actually, the discontinued LightSpin bottle dynamo was slightly more efficient than the SON, according to a German cycle magazine. Most bottle dynamos are designed to a price.

It was common for French randonneurs to use that set-up. It is pretty reliable and easy to flip the lights on and off without stopping (e.g. tunnels, hanging in a bunch as dusk falls).

Hadn't heard of that before.
I found this video: http://www.youtube.com/watch?v=nrw-i5Ku0mI

An even better one: http://www.youtube.com/watch?v=30oPZO_z7-4