2_i 

Were you in a serious rain? Did you, in particular, try to simply pour water onto the dynamo and the rim, eliminating the need to experience a serious rain? The lack of any slippage is surprising given that the best rim brakes lose much of gripping power.

Regarding the plots, the normal expectation is that the dynamo begins to act as a current source at higher speeds, with ~0.55 A being about the standard value. I.e. you expect the current to flatten at high speeds, no matter what the load. However, this dynamo continues upwards in the current at high speeds.

Optimization of dynamos for LEDs can be a bit nebulous, since there is no standard for LED lights, other than those lights need to account for standards developed for the incandescents.

dwmckee

As far as rain, I had it out several times on wet roads and a light drizzly rain. I purposely rode through some puddles and did not encounter any detectable degradation in light output, but as you might guess I did not have instrumentation on during the rides. As far as comparing to rim brakes where you have rubber against wet metal and are trying to slow 100 - 200 pounds of force with friction, you would expect and have rim brakes slip a lot more when wet than when dry. With the rim dynamo you have a wet rubber o-ring with maybe 10 pounds of pressure toward the rim for traction and maybe an ounce of resistance of the generator rotor force. I do not think there is much similarity. Anyway, despite any expectation, actual testing shows no detectable degradation in light output. I can tell you that with the dynamo engaged on the rim if you hold the dymano still and try to pull the rim past the o-ring by hand it takes more than 10 pounds of force (just an estimate, no scale used here) to get slippage. Compare that to the rotor's resistance force to turning of less than an ounce and you have a huge margin of rim traction. And if you do get slip you can adjust the bracket to apply more rim pressure to compensate.

As far as current leveling, regardless of what you might expect the data is simply the data. That is what it is. The graphs were developed by my brother-in-law in a lab at RIT where he is a professor teaching classes on electrical powered vehicle technology. Maybe they flatten at 30 or 40 kph? He only tested to 20 kph.

To your last point, this thing has less power than a big hub unit yet plenty to spare to power the Edelux II which is one of the more powerful LED lights today. I cannot comment on how it might work with other lights or if you are trying to drive multiple lights simultaneously or a USB charging system. I guess we will have to wait and see when someone tests that configuration.

But as far as the setup I am running I can give it a TWO THUMBS UP!

2_i 

Sure, you apply the force on the break pads and on dynamo roller in proportion to the friction force you need to get out from the contact, but the friction coefficient (to the extent you can employ it here) degrades similarly in the two cases, if water gets in. Thus, principally there is similarity. However, if you find that the setup works, that's the practical experience. Maybe they worked much harder on the compound in the roller than has been typical for the manufacturers till now.

I looked at data from other dynamos and they already flatten between 15 and 20 kph. Regarding the load from the lamp, the LED technology decreases the power demand by something like ~35% in my experience. In principle this alone could shift the moment when the dynamo started slipping when wet. Without saturation for this dynamo, I am not sure though how to put the reduced power demand into the context.

Anyway, it is good to know about viable options in the market. Have you got any personal impression of the efficiency of that dynamo? One way would be to have the dynamo engaged and flip the switch on the lamp. With the hub dynamos you practically sense nothing and if Velogical indeed has the claimed 70% efficiency, you should not practically feel anything either. Standard bottle dynamos mount much more and noticeable resistance when the circuit is closed than when open.

Reading more at the Velogical site, I see that this 70% efficiency pertains to speeds above 30 kph, of not much interest to me. Extrapolating the numbers they quote, it seems that the efficiency might be 50% at 20 kph, i.e. in-between the standard bottle and a hub, though a bit closer to the hub.

Weatherby

I have read with interest as this might be a lighting solution for my needs. I could not imagine slippage being a problem wih such a small contact patch but I wonder about noise.

Is there any audible noise from the unit? If so, to what extent is it speed dependent? Of does wind noise cancel the unit's noise about a certain threshold, say at 12mph you can't hear it?

A quick look at the drag figures look impressive but I would need to compare to the SON deLux. The nice part is it only weighs 60g and can be turned off completely unlike a hub that always has some drag and unlike a battery that weighs 120-400g (these are my current ranges depending on capacity needed). Now, adapting it to charge electronic devices and it sounds like a winner.

Weatherby

No need to extrapolate, the complete data is on their website and it is right up their with SoN, which only lists a single point....65% efficiency.

dwmckee

This seems to have way more rim friction than it needs so even when wet no problem.

This is definitely audible and speed sensitive. I plan to remount on the rear wheel to see if that makes it less noticeable. Try that with your hub dyno! I cannot compare to other dyno types as this is all I have.

dwmckee

If you do buy one the mount is rather crude but works quite well once you have it adjusted. Plan for several weeks to receive it from Germany.

dwmckee

If you do buy one the mount is rather crude but works quite well once you have it adjusted. Plan for several weeks to receive it from Germany.

dwmckee

I have had a PM asking about the noise. You can hear a whir sound and at about 9 - 10 MPH it hits a brief harmonic vibration then quiets down as speed increases. I cannot compare to other hubs though. At over 15 mph the wind noise drowns out the whir sound. You can feel a bit of drag when this is on at higher speeds and it is easy to compare with and without because it is so easy to switch on. The nice thing is that when off this is completely off!

Road Fan

I think the lack of saturation is plausible based on the generator frequency combined with lower power rating. At 20 mph a wheel rim (27 inch wheel diameter) is traveling about 350 inches per second. Assuming the generator wheel circumference is 2 inches, the generator shaft frequency is about 175 revolutions per second, or 175 hertz. For a hub generator at 20 mph, the shaft frequency is the wheel rotational frequency is about 4.2 revolutions per second or 4.2 hertz. I think typical hub generators might have an electrical frequency about 20 hertz (I think this goes back to Pilom's papers), and I'd expect the Velogical to be single-phase and simple. So the ratio of operating frequencies is about 10:1 (=175/(4*4.2)). At equal power output the Velogical design requires one-tenth the iron for the same degree of saturation, and that cuts in half again based on 50% power, for a 1/20 factor in minimum amount of core iron.

But the core has to be sized to accommodate all the wire, so usually the core is upsized to handle the wire, ensure heat transfer, and provide for good manufacturing. So the Velogical core is probably well above the size that will show saturation.

I think it's perfectly normal that it does not show saturation like the lower frequency hub dynos do.

The efficiency is then dominated by wire resistance once the diode turns on above about 2 volts, and other effects that are linear with speed, such as rolling and seal frictions.

I don't know how it compares to conventional sidewall generators.

unterhausen

these things are really neat. It probably will not get me to convert from hubs though, the only bike I own without a hub dyno is my fatbike, and that's on the list

dwmckee

For what ever it is worth, at higher speeds this is putting out about 6 watts. That output has to come from some input which is your legs, If you are putting out 120 watts on average you loose about 5% of your power to the generator (at 100% efficiency). You cannot get out more than you put in. Good hub dynos that put out 5 or more watts have the same situation, the watts of power that come out have to come from your legs. I am finding I do not need as much power as this puts out so for me, I probably would have been better off to buy the lower output unit to be best matched to my riding. (I bought the middle output version and there is a higher and a lower output unit available to march to your needs.) It is actually nice that these are available in 3 output levels so you can buy one matched to your needs instead of a one size fits all hub dyno that likely puts out way more power than you need (and sucks way more power from your legs than you need to.)

dwmckee

I set this up so I can easily move it from bike to bile as well so if you do ride different bikes it can save some cash by only needing to have a single dyno for all bikes.

noglider 

Have you got pictures to show us? I've been thinking about movable dynamo light systems.

I do not perceive the drag from my Sanyo dynamo hub, and this might be the draggiest hub there is. I realize 5% is appreciable, but it's on my heavy bike, so maybe that's why I don't feel it.

fietsbob

yea But, they put out a regulated 3 watts .. @ 6Volts .. though it may take a bit of wattage extra,from you, to generate that 3.

noglider 

The perceived drag is more important to me than the actual drag. As I said, I don't notice the drag from my Sanyo. Maybe I would if I installed it on a lighter bike.

dwmckee

My setup is identical to the picture at the start of this thread, same bracket and same position. From my experience, I'd say if you are a pretty fit rider averaging better than 15 MPH you could easily get by with the lowest output unit as long as you are driving just an LED headlight. That would have less total resistance. This is audible though, I have to warn you. Not terrible, but a definite audible whir sound. Mounting on the rear makes it less audible and when you are over 18 MPH the wind drowns it out. Remember, when this unit is disengaged it has no drag at all and works with any rim that has enough sidewall for a brake pad. It is really light compared to a regular hub dyno. Your output will drop when you are climbing a steep hill, but heck, when you are at 5 MPH you do not really need to see all that far ahead. The Edelux II is a great pairing with this dyno also.

dwmckee

I think you are still putting in more watts, the 'regulation' just dumps the excess generated to ground so you don't burn out electronics. Are you sure regulated to 3 watts; I thought they were regulated to 5 or more watts. Actually, I thought it was voltage regulated, not wattage...I

I really like the fact that you can get this in 3 output levels so you can pick the size best suited to your riding. A hub dyno is available in just one size which is the highest output (and input). Because you can size this to your needs and totally disengage it you can really optimize it for minimal wasted human effort.

dwmckee

I ride the same loop frequetly with and without the dyno engaged and I really know the route so maybe I am alittle more aware of the difference so I just am more likely to notice it. I do not feel it at low speeds but when I am up around 20 MPH is when I can feel it (and when it is putting out higher watts). At 10 MPH I can barely detect it.

noglider 

Well, that's really a great review. Thank you! Maybe I'll try it.

dwmckee

I'd be happy to help you out in any way if you decide to go this route. The mount is very solid but looks a little basic. There are three types of mount blocks depending on how you want to mount it. I bought two mounts for use on different bikes but have only used one of them so far. Like I said, a bit on the noisy side but it seems very well made and dependable so far. I am pretty happy with it. You will be the only kid on the block with one if you do go this route!

noglider 

OK, thanks. Currently I have a ridiculous collection of hub dynamos, sidewall dynamos, and lights. I don't even have an inventory of it all.

I have old sidewall dynamos on a couple of bikes. The noise they make is comical but not altogether unpleasant, and for short trips at night, not that burdensome.

dwmckee

Cool - If you get one you will immediately see it as a fabulous piece of German engineering. It is beautifully made and really cool in my opinion as well as quite tiny (smaller than a 35MM film can). I find the noise is just about right for nearby pedestrians to notice you which is sort of a safety feature in my eyes (like the sound some hybrid cars generate to keep from sneaking up on pedestrians).

Good luck,

Don

dwmckee

I am just curious if any other BF readers have tried out the Velogical yet. If you have, please post your experience. I have had mine for 2 years now and still find it to be a great solution for occasional use, but if you use your light all of the time, you are better off with a dedicated hub unit.

zacster

Never tried the Velogical, but I did get another Magnic light finally. The new model has user selectable modes for flashing and brake lights. I had it mounted on the left side brake boss, with my pannier on the right, and this combo didn't work for a number of reasons. First, you could only see the light from the left, but in NYC you ride on the left on the one-way streets, and most of them are. Second, I had heel strike on the right with the pannier and I never had that on the left. Third, what was third??? Whatever.

In any case I created a mount so that the light is now on my rack, and at the upper back of the wheel, at about 10 o'clock, and on the right side. It is now very visible from any direction and much more rigidly connected.