# Mountain Bike Dynamo Light!



## robdeanhove (Dec 8, 2005)

*Dynamo A Go-Go!* (blog link to more detailed words and pics)

Once an engineer, always an engineer. I always hit upon the problem of lights & winter. Specifically losing track of battery charge through daily usage as well as getting bored of constantly charging batteries and having stuff charging up on every available surface. I have spent the last 18months riding illuminated by a hub dynamo powered light that has slowly evolved empirically: the deanamo.

I made my first light over two years ago and was pretty convinced enough light could be had to make this viable off road and in technical trails, but there were several problems:

The light turned off when I stopped
The light didn't even come on until I was moving at a half decent speed
The speed needed to get a decent amount of light was actually pretty fast
When the light finally came on, with my crude smoothing, it was so flickery, it made your eyes hurt
Did I mention it turned of when you stopped?
Oh, and I knew little about how to overcome these problems
Two years of prototypes later and I think I've overcome all of this. My little winter project, that has actually taken hundreds of hours, is finally done! The final step was to get in touch with Ktronic from here (aka Australia's K-Lite), as I know he has long been tinkering with dynamos to make sure I'd not missed a trick. We exchanged a few notes, swapped tips and thoughts, I have got my hands on one of his lovely head units and his latest circuit with some of these final tweaks incorporated. The end result is a pretty kick ass product (although I must confess to putting a new circuit on it with my latest idea for a tweak between receiving it and mounting it on the light!). Is the battery light dead? I certainly haven't strapped a battery to my stem or top tube for a long while!

The final piece for the puzzle was the super light (410g) & super efficient disc dynamo hub, made by SP Dynamo and available from Intelligent Design Cycles in a plethora of colours.

630lm when "just riding along" a 420lm standlight when you come to a stop. Yes, your battery light might put out >1000lm, but I bet you're constantly dipping low to save battery power ;-)

Anyway, enough procrastinating...... Here it is:









The lovely little (and light) K-Lite head unit









Yup, that standlight definitely works when the bike's stationary!









Circuit tucked at the bottom of the fork leg









Powered by the tiny, beautiful and efficient SP Dynamo Disc Hub PD-8

And before you ask

No, it's not heavy, the weight is ~150g, yes there's a dynamo hub at 400g, but you'll need a front hub too, the total extra weight is about 300g. How much does your lamp, battery and front hub weigh? More than that I'd wager
No, it's not "draggy", it pulls ~6W, which is 5kcal an hour, or 5% of the energy provided by one cookie!

A few more words HERE on my blog


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## nexus666 (May 14, 2010)

that looks very cool, how long will it run while stationary? i dont commute to work anymore, but if i get back into it id definatly look at a setup like this. For me when commuting, having a bright light wen moving slowly is very important because thats when im interacting with traffic and pedestrians, when im moving at higher speeds that will be on dedicated bike paths.


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## brad72 (Jun 12, 2009)

Very nice indeed. I can certainly see the advantage for commuters and daily riders with not having to keep rotating packs on the charger and not accidentally going out with the nearly flat one. 

Would I be correct in assuming you have a super cap hidden on the fork leg so you have light when stopped?

I see from your race results that you are a fit bugger so the 5kcal might be difference for my weak unfit legs getting me to the top of the hill or not Might have to turn the dynamo off till i get to the top. 

Again, very nice.


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## robdeanhove (Dec 8, 2005)

oops, deleted


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## robdeanhove (Dec 8, 2005)

nexus666 said:


> that looks very cool, how long will it run while stationary?......


The light will be on full power for a minute or two (depending on the circuit) and will dull very, very slowly, remaining bright enough to run through singletrack fast for several minutes (I tried by disconnecting from the hub!), and will remain bright enough to be seen clearly in traffic for a *LONG* time. There's also enough light to see with generated at walking speed (or when in slow moving traffic).

I came downstairs for breakfast after a night ride when I left the bike by the front door and wondered what on earth the light I could see was.... turns out it was the standlight, which still glowing pretty strongly


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## robdeanhove (Dec 8, 2005)

There's certainly something hidden in the old piece of road innertube at the bottom of the fork leg, shown in the pic. I'm very happy with the crazy small size and low weight. And there's certainly not a battery involved in any way, shape or form!

So, yes, well it's either capacitor based or some tiny hamsters spinning a tiny hamster wheel ;-)


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## bumphumper (Jan 8, 2009)

Blimey what a blast from the past!

It was your dabbling with homebrew led bike lights on another forum about 6 years ago (maybe longer) that gave me the inspiration to make my very first light!!!

Thanks a lot you've cost me a fortune! 

Those hubs do look sweet, nice setup.


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## Bill in Houston (Nov 26, 2011)

i really like the idea of not having to replace batteries.


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## nexus666 (May 14, 2010)

are you willing to share the circuit or is it something your looking to sell?


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## troutie-mtb (Sep 20, 2007)

Nice one Rob been wondering since your emails last month when we would see something 
on the web .

Bumpy you may find its more than 6 years ago


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## robdeanhove (Dec 8, 2005)

Cheers, I think that's the nicest thing anyone could say (apart from the costing you a fortune bit!), it's great to hear I sparked an idea or the thought "I want to try that" in someone else's mind.

You'll be pleased to hear that the SP hub is, indeed, sweet and truly tiny. I can't wait for the colours to become available, until now only silver or black has been available from their competitors and who doesn't like a colour matched anodised component! ;-)


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## robdeanhove (Dec 8, 2005)

Bill in Houston said:


> i really like the idea of not having to replace batteries.


So did I, and 2 years later..... ;-)

The reality of not having to replace batteries is even better than the thought of it, I can assure you! It means no more getting caught out by sunset. I thought I might end up swapping wheels a bit but the reality is it's all so light weight and small I just have a light available on my bike all the time


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## troutie-mtb (Sep 20, 2007)

robdeanhove said:


> So did I, and 2 years later..... ;-)
> l I just have a light available on my bike all the time


in that case you need to build one like this


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## robdeanhove (Dec 8, 2005)

troutie-mtb said:


> in that case you need to build one like this


Cheers Troutie! A small machine tool is on the Christmas list to Santa. In the meantime I'm stuck using plumbing pipe and other people's head units (nothing changes in all these years!)

However, as the standlight stays on so long, it draws a lot of attention to the bike when parked outside a shop, so being able to quickly remove the head unit and pop it in my pocket is valuable. I use the bike for commuting to work and park it in the work bike stand and outside the supermarket when ducking in to grab my dinner on the way home!

I guess I should incorporate an on/off switch at some point....


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## troutie-mtb (Sep 20, 2007)

Be a big sod who would want to nick your bike 
I think the seat came to my shoulder height


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## brad72 (Jun 12, 2009)

You have certainly sparked my curiosity. I have seen plenty of dynamo lights over at CPF and seen Kerry's tinkering and love the lightweight hub you have chosen that I might have to save up for one ready for winter next year.

The big thing will be whether I can get a hub with a 20mm thru axle


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## borrower (Feb 26, 2011)

I'm very impressed. Thanks for sharing. One question, if I may: what did you seal up the innertube with? (I've been wanting to waterproof batteries and I'm thinking contact cement, but haven't gotten around to trying anything.)

And not meaning to hijack, but is that stemlight a troutie original? I don't think I've been around long enough to have seen it before.


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## robdeanhove (Dec 8, 2005)

borrower said:


> I'm very impressed. Thanks for sharing. One question, if I may: what did you seal up the innertube with? (I've been wanting to waterproof batteries and I'm thinking contact cement, but haven't gotten around to trying anything.)


You're welcome  I used outdoor guttering sealant that I had in the shed and that is available from any DIY store. It takes ages to dry, so I'd go with bathroom sealant for the next one. Cheap and readily available, it's not a tough sealing task. Most silicone sealants should work just fine. They'll be nice and flexible too. I'd be careful making an airtight battery container though.... (although I'd recommend you ditch the batteries altogether to be honest )


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## borrower (Feb 26, 2011)

Rob, thanks for the sealing info. My dirty little secret (and one I dare not tell the board at large) is that I mostly use my headlamp for running. Perhaps I need a little wheel off my back.


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## robdeanhove (Dec 8, 2005)

borrower said:


> Rob, thanks for the sealing info. My dirty little secret (and one I dare not tell the board at large) is that I mostly use my headlamp for running. Perhaps I need a little wheel off my back.


You need one of these! :arf:


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## BrianMc (Jan 5, 2010)

These hubs are great. Swhs on CPF has a blog page where he has tested them, if you are interested. 
They have an Al axle so how it stands up to trails would be of interest. 

On a different issue, I mistakenly used household sealant but the acetic acid it gave off ate the circuit. I now use potting compound which is safe for electronics and or the new 3-M waterproof electrical tape which bonds to itself like it was dipped. 

BrianMc


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## brad72 (Jun 12, 2009)

BrianMc said:


> These hubs are great. Swhs on CPF has a blog page where he has tested them, if you are interested.
> They have an Al axle so how it stands up to trails would be of interest.
> 
> On a different issue, I mistakenly used household sealant but the acetic acid it gave off ate the circuit. I now use potting compound which is safe for electronics and or the new 3-M waterproof electrical tape which bonds to itself like it was dipped.
> ...


Brian, that interesting that the acetic cure silicone eats the circuit boards. If you want a sealant that sticks like sh#t to a blanket use Silkaflex. It is fantastic.


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## phburns (Sep 30, 2008)

Nice system Rob, your setup is thought provoking. I wonder how long before someone sets up a regenerative braking circuit to capture lots of energy that now gets dissipated in the heat ring we call disc brakes. Then we'll be able to run higher drain lights without batteries, and possibly without drag on the uphill. Fascinating stuff. 

Thanks for sharing!


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## Vancbiker (May 25, 2005)

brad72 said:


> Brian, that interesting that the acetic cure silicone eats the circuit boards. If you want a sealant that sticks like sh#t to a blanket the use Silkaflex. It is fantastic.


The GE silicone II household sealant is a neutral cure type. OK to use around electronics.

In the US, Sikaflex is a bit hard to find. I have only seen it at larger marine supply stores. Mail order is probably pretty easy. 3M 5200 sealant is the same as Sikaflex (polyurethane based) and more widely available in the US. Only downside I have to say about the polyurethane based sealants over silicone is the longer cure time. As Brad72 says they are much stickier and tougher than silicone based sealants.


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## troutie-mtb (Sep 20, 2007)

If you are making a pouch from an innertube then use the rubber solution for patching 
or even neoprene cement


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## robdeanhove (Dec 8, 2005)

phburns said:


> Nice system Rob, your setup is thought provoking. I wonder how long before someone sets up a regenerative braking circuit to capture lots of energy that now gets dissipated in the heat ring we call disc brakes. Then we'll be able to run higher drain lights without batteries, and possibly without drag on the uphill. Fascinating stuff.
> 
> Thanks for sharing!


I'm not sure regenerative braking is a good evolution, with massive power draw, the nature of a dynamo would put a terrible amount of vibration through the bike.

As for greater outputs, I'm happily running around with a >800lm light, and it stays that way all night. The rides I go on my lights are rarely the light with the quoted maximum brightness, I concede most people seem to run somewhere between 1000lm and 2000lm. However, due to burn times their lights are often dipped, so my light is the brightest light on a ride most of the time!

The dynamo is particularly attractive now it's winter, I did a 3-day ride/trip with my girlfriend over this weekend with an extended night riding period and, due to the temperature being below 0°C for much of the time, we got not much more than 50% of the quoted run time from her light's batteries (which normally happily, consistently, deliver 100% of the burn times in the summer). I must get around to building her a dynamo wheel!


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## zahgurim (Aug 12, 2005)

This is awesome.

I've just been toying with the idea of purchasing a dynamo and building a light for longer endurance races/rides, and wondering about how I'd overcome the same drawback you thought of: no wheel spinning = no light.
(Was just looking at those same dynamos yesterday...)

Capacitor-in-a-tube?


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## robdeanhove (Dec 8, 2005)

zahgurim said:


> This is awesome.
> 
> I've just been toying with the idea of purchasing a dynamo and building a light for longer endurance races/rides, and wondering about how I'd overcome the same drawback you thought of: no wheel spinning = no light.
> (Was just looking at those same dynamos yesterday...)
> ...


Yup, the answer to "no movement, no light" is a capacitor.

The complexity, cost and weight of controlled charging and then discharging of batteries makes them a non-starter for me. Not to mention their cold weather drop off in performance.


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## robdeanhove (Dec 8, 2005)

Has no-one else tried anything else like this? I tried the search tool and couldn't find anything on the forum about a usable mountain bike dynamo light. A road light is relatively straightforward, and is well served by the Supernova 3 Triple (although it could be brighter), but given all the amazing work on battery lights I was hoping to pick peoples brains and see what solutions other people had come up with.....

Here's hoping!


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## kadikater (Oct 26, 2008)

robdeanhove said:


> Has no-one else tried anything else like this? I tried the search tool and couldn't find anything on the forum about a usable mountain bike dynamo light. A road light is relatively straightforward, and is well served by the Supernova 3 Triple (although it could be brighter), but given all the amazing work on battery lights I was hoping to pick peoples brains and see what solutions other people had come up with.....
> 
> Here's hoping!


look there:
Steuerung für Dynamolampen - MTB-News.de | IBC Mountainbike Forum


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## ThinkBike (Jun 16, 2010)

Rob,

Have you given any thought to running a hybrid of a battery AND dynamo?

You could run a battery pack, which would allow you to produce a brighter light and continuously charge the pack to extend the run time.

It would be interesting to run the numbers and at least theoretically see what kind of output versus run time you could get. Some of the newer 18650 Panasonics only weigh 45 grams each. It might be nice combo. Best of both worlds.


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## robdeanhove (Dec 8, 2005)

ThinkBike said:


> Rob,
> 
> Have you given any thought to running a hybrid of a battery AND dynamo?
> 
> ...


No way! And here's the two reasons why not:

1) A lithium battery only has a few hundred, maybe a thousand cycles before it's dead. I ride my bike most days of the week, maybe 20hrs a week, and would put many charge discharge cycles a day onto the battery, giving it a theoretical life way less than a year and that's without taking into account the havoc the cold weather in winter will play with the battery performance

2) A battery is a potential difference device, an LED is a constant current device, we currently have quite complex circuits to control the battery power through an LED efficiently. A dynamo hub is also a constant current device and can be connected, via a few, robust, discrete components to drive the LED directly, soring power in capacitors for the slow/stationary periods. To charge a battery would require a second complex circuit, in addition to the discharge drive circuit. A battery would not allow brighter burn times as, on longer rides (6hrs) or for regular commuting, the power available for the light is only equal, to the power available from the hub, the small amount of additional power from a single battery would soon be spent by my triple LED head unit.

Best of both worlds? I suspect it would be all the weight, cost, large package size and complexity of a battery light with all the hub weight and cables of a dynamo... sounds like the worst of both worlds!

When I set out on this project I set myself the goal of not resorting to a battery solution for those reasons! I've been running this light (and a couple of other prototypes) for a couple of years now without any issues. I've seen plenty of friends' lights either run out of battery charge or have problems with their ciruitry during that time, so I stand by my reasoning 

Hope that makes sense?


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## robdeanhove (Dec 8, 2005)

This light, in a different package, is now reviewed on Singletrackworld.com's "Fresh Goods Friday"!

CLINKY LINK HERE

They say:

*The Deanamo Light*










Remember the original, massive, home-brew lights forum thread from years ago? Well chief protagonist and engineer Rob Dean is still spending his spare time fiddling with wires (as well as riding and racing an awful lot) and has sent us a Deanamo light to play with. That's a Euro-style Shimano XT disc hub dynamo in the background, which we're going to build onto a 29in WTB rim the minute it arrives (hurry up postie!).

Facts and figures:
The three-LED beam gives 650 lumen at ~7mph or above, whilst the two-LED standlight (illuminated above) gives 410 lumen minimum when you're travelling below ~7mph or stationary. Yes, the hub is heavy but, with no battery, the lamp is lighter: a full system of circuit, leads, lamp and hub weighs less than an Exposure Lights MaXx-D/Hope Pro 2 set up. And if you're thinking that the dynamo will suck the power from your feeble legs then think again: the draw is a mere 5W per hour, which is the equivalent of 0.06 of a McVities digestive biscuit. There go our excuses for eating more cake&#8230;

From: Big Rob Racing

To which I say: "Woo-Hoo!!!"


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## Drbo (Nov 21, 2010)

troutie-mtb said:


> in that case you need to build one like this


That light is awesome! Do you have these for sale?


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## mattthemuppet (Jul 16, 2004)

robdeanhove said:


> This light, in a different package, is now reviewed on Singletrackworld.com's "Fresh Goods Friday"!
> 
> CLINKY LINK HERE
> 
> ...


nice job  Let us know what they think too - I head over there occasionally but it would be a shame to miss the review (esp. if it's behind their paywall). I'd love to see how you got everything in the back of that Easy2LED housing - they're sweet little housings but they don't have a huge amount of space in them!

I've no need for a dynamo light right now (or money for the parts, more importantly) but I can certainly see the appeal. Now that dynamo hubs seem to have come of age in terms of weight and drag, the time certainly seems right.


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## ktronik (Dec 23, 2006)

Kerry @ kLite.com.au is the AUS/NZ dis for these cool hubs...


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## savvas (Mar 21, 2011)

robdeanhove said:


> The three-LED beam gives 650 lumen at ~7mph or above, whilst the two-LED standlight (illuminated above) gives 410 lumen minimum when you're travelling below ~7mph or stationary.


Rob, I've been doing (I think) some similar experimenting with a 'slow speed' standlight circuit. I find my efforts limits by the physical size of the caps I've found. Are you able to tell me what tuning, smoothing caps and standlight caps you've used and where you found them? They are obviously all a lot smaller than the ones I have had access to!

thanks,

Sam P.


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## teatreetim (Nov 14, 2011)

Slow speed light is about getting the voltage drop low not what the capacitance of the circuit is. If you use a normally closed solid state relay to bypass 3 of your 4 front LED's the first LED will come on quickly (2 - 4 km/hr). Note it will strobe at such slow speeds. Use the lower power rear to turn off the relay (thereby turning on the remaining front LED's) when the potential increases. I cant find my old circuit diagram anywhere but it should look something like the attached. This is from memory from about 5 years ago now so forgive me if I made a mistake. I'd double check but the circuit was embedded in polyurethane inside the steer tube!

The MOSFET is just a current limiter. The way it is doped it wont let more than 40mA or so through so it's good for rear lights. If you want to drive a high powered rear LED, you'd just put it in series with the front LED's. When the potential seen by the resistor grows above so many volts the solid state relay will open, forcing the current through the LED's. By this time the potential across them should be high enough.

Looks complicated but it isn't, the main point is the turn on potential difference is one front LED plust the SSR, or around 4volts which is better than multiple LED's in series.

EDIT: PS the capacitor should match the inductance of the motor for phase correction. Many years ago there was a thread about it if you can still search back that far. If you want to power LED's while stationary then adding a resistor to the capactior will slow the discharge but will mess with power correction and efficiency. Don't know what the OP does.

PPS sorry forgot to rectify the generator! You know what to do 

PPPS found a non early start circuit so you can see how the MOSFET is supposed to look  Last edit I promise.


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## robdeanhove (Dec 8, 2005)

That's a neat idea to bypass a chunk of LED Vf at lower speeds - I think I'll be getting the soldering iron out!


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## rschultz101 (Oct 5, 2009)

neat idea !
never new about the off-road disc dynamo ! great news.
with batteries, there is hope .
with some new tech, and circuit, 5years plus , for the daily commuter , should be possible.
the Alaska version, might need some hand-warmers ,...
cheers, Rob


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## robdeanhove (Dec 8, 2005)

Hi rschultz, thanks for the compliment.

I'm not sure I follow quite what you mean when you say:



rschultz101 said:


> with batteries, there is hope .
> with some new tech, and circuit, 5years plus , for the daily commuter , should be possible.


Can you clarify for me? The point of my dynamo (and one of the challenges I set myself) was to implement a no battery solution to minimise the electronic complexity (and hance reduce weight and increase reliability) and to get away from the finite number of charge cycles and poor cold weather performance of lithium batteries? What are you referring to when you say _"5 years"_ (maybe I just need more coffee this morning!)

I'm always open to new thoughts and ideas as, hopefully these will prompt thoughts to help me develop better lights in the future - the collective imagination of the forum is a lot better than just me on my own!

Cheers

Rob


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## rschultz101 (Oct 5, 2009)

Hi Rob,
note: grew up in germany, as such was riding with dynamo powered light,
what needed to meet StVZO standard.

did take a look at the SP dynamo, they did come along , and improved.
First thoughts :
- do they have a disc version ? ok they do
- how much is it? $300 + ! by the time you add shipping and building a wheel it's $500 plus for starters ! for hard core commuters ok, for mtb weight weenies, not really.
- can I fit it on my bike ? got a giant reign, with that new QR 15mm front fork, !! argh
I ain't buying a new fork , for just a dynamo !!!
----
for mtb and dynamo's, I'd think, they need to have 15mm and 20mm hub version,
that includes disc. 
---
the next version, should probably be a modular approach, like the spoke generator.
just a little fancier, maybe timeing belt driven , with an on/off roller-clutch, 
and I'd like a 12V version.
---
for batteries:
less is more, more or less.
keep it simple is good, and batteries are the first thing to fail. 
supercaps, and electrolytic caps are fragile too.
.. battery life, most circuits (pcb's ) are geared towards max capacity, and not designed to prolong
the life of the batteries. at so many cycles, the battery will have less than 75% capacity,
and since most lights , etc, are not designed to have really extra capacity or runtime,
mostly because the consumer, wants to squeek by, with a cheaper price, or in case of bikers, 
also a lots of weight weenies. 
back to subject, if you want a 3hour runtime, and new in a sunny lab environment ,
you could do that with 4 cells, than in a cold winternight, 2 years down the road,
you should have bought at least a 6 cell battery. by the time you go past -20C, 
you'd be looking at 8 cells.
now a little example of lithium batterie life.
Lipo's are the flat ones, and batteries can be temperament-full at time,
including some flaming response back, when not treated right.
regular li-ion, they say, charge to 4.2V and discharge not past 2.5V ...
now the better RC chargers, don't let you discharge li-ion or lipo's past 3V,..hmm
good praxis, for the lipo's to charge to 4.1V, and discharge to 3.2-3.3V .
little thing like that prolongs the batterie life. capacity difference ~7-10% ,
where it charged / discharged full, after 50 cycles, you probably lost capacity in that range.
for Lithium batteries, and cycle time, the cobalt ones , would not be on top of my list.
the manganese seam to be more stable, and the ferrite ones , also have better temperature response.
so , double the capacity, and cutoff peak charge and discharge by 10-15%,
with decent lifepo4 cell, should get you past 5years. 
this does not include deep freezing temperature, that's a different challenge.
---
in the near future, batteries will improve,
did see test reports, white papers, prototypes, etc, some of them couple of years old,
doing the magic sound barrier 1000W/kg,.... 2000W/kg ,... 
right now , be more than happy to get an off the shelf 500W/kg rechargeable batteries.
the future battery , will not necessary contain any significant amount of the dangerous and rare element Lithium,...
---
back to subject...
for dynamo, would want one,
where it could be switched off, with no additional drag,
(from handlebar, while riding). ok, SON ,has one,with ~1W drag, at off, should be ok.
so for the up-hill challenge, would want that tinny battery pack,...
to turn the dynamo off , for that section.
and afterwards, when to goes , downhill, I'd still want the battery's extra power,
to turn on an extra high-beam, 5sec, 10-15sec, anything be good, even just a 1-2sec bleep, be groovy. just some thoughts.
----
if you are happy with your dyno power, and don't need the killer 3000plus lumens,
could think of a light, say 8hrs runtime, 12hrs if need be, that should be enough, unless you are in the artic circle, or doing the iditarod, for weeks,..., still be chargers, cables, and plug,unplug, wait, guessing capacity, paying extra for backup, etc,...
----
summary:
if you don't need to, be happy. no batteries
I would still consider, bringing a backup system.
and at that point, maybe put it to use, says half power, to still have some backup,...
a 10-15 sec burst, still be nothing, compared to a 3600sec / hr,
and initially, does not even have to be integrated. should function as a backup, 
but be accessible, means handlebar switch !
for starters, could be just regular AA nimh batteries.
----
for the more concrete stuff, shoot me an email,
my writing or style might not be pleasant, still trying to be helpful .
cheers, Rob


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## robdeanhove (Dec 8, 2005)

rschulz:

I disagree with your comments abut batteries. Riding around town on a dynamo does not compare to riding technical off road trails at speed and long off road climbs in the woods. I use my light for technical trails, commuting in town and long distance, multi-day touring. Batteries are a worse option for me for all of these uses. The two extreme uses are town = always want light so worried about charging and when I last charged the light all the time and multi-day trips where no battery will have enough power. All other riding falls between these two with both demands a consideration.

I believe your experience of dynamos is out of date and not relevant to this product. With a modern, high efficiency dynamo hub, and a well designed circuit, enough light is available, even at a walking speed, to ride off road, let alone be seen, even on the steepest, slowest climbs. This low speed performance is the key to the latest generation of lights and means the complexity of circuit required for a battery system is no longer needed.

Even 8hrs burn time is not enough for me for a battery system, in winter I do more than this every week and do not want to worry about my battery burn time every couple of days and be constantly charging lights, so dynamos are an obvious choice for me. Riding every day, with battery life of 500-1000 cycles, I will kill batteries in <2years and suffer reduced burn times after a few months.

Dynamo hubs are not $300, see HERE, they are $125 for the lightest and most efficient dynamo available. I bought my town bike dynamo for $20.

Dynamo light + dynamo hub is lighter and has fewer components than any LED light containing batteries and a lightweight, normal, front hub.

If you want 8hrs burn time when your bike is not moving, you want a torch, not a bike light! If you want long burn times when riding, without reducing brightness, you want a dynamo light.

The complexity of controlling charge and discharge of a battery makes it a much more complicated and expensive product than a "pure" dynamo light.

I have been developing mine for a few years and I understand why no-one makes such a product. In my experience those that say "use a battery" have not tried the latest dynamo lights and certainly haven't tried making them work as a usable product, lots of intelligence needs to be in the circuit to manage the power split from the dynamo to the light and battery charging as well as when to output power from the battery, making it a huge challenge and the product complicated, inefficient (energy required to manage the power steals energy from the main light at low speeds!) and expensive.

For an uphill, you would not need a battery a well throughout capacitor system will be lighter and provide enough light for a few minutes of light, while a cleverly designed circuit will extract enough light for riding, even at very slow speeds. I suspect your experience comes from very cheap, poor lights that provide extremely weak light, or even no light, at low speeds.

Lastly, your mail is quite patronising, pointing out basic things, but you do not seem to have tried to implement any of the solutions yourself? Maybe then you would see why everybody else does something different. I am very happy indeed with my dynamo light, it offers a better (lighter, brighter and more robust due to having fewer complicated components) solution than any battery product available, for me and my riding and it contains no batteries.

I can not comment on your "request" for a bolt through dynamo or a modular, clip on system as I am not responsible for making or developing dynamo power sources, who are these comments aimed at? My post is about the light unit that I have developed! Although clip on products are available (SEE HERE) and I believe bolt though dynamo hubs are in development in Taiwan.

I hope that helps you to explain my product and why it is how it is. Thank you for taking your time to explain your requirements from a dynamo system, but I would ask you rethink your approach, with the availability of good light power at extremely low speed with a modern, very efficient dynamo hub, the latest low power requirement LEDs and a cleverly designed circuit to make the best use of these combined characteristics.

Rob


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## savvas (Mar 21, 2011)

robdeanhove said:


> I hope that helps you to explain my product and why it is how it is. Rob


Hi Rob,
In asking about details of your dynamo light design in my earlier post (a few weeks ago now) I'm afraid I must have missed something. I see you refer to your 'product' above. Does this mean you intend making this light commercially? Or maybe having someone make it for you?
ta,
Savvas.


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## ktronik (Dec 23, 2006)

savvas said:


> Hi Rob,
> In asking about details of your dynamo light design in my earlier post (a few weeks ago now) I'm afraid I must have missed something. I see you refer to your 'product' above. Does this mean you intend making this light commercially? Or maybe having someone make it for you?
> ta,
> Savvas.


HI Savvas, I am have been making small production runs of this dynamo light, using this light head. And soon a 35mm lens version...

hope this helps

Kerry


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## savvas (Mar 21, 2011)

Hi Kerry,
Thanks for the reply and explanation. I've had a brief look at your facebook pages and I'm glad to hear you are getting back into dynamo light production. I am really interested in this new 'RD' light - mainly because it seems to crack the stay-bright-at-low-speeds issue - something I strike quite often when commuting on my rather slow freight bike. 

I take it the circuit is somewhat different to the modified-Martin design you have used previously and I'm intrigued by your mention of a 35mm version. Although I've never actually seen either your dynamo light nor the Supernova triple, I must admit I was somewhat deterred by various reviews and opinions which suggested that the 20mm triple optics didn't quite have the throw of larger or single lenses. And the Philips dynamo light has been quite a satisfactory distraction for me with it's shaped beam and long throw. However I do wish it was a bit brighter!

Will you be making your own housing for a 35mm version? It will I guess be a triple as I think I recall RD saying his design keeps 2 leds on at very low speed. How are you selling you new light? 

best wishes,

Savvas.

ps; will you also be making the tail light again???


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## ktronik (Dec 23, 2006)

HI Savvas, for such a simple and robust design, it does a very good job of keeping things lit when going slow or stopped, rob and i teamed up to work this idea further, and I am super happy with the results!

currently I am seeing how far we can push the racing / bike packing light system, for lightness and brightness. thus the 20mm optic, in a tiny housing, and a small cap-battery standlite of 11v / 1F.

A bigger cap-battery will work better, and a 35mm lens will be better for a higher lux output. but not as good for bikepacking or racing, due to the extra weight, So we have started making a slightly bigger XML version with a 35mm lens, that will be dynamo or battery driven, for the non racing market... this will have a bigger standlite...with the same deanamo type circuit.

once built I will be selling them on the kLite.com.au website, and info in the facebook site...

I have DIY kits or complete built lights if anyone needs them...also I am the AU/NZ dealer for the SP hub range.

hope this helps

Kerry


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## ktronik (Dec 23, 2006)

Here is a shot of the current racing / bikepacking units...with AAA charger and AA charger, that doubles as a USB charger as well (when stopped), after you charge the AA's inside, via the dynamo while moving. Or take the battery's out for your device.

Its smiple, with little to go wrong, light and quite bright for a dynamo light w great standlite function...


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## brad72 (Jun 12, 2009)

So has anyone come across a dynamo hub with a 20mm through axle? I have hunted high and low but to no avail.


.


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## robdeanhove (Dec 8, 2005)

brad72 said:


> So has anyone come across a dynamo hub with a 20mm through axle? I have hunted high and low but to no avail.


Sadly, no, and neither does anyone make one QR15, for which there is surely a much bigger market.

A German company make a 24mm compatible adaptor set to put a dynamo into a Maverick fork, but this is all I am aware of at the moment. I'm looking forward to some better news from friends who have gone to the Taipei bike show this week and are looking out for just such a thing!


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## brad72 (Jun 12, 2009)

robdeanhove said:


> Sadly, no, and neither does anyone make one QR15, for which there is surely a much bigger market.
> 
> A German company make a 24mm compatible adaptor set to put a dynamo into a Maverick fork, but this is all I am aware of at the moment. I'm looking forward to some better news from friends who have gone to the Taipei bike show this week and are looking out for just such a thing!


Thanks for the info, this is what I was unfortunately expecting. I am really keen to put a Dynamo on my Enduro to save always having to get my battery packs ready every night. With a triple xpe and 20mm optics you can get a really good output and like Kerry said still get to keep the weight down as you don't need such a large surface area to cool the light.

So I will just have to patiently wait till someone makes one, or I make my own


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## ktronik (Dec 23, 2006)

@brad72: Xpe?? Na... You should get a xpg s2 and snip off the dome...your die now looks the same as your xpe die does with the dome on..

If you need a housing let me know...they new take the newer 21mm deeper optic, for higher lux again...

K


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## brad72 (Jun 12, 2009)

ktronik said:


> @brad72: Xpe?? Na... You should get a xpg s2 and snip off the dome...your die now looks the same as your xpe die does with the dome on..
> 
> If you need a housing let me know...they new take the newer 21mm deeper optic, for higher lux again...
> 
> K


Thanks mate, I forgot about the xpg S2 after all the XML excitement.

Which is the new deeper optic out of interest.


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## troutie-mtb (Sep 20, 2007)

ktronik said:


> @brad72: Xpe?? Na... You should get a xpg s2 and snip off the dome...your die now looks the same as your xpe die does with the dome on..
> 
> If you need a housing let me know...they new take the newer 21mm deeper optic, for higher lux again...
> 
> K


K

Which optic are you refering too ??


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## ktronik (Dec 23, 2006)

Satu-XP Optic
The Satu Optic is a multi led optic suited to most small size Power Leds like Cree XP family and will function with triple boards laid out to suit several 20mm Triple Optics
Description
Cree XP 21MM TRIPLE OPTIC, MED
For Use With:Cree XP Series of LEDs
Lens Type:Lens without Holder
Beam Type:Spot and Medium
Beam Angle:Spot ± 9°,
Lens Diameter:21.8mm
Lens Shape:Round
Lens MaterialMMA
Accessory Type:Medium Lens

kicks arse over the Carclo 20mm...even better with snipped LED domes...


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## brad72 (Jun 12, 2009)

Thanks for that K. I was wondering what he Satu optic was like.


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## kwarwick (Jun 12, 2004)

ktronik said:


> Satu-XP Optic
> ....
> kicks arse over the Carclo 20mm...even better with snipped LED domes...


Interesting... based on spec the Satu +-9 degree beam angle is not any better than the narrow Carclo. Have you compared the two because feedback from others on the forums say the Satu is no better and is actually a little worse?

I'm curious to hear more about snipped LED domes too.  Comparison beam shots would be great if you have any.


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## ktronik (Dec 23, 2006)

kwarwick said:


> Interesting... based on spec the Satu +-9 degree beam angle is not any better than the narrow Carclo. Have you compared the two because feedback from others on the forums say the Satu is no better and is actually a little worse?
> 
> I'm curious to hear more about snipped LED domes too.  Comparison beam shots would be great if you have any.


Hey,

better / worse can be very subjective...I like it more as my light now has a smooth beam, from the outside to the center, almost like a reflector...I like that, some don't

I like that it has a brighter hotspot, that is totally smooth to the edges...

back in the day we took the domes off XR-E led, so the 'apparent' die size 'looked' smaller to the optic, giving a higher LUX value...a few days ago I cracked the shits with the new XTE's I got, that were not much better, or anything close to what we all thought they would be like...and ripped the domes off the XTE's to see if I could get a higher LUX...yep, it worked, but tint went out the window...So I did the same to the XPG S2...OOhh yea...apparent die size was much smaller, and gave a brighter hotspot, but shifted tint one to the warm side..which was fine...result, higher lux for my helmet light...and a smoother beam...

I now just snip off near the base, rather than remove the whole dome, as that can hurt the tiny wire bonds, that drive the LED die...

will try to get some pics done...

K


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## robdeanhove (Dec 8, 2005)

Just got a great new dynamo from the guys at SP (Shutter Precision)

It's switchable with a totally clutchable dynamo mechanism. Anyone that's picked up a dynamo and turned it will testify to, even the top of the range dynamos, feeling "notchy". This results in something imperceptible when riding and near zero drag, but you know it's there and near zero is a worry for some people. This hub solves that. Genius! The switch is a huge. chunky disc and is easily switched by me even with my largest winter gloves on

HUB IN WHEEL









SWITCH









There are a few more words, on my blog HERE

I'm really happy with this product, it does exactly what it's supposed to do simply and without fuss


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## BraggCreek (Mar 17, 2012)

good work!


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## cgeiser (Jul 17, 2011)

ktronik said:


> @brad72: Xpe?? Na... You should get a xpg s2 and snip off the dome...your die now looks the same as your xpe die does with the dome on..
> 
> If you need a housing let me know...they new take the newer 21mm deeper optic, for higher lux again...
> 
> K


I can't find any info on snipping off the dome - is it as simple as it sounds? Any tricks? 
Thanks!


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## ktronik (Dec 23, 2006)

cgeiser said:


> I can't find any info on snipping off the dome - is it as simple as it sounds? Any tricks?
> Thanks!


back in the day we took the domes off XR-E led, so the 'apparent' die size 'looked' smaller to the optic, giving a higher LUX value...a few days ago I cracked the shits with the new XTE's I got, that were not much better, or anything close to what we all thought they would be like...and ripped the domes off the XTE's to see if I could get a higher LUX...yep, it worked, but tint went out the window...So I did the same to the XPG S2...OOhh yea...apparent die size was much smaller, and gave a brighter hotspot, but shifted tint one to the warm side..which was fine...result, higher lux for my helmet light...and a smoother beam...

I now just snip off near the base, rather than remove the whole dome, as that can hurt the tiny wire bonds, that drive the LED die...


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## robdeanhove (Dec 8, 2005)

BraggCreek said:


> good work!


Thanks, glad you like it

Can't wait to see what other people (aside from Kerry's great work discussed further up the thread) might be doing on here that might be similar, hoping to start a bit of discussion and maybe even generate a few new ideas (other than "why don't you use batteries ;-) !!!!)


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## cgeiser (Jul 17, 2011)

*question for teatreetim or others that can help explain his ckt*



teatreetim said:


> PPPS found a non early start circuit so you can see how the MOSFET is supposed to look  Last edit I promise.


teatreetim,

I've been building some dynamo circuits using Martin's circuits, but i really like the idea you proposed of bypassing 1 or more LED's when there is not enough power available (low speed).

There are three points that I'm confused on as I'm no electronics expert.
1. You're first drawing shows a resistor. Am looking at this correctly for calculating the resistor value and the power that will be burnt up here? I'm assuming a 3 LED system where the Vf is 3.5V each or 10.5V total. R=V/I so R=10.5/.01=1k ohm, then P=I^2 x R = .0001x1000=.1W
2. You're PPPS talks about a non early start circuit. I'm not sure what that means exactly and Google didn't help a whole lot. The last drawing in your post though makes it look appealing though I don't fully understand it. Aren't both the MPF102 and 2N5484 transistors? The drawing shows one transistor and one MOSFET though. Are the 2 transistors just examples of what one might use for the transistor and the MOSFET is to be chosen so it's 100ma limited? 
3. How does the transistor shown in the drawing turn on? It seems like it turns itself on by how would the current ever begin flowing from the collector to the emitter in order to provide the base voltage?

I've tried to attach pics of my current light that uses a voltage doubler with the throw of the switch. Unfortunately my post count is too low to post pics. Works great but I don't like having to use a manual switch. The housing design concept came from another forum poster, nicknoxx. Thanks nicknoxx!

Thanks,
Che


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## teatreetim (Nov 14, 2011)

cgeiser said:


> teatreetim,
> 
> I've been building some dynamo circuits using Martin's circuits, but i really like the idea you proposed of bypassing 1 or more LED's when there is not enough power available (low speed).
> 
> ...


Hi,
I'll explain the second one first:

The left transistor is an N-Channel amplifier chosen for its switching thresholds. The right transistor is a P-Channel internal substrate enhancement mode MOSFET. Together they simply limit current to 100mA through the rear LED. The rest of the current will go through the front LED (bar a few mA through the transistors). P-Channel means that it is 'normally on' so at slow speeds it is getting as much current as the system can deliver, rather than being proportionally lower and therefore being dim at slow speeds. This is an efficient system and simpler than using a pulse width modulation limiter. You wont find transistors to limit above 100mA, so if you need to limit the front, you'd be better shopping for a PWM that can do front and back. That's all there is to that circuit really.

Non early start means that you need around 10 volts across the system before lights come on. At slow speeds the lights will strobe.

The first circuit uses a normally on solid state relay. This means at low voltages, the 3 front LED's are bypassed and only one of the front and the rear are illuminated. The lights will strobe at slow speeds (around 2km/hr). By 5km/hr it will be consistently illuminated.

I would use the second diagrams limiter, not the one in the first diagram. The first diagram was from memory only. I will try and build it tommorrow and do an accurate diagram. It might take a few days.


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## cgeiser (Jul 17, 2011)

Thanks for the great explanation. I have been slowly learning as I try and decipher data sheets and have been looking at PWM to control the fr


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## cgeiser (Jul 17, 2011)

Thanks for the great explanation teatreatim. I've been slowly learning more about circuits and IC's as I try to decipher datasheets. I've been leaning towards a DC-DC controller w/ PWM but thought you might have come up with some magic to avoid the need to go down that road. 
Thanks again!


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## teatreetim (Nov 14, 2011)

I have a working circuit but I'm not 100% happy with it. The problem is the current limiting diode is around 3mA and the zener needs at least 3mA. Also the zener switch over is a little temperature sensitive and the potential drop is in competition with the limiting diode and SSR LED. The switch over is at around 8km/hr but is a little flaky for these reasons. 

The SSR is supposed to need 15mA but 3mA works.

The MOSFET I use to limit the rear light needs to make up the difference in potential (the rear has a lower voltage drop) which is an inefficiency. Otherwise I think it's about as efficient as I will get. Notice you dont need to bias the gate.

Is it worth all the hassle? I haven't decided yet.


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## iggs (Oct 18, 2007)

I've just brought a Surly Moonlander and have some trips planned that a dynamo hub powered light with enough ummmmph for riding off road would be super cool

But the front wheel has a 135mm hub with 'rear' disc spacing. Is there a 135mm dynamo hub out there that would fit this configuration ? Or is there a work around that anyone knows of?


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## robdeanhove (Dec 8, 2005)

iggs said:


> I've just brought a Surly Moonlander and have some trips planned that a dynamo hub powered light with enough ummmmph for riding off road would be super cool
> 
> But the front wheel has a 135mm hub with 'rear' disc spacing. Is there a 135mm dynamo hub out there that would fit this configuration ? Or is there a work around that anyone knows of?


Yes there is! No-one makes a 135mm dynamo hub (that I know of), but you can purchase a bolt on solution, designed for the non-drive side of your rear wheel. This may be able to be made to work with the non-disc side of your front wheel.

It's called the Sunup Eco DS-1R Spoke Dynamo, you can buy it from IDC on eBay, the link is HERE

It looks like this:


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## iggs (Oct 18, 2007)

robdeanhove said:


> Yes there is! No-one makes a 135mm dynamo hub (that I know of), but you can purchase a bolt on solution, designed for the non-drive side of your rear wheel. This may be able to be made to work with the non-disc side of your front wheel.
> 
> It's called the Sunup Eco DS-1R Spoke Dynamo, you can buy it from IDC on eBay, the link is HERE
> 
> It looks like this:


Wow, I wasnt expecting a +ve answer

Rob- the sales pitch on the link makes it sound amazing!! is this just BS or has it the potential to live up to what it says?

Would this be an option to run your system?


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## robdeanhove (Dec 8, 2005)

I would have thought so, it's just 3-phase DC not single phase AC, but no other regulation difference.

I'd recommend getting the Exposure Lights dynamo, which I believe is significantly upgraded from the prototype shown at the London Bike Show in January, when it's available to buy later this summer ;-)


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## iggs (Oct 18, 2007)

robdeanhove said:


> I would have thought so, it's just 3-phase DC not single phase AC, but no other regulation difference.
> 
> I'd recommend getting the Exposure Lights dynamo, which I believe is significantly upgraded from the prototype shown at the London Bike Show in January, when it's available to buy later this summer ;-)


Looks like a simple solution. Be interesting to see how it fits.

Will it work with the larger axel hubs too from what you've seen?

I wonder if it will swap easily between bikes too, road to FS to FAT

Save the problem of charging batteries!!


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## ktronik (Dec 23, 2006)

I will test that unit, I have one here, and my mate has a moonlander... I will test to see if we can run it backwards, and on drive side.... Keep ya in the loop...


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## iggs (Oct 18, 2007)

ktronik said:


> I will test that unit, I have one here, and my mate has a moonlander... I will test to see if we can run it backwards, and on drive side.... Keep ya in the loop...


Be really interesting to hear about this


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## ktronik (Dec 23, 2006)

iggs said:


> Be really interesting to hear about this


well hear this, the unit produces a positive voltage, no matter what direction I spin it, so no problem to be mounted on either side and still work.

will do a mounting test next...K


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## iggs (Oct 18, 2007)

ktronik said:


> well hear this, the unit produces a positive voltage, no matter what direction I spin it, so no problem to be mounted on either side and still work.
> 
> will do a mounting test next...K


I'm listening :thumbsup:


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## ktronik (Dec 23, 2006)

Ok, jammed it on the moonlander front wheel, due to the wide hub shell and less exposed axil, it's a tight fit, but it does roll as it should, so should work just fine, but need to hook up a light and go for a spin for a real world test... I will put up the video on my kLite FB site, that I did tonight of the wheel rolling... So good news for moony mates....K


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## robdeanhove (Dec 8, 2005)

ktronik said:


> Ok, jammed it on the moonlander front wheel, due to the wide hub shell and less exposed axil, it's a tight fit, but it does roll as it should, so should work just fine, but need to hook up a light and go for a spin for a real world test... I will put up the video on my kLite FB site, that I did tonight of the wheel rolling... So good news for moony mates....K


Great work Kerry! :thumbsup:

Now a fatbike with a dynamo powered light is super-niche. I NEED to se a picture of this. Hope the test ride's successful


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## ktronik (Dec 23, 2006)

Ok just put it up on my kLite Facebook site linked on my sig.... Enjoy K


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## iggs (Oct 18, 2007)

hmmmm, very interesting


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## vawt33 (Jul 7, 2012)

Cool Stuff in here


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## unterhausen (Sep 28, 2008)

just ordered a SP dynohub. Wish I'd noticed it ships fom Taiwan before now.


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## cgeiser (Jul 17, 2011)

Unterhausen,
I wouldn't be too concerned - I ordered one a while back and it arrived quickly. I've been very happy with it!


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## robdeanhove (Dec 8, 2005)

unterhausen said:


> just ordered a SP dynohub. Wish I'd noticed it ships fom Taiwan before now.


I've had more than one. All have arrived quickly and values set on postage to avoid import tax costs. They're fast a friendly. As already said, no need to worry.


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## unterhausen (Sep 28, 2008)

got it today. Nice looking hub, can't wait to get it laced up


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## ocean breathes salty (Oct 1, 2006)

unterhausen said:


> got it today. Nice looking hub, can't wait to get it laced up


I've just had my wheel built and am now running a K-lite. I've been sick for nearly a week and haven't had a chance to take it into some techy single track. I can't wait to see how it goes.

Kerry added a switch to mine to kill the light and take the load off the hub for riding during the day. Nice touch.


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## unterhausen (Sep 28, 2008)

I'm probably going to build a light. Have to look through my bag of parts because I bought a batch of lights and then promptly ignored them.


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## robdeanhove (Dec 8, 2005)

unterhausen said:


> I'm probably going to build a light. Have to look through my bag of parts because I bought a batch of lights and then promptly ignored them.


Dare I ask if you've made any progress, I will be super interested to see what direction you go in. Good luck, and enjoy the DIY adventure!


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## robdeanhove (Dec 8, 2005)

Pearl4611 said:


> Very nice indeed. I can certainly see the advantage for commuters and daily riders with not having to keep rotating packs on the charger and not accidentally going out with the nearly flat one.


Also useful on this week's mid-week mountain bike night ride, which unintentionally turned into a 5hr epic as it was such a nice night we kept on riding. Everyone was struggling with burn times and batteries going flat...... except my dynamo light which kept pumping out 800lumens until I got home and turned off the standlight


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## mattthemuppet (Jul 16, 2004)

your friends need to get bigger batteries


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## robdeanhove (Dec 8, 2005)

So, has anyone else actually been riding with a dynamo off road? I'd love to see what others on here have been up to.

What was good? What was bad? And how could it be better?

I've been using mine off road, on road, touring, commuting and just smashing round the woods after work, and I can't fault it, I am a very, very happy dynamo convert, I just want to learn from all your experiences, as the battery boys have a great cross fertilisation of ideas!


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## bikeny (Feb 26, 2004)

*Wow!*

Just stumbled onto this thread without really looking for it, and all I can say is wow! I REALLY like the look and performance claims of this, but have a few questions. First, I checked out the Ktronic website, and while I found some links for the SP dynamo hub, I don't see anything for sale except the light head. Is the dynamo circuit for sale? Can I buy the circuit and provide my own light head, or do I have buy the whole setup?

Also, I investigated the SP dynamo hub, and it seems there are few different versions. I see the PD-7, SD-8 and PD-8. Looks like the PD-7 is heavier but has the clutch to dis-engage the dynamo? If I am correct here, I guess the user has to decide if it's better to carry around more weight or have more drag when not using the light, not sure what the answer to that is!

Anyway, thanks to everyone involved for spending the time/money to get this off the ground, it's a very worthwhile endeavor!

Mark


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## ktronik (Dec 23, 2006)

Hey Mark, jump in the facebooksite on my sig, for more details, currently re-branding the website to dynamo stuff...but more details and specs, test are on facebook...

I am the dealer for SP, its so lite action than dynamos you know, I don't use the one with a clutch, I go the PD-8 (I have disk brakes) I just ride it everywhere and never put in my regular wheel. I have riders that even leave there light on in the day!! they say then can't tell if its on unless they look to see if light is coming out... trust me, its 10x better than you currently think it will be, as you become released from worrying about lights...you just get on and ride.

full review of a proto system I built for the 'Big huRT' 750km off-road non supported race through Australia. Yep the guy with the kLite lights and charging system won!! 

Linky


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## ktronik (Dec 23, 2006)

Its so easy to build, you MUST do it...can be done with very few parts....


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