Dynamo Drag and Resistance Tested: Myths Busted

How much do bicycle dynamos REALLY slow you down? Are bicycle dynamos 6Volts and 3Watts only? Bicycle dynamo efficiency explained. The SON28 vs SONdelux bicycle dynamos tested. ALL bicycle dynamo myths tested and busted! Bicycle dynamo Load Explained. Project X - the better more powerful bicycle dynamo introduced.
0:06 Disclaimer
0:15 Introduction
0:44 Why This Video?
1:08 Bicycle Dynamo "Myths"
2:12 What are Bicycle Dynamos?
3:12 The Dynamo Advantage
3:59 How Do They Work?
5:29 Project X More powerful bicycle dynamo introduced
6:38 Are they REALLY 6V?
8:03 German Regulations
10:59 Myth#1 BUSTED
11:25 Are Bicycle Dynamos 3W??? Dynamo load explained.
17:23 Myth#2 BUSTED!
18:23 Bicycle Dynamo Efficiency
21:09 SON28 vs SONdelux Dynamos (Myth#3 CONFIRMED)
25:00 How to Measure Bicycle Dynamo Drag?
28:17 Example of Bicycle Dynamo Drag
28:59 Bicycle Dynamo Drag Outdoor Setup
30:01 RESULTS: Bicycle Dynamo Drag vs Regular Hub
31:03 Myth#4 BUSTED!!
32:04 RESULTS: Bicycle Dynamo Lights on vs Lights OFF
35:34 THE BETTER WAY TO DO IT?! - The Companion
38:11 Battery Power - A Personal Story
44:13 Another Personal Story
45:39 A Better More Powerful Dynamo and Conclusion
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Updated Dynamo Test Data (Olaf Schulz)
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Dynamo Load Tests
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LIGHTS OFF TEST on Strava
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REGULAR HUB TEST on Strava
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[@khwolter9038]

Very informative video! When I was commuting ~29K to work in the dark, I quickly tired of battery lights. I laced a Shimano Nexus dynamo hub into my wheel, but found the incandescent light too dim. I made some crude voltage/load measurements and wound up putting a couple Luxeon LED's in series, one fitted with beam optics, and the other with optics that gave more of an oval pattern. I simply rectified the output from the hub with 4 shockley diodes, and fed that directly to the LED string. I also designed the structure holding the LED's to be simple, lightweight, and chose the mounting point such that the mass of the unit was divided equally to minimize the unit re-aiming the lights with ever bump in the road. Worked great! It was very common to have cars come to an intersection and wait for up to half a minute to see what the heck was coming their way.

[@CustomPurple]

Ah yes, LEDs being 'current driven' devices and dynamos being 'current limited' you can make some really simple yet powerful lights. I had similar experience with cars paying MUCH more attention to me when I got my very first dynamo setup (SON on a Brompton).

[@davidbee9563]

@@CustomPurple So I checked the gearing again ...and I was wrong. What I thought was a 16 on the back wheel is actually a 14?? This means the ratio is 2.7 not 2.375 giving an equivalent chain ring of 43 vs 38. That would explain much of the inertia effect.

[@CustomPurple]

Glad you figured it out! =)

[@MartininitraM]

I have no idea how KZbin reccomended me this video, but it was really worth the time viewing it. Great work. And I do grab my Brompton with a dynamo vs the one with battery lights every time during the dark season.

[@CustomPurple]

Thank you for your comment and for watching the video. Bromptons have the other feature that they always put a smile when ridden as well. =) My first dynamo was a SON upgrade for my stock Brompton (literally 2 months after buying the bike, clip on battery lights were not doing it at all for me). It was a VERY expensive option almost 30% of the total bike price, though knowing what I know now I wouldn't have hesitated at all to order it directly fitted. I have been fascinated by the technology ever since!

[@kai_v_k]

Thank you for the great video. I am looking forward the dynamo you are talking about. The sealing drag you mentioned on a Chris-King hub is probably almost as high on a SON-hub because they also use well sealed bearings, though SON uses (high quality) SKF-Steel bearings. I personally switched to dynohubs because I was tired of lights always giving up in the most inopportune moments. I generally agree with the statement of the importance of seals on bearings; I haven't destroyed my SON-bearings though they have seen about 30000km of all weather commuting with quite some muddy stretches and even some road salt. I have had a couple of bottom brackets giving out in the meantime though.

[@CustomPurple]

Hi there and thank you for watching and for your comment. Project X is moving along, so best way to stay up to date is to subscribe. I might have something coming in the next week or so, unless it gets lost in the mail in the end of year chaos....(fingers crossed). ;) Efficiency (ie converting mechanical to electrical) is just one part of the big picture and why the Project X really got born as an idea (and potentially a commercial product) is the so called '6V/3W' ecosystem, which as I mention in the video is extremely outdated and limiting with regards our constantly evolving power needs on the bike. Electronics nowadays are what can really make the difference, like The Companion front light with dimming as an example to significantly lower drag. Project X will be designed to fit even better with modern electronics. With regards the Chris King/SKF bearing drag, I do have a set of Chris King r45 hubs (different rim so don't know how relatable that is as a test...might just try it one day), though those hubs (r45) do feel significantly less draggy when spun by hand. Funny story is that I had already made some tests last summer (and saw there was no difference in drag) and while talking to SON, their latest dynohub is made to feel MUCH less draggy when spinning by hand, because customers complained that it must slow them down. I said that I have actually measured it and it does not, but SON's response was a just a shrug and that customers did not know that. Perception is a powerful motivator. In the words of Bob Dylan - we gotta serve somebody, though I digress. The hub I used for testing in the video actually has at least 24,000km (possibly much more) mostly commuting and the bike spent a good part of its life outside locked up in all conditions. And the SON28 classic model does not have the pressure compensation system (that prevents condensation of entering the bearings when taking the bike from warm house to cold outside, etc.) which further attests to the SON quality. While after my many hours dealing with electronics and dynamos, I do believe batteries are a superior power source, HOWEVER, their disadvantage is too great to forgo what dynamos actually provide you, even at some drag penalty. In any case we are not Carlos Sastre at the final time trial of the 2008 Tour de France (where mechanics allegedly removed seals of the hubs and used oil and not grease) so we can live with a couple of seconds/minutes here and there. =) Have a great day. Best, -Nikola

[@john-r-edge]

In praise of STVZO. I acknowledge Nikola's comments about how STVZO regulations have created a situation where reported numbers like power output do not match real world experience. But there is a plus point in that the regulations requiring anti-dazzle beam cutoffs have resulted in Germany to make lights with the best optics. I have both STVZO and non-STVZO lights of similar output - and the STVZO have better optics which put the photons where you need them, neither spread too wide nor confined to an intense pool of light a few meters in front. Speaking with experience of B&M Cyo T lights, Supernova E3Pro2 - and with non STVZO Lezyne lights.

[@Frostbiker]

A key feature I would love in a dynamo light would be ambient light sensor to automatically adjust their brightness from "be seen" during daytime to "see what's ahead" at night. Ideally there would be a switch so that daytime it would have different modes: low constant brightness, pulsing from low to high brightness, and high (night time) constant brightness. Where I live there is no regulation against pulsing lights.

[@HagobSaldadianSmeik]

The 'SON Edelux II' has this feature.

[@CustomPurple]

The SON/Busch & Muller lights have a light sensor that switches on when dark. (Probably due to the regulation I mentioned in the video) the light intensity does NOT change according to conditions. Also besides the very early IQ Cyo lights (I am thinking 2009ish) the sensor is too sensitive (you can be too safe I guess) so it is always on, even in bright sunlight, therefore might as well not be there, at least in my experience that feature does not work very well. Also when it comes to pulsing/blinking, this is actually illegal in most jurisdictions and it is is quite annoying for other road users (why it is illegal most likely...yeah I know blinkies are sold left right and center....) so for the time being this is a hill I will die on and in normal use, my devices will not blink. =)

[@CustomPurple]

Dimming of dynamo lights was the first challenge that I had to overcome so I have some things (in the pipeline) that will potentially use an ambient light sensor to provide automatic control. Though we are entering in the limbo world between analog and digital - which means LOTS of real-world testing and head scratching/banging against the wall. If you subscribe to the channel, I will most likely talk about projects that use a similar feature.

[@adophgraphytheartandscienc8426]

@CustomPurple 1) The B & M light that I am currently using has a switch to switch to different modes. I currently have it in the 'Senso' mode. It has two 'daytime running lights' at the base of the housing which are on constantly during the day. At dusk/night fall the sensor automatically enables the full light. I have never had a problem with the ambient sensor being too sensitive causing the main light to be on at all times. Perhaps such a flaw is present on the cheaper B & M models or previous generations of lights. (2) Re blinking/pulsing lights. The jurisdictions that ban such lights are overbearing over bureaucratic idiotic jurisdictions. Research shows three things. Firstly, flashing lights are way easier to notice. Secondly, such lights make it clear that a vulnerable cyclist is up ahead. Third, flashing lights make it hard to gauge distance to the light; a solid beam is far better in this regard. The solution therefore is breathtakingly simple. Either have a light fixing with a solid light at its centre surrounded by flashing LEDs or have both a solid light and a flashing light on your bike. To outright ban the flashing variety is first-class stupidity and reminds me of the time around thirty years ago when boring old cowards afraid of new tech would ban the use of mobile phones pretty much everywhere (I even experienced idiots who refused to call me or do business with me if I gave them my mobile phone number; the ban on flashing lights is equally retarded)

[@CustomPurple]

Thank you for sharing your opinion and experience. Actually I have one of those Bumm front lights and everything is on all the time. I never knew it was supposed to do it differently and since I run it as daytime running light it never bothered me. Maybe I just have a defective one...*shrug* The Bumm one that actually turns on in the dark for example in a tunnel (awesome by the way😎) though it doesn't switch off afterwards. Like I mentioned doing it right requires dealing with the analog to digital world conversion and this is not trivial to be executed correctly. Most lights use a simple on/off photo transistor type circuit. As an example the Mercedes Intelligent LED is a led control system done right, though this is a thousand+ option, not a 50eu light. Re: Blinking lights, let's keep regulation out of it since we all feel similar about it though I am against those lights due to personal experience. Almost everywhere (that includes cycling paradise like the Netherlands to a degree) cyclists are seen as a nuisance on the roads and flashing lights add to that, I hear it actually mentioned enough to not ignore it (sad but true unfortunately) I have actually 'seen' what a flashing light can do on a hill on my commute. In between 'flashes' the cyclist was invisible and at 36kph that is 10m/s so at 1Hz blinking he passed a driveway and a side street while being invisible; like you correctly said distance cannot be judged correctly. We all have cycling related scars/scares that took less than a second. I once (during a 400km brevet) biked behind a guy with those auto blink/sensor brake lights and every time he would get out of the saddle I would get blinded because the sensor thought he was braking. Any kind of night vision adaptation was gone in a flash (pun intended). I have only seen 'bigger and brighter' and not better when it comes to blinkies so until that time I remain largely unconvinced and skeptical.

[@john-r-edge]

Additional way of connecting to SON dynamos fot those of us too mean to buy the SON own-brand coax connectors. On two bikes with SON dynamos I am using the regular Shimano dynamo hub connector, which work ok provided you put a thin plastic packing piece into the connector - necessary since the Shimano connector lugs are a bit thicker than the SON ones. Shimano part number Y-2SS98030, cost about EUR 4.

[@CustomPurple]

Yes excellent point and the Shimano style connector has the other advantage of being field serviceable when we forget we have dynamo attached...in the middle of the night repairing a flat.

[@derek75116]

Yes, you can not beat dynamos for reliable lighting 👍 I’m currently integrating a Son delux into my beautiful Look 765 frame. Ill be using the Ahead charger circuit from Jens During. Schmidt is about to release an Edelux variant with USB out which might have interest me. But as always, a design in time 😊 The dimmable LED sounds a valid idea! I was running filament ‘Union S6’ lights in the early days and the lesser light was adequate then. Very easily we get swept up into brighter being better. But it’s not necessary. Ive done PBP 91 and 99 Great video. Love the passion 👍

[@CustomPurple]

If the Jens Duhring charger is the forums lader, it is actually the one device that currently can squeeze the most possible power put of "3W" dynamos. I actually met the SON people when I had the prototype of The Companion in 2023. They had just announced their light + charger. This is how we got to talking about other dynamo projects over the months that followed. Enjoy your nice bike!

[@john-r-edge]

Wrt SON dynamos which handle different rotation speeds. I have a Brompton (folding bike with 16 inch wheels) from around 2009 which included the (far from cheap) extra of a hub dynamo. This is a SON model XS (rated 6V 3W) which (I have read) was specially made for Brompton. Possibly the first dynamo that SON made for smaller wheels (higher RPM). With a B&M CyoTPremium I get plenty of light. Current Bromptons use a Shimano branded dynamo hub, as I understand.

[@CustomPurple]

According to Wilfried Schmidt himself he got a request from a guy in The Netherlands for a Brompton dynamo and as the saying goes - the rest is history. Actually this WAS the first dynamo I got, (it cost me an eye watering ~330+ euros way back in 2009) and I still have it and used it last October after sitting for years packed in a shed - the contacts of the switch for the Bumm light were oxidised, though after a couple flicks of the switch I had lights and nothing to worry about. I am sure that data is out there though the SON XS will not 'meet regulation' in 'regular sized' wheels, though it is perfectly adequate at higher rpms/with LEDs. The Shimano Brompton dynamo came after the SON, as a lower price option for dynamo lights since before that it was either the SON XS or a bottle setup (which in my opinion was so janky, I am surprised it actually worked!), I am pretty sure it was done as per Brompton request.

[@john-r-edge]

Do you have any info on the performance of the modern rim dynamos? Velogical is only current mfr I am aware of - Pedalcell had a comparable product, but they ceased operations in 2023. They claim that they can generate more power as the dynamo spins faster. These dynamos can be three phase. They would appear to have some advantages for inititial use, in that they can be fitted without having to build a new wheel.

[@jaro6985]

velogical tells you the performance right on the site, 60-75% efficient, in ideal conditions. Probably not that much power. Quite expensive for a simple friction dynamo.

[@CustomPurple]

I realised in post edit that I did not mention it. Though the bike I used for the tests was made to be very lightweight (comes sub 9kg currently) and as such it was built with a Velogical dynamo directly mounting on a braze on the fork. (www.flickr.com/photos/40790580@N04/51278904464/in/album-72157719470695118). While lightweight, I had it slip *every* time it rained and even in high humidity/fog. Thankfully some of my lights (The Companion) have a buffer battery so I could use that to save me. I tried many adjustments to no avail. After a season of randoneering/weekend riding I also wore out the rubber ring so it was slipping even more and almost running metal on metal, while in the manual, since when do we think about doing maintenance on dynamos (*shrug*)??? That was valid even with ~1W LED lights (my design) so with anything with more power (ie '3W light' and hence drag/resistance, slipping would be even worse. Also the whirring noise was quite annoying and while one of the 'marketing points' of the Velogical was that you can disconnect it so you have no drag when not using it, I had just disproven that point. Therefore, the user experience of the Velogical is enough to dissuade me, no matter efficiency and other points (lightweight/cheaper than SON, etc.). My 2 cents.

[@kuchenblechmafiagmbh1381]

There is an interesting German company called Magnic lights and these are literally dynamo-powered but without physical contact to the wheel, the original models come with attached brake shoes (you can choose between sidepull, V-Brakes and cantilever, the pads are changeable) and the newer Wega models work with disc brakes. And they're road legal in Germany.

[@imrevadasz1086]

​@@jaro6985I'm using the velogical rim dynamo on one of my bikes and it works really well, and it's very convenient for a touring bike. Much more convenient than a dynamo hub. Mounting it correctly also was quite easy (I used the cantilever stud mount), and they have a good guide. It also already comes with replacement O-rings for the pulley-wheel and shrink-tubes for the cabling. Velogical actually has detailed efficiency measurement charts with several different lights for download. Efficiency numbers are always very misleading when you quote them out of context, because it mostly depends on your speed and what load you have connected. If you only use it with lights, the velogical dynamo on the "Sport" version is easily one of the most efficient dynamo solutions (other than the "1.5W" version of the Shutter-Precision dynamo hub).

[@imrevadasz1086]

Another huge advantage of a rim-dynamo (or any classic bottle dynamo) is that you won't have a flickering light at slow speeds, but continuous light already at a slow speed. That is because a bottle dynamo will create proper AC current at a much slower speed than a dynamo hub, because rotation speed is far higher. A dynamo hub will basically generate something more like short bursts of DC in alternating direction at a slow speed, which gives visible flickering. The higher rotation speed also makes good bottle dynamos inherently lighter than a dynamo hub.

[@davidbee9563]

I am trying a set up with a Son 28 dynamo, BM front and rear light with capacitor. Once moving it rolls OK but feels like the brakes are rubbing on the rime when starting. On the stand the front and rear hubs turn smoothly. With the lights on the drag seems noticeable. My other question is regarding measured resistance when the lights are on. If the system is producing 3W of power to the lights would the drag not be more like 5 or 6W? No system is 100% efficient.

[@CustomPurple]

Without seeing a schematic/more details of your setup I am only guessing, though capacitors when empty look like a short circuit (ie maximum current/drag) so this is probably what you are feeling. B&M taillights (and the SON rear light that uses the same electronics) do have quite a 'surge' when first powered while the stand light capacitors charge. When you say the drag seems noticeable do you mean on the stand or when riding? With regards efficiency I mention it on my slides (33:28) so the SON28 classic with ~57% efficiency equals to a total of ~5.7W of drag. So you are 100% correct here.

[@davidbee9563]

@@CustomPurple I watched the video again and your explanation makes sense. The ride in town was not a steady speed but stop/start and flat/incline. And I was using both lights on. This set up is a single speed with a similar gear to my winter bike. The effort to start felt much higher than with a normal wheel. Almost like you are running a much taller gear. My curiosity was to determine if the dynamo set up would work vs USB lights, I will do a comparison of a flat road at a steady speed to see how it feels.

[@hluos7uhluos7u94]

I use a Shimano Dh2 or something with disk brakes. They work good and are very well sealed; I've never had one fail. I also dont feel that it slows me down.

[@CustomPurple]

I have a Shimano 12x100 thru axle model, that I used for commuting for quite some time. It did have some vibrations around 23kph other than that, it did it's job. :)

[@hluos7uhluos7u94]

@@CustomPurpleoutput: I have a QR version on my Surly. My bike weighs 26 kg, so I don't feel it as much, but there are vibrations, but they don't bother me much. I use my DH as an "engine brake" on downhill. It's not much, but I just do it. Can you also test entry-level hubs like my Shimano hub? Thanks for your work.

[@krollpeter]

My Shimano hub dynamo is 24 years old. I attached two headlights to it. That way I don't have any light until about 7, 8 kph, but then it's better than faster I ride.

[@CustomPurple]

In the link to the dynamo tests (in the description) there is some data on other hubs (Shimano, SP, Sanyo and others); I just showed the ones directly related to my video. So in theory you can do some calculations and using my results you can correlate it and get you close. Though nothing beats a good measurement...for that I would have to build one wheel per hub with identical rims, so depends if there is enough interest. Overall ("6V/3W") dynamos are pretty close, but I have definitely thought about it. To be seen. =)

[@CustomPurple]

Ah yes this is the classic way to do it (2 headlights in series). In the tests (link in the description) I think Olaf Schultz tested some dual headlight setups as well. You would get double the power, so double the drag as well, but if it means you can descent faster with more confidence on unknown roads it is a good tradeoff.

[@tobiasmeiser6488]

nice Video :)

[@marcelchaloupka]

I run dynamo hubs on all my bikes. MainlySon28 but also an SP. yes expensive but I never have to think about lights but when it comes to lights and changing that’s when it gets a little complicated, I’ve never been able to get it all to work properly

[@CustomPurple]

Thanks for your comment. We have too many things that need charging nowadays so even with the best of efforts we are bound to forget sometimes, flicking a switch is hard to beat as convenience!

[@adophgraphytheartandscienc8426]

Have you had any experience with the following bottle/sidewall dynamos: 1. Velologic 2. AXA HR Traction Control If so, what are your views (positive and negative) on these two products? Thanks

[@CustomPurple]

Hi there, I already answered in detail about the Velogical in another comment, you can check it out though to summarize: it's lightweight but it always slipped in the rain for me and it is noisy. The AXA one I used maybe 10+ years ago on a dutch daily bike and the dynamo worked, nothing much else to say. What surprised me actually was that I had the plastic wire port break and I could order it as a spare. All in all hub dynamos are better if you can get them, in my opinion.

[@paullevy-adophy9198]

​@@CustomPurple hi, thanks for the reply. Also, in what ways are hub dynamos better than good bottle dynamos (e.g. AXA HR) ? Thanks in advance

[@kuchenblechmafiagmbh1381]

@@paullevy-adophy9198 Not all tires have sidewalls with a profile to provide better traction for bottle dynamos and it's literally like rim vs. disc brakes, the rim types can limit the tire clearance if the frame doesn't and I'm sure these also would have trouble to get grip on modern over 50mm wide balloonish MTB tires. Seriously I see literally almost no modern bikes with sidewall dynamos anymore except these cheapo Elops/BTWIN city bikes by Decathlon (they also got only 6-speed rear derailleur with old frewheel instead of a freehub, reminds me of their cheapest road bike, only 7 or 8 speed, no front derailleur and the shifter is nearby the stem - no modern "brifters" brake levers with shifting included) and probably some other super cheap bikes where I would rather recommend to get a used one that has higher-end quality components. Went from bottle dynamo to hub around 18 years ago (only my road bike and MTB have battery powered lights) and never looked back.

[@Alex2OC]

Backwards Compatibly? Rückwärts Kompatibilität?

[@CustomPurple]

You ask a very general question so I am not sure what you mean though if you are asking about the Project X dynamo: The Project X dynamo (if it comes to market) will fit 9x100 quick release and 12x100 thru axle forks. It will use the same connectors as other SON dynamos and also SL (connectorless) will be available as an option. Disc brake version and you simply don't use the mount if you want to use rim brakes. Electrically, like I mention in the video it is electronics that make a difference. The '6V/3W' ecosystem is ' very outdated' and currently served by ALL dynamo related products. I have a first product that will be able to take full advantage of the Project X power and efficiency capabilities - The Stalker (custompurple.com/product/stalker/). The Stalker and all future devices I make *will be compatible* with '3W dynamos,' however, they will also take advantage of the features of Project X for a MUCH better user experience. As there are literally millions of devices in the "6V/3W" ecosystems, backwards compatibility is not a priority for me. I make electronics devices and hopefully dynamos to work together and fit the features/price point so that they can be used/enjoyed by the people interested. Like I mentioned my electronics WILL be compatible with 6V/3W dynamos. Let me know if you have any other questions.

[@adophgraphytheartandscienc8426]

@CustomPurple Regarding your Stalker light. How powerful/bright is it compared to the most powerful (100 Lux) B & M dynamo lights? Also. If your dynamo becomes available for sale, what advantages will it offer in combination with the Stalker light that current systems do not offer? Thanks in advance

[@CustomPurple]

I will have a separate video to discuss all the features of The Stalker since there is only so much you can put in a comment 😄 Though it has a LED Matrix with dimmable low and high beam as well as USB-C charging (even with the lights on) as well as absolutely no flickr at low speeds. Subscribe/come back to the channel for more details (on more dynamo projects) is all I can say at this point in time. 😁