IDC BLOG

Notes on wiring hub dynamo lighting systems

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Because generator based lighting systems have not been popular outside of Europe for decades, many simple techniques for doing good, i.e. nearly invisible, wiring have been lost or are only now slowing reemerging. The reason for this is that during the era of incandescent lighting, standard hub dynamos simply could not produce sufficient power and thus light for cyclists to travel safely at speed on unlit roads. The advent of LEDs has changed all of this. Today, the most powerful generator based lighting systems relying on the same incandescent era hub dynamos can produce almost 1000 lumens thereby nearly matching the output of conventional automotive headlamps!

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Similarly, advances in hub dynamos have relegated noisy unreliable “bottle” dynamos of yesteryear to near obscurity even in Europe except on low end bicycles sold in countries requiring generator based lighting systems to be installed on all bicycles intended for use on public roads. The modern hub dynamo is “contactless” meaning that the mechanism does not rely on contact between any moving parts when generating electricity.

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Although contact between bearings and races remains necessary for the hub itself to function, the lack of contact between moving parts in the generator mechanism itself means: (1) that the dynamo does not suffer from any “frictional” loses, (2) is not subject to mechanical wear, and (3) is thus highly reliable and durable over prolonged use. Still, as is the case with all bicycle hubs, the bearings of the “hub” mechanism itself are subject to mechanical wear during use. In addition, the dynamo nevertheless does create some drag (despite being contactless) because the movement of magnets within dynamo creates invisible magnetic currents called “eddies” as the wheel turns.

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Intelligent Design Cycles has over the last several years been developing our own and testing the dynamo lights of top manufacturers from all over the world. This process has created myriad opportunities to experiment with and assess different “strategies” to minimize the appearance of ungainly wiring on the bike without compromising the efficiency and durability of the lighting system. Frankly, it still seems something a little “too good to be true” to me when I consider that a well installed quality hub dynamo lighting system can provide reliable and effective lighting for speedy travel in pitch black conditions … for multiple years without any form of subsequent maintenance. Of course this is made possible by very efficient “high-powered” LEDs, which have a breathtaking theoretical life span of 5 years under continuous operation before they are considered due for replacement. Of course this requires that the LED is adequately cooled and powered by electronics to regulate current. In this respect you can rest assured that all dynamo lamps carried by IDC have been extensively tested for reliability.

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In the photos, you can see my trusty “traditional British touring bike” extensively kitted with a Dosun U1 dynamo headlamp and two rear lamps including a Herrmans H-Track rack lamp and Spanninga Pixeo fender lamp. Yes, for those interested, standard hub dynamos produce sufficient power for headlamps and two rear lamps to run simultaneously. They can even be used to power two headlamps if you ride quickly although I have not tried this … yet. Note that although I have routed the wire from the headlamp to the dynamo plus a Biologic voltage regulator behind the fork blade. I have not cut excess wire to the exact length of the extensions and instead wrapped excess wire neatly around the fork tube. This was done because we are forever testing new lights at IDC and connecting new lengths of wire with heat shrink on a regular basis in not fun. Cyclists interested in reducing the appearance of wiring to a minimum are welcomed if not encouraged to trim wire to exact length for a cleaner look.

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Many initial attempts to install hub dynamo lighting system reflect a natural effort to seek the shortest route between the dynohub and the lamps meaning that many will run the wire from the headlamp to the rear lamp underneath the top tube of the frame. While this method will of course work, it may interfere, for instance, with the mounting of a frame pump. It is also visually unappealing.

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For a cleaner look, we recommend running the wire from the headlamp to the rear lamp beneath the downtube and under the bottom bracket. This not only keeps the wiring out of sight (when the bike is viewed from standing height), it also reduces the possibility that wiring will interfere with accessories that you may have mounted elsewhere on your bicycle.

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From under the bottom bracket there are a number of options on how best to complete the routing. A method I picked up from an entry-level city bike I spotted near my previous workplace in Paris was to wire it underneath the mudguard (if you have one). The look of the bike was so clean that I initially thought that the producer somehow routed the wiring inside the frame – indeed some of the wiring actually was conducted thought the frame tubes. I could only smile when I figured out how they did the mudguard bit.

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It is useful to note that there are truly many choices in ways to mount dynamo lamps. Cantilever bosses are an excellent mounting point for hub dynamos lamps, both front and rear. Indeed even the seatpost can be a good mount point with the visibility of wiring kept to a minimum also via routing under the bottom bracket.

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On folding bikes, wiring is trickier due to the complication of folding actions that must be accommodated. I wrapped the wire around the rear brake cable housing (this is normally a “second best” solution – visually), because: (1) I did not have zipties large enough to go around the frame tube; (2) putting two zipties together would have looked less good; and (3) even if I had large enough zipties, the approach may have compromised the dependability of the installation. Keeping the wire wrapped along the brake cable assured (I hope) that the wire would be protected from movements when folding the bike. The reasoning is that the cable routing should intuitively be designed to accommodate the folding actions of the bike without unduly stressing the cables – and thus also the wiring for the hub dynamo lighting system.

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From there, I returned to a more traditional under the chainstay routing of wiring which to me seems visually nicer than wrapping wire around cable housing, despite the appearance of zipties.

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Perhaps a bit risqué, I then ran the wire along the inside of the frame beside the cog set thus keeping it nearly invisible until it reappears along the inside of the ingenuous “folding” rear rack that Bike Friday produces for the Pocket Lama folding bike.

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Extending the wire up the rack to the rear lamp is straightforward.

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These are only a few of the ideas I have accumulated over numerous installs and reinstalls. Should you have any further techniques you would be kind enough to share, we would glad if you would pop us an email with photos at: info@IntelligentDesignCycles.com so that we can share them with others … and use them ourselves.

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Sep 20 2018

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Jan 01 1970

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