Testing the Magnic Light Against a Supernova E3

The Magnic bicycle light (www.magniclight.com) is an amazing contactless dynamo light. It generates light through its proximity to a moving wheel.  I supported it through the inventor’s Kickstarter campaign, and as part of this received a pair of front lights and a rear light suitable for my road bike.  I was particularly attracted to the fact that with the Magnic one does not need to have a wheel built around a dynamo hub, or by being contactless it avoids the noise issue with rim dynamos. What follows is my assessment of the Magnic light, in particular its suitability for long-distance endurance riding.

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The Magnic light works best as a commuter’s light. It gives sufficient light to see ahead, particularly in lighted conditions. However, if you need a lot of light it simply does not compare with a dynamo light.  If you have a battery front light, get the Magnic rear red light. It is great, needs no power, and can be seen from a good distance. It also stays on (as does the front light) for a time once you stop the bicycle.

Testing Protocol

I mounted the Magnic lights (one on each side of the rim) on my Trek road bike which was also fitted with a Shutter Precision (SP) dynamo hub attached to a Supernova E3 light (see below). I then did two sets of tests: dynamic and static.

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Dynamic Testing: For the dynamic testing I needed to get up when it was very dark. Since it is summer in New Zealand and the sun comes out at 05:30 this meant an 03:00 wake up. Good thing my sleeping patterns have been disturbed by some medication I am on!

I live in the country so it was simply a matter of going to the end of our driveway, turning onto the road and coasting down the hill. This gives a speed of over 30 km/h at the peak and it is about 850 m before one coasts to a complete stop. I mounted my Sony Xperia phone facing forward and videoed the coast down runs—one with the Magnic and one with the Supernova.

Static Testing: The front wheel of the bike was mounted in a stationary trainer to hold the bike in place. I mounted a variable speed multi-tool under the back of the front wheel which, when turned on, would turn the wheel and thus power the Magnic or Supernova lights.  The photos below show the setup.

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My original plan was to do the tests at variable speeds so I mounted a Garmin speed sensor (it was the new version which is accelerometer based) to the front hub and connected it to my Garmin Edge 1000 computer. Unfortunately, the speeds it gave were rubbish and I could not work out why so I was unable to record the actual speeds.

To record the light I installed the Android App ‘Physics Toolbox Light Sensor’ which records the luminousity in lux to a CSV file. This file was then exported to Excel for analysis. I mounted the phone 1 m above the ground using a bicycle mount attached to a pole. The photo below shows the set up.

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I ran two sets of tests. The first was to record the luminosity at 1 m intervals at ‘slow’ and ‘fast’ speeds with each of the two lights.  The speed was set and 20-30 seconds of data recorded at each 1 m interval with one light, then repeated for the other light at the same speed. In the absence of my speed sensor working this was of course very subjective. One complication was that when the Supernova was turned on the speed of the wheel noticably slowed down—obviously by multi-tool was not overly endowed with torque for applications like this!

Test Results – Dynamic Testing

The full videos of the coast-down tests are available at:

The videos show a lot of vibration but show clearly that under the same conditions the Supernova provides much more light than the Magnic. Below are some extracts taken at approximately the same point from the two videos. With the first set one can see the signs much more clearly illuminated with the Supernova than the Magnic; the second the pavement patching (and sign) is much clearer with the Supernova.

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Supernova

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Magnic

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Supernova

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Magnic

Overall, the Supernova was not only brighter but cast a wider area of light and so had far superior lumination.

Test Results – Static Testing

The chart below shows the luminosity in lux at 1 – 5 m from the tests. Unfortunately, the slow-speed Supernova test was not saved correctly.

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The results were very counterintuitive given the earlier dynamic testing results as they suggested little performance benefit from the Supernova over the Magnic beyond 2 m, even though when I was riding with both the Supernova appeared much brighter. So I tried a different set of tests.

I set the luminosity sensor at 5 m from the lights and then recorded the data alternating the lights (i.e. Supernova then Magnic), increasing the speed each time. The results are shown below.  The luminosity of the Supernova increases from 74 lux at the slow speed to some 241 lux at higher speeds. The Magnic gave a maximum average reading of 36 lux at 5 m.

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This shows that the first set of tests had the speeds set too slow for the Supernova to show its performance. Blame the Garmin speed sensor not working!

Rear Light

During the dynamic testing the rear light showed itself to imagebe very bright. I didn’t bother to measure it as the luminosity would be similar to the front light.  The photo to the right shows the light with the wheel spinning on my bike stand.

A video of me playing with the light – and showing up close the contactless approach – is available at https://www.youtube.com/watch?v=Nn7ezyjbWbA.

One comment on the rear light: the ‘standard’ mounting system isn’t ideal. Magnic proposes that the light be attached to the brake caliper with an extended bolt through to the brake shoe. I could not get it to work well with the brake shoes that I have, and my preferred brake caliper reach.  Magnic are getting custom brake shoes to get around this issue. I made my own mount using the base of a Digirit torch attachment and the ubiquitous Garmin rubber bands along with the Magnic aluminium arm. Worked quite well.  The stock front mount worked fine.

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Final Conclusions

I’ll be using the Magnic lights on my commuter bicycle that I leave in Washington D.C. They are more than sufficient for this purpose and will not run the risk of the battery going flat which happens because the bicycle is used infrequently. However, for my long-distance endurance racing I will be keeping the hub dynamo, which also charges my GPS and cell phone. The huge improvement in light from the hub dynamo makes such a difference, particularly on dark rural roads.

The rear Magnic light would be great for any rider. It is bright enough and has the advantage of always being on, with no noticeable drag on the wheel. So for endurance riders who do use a battery light rather than a dynamo, I would definitely recommend the Magnic.

The developer Dirk should be completmented on coming up with such a novel system. It really is a neat bit of technology and one of the more successful Kickstarter projects that I have supported!

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One response to “Testing the Magnic Light Against a Supernova E3

  1. Pingback: Powering Your Gadgets For Endurance Races | Chris Bennett's Triathlon and Cycling Blog

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