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Welcome to Velo Vision magazine, covering specialised bikes, cycling as transport and human power. It's a quarterly dose of cycle inspiration.The current issue is Issue 16. The next issue is out early March 2005.
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Schmidt tests 12V hub dynamo prototypeSchmidt's hub dynamo is pretty much universally regarded as the best you can buy. Now, he's taking advantage of new German lighting regulations to develop a 12 V version. New German regulations for cycle lighting will soon legalise the use of 12V, 6.2W systems alongside the usual 6V, 3W versions which have become an international standard. The regulations specify that the front light should have a 5W power rating, and the rear 1.2W. Wilfried Schmidt Maschinenbau, who make the SON (Schmidt's Original Nabendynamo) hub dynamo, are working on a new model to meet the standards. Other companies are following suit.  The obvious significance of this is that bike lights powered by dynamos could soon become seriously bright - perhaps bright enough to woo back some of those who have been tempted onto the new generation of high-power rechargeables. But you don't get something for nothing: that power comes from your legs. Schmidt's project, called the 'SAMSON', promises an efficiency of 70%, which even with the increased power rating should still result in drag lower than that of a 'normal' 6V bottle dynamo. Schmidt says that compared to a 6V dynamo, the new model poses problems: keeping size, weight and price down is tricky. A slight increase in 'switched-off' resistance is also unavoidable. He suggests that one way to keep overall size and weight down would be to 'flatten' the voltage curve, so full voltage is only developed at say 15km/h instead of at 10km/h. It's not yet certain that the 12V version will make it into production. Although Busch und Mueller, who make the headlights for the existing SON range, already have a 12V dynamo in their catalogue, it (and the lights, bulbs etc to go with it) won't be around until later this year. Schmidt is apparently waiting to see if the idea catches on before sinking too much development into the project. Schmidt also points out that it's already possible to get 6W lighting out of an existing SON - simply couple two lamps in series. You only get full voltage at high speeds, so Schmidt suggest wiring the lamps so that one can be switched out of the circuit for use at lower speeds - that way there's always one running at full power. Using a hub dynamo designed for a 28" wheel in a smaller wheel will also work, giving plenty of power, but Schmidt points out that this is illegal in Germany (it doesn't exhibit the right speed/voltage characteristics) and that a voltage regulator will also be needed. The manufacturer's homepage: http://www.nabendynamo.de/ is very informative, and has circuit diagrams for the above systems, but is only in German. Further English-language info about the SON is available on, among others: www.peterwhitecycles.com/Schmidt-Lumotec.htm simon.trinhall.cam.ac.uk/bike/schmidt.html Posted on 04 February 2001 Your comments ...
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