|Prototype SP PD-7 switchable dynamo hub, with clutching dynamo mechanism. Nice tyre name too! ;-)|
The first thing I did with this out the box was, obviously, to fiddle with the clutch and spin the axle and, to my great delight, it does exactly what it says it does; disengage the clutch and you'd never know there was a dynamo inside. What's more, it means I can miss off a small, fragile sub-miniature switches from my deanamo, my off-road dynamo LED light, keeping down the part count, the number of soldered connections and deleting what I felt was possibly the weakest part of the light I made for this bike.
|Big, positive, mechanical switch, easily operated in winter gloves with cold, numb hands, as tested by me :-(|
The SP 7-Series switchable dynamos and 8-Series super lightweight dynamos are available through Intelligent Design Cycles.
For those that are interested, here's the performance specs os of the SP 7Series dynamos. Makes for impressive reading:
And here's a little video demonstrating the benefits of the switchable mechanism, if you prefer actions rather than graphs!