Friday, 16 March 2012

Prototype Switchable Dynamo Hub From Shutter Precision

A shiny new hub turned up this week, a prototype, 32H, disc, dynamo hub from the guys at Shutter Precision. This is no ordinary hub, it's a switchable dynamo. The hub has a large flange on the connector side that clutches the dynamo in or out. When disengaged, the hub acts just like a normal hub, only providing any resistance when the clutch is re-engaged. The hub is based on the 7 Series range PD-7 model, but has been sent to me with a special, not yet available, 32H drilling so I can use my preferred rims, rather than the currently available 36H version. Aren't I a lucky boy? :-)
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 :-(
"But why do I need to turn my dynamo off?" I hear you ask. Is this a solution looking for a problem? No it isn't, although this did cross my mind too at first. Try wheeling your bike through a UK railway station with the dynamo light blazing away, and you'll soon be yelled at with a light on; you'll confuse the drivers who might think you're a signal apparently. Several of my friends have been caught out with this and dynamos. In town, riding my bike, I do always have the light on. I mean, why would I choose to make myself less visible, even on a sunny day? But out on the trails, off road was where I have used this switch (or clutch) the most. I found I was regularly getting flagged down by other trail users if I went anywhere busy, helpfully pointing out to me I had left my lights on and my battery would go flat, something that got VERY boring after not very long at all!

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!

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