Thursday, 6 October 2016

Dynamo!

For years I've been threatening to upgrade to a dynamo hub as the idea of generating the power you need to light your way yourself has always appealed to me. Add to that the fact that I enjoy all-night rides, where battery power can rapidly become a problem, and dynamos start looking ever more appealing.

Shimano DH-3D32 dynamo hub
A number of years ago I purchased a Nokia DC-14 kit, which is designed to keep Nokia phones (remember those?) charged up while cycling. The DC-14 relies on a bottle dynamo which, while it does work, is very noisy. Annoyingly so.

The DC-14 does however offer sealed, waterproof circuitry that takes the fluctuating 6V AC feed from a dynamo and converts it to safe, smooth USB. More on this later.

Anyhow, something that always prevented me from buying a hub dynamo and dynamo lights is the fact that it didn't make sense to do so. Bear with me while I explain.
My main light used to be a 5 x Cree T6 light, driven off a 6-cell battery. A single Cree T6 chip outputs anything between 700 to just over 1 000 lumens, though lights like this are more often than not sold with greatly exaggerated lumens claims. In fact, mine was claimed to be 8 000 lumens, which is of course total rubbish.

I always calculate the lumens on the lowest rating, so a 5 x T6 light outputs around 3 500 lumens. That's a lot of light - enough to make oncoming drivers dip their headlights on country lanes before rounding the bend. It is also not possible to drive a light like that off a 6V dynamo - the physics simply don't add up.

And this was my problem: by moving to dynamo lights, I'd have less light. Several people tried telling me that while this is true, dynamo lights focus the light just where it's needed. As a result, while having less light overall, the available light is used better.

What doesn't help, and makes direct comparisons so much harder, is that battery lights tend to be rated in lumens, while dynamo lights are rated in lux.

Despite that making perfect sense, I wasn't ready to commit until I saw a dynamo light being used in anger. My 5 x Cree T6 light would light the road ahead of me, and the hedges to the side and the trees hanging overhead, so I know just a small amount of overall light produced actually directly lit the way.

When I rode the Exmouth Exodus this year (2016), one of the riders in the group I was cycling in had a dynamo light and his light was pretty good. Unlike me, he didn't have to worry about swapping batteries and he had enough light to cycle safely at a fair pace.

That was the turning point, and a while later I bought a Shimano DH-3D32 dynamo hub from Rose Bikes in Germany. For some unfathomable reason they were cheaper overall, including delivery, than any UK-based supplier. Along with the dynamo, I also bought a Herrmans H-One-S dynamo front light.

Once the bits arrived, I removed the front wheel from my Genesis CdA and removed the hub, before rebuilding the wheel around the dynamo hub. I was quite worried at one stage that the hub I'd bought was a dud: When trying to spin the wheel, while holding the hub in my hands, it wasn't free-spinning at all, but rather had distinctive "clicks". I was concerned that cycling with the hub was going to take LOTS of extra effort, which isn't how hub dynamos are supposed to be.

A quick Twitter conversation with a good Twitter friend and dynamo hub evangelist later I was assured the hubs behave like that when not clamped in the forks by the QR. Sure enough, once properly fitted back on the bike, the hub was smooth and free-spinning.

With the addition of a dynamo hub, my Genesis CdA has taken a big step forward to becoming my "one bike to rule them all". Though (obviously) heavier than my road bike, the CdA is still quite a fast bike. Essentially a CX bike with road tyres, it's sturdy enough to tackle rough terrain and the rack mounts means it can carry  a load too.

Though I've yet to add full mudguards and a new rack, my CdA is almost at the point where it is (to me!) the perfect commuter and light tourer. Dynamo lighting means I will no longer have to worry about charging up batteries.

After the rack and panniers, the final step will be to fit my Nokia DC-14 to the bike and wire that in (via a waterproof switch) to the dynamo. This will then allow me to charge various USB-powered gadgets up during the day, when I don't need the dynamo lights switched on.

The plan is actually to use the DC-14 to charge up a power bank, which in turn can be used to charge up or power any gadgets that may need charging or powering up.
The CdA has 3 bottle cage mounts, with the third on being on the underside of the down tube, forward of the bottom bracket, and I'll be using a bottle cage (and some cable ties!) to securely hold a water bottle repurposed as a waterproof enclosure for the power bank and the DC-14.

Here's to brighter cycling!