Exposure Revo light and dynamo hub

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In situ (on a 'cross bike...)
Revo in situ (on a ‘cross bike, natch…)

There’s something a bit ‘dark arts’ about dynamos, especially if you’re used to regular bike lights that are very bright indeed until the battery dies and then they are – well, fearfully dark.

Dynamos work the other way around – there’s a moment’s unlit apprehension as you put in that first pedal stroke to get the wheels turning, then a gradual swelling of light over the course of mere seconds and you ride off into the (fake) light-of-a-thousand suns, smug in the knowledge that it’s not going to go dark again until you stop – and, in the case of the USE Revo (and any other dynamo with a standlight), not for some time after you stop, either.

As you can probably tell from the above, I’m not a physicist or a mathematician. Like most riders I’m not particularly interested in how my lights work, I just want them to do it, and keep doing it, in the simplest and most reliable way possible. It seems to be the law that you can’t run a dynamo setup unless you know about voltages and currents, and you own a soldering iron. I don’t even own a clothes iron, let alone know which way a current is meant to flow (unless it’s a misspelled currant going out of a packet and into a cake mix) – and so I thought I was pretty well suited to see how Exposure’s Revo set-up works in the real world, with a real, not-scientific, rider.

Pleasingly small and sleek hub body inside which the magic happens.
Pleasingly small and sleek hub body inside which the magic happens.

What’s in the box?

A dynamo hub with 15mm axle and 9mm Q/R adapter; the Revo light unit; USE’s standard hot-shoe/hex key handlebar clamp, and the connector cable kit, which includes a nice long cable with the light plug on one end and two bare wires on the other. There’s also a two-part plug ready to attach to the bare wires once you’ve trimmed the cable to length, and sticky cable mounts for your forks.

Underbelly - with hot shoe.
Underbelly – with hot shoe.

The mount is Exposure’s standard hot shoe fitting attached to a simple bar clamp which fits with a hex key; it’s a beautiful bit of machining and over the long term just needs the occasional bit of lube around the lock pin and the clamp pivots to prevent corrosion and keep it working smoothly.

Individual clamps are available for 31.8 and 35mm bars (£19.95 each), as are connector/cable kits (£12.49), so you could easily run this light across several bikes with the minimum of faff – leave clamp and cable in situ, swap wheel and light from bike to bike as you need them. The adaptable hub adds to the versatility, too.

That lovely clamp...
That lovely clamp…

You’ll need to get the hub built into a wheel of your choice, and if you don’t want to do that bit yourself your local bike shop will probably be more than happy to help, as it’s just like building any other wheel.

Compact.
Compact.

And then, once you’ve got your wheel back and tyred-up, you need to set it up. Which is dead simple (hurrah!): first fit the wheel to the bike, with the connector in a sensible place (behind the fork leg is a safe enough option), then fit the clamp and the light to the bar. Then check the cable length (shorten it if you want to and strip the cable ends according to the simple instructions); attach the two-part hub connector to the bare cable ends (which is the only fiddly bit of the whole process – if you have a child with small fingers they can earn their pocket money here); and plug the cable into the light. Spin the wheel, and…

Nothing?

Don’t panic! If all you’ve done is what I’ve outlined above, then you’ve (probably) done it right – just take the bike for a five-minute spin around the block and the LEDs will soon light up, growing brighter as you go. This delay is only apparent after the first use – subsequently it’s taken just moments for the light to kick in at the start of each ride, but there’s nothing in the (otherwise clear and helpful) quick-start instructions to warn you about the initial delay on first use.

On the trail

Riding with the Revo is extremely simple: just do it. Once it’s set up on the bike then you don’t need to do a single thing to it, except remember to unplug the connector at the hub when you’re removing the front wheel. The slight notchiness that’s noticeable when turning the hub by hand doesn’t feature in the experience at all; though the mechanism of the dynamo creates resistance, it’s completely unnoticeable when you’re riding, either in your legs or your speed.

As far as lighting goes, Exposure claims the Revo kicks out a maximum of 800 lumens from its 4 Cree XPG R5 LEDs. This output is governed by the speed at which you’re riding; if you go faster it gets brighter (I reckoned I was getting the maximum power at around 14mph and above), if you slow down then it dims, and if you stop then two of the four LEDs remain lit for ten minutes (usefully – they emit a gradually diminishing glow for hours afterwards), thanks to the standlight.

Four Cree LEDs.
Four Cree LEDs.

The standlight means that the light itself has an internal battery which is charged by the dynamo while the light is lit, and then continues to power the light if the charge from the dynamo drops for any reason. You can actually unplug the Revo and it will remain lit – there’s not really enough light to ride by but you will at least remain visible, or be able to use it to read a map.

There’s no way for the rider to control the amount of light the Revo kicks out, other than to alter your speed, and this is where the limitations of this light for off-road use start to make themselves felt. If you’re going slowly on the road it’s normally because you’re in a situation where you don’t need much light – climbing, for example, or eating pie. Off road, you may well still need just as much light when you slow down, as what impedes your speed may be technical features (up or down) or tight trails, and if you can’t get those lit up well enough to see clearly, then you’re going to be going even slower (or straight to A&E).

The straightforward way to get round this is to use an additional helmet light – which would be a standard bit of kit on night rides for many riders anyway (the much-loved Exposure Joystick is a very good starting point here). 800 lumens is not bright as far as bike lights nowadays go, so some supplementary candlepower to get the most out of your trails is probably a good idea anyway. Just remember that the helmet light is relying on a normal battery for its power, so is going to run out of juice at some point – unlike the Revo (ahem).

Two-trick pony

And while we’re talking about juice… The rear of the light has two ports: one input, where power from the dynamo goes in and one output, where (obviously…) power from the dynamo comes out. The output port can be used to run one of Exposure’s RedEye rear lights (not much good for off-road riding in a group unless you want to be at the back all the time/don’t actually like your riding companions, but highly recommended for road use/enacting Satanic rituals).

Innies and outies.
Innies and outies.

You can also plug in one of USE’s ‘Boost’ cables, which opens up the possibility of using the hub to charge USB devices. The output does not give you much juice and the practicalities of attaching expensive electronics (eg. an iPhone) to a bike within reach of the port are more of a risk than I consider to be worth, though, so I’ve gone with plugging a USB power pack into the light and then charging devices from that.

Hub connector.
Hub connector.

The usefulness of this does have its limits – there’s not enough juice available to resurrect a dead Garmin or phone to full charge, for example – but on multi-day trips it could a valuable way to keep devices topped up without needing to resort to poaching power in cafés or shops. This is one of the areas that Exposure could improve on the current Revo, by adding more power and control to the output port. I’d also like to see an override or boost function for the light output, to get around the problem of trying to ride slow-speed trails with a diminishing light. And a sturdier hub connector would be good – I managed to separate the wires and cover a couple of times by being no more clumsy than usual, so ‘fixed it’ permanently with Sugru, but something a bit tougher as standard would be reassuring.

The bare ends of the wire...
Fitting the connector plug: the bare ends of the wire…
...ready for capping...
…ready for capping…
...and the finished connector.
…and the finished connector.

These quibbles aside, I’ve thoroughly enjoyed learning what the Revo’s best at, and at least one of my bikes will be staying a dynamo convert for the foreseeable future as I see how the Revo fares after some more months of riding. For now, I’m happy to report that endless lighting is a wonderful thing – and still a little bit magical for me.

Overall: A neat, fit-and-forget lighting system. Needs to be teamed with a reasonably powerful helmet light for high-speed or technical riding, but is very good for everything else. I’m looking forward to seeing what Exposure has lined up for the Mk2.

Review Info

Brand:Exposure
Product:Revo light and dynamo hub
From:ultimatesportsengineering.com
Price:QR15 hub £149.95, Revo light £199.95
Tested:by Jenn for three months

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