Novatec front Dynamo Bike / Cycle Hub with lights??

[beatlejuice]

On the Bay of Flees the above titled item is for sale linky. I am thinking of building a new front wheel for my commuter with it, as a winter project. Does any one have any experience of it?

 

[beatlejuice]

That was a bad idea. Instead I brought a 622-19 wheel with a Shimano DH-3N20 hub dynamo for £38.63 from Taylor Wheels, a Busch & Muller Toplight LED Line rear light for £32.34 and a Busch & Muller Lumotec Lyt B N Plus Headlight for £29.99. Both lights stay on for a few minutes when stationary. It was fairly easy to install however I wish the rear light had a lead to contact it to the front light. The rear unit is excellent however the front light is barely adequate for an unlit road. I use it with pair of Decathlon B'Twin V100 lights which I use on flashing mode. Hopefully it will be fit and forget but I could have brought a shed load of batteries for same price.

 

[beatlejuice]

[QUOTE 2775941, member: 45"]You could have bought a dynamo light bright enough for unlit roads for not much more than the light you bought. And a dynamo rear light for less than 20 quid.[/quote]

Please let us know who makes it preferable with a link.

 

[beatlejuice]

I could have saved a bit with them but not that much.

 

[beatlejuice]

I got a bit muddled by the difference between Lux and Lumens. It seems that there is a rule of thumb of X 10 to convert Lux into Lumens. I think would need at least 35 Lux to be effective on unlit roads. The beam on Busch & Muller front light is very focused in a small rectangle directly in front you.

 

[andrew_s]

You can't convert between lux and lumens.
Lumens is how much light comes out of the front of the light, lux is how brightly what the light falls on is lit. For a given light (in a constant mode), lumens remain constant, but lux readings will vary depending of which part of the beam you measure and how far away from the light you take your reading.
Lux readings are a simple matter of using a light meter, but lumen measurements are fairly complicated as they require all parts of the beams and sidespill to be measured and added up. Because they are complicated to measure, many (but not all) light makers give up and just quote the LED manufacturer's spec sheet, which can give a number that's up to double the real value.
The lux figures that B+M quote are those from the German approval tests, and are for the brightest part of the beam at 10m. These tests also require that the beam at certain angles away from the brightest point must also reach minimum percentages of the bright spot lux values, so lights aren't focused to a small very bright spot, as some lights have done.

In practice, something like 40 lux will allow you to ride at near daylight speeds while still being able to spot most potholes in time.
Before LED lights came out, a good halogen bulb dynamo light would give something like 15-20 lux, and that was about as good as it got for most road riding.
It is possible to ride at much lower lighting levels provided that you moderate your speed. For example, it's quite easy to ride by a full moon at 12-14mph, and a full moon is in the range of 0.5 - 1.0 lux, depending how high it is.

[edit to add]
The other light value you may see quoted is the candela (or candlepower), which is often quoted for rear lights (usually in millicandelas). This is how bright the light is in a particular direction.
It still depends on which part of the beam you measure, but is independent of distance.

1 candela is the same as 1 lux when measured at 1 metre.
If you are 10 times as far away, the light is spread out over 100 times the area, so 40 lux at 10m is the same as 4000 candelas.

Lux are lumens per square metre, candelas are lumens per solid angle.

 

[beatlejuice]

Thanks for clearing that up andrew_s. Perhaps this needs to be made a sticky Shaun?