Dynamo set

Seaswimmer

Having just come back from the continent and observing how all the functional bikes over there have dynamos, i am wondering if anyone on here has bought one. I did a quick search on CRC, wiggle ect but canot see anything. I am not interested in the hub version as it entails a new wheel. The continental ones are mostly the old traditional rub on the side of the tyre type. It would be only for short trips around town so i am nott to worried about drag, astetics ect. The big advantage (for me) is that I would not have to remove lights when i lock the bike or worry about batteries. I realise that they are not the best solution for being ultra visible but for my type of cycling would do the trick..

ednwireland

plenty of options

http://www.google.ie/search?source=ig&hl=en&rlz=&q=dynamo+cycle+lights&meta=lr%3D&aq=f&oq=

quite like this one myself (http://www.freelights.co.uk)
appeals to the geek in me (does it work - no idea !)

DualFrontDiscs

Check out: http://www.kinetics.org.uk/html/lighting___safety.shtml

and

http://www.peterwhitecycles.com/lightingsystems.htm

I bought my hub dynamo wheels from Ben in Kinetics and use one of the setups described on Peter White's site.

I bought a set of Reelights for a friend. They're a great way of being seen.

DFD

Civilian_Target

I have a Shimano Nexus Hub Dynamo in my front wheel, which provides enough power for front and rear lighting. Sure, I never have to change batteries but frankly... maybe it would be cheaper! The dynamo came with the bicycle, but fitted new would probably cost the guts of 100 EUR. The LED lighting rig I added myself (because the original one was old) and cost about 70 EUR. Granted, it puts out a lot of light, enough to see the road clearly in unlit areas, but the total cost of installing such a thing new is closer to 200 than 100 EUR.

I think if you are going to do dynamos, you have to go for hub ones. Bottle dynamos are unreliable, high maintenance and high resistance. You'd be as well off with batteries. At least hub dynamos produce consistent output at low drag.

I can only recommend them though as a serious investment to your bike. If you're not going to get at least 2 winters out of it, don't bother.

Al Wright

My current dynamo on my commute bike is an AXA type HR sidewall, have it for 5 years, used over average of 1100 miles per Winter. Never had any trouble, but the roller is now getting worn and could slip when wet.
Generally this type of dynamo delivers 3W electrical. When new, I checked the mechanical input, 12 watts at approx 18 mph. Given that I'm capable of working at the rate of well over 200W for hours, the energy input to the dynamo is not a concern, it just adds to the value of the execise.

The model by Busch & Mueller is more expensive but probably the most efficent (less drag) available.

DualFrontDiscs

Al Wright wrote: »

Never had any trouble, but the roller is now getting worn and could slip when wet.

You can buy replacement rollers. http://www.sjscycles.co.uk/cid/BRQ5N70J82E7KZN65GHRUOEXDMTRAH8F/product-Axa-Replacement-Rollers-for-HR-Dynamo-Unit-13206.htm

I used to use sidewall dynamos, but 'upgraded' to a SON hub. CivilianTarget is right, they are expensive, but over a lifetime, I think they're good value.

DFD.

DualFrontDiscs

Al Wright wrote: »

Generally this type of dynamo delivers 3W electrical. When new, I checked the mechanical input, 12 watts at approx 18 mph. Given that I'm capable of working at the rate of well over 200W for hours, the energy input to the dynamo is not a concern,

Some information on drag in Watts here

A SON hub at 18mph (c.30kph) generates about 7 Watts of drag, which is less that a 4% overhead based on your 200W output. And as you say, it all adds to the exercise. I think they're the perfect addition to a commuting or training bike, particularly if you need to see as well as be seen.

DFD.

penexpers

I have the Shimano Nexus hub too and find it quite good. Would agree it's quite an investment. I run it with a B+M Lumotec IQ Fly Senso Plus on the front (cost c.100 euro) and a B+M Seculite Plus on the rear (cost c. 35 euro). Probably more bright than what I need but there are some pretty poorly lit roads near where I live and not having to ever worry about batterys is great.

Civilian_Target

Cool, that's nearly exactly my setup to penexpers, although I went without the senso, so like a swedish car, it's on during the day too.

I must admit, i was impressed by the visibility the front light gives, it's fine even in the countryside.

Sheeps Head

Anyone any idea how much drag a hub dynamo gives when not actually supplying any power? (lights off).

OK I know it should be zero, but there is still some drag.

Wondered what sort of level that would be?

DualFrontDiscs

Sheeps Head wrote: »

Anyone any idea how much drag a hub dynamo gives when not actually supplying any power? (lights off).

OK I know it should be zero, but there is still some drag.

Wondered what sort of level that would be?

My understanding is that it is always providing power/ creating drag. That's why the lights have switches, to save the lights, not reduce the drag.

DFD.

Sheeps Head

DualFrontDiscs wrote: »

My understanding is that it is always providing power/ creating drag. That's why the lights have switches, to save the lights, not reduce the drag.

DFD.

Well, they should only make drag when power is being used, that's where the effort from the drag goes, creating current in the windings that flows to the lights.
Turn the lights off and no current flows so no/less drag.
But there are magnetic losses and eddy currents.

If someone with a hub dynamo and switchable lights could turn the lights off, spin the wheel, then turn the lights on while it was spinning, there should be a definite slowing down.
Be interesting to know what the difference is.

DualFrontDiscs

Sheeps Head wrote: »

Be interesting to know what the difference is.

Happy to be corrected. Look at the graphs near the bottom of http://www.peterwhitecycles.com/schmidt.asp for comparisons of lights on and off.

I've taken my hub off for a tour this weekend and can't be bothered putting it back on tonight

DFD.

Sheeps Head

DualFrontDiscs wrote: »

Happy to be corrected. Look at the graphs near the bottom of http://www.peterwhitecycles.com/schmidt.asp for comparisons of lights on and off.

I've taken my hub off for a tour this weekend and can't be bothered putting it back on tonight

DFD.

Hey thanks that's really interesting.
Good graphs.

I like this part:

When the light is turned off, the drag from the hub is roughly equivalent to climbing one foot every for mile you ride. With the light turned on, it's about the same as climbing five feet every mile. That's why (in the daytime) you can't really tell that it's on, except at very low speeds (2 - 3 mph) when you can feel the hub pulse just a bit.

That's nothing is it? :)

DualFrontDiscs

Sheeps Head wrote: »

That's nothing is it? :)

I genuinely don't notice any drag and it is very reassuring knowing you've always got light when you need it. The better lights have standlights built in, so when you stop, you still get a few minutes of lower level light output. Perfect for red lights, etc.
DFD.

Sheeps Head

DualFrontDiscs wrote: »

I genuinely don't notice any drag and it is very reassuring knowing you've always got light when you need it. The better lights have standlights built in, so when you stop, you still get a few minutes of lower level light output. Perfect for red lights, etc.
DFD.

Thanks DFD.

Might have to raid the piggy bank....:eek: