Dynamo dilemma ;)

[Mandicky]

Hi,

I've decided that I need to fit a dynamo to my bike, primarily for lighting up the night. I'd also like to use it for re-charging my GPS & phone if possible. Having trawled the internet I've been drawn in to the current thinking that a dynamo hub is the ideal solution - but is it?

I have a 15mm thro' axle on the front wheel so I'm limited on choices of hub. All of these dynamo hubs are expensive, heavy, permanently engaged and, when they break/require servicing you're without a wheel. I also worry about a dynamo mounted at a point on my bike that often finds itself underwater - muddy, gritty water at that.

Now, when I used to cycle to school (a few years ago...) I had a lovely bottle dynamo lighting set that sat on my bike that I could click on and off whenever I needed it. Mine sat on the rear wheel, near the top (I'm in trouble if the water's this high). There are modern versions of this for sale. They cost a lot less - around £40 for the most expensive I could find. They weigh around 180g typically. If it breaks I can keep both my wheels and just fit a new dynamo. I can also swap it between my MTBs and CX bike with no real problems.

6v, 3W appears to be the typical dynamo output and the Busch & Muller dynamo claims this - albeit with a lower efficiency - around 40%.

http://www.sjscycles.co.uk/busch-and-mu ... -prod1061/

So, what are the problems? Obviously it needs to press on the tyre sidewall to work. I guess too much contact pressure and you could damage the tyre eventually, too little and the dynamo will slip and not generate power. A buckled wheel could produce some disco strobe effects but I'd probably fit a high value capacitor to level out any power fluctuations and provide some 'stopped at the road junction' illumination.

Obviously it isn't as sexy as a hub dynamo

Thanks,

Richard

[composite]

expensive,

Compared to what? The SP is marginally more expensive than a hope evo or a DT Swiss 350 and a lot cheaper than a DT Swiss240.

heavy

Read Rob Deans comparison on weights. Remember that you won't have to carry the heavy battery pack of an equivalent light. Even if it was heavier, if it's a bikepacking bike it's such a small fraction of the weight (with luggage) that you won't know anyway

permanently engaged

Personally I think any one who says they can notice the drag is just looking for reasons to knock it, I have never noticed the difference and frankly never will. Again if on a bikepacking bike you will never know. There is far more noticeable drag from big tyres than from the hub.

when they break/require servicing you're without a wheel.

When any hub breaks you are without a wheel. In terms of servicing it will take longer to get SP to change the bearings for you but it is free. I can live with that hassle every 3-4 years or so and you can plan it for when it's going to be the least pain in the arse to have done.

I also worry about a dynamo mounted at a point on my bike that often finds itself underwater - muddy, gritty water at that.

How often are you actually going through hub deep water? If it's the splashing you are worried about then OK it's difficult to know how good the seals are but after crossing the river in this video: https://vimeo.com/92043962 (about 3mins in) and it being fine afterwards I'm pretty confident it will survive some muddy puddles.

[Mandicky]

Compared to what?

I guess I was comparing hub and bottle dynamos for price, weight, reliability etc. I've already got a bike with 2 wheels so adding a hub dynamo is a lot more expensive than fitting a bottle dynamo

Cheers,

Richard

[Chew]

Looking at the link, they look like the ones from "when i were a lad" that you'd find on audax and run around city bikes.

Unconvinsed they would work in an offroad environment during autumn/winter when you'll be using them for lights and riding through wet conditions. Your tyres will be working there way through puddles and be coated in mud and grit which will then be transferred to the dynamo wheel. How that wheel is going to keep in contact through the mud and how well the unit is sealed is going to determine its power output and longevity.

Have a go and let us know how you get on

[Bearbonesnorm]

I reckon for that sort of money it must be worth a go.

I don't think there'll be any real issue with the tyre / dynamo contact ... it's rubber against rubber. The only thing that seems a bit poor is the 40% efficiency rating but you never know, even at 40% it may well be enough.

If only I'd kept the aftermarket silver metalflake seat off my Chopper

[Zippy]

What about something like the Siva Cycle Atom? Halfway house between bottle dynamo and hub dynamo...

http://bearbonesbikepacking.co.uk/phpBB ... f=7&t=2033

And http://sivacycle.com/#home

Not available yet though....

[Bearbonesnorm]

What about something like the Siva Cycle Atom?

Thought it didn't play well with disc brakes?

[Zippy]

What about something like the Siva Cycle Atom?

Thought it didn't play well with disc brakes?

Only in terms of packaging. Whack it on the front fork should be the workaround, but may need a few adaptor bits made up I guess. Only non disc compatible due to it being primarily designed around sitting on the non drive side of the rear triangle. I haven't made up my mind yet on what setup I may end up with, so I may or may not confirm this in several months time.

[Richpips]

I've decided that I need to fit a dynamo to my bike, primarily for lighting up the night. I'd also like to use it for re-charging my GPS & phone if possible. Having trawled the internet I've been drawn in to the current thinking that a dynamo hub is the ideal solution - but is it?

From experience of an SP hub dynamo which is more efficient than the bottle dynamos. If you are doing less than 5-6mph, forget charging anything.

Bottle dynamos with their low lumen lighting are OK, but I reckon there's no way you'd get enough gas to run a Revo or similar off of one.

[Mandicky]

Thanks for all the feedback

I'll have my Battery light for any technical bits, using the dynamo light for road/fireroad where I can get away with 'relatively' poor illumination. I'll get one ordered soon so I can get some experience with it before, hopefully, using it on the BB200.

Cheers,
Richard

[ianfitz]

Apparently the hub internals in an SP are top notch, and a cut above most hubs. This is due to the tolerances involved in pressing the bearings in through what is a very strong magnet. Therefore likely to last at least, if not longer than even a 'best quality' hub.

The distributors won't replace the bearings. They will send you a new hub (built up into a wheel) if anything goes wrong. This happened with mine. I bought it and had it built by 18 bikes in hope who have a courtesy wheel with a shimano dynamo hub that can be borrowed free in case of any service issues.

As with any bike components I'd recommend buying from 18 bikes for advice, service and being all round good guys who will go the extra distance to make sure you are a happy customer.