Hub Dynamo for a 20 inch wheel?

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Hub Dynamo for a 20 inch wheel?

Postby eddiewalkling » Thu Dec 16, 2010 6:28 pm

Hi,

I want to put a hub dynamo on my recumbent which has a 20 inch front wheel after success with a hub dynamo on my Dawes Galaxy. I realise though that this wheel will rotate faster for a given speed than a larger wheel would but don't understand the effect this will have.

Will bulbs just burn out when a decent speed is reached? Do I have to buy a specific hub dynamo, or just higher rate bulbs?

I would also be very interested in hearing from anyone who has used the systems that allow you to charge mobile phones or run sat nav ect from hub dynamos.

Thank you, Ed
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Re: Hub Dynamo for a 20 inch wheel?

Postby ConRAD » Fri Dec 17, 2010 7:27 am

eddiewalkling wrote:...I realise though that this wheel will rotate faster for a given speed than a larger wheel would but don't understand the effect this will have. Will bulbs just burn out when a decent speed is reached? Do I have to buy a specific hub dynamo, or just higher rate bulbs? I would also be very interested in hearing from anyone who has used the systems that allow you to charge mobile phones or run sat nav ect from hub dynamos.
Thank you, Ed

Hi Ed,
don't worry for bulbs burning, all modern lights are overvoltage protected so ... the faster the better.
As far as charging electronics is concerned, please have a look to the below diagram, now it's over one year that I'm using it and it's simply fantastic.
ONE YEAR ZERO BATTERIES !!! ... that's a great success.
Corrado
Image
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Re: Hub Dynamo for a 20 inch wheel?

Postby rollinbone » Fri Dec 17, 2010 11:56 am

see thread: URGENT HELP WITH SON DELUX

I started that thread to find out about the Son delux dynamo hub
and if it was suitable for bike with wheels ABOVE 20"

seems the SON 20R has been replaced with the SONdelux
the old SON 20R was only legal in Germany for up to 20" wheels
now it seems its been renamed the SON delux and is OK for wheels up to 28"
even though its the same thing, so it will include your 20" wheels

So I guess the SON delux, although expensive, would be an option.
Reading tech descriptions of products if in doubt is always worth while

To buy a SON go to:
https://www.starbike.com/php/suchen.php ... n&b=SON&q=
and take your pick (they charge £12 (15E) for delivery but it will arrive by courier in 3 days) or

the (mostly in german) Son dynamo pages for general info
http://www.nabendynamo.de/english/index.html

In my investigations SON dynamos are the cats meow,
mine is currently on its way to me for use next year on my 26" wheel tourer with M&B lighting and an EWerk
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Re: Hub Dynamo for a 20 inch wheel?

Postby ersakus » Fri Dec 17, 2010 11:57 am

Son delux (used to be called R20) is good on 20inch wheels. It is actually optimised for this size. It is quite efficient, capable of lighting the dark roads and still supplying 200mA which charges my gps. When lights are off it can charge two devices at once (provides around 600mA current). This is on 700 wheels. The difference on 20inch is the speed you need to reach optimum electrical output is lower. ( I ride at 12-20mph on 700C wheels which is good enough to reach optimum output).
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Re: Hub Dynamo for a 20 inch wheel?

Postby [XAP]Bob » Fri Dec 17, 2010 12:57 pm

Now called the delux - SON say they are only for use with LED lights on larger wheels, because they can get to decent (german) brightness at lower voltages.
You can of course use them for anything on a smaller wheel
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Re: Hub Dynamo for a 20 inch wheel?

Postby speedsixdave » Fri Dec 17, 2010 2:08 pm

There's the SONXS and XS100 too, narrow versions for certain applications which might be useful for you on a recumbent. Or they might not. Whatever you do, Peter White's page on generators is well worth a read, as is his whole site.
Big wheels good, small wheels better.
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Re: Hub Dynamo for a 20 inch wheel?

Postby ConRAD » Fri Dec 17, 2010 9:22 pm

eddiewalkling wrote:... I want to put a hub dynamo on my recumbent which has a 20 inch front wheel ... do I have to buy a specific hub dynamo ?

ANSWER: NO, any dynamo, hub/spokes/bottle etc. will fit.
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Re: Hub Dynamo for a 20 inch wheel?

Postby meic » Fri Dec 17, 2010 9:33 pm

However you may decide to have it laced on in a different way as the hub flange is bigger.
With such a small gap between the hub and rim you may choose to have the spokes only cross twice instead of three times.
Finding short spokes may be a problem too.
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Re: Hub Dynamo for a 20 inch wheel?

Postby eddiewalkling » Fri Dec 31, 2010 5:38 pm

Thanks to all who responded. Very helpful.

Great to hear I can use a standard hub as the Sons, though a work of art are out of my league. I have also been happy with the shimanos I have tried.

Since I posted the question I have recived a Shimano N30 26 inch hub dynamo wheel and am initially very impressed even though it is I think the cheapest one they do. I'm even running a rear light with this one and the front is bright enough for me and no noticeable drag again. Peter Whites pages helped plenty as I hadn't wired a rear light in before.

ConRAD Is this a system you have brought or made yourself? It looks great and is where I'm heading next as I will need to keep things charged up when touring.

The Ewerk also looks great but again a little pricy. I may of course find that there is no cheaper option and have to wait for the trickle down effect.

Thanks again for all the help. Edward
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Re: Hub Dynamo for a 20 inch wheel?

Postby willem jongman » Sun Jan 02, 2011 6:57 pm

Using a 28 inch hub with a 20 inch wheel really is not a good idea. Yes modern lights have overvoltage protection, but that is not designed to cope with chronic overloads. The second reason for not doing it is that you have unnecessarily high resistance. The best fix would be to use a second headlight so you actually use the extra output.
The story with bottle generators is an altogether difrerent one, as these are not influenced by wheel circumference. FInally, for spoke pattern, this is not something to be decided at will. Generator hub manufacturers have specific recommendations that you need to comply with. Read the manual.
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Re: Hub Dynamo for a 20 inch wheel?

Postby oox » Sun Aug 28, 2011 1:20 am

Hi Ed,
don't worry for bulbs burning, all modern lights are overvoltage protected so ... the faster the better.
As far as charging electronics is concerned, please have a look to the below diagram, now it's over one year that I'm using it and it's simply fantastic.
ONE YEAR ZERO BATTERIES !!! ... that's a great success.
Corrado
Image


Hi ConRAD

I am thinking of setting up something like what you have on a new touring bike.

It would help me and others alot if you could give details (and photos/vids if you have time) of all items in your system, such as your batteries i'm thinking of getting a X-Pal 18000 but cant find any details of if i can actually charge it from a dynamo or i have to use mains only for it.

thanks in advance

Nick
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