[OrRando] Dynamo Hub lighting/lights connection question

David Rowe david.readytoride at gmail.com
Wed Nov 21 06:39:12 PST 2007


Here's a case study that builds on Andrew's ...

I set up the Raleigh Super Course with a Shimano Nexus front hub [
http://www.peterwhitecycles.com/nexus.asp.] I mounted a Lumotec N light to
the front fork by attaching a Chronometro NOB [
http://www.peterwhitecycles.com/accessories.asp] to the fork. It is made
entirely of plastic, so that would insulate it from the frame, but to make
sure it didn't slip, I used a section of inner tube wrapped around the fork,
and secured the C-NOB to that, and them mounted the light to it. At this
point a lightning bolt would cross the gap.

I also mounted a generator powered tail light to the rear fender - a
Seculite Plus 0.6 watt, which is recommended for use with a 2.4 watt
Lumotec. I ran a single wire connector that Peter shipped with the system
from the Lumotec to the Seculite. I switched on the light and rolled out of
the driveway on the test ride and it all worked ... I thought. Turns out
that the switch did not have control over the tail light; it was always on.
So I ran it that way until a second wire arrived from Peter in the mail (he
and I brainstormed a solution as he did not think that the Nexus needed to
be grounded).  I pulled the wire and replaced it with the paired wire, which
includes  positive and negative leads. I connected both to the Lumotec, and
ran it back to the tail light and connected both there.

Magic.

Interesting side note: I tried to ground the entire system by running a
ground lead from the Lumotec to the front axle bolt, and to the front brake
fixing bolt, with no luck. With the Nexus, it seemed to require a closed
circuit.

More for the archives, I guess.

See you on the road!

dr

On Nov 20, 2007 11:42 PM, Andrew P. Black <apblack at ownmail.net> wrote:

> As far as I understand things (and this is book-learnin' only; I don't
> have one), the sitiuation is like this.
> The SON dynohubs don't ground to the frame.  They have two wires coming
> out of them.  So long as you connecet both wires to the light, you should=
 be
> good.
> Yes, they do generate variable-frequency AC, but that has nothing to do
> with whether or not they are grounded.  The Shimano hubs ground via the a=
xle
> bolt; the old Sturmey-Archer hubs, like the SON hubs, had two wires.  They
> all generate AC.
>
> The complexity with two light arises because some of the lights, notably
> the Lumotec Oval Plus, don't insulate the current-carrying parts of the
> light from the bolt that holds them to the frame.  So, once you have bolt=
ed
> the light to your frame, the frame may become "live".  If you bolt on a
> second light, and you wire the lights in series, and that second light al=
so
> grounds one side of its inputs, then you will have shorted out the first
> light.  This can be avoided by insulating the light at the mounting bolt,
> e,g. by using a nylon washer, electrical tape, or whatever.
> On 20 Nov 2007, at 9:10, fitzbase at comcast.net wrote:
>
> Anyway, Cecil chimed in that I'd have to worry about grounding, since I'm
> mounting the light to a rack.  A read of Peter White's page seems to
> indicate that grounding is only an issue if I'm running a primary and a
> secondary.  At 40 lux, I'm thinking I don't need a secondary.
>
>
>
> _______________________________________________
> OrRando mailing list
> OrRando at tire.patch.com
> http://tire.patch.com/cgi-bin/mailman/listinfo/orrando
>
>


-- =

Carboload your mind at http://www.readytoride.biz
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://tire.patch.com/pipermail/orrando/attachments/20071121/cefc8ea2/=
attachment.htm


More information about the OrRando mailing list