[mattm]

So i've got a shimano dynohub & a schmidt E6 to go with it - I'm lovin it!!

I had it running on my bianchi, no problem, and then switched it all over to an older miyata frame. BUT when i did that, the light no longer worked! All I got was lots of resistance when rolling the tire, with the switch off or on (and no light was coming out).

To fix this, I reversed the wiring (just at the hub-contact end, not the end that goes into the E6), which worked.

But I don't understand! Why would I need to reverse the wires if it worked previously with the same setup, but on a different bike? The only thing I can think of is that the Bianchi had a carbon fork, and the Miyata has a steel one - could that (un)ground the setup and force the switch?

I just want to understand what was up with it, any thoughts?

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[ModoVincere]

So i've got a shimano dynohub & a schmidt E6 to go with it - I'm lovin it!!

I had it running on my bianchi, no problem, and then switched it all over to an older miyata frame. BUT when i did that, the light no longer worked! All I got was lots of resistance when rolling the tire, with the switch off or on (and no light was coming out).

To fix this, I reversed the wiring (just at the hub-contact end, not the end that goes into the E6), which worked.

But I don't understand! Why would I need to reverse the wires if it worked previously with the same setup, but on a different bike? The only thing I can think of is that the Bianchi had a carbon fork, and the Miyata has a steel one - could that (un)ground the setup and force the switch?

I just want to understand what was up with it, any thoughts?

You have a two wire connection, right?
If so, the ground is not part of the light itself.

[mattm]

I think so - there's only one cable coming out of the light, but two distinct wires poke out of it.

So maybe grounding isn't the issue, but what was? I'm confused. It works but I want to know why!!

thx..

[ModoVincere]

I think so - there's only one cable coming out of the light, but two distinct wires poke out of it.

So maybe grounding isn't the issue, but what was? I'm confused. It works but I want to know why!!

thx..

Well, I could make up a lot scientific sounding babble. But the honest truth is I have no clue as to why.

[Pig_Chaser]

Forgive me i have no experience with dyno hubs so if the following is ridiculous just don't flame me too hard.

Does the hub output DC power and if so is the light polarized like say for instance an LED? If that's the case then it may be that the hub was mounted on the new frame so that it spins in the opposite direction resulting in a reversal of polarity requiring you to reverse your wiring to get the light to work (two wrongs do in fact make a right).

However, the above does not account for an increase in resistance regardless of switch position.

[mattm]

Pig_chaser, i should've clarified, the hub is spinning the same way it was before (on the same wheel), and this is a halogen lamp, not LED. Also there is no more resistance, now that I've switched the wires.

Thanks all for your ideas.

[znomit]

I think one terminal on the dyno is earthed, and one on the light.
Get it wrong and no workie.
With the carbon fork the earths aren't connected so you can plug it either way.

[mattm]

znomit, i think you're right, that's what it has to be.

thx!!

[Six jours]

From Peter White's website: "The two female spade connectors are slid onto the two male connectors on the SON axle. It makes no difference which wire connector goes on which axle connector, as the hub is not grounded to the frame."

Unless the OP is absolutely sure that there has been no increase in resistance from before and after switching the wires, I would tend to think that there was simply some crud/corrosion on the spade plugs and swapping them around scraped enough of it off that the connection was established. I'd be interested to hear the results of switching the connectors back again.

[znomit]

Ah yes, but its not a SON.

More from Peter Whites website (http://www.peterwhitecycles.com/schmidt-headlights.asp):
"The difference is that the SON does not ground electrically to the dropouts, and the Shimano dynohubs do ground to the dropouts via the axle."

[Six jours]

My mistake. I saw "Schmidt" and just assumed the OP bought good stuff all around... :p

[znomit]

Sometimes we have to slum it :D
(though the shimano isn't all that bad)

[vik]

Ah yes, but its not a SON.

More from Peter Whites website (http://www.peterwhitecycles.com/schmidt-headlights.asp):
"The difference is that the SON does not ground electrically to the dropouts, and the Shimano dynohubs do ground to the dropouts via the axle."

Sorry if this is dumb, but the whole bike is rolling on rubber tires so how can you ground anything attached to the bike via the frame???

[znomit]

"ground" in this case means the frame. Means you can just run one wire to the light and the electricity flows back to the dyno through the frame.