Reuse bottle dynamo wiring for hub dynamo?

[brokenbetty]

I've picked up an old bike that has a working set of dynamo lights powered by a bottle dynamo. The wiring to the back light goes through the frame, and is a single wire.

I'm going to replace the wheels with a hub gear and a dynamo at the front (shimano N72). Is there any way to reuse the existing cabling?

 

[jimboalee]

I've picked up an old bike that has a working set of dynamo lights powered by a bottle dynamo. The wiring to the back light goes through the frame, and is a single wire.

I'm going to replace the wheels with a hub gear and a dynamo at the front (shimano N72). Is there any way to reuse the existing cabling?

Yup.

You'll need similar colour cable, a soldering iron, heat shrink sleeving and suitable connectors.

The bottle dyno uses the frame as one half of the circuit. Not negative or Earth as it is AC. You will need to strap a length of cable from one output of the dyno hub to the frame to make continuity to the bulbholders.

 

[Wobbly John]

The bottle dyno uses the frame as one half of the circuit. Not negative or Earth as it is AC. You will need to strap a length of cable from one output of the dyno hub to the frame to make continuity to the bulbholders.

Depends on the hub dynamo - some have one side earthed same as bottle dynamos.

You would need to identify if this is the case, or try it and if it doesn't work, try swapping the wire to the other terminal.

 

[jimboalee]

Depends on the hub dynamo - some have one side earthed same as bottle dynamos.

You would need to identify if this is the case, or try it and if it doesn't work, try swapping the wire to the other terminal.

Its an Alternate Current system. There's no such thing as 'Earth' in it. The electrons are moving back and forth each time the winding passes the magnet poles, North and South alternately.

If there is one terminal on the dynohub, take it to the centre contacts of the bulbs. The body of the bulbholders will be to the bike's frame and therfore back to the other end of the windings in the dynohub.

 

[brokenbetty]

Thanks Jim, I'll check it out when I get the hub.

 

[Wobbly John]

Its an Alternate Current system. There's no such thing as 'Earth' in it. The electrons are moving back and forth each time the winding passes the magnet poles, North and South alternately.

If there is one terminal on the dynohub, take it to the centre contacts of the bulbs. The body of the bulbholders will be to the bike's frame and therfore back to the other end of the windings in the dynohub.

Sorry, I thought that by describing it as 'earth', anybody would understand that I was referring to the frame side of the lighting circuit .

On some hub dynamos (such as my N72) one of the terminals is connected to the axle, and therefore the frame. If you are using a single wire lighting system, you will need to connect to the other terminal (the bronze one on my dynamo hub)