Which carbon brush for bonding anode to propshaft

[Plum]

The only way to connect my hull anode studs to the propshaft is by using a carbon brush. There is very poor continuity (high resistance) between gearbox and output flange and no exposed external shaft to fit an anode direct to it. I have tried using a pair of 11mm X 6mm cross section electric motor brushes but the electrical resistance of the brushes is too high (10 ohms top to bottom) and the resistance between brush and shaft is too high (over 100 ohms even after cleaning and motoring for many hours) so I need to source some very low resistance brushes. I can't find any brushes for sale that have a specified resistance. Should I be using copper rather than carbon? Any advice?

I have 0.0 resistance between the studs and the copper braid attached to the brushes.

Www.solocoastalsailing.co.uk

 

[pvb]

If all else fails, you could try an MG Duff "Electro Eliminator" - http://mgduff.co.uk/yachts-and-powerboats/products/electro-eliminators/ee1

 

[jiris]

I believe any brushes made for 12 V starter motor will do the trick neatly. Just watch out: having a high copper content they are very soft and wear fast.

 

[William_H]

I think OP is excessively worried about resistance. In a circuit concerned with electrolysis a high resistance does not matter. Of course a high resistance in many places might indicate a tendency to corrosion and rapidly turn to no connection but I think the brushes you have showing 10 ohms will be fine provided they stay at 10 ohms. ol'will

 

[Plum]

I think OP is excessively worried about resistance. In a circuit concerned with electrolysis a high resistance does not matter. Of course a high resistance in many places might indicate a tendency to corrosion and rapidly turn to no connection but I think the brushes you have showing 10 ohms will be fine provided they stay at 10 ohms. ol'will

That's interesting. Advice from other sources is to ensure less than 1 ohm between anode and item protected.

Www.solocoastalsailing.co.uk

 

[Plum]

If all else fails, you could try an MG Duff "Electro Eliminator" - http://mgduff.co.uk/yachts-and-powerboats/products/electro-eliminators/ee1

I was attempting to apply the PBO philosophy as they are over £70 but you prompted me to investigate and I found an unused one on ebay for £34 so thank you!

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