i went to the effort of stripping a magneto and rewinding it to pull 32 volts, unloaded.
it drops seriously under load...(18 watts!) down to about 10 volts, max...current unknown. it sure wasnt lighting up to full brightness!
the voltage is a function of turns of wire, rpm, magnetic strength, and load... theres only so many watts you can suck out.
(basically...a short circuit is no volts, full current...open circuit is no amps, full voltage. make sense?)
i ordered a brushless motor of 80kv with the intention of setting it up to be both the chain tensioner and dynamo.
why 80kv? because then it will produce (approximately) one volt at 80 rpm. the lower the kv rating, the slower it has to spin to produce a given voltage. a 3500kv would be useless in this application (chain tensioner would only spin at 530 rpm or so, max...making for about 30 volts...unloaded.).
it hasnt arrived yet, and now the laws changing where i live so motorised bikes will be illegal in two weeks(october 1), so... i guess ill be using the brushless motor for some totally unrelated project when it does arrive.
ive only ever had one stock magneto with the white wire that got an LED spotlight to work. those mr16 4w LED ones. 4w would have worked fine on my rewound magneto, i guess... but 18w was just a bit excessive!
gunna be a good spottie on my new motorbike but
oh. run the "old school light" but give it an LED bulb instead of the standard, dim lil incandescent... use a yellow one if the colour is a concern
(have two reverse wired as the dynamo will output AC, rather than DC)
or green, to match the paint job...(you will paint it green, right?
)