Abate Holding Your Breath...Thompson's Design

According to one reference, some models of wheel hub generators had problems with water entering the enclosure when the bike was moved from a warm garage to the cold outdoors and ridden in the rain. The temperature differential created a relative vacuum in the hub which sucked water in through the seals which were not designed with that in mind. Newer models apparently corrected the problem. But if water does enter the assembly it tends to corrode the rotor and stator poles which have very small clearance and cause them to bind.

Paul

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The old SA 'dynamos' have no seals of any kind but water can easily run out, with the combined generator/gear hub there's a tendency for the generator internals to get well oiled via the bearing.

I've never seen one corrode.

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

The type used on motorcycles has a "claw" type poles arrangement, but instead of them being fixed to a core in the middle with the field winding on - the claw fingers are brazed together with non-magnetic spacers.

The field winding is static and magnetically coupled to the claw poles coaxially. The inner claw is integral with the taper that fits on the end of the crankshaft and also extends to form the center pole.

The outer claw poles are simply a brazed on ring of poles that form the outer of the coaxial poles.

That's NOT the Magdowski model. I suggest you re-read the Magdowski paper... it has some shunt losses.

I didn't know that [snicker]

Maybe Ian should build your solution and report back ?>:-}

I'm thinking of buying a recent vintage hub just for yucks and characterizing it myself. Quoting a line from "The Sting", "I already know how to get drunk" :-) ...Jim Thompson

Marcel's graphs, and others I've seen, are consistent with the simple model of a voltage source (voltage tracking frequency) in series with a resistance and an inductance. After all, that's what's actually inside the hub.

If the pole pieces have funny shapes, the waveforms can be non-sinusoidal. In as much as the designs usually attempt to deliver constant current into a load, waveform distortion is equivalent to higher frequency, which only helps.

Loading will make the current waveform more sinusoidal than the open-circuit voltage waveform.

If one desires to rectify and filter, and then switch down, the lightly-loaded capacitor voltage could be very high if the distorted waveform has a high crest factor... you could get higher DC than the RMS voltage suggests.

John

Hey, I suggested that, but didn't think it would work! I figured there would be too much reluctance in the field path, but that geometry seems to fix that.

John

Build it, Ian, Larkin says it'll work O:-) ...Jim Thompson

nope, PM rotor. fixed winding on the stator, no moving contacts. lamps don't care if it's AC.