-=> MIKE ROSS wrote to WAYNE CHIRNSIDE <=-

 MR> "WAYNE CHIRNSIDE" bravely wrote to "MIKE ROSS"
(01 Sep 03  21:14:00)
 MR>  --- on the heady topic of "Re: Vehicle LED's"

 WC> When I was a kid my bicycle had a generator that was part of the
 WC> hub. Back in 1967 a 3 speed with this arrangement cost
 WC> somewhere around 100 dollars.
 WC> Far better than those little things that rub the tire.

 MR> How was the power taken out, insulated slip ring?

Yes.

 MR> I'm guessing it
 MR> required a lot of poles to generate any kind of power? Since the
 MR> rotational speed of a bicycle wheel is much slower than its radial
 MR> velocity, it must have been dim at slow speed, no?

 Dimmer but effective at all but a crawl.

 MR> Consider that 1mph is about 1.5ft/sec and a wheel periphery measures
 MR> about 7 ft, then 1 revolution/sec = 4.75mph, so 20mph is only about 4.2
 MR> rps or 252 rpm. A 60 hz generator needs turn at 3600rpm! Luckily with
 MR> the rim generator, the gear ratio is about 35:1 so in priciple at 20mph
 MR> it is generating at about 150Hz.

This generator was perhaps 5 - 6 inches in diameter.

 MR> At 252 rpm the hub generator would require the equivalent of the gear
 MR> or 35 poles. OTOH maybe there was a gearing system inside? Then it must
 MR> have used some really good metalurgy in the gears?

I don't think any gears were involved.
The thing was silent and pretty much undetectable in operation.
Switching the light off  you could feel a slight difference
in the load you were pushing but not a great deal.

 MR> Was there a way to
 MR> disengage the generator when not needed?

Nope and in my opinion it was not needed.
 
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