On 14/08/2016 13:53, The Natural Philosopher wrote:
On 14/08/16 09:15, charles wrote:
In article , harry
wrote:
On Saturday, 13 August 2016 10:25:36 UTC+1, Fredxxx wrote:
On 13/08/2016 06:55, harry wrote:
On Friday, 12 August 2016 10:24:48 UTC+1, Dave Plowman (News) wrote:
In article ,
Clive George wrote:
Yup. Although the bottle type tended to give a brighter light in
the days when I cycled. But a friction drive is horribly
inefficient.

Sturmey hub vs other bottle? Yes, the sturmey hub wasn't very
powerful - the wheel turns quite slowly, so the magnets required
weren't available (or at least not at a sane price) back then. The
modern hub dynamos give rather more.

That certainly makes sense. Modern low voltage DC motors have also
been improved out of all recognition by better magnets.

There is no such thing as a DC motor. I've told you before.

So what type of voltage do you apply to a "low voltage DC motor"?

It runs on AC. It needs a mechanical inverter to make it run.
https://en.wikipedia.org/wiki/Commutator_(electric)

sitting in front of me on my desk is a small fan which runs directly form
the 5v DC USB supply. There is no mechanical inverter.

Then there is an electronic one

The synchronous application of voltage to a motor winding is normally
called commutation, and the definition of "inverter" it is the means of
converting DC to AC.

If I should apply an AC current from Harry's inverter to a DC motor,
with a permanent magnet providing the field, I'm sure all you would hear
is a hum.

Nevertheless, I would still apply DC to a DC motor.