On 3/13/2017 11:00 PM, Jeff Liebermann wrote:
On Mon, 13 Mar 2017 12:38:07 -0700, Joerg
wrote:

However, in your link they say, quote "Hubs don't go into saturation
easily so that at moderate to high speed, they develop a higher voltage
than bottle dynamos, assuming they are not loaded with the typical 6 V /
3 W lights. To see whats possible, I ran a Shimano DH-3D71 at 136 km/h
in a test stand. The voltage generated was sufficient to ignite a
fluorescent tube and subsequently drive it at 55 V and 500 mA".

55V at 500mA. This is encouraging.

That's 27.5 watts out of a 3 watt dynamo. I was impressed, until I
converted 136 km/hr and found that it was 84.5 mph. With a rocket
assisted bicycle, I might be able to do that.

The author is mostly correct about hubs not going into saturation as
easily and bottle dynamos. However, they do go into staturation, just
at a higher RPM.

I could make 12V filament lighting glow like halogen at high speed.

I don't know anyone that regularly rides at 136 km/hr (84.5 mph). My
average riding speed is probably a leisurely 15 km/hr (9 mph).

It's best to try that out on the bench, using a rechargeable drill and such.

I was thinking of building a benchtop dynamometer sized for bicycle
lighting. I don't have the equipment to calibrate it so I could
measure overall efficiency, but certainly can make comparative
measurements of the input power(s) required to light an oversized load
or bulb. Basically, just a DC motor with a DC wattmeter on the power
leads.
http://www.ebay.com/itm/122373782338
(Yet another project that I'll never finish).

What are you intending to measure? Input power to a bike dynamo?



--
- Frank Krygowski