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  #131  
Old March 15th 17, 06:15 AM posted to rec.bicycles.tech
Jeff Liebermann
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Posts: 4,018
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On Wed, 15 Mar 2017 15:14:56 +1100, James
wrote:

On 15/03/17 13:43, Jeff Liebermann wrote:
On Tue, 14 Mar 2017 07:54:26 -0700, Joerg
wrote:

On 2017-03-13 20:00, Jeff Liebermann wrote:
On Mon, 13 Mar 2017 12:38:07 -0700, Joerg
wrote:
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.


Well, yeah, they just wanted to see where the limit is. I guess the
enameled copper wire inside would smoke out if you kept that speed for long.


Only the resistive part dissipates power in the wi
P = I^2 * R = 0.5^2 * 2 = 0.5 watts
So, it won't be the wire that gets hot. However, the cores in
saturation are going to get warm. Offhand, I don't know how to
calculate how hot.


Do you mean eddy currents in the core?


Nope. I meant hysteresis losses. Eddy currents do contribute to
losses by "bucking" the build up and collapse of the magnetic field,
but most of the heat is produced by hysteresis losses:
https://www.quora.com/What-is-hysteresis-loss-Where-does-the-loss-actually-occur
See an induction heater or stove for an extreme case of heat being
generated by eddy and hysteresis currents:
https://en.wikipedia.org/wiki/Induction_heating



--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
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  #132  
Old March 15th 17, 06:45 AM posted to rec.bicycles.tech
James[_8_]
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Posts: 6,153
Default More About Lights

On 15/03/17 16:15, Jeff Liebermann wrote:
On Wed, 15 Mar 2017 15:14:56 +1100, James
wrote:

On 15/03/17 13:43, Jeff Liebermann wrote:
On Tue, 14 Mar 2017 07:54:26 -0700, Joerg
wrote:

On 2017-03-13 20:00, Jeff Liebermann wrote:
On Mon, 13 Mar 2017 12:38:07 -0700, Joerg
wrote:
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.

Well, yeah, they just wanted to see where the limit is. I guess the
enameled copper wire inside would smoke out if you kept that speed for long.

Only the resistive part dissipates power in the wi
P = I^2 * R = 0.5^2 * 2 = 0.5 watts
So, it won't be the wire that gets hot. However, the cores in
saturation are going to get warm. Offhand, I don't know how to
calculate how hot.


Do you mean eddy currents in the core?


Nope. I meant hysteresis losses. Eddy currents do contribute to
losses by "bucking" the build up and collapse of the magnetic field,
but most of the heat is produced by hysteresis losses:
https://www.quora.com/What-is-hysteresis-loss-Where-does-the-loss-actually-occur
See an induction heater or stove for an extreme case of heat being
generated by eddy and hysteresis currents:
https://en.wikipedia.org/wiki/Induction_heating




Hysteresis losses are different from saturation. Saturation shouldn't
occur if the core has been adequately designed to accommodate all the
permanent magnet flux & MMF.

--
JS
  #133  
Old March 15th 17, 08:07 AM posted to rec.bicycles.tech
Jeff Liebermann
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Posts: 4,018
Default More About Lights

On Wed, 15 Mar 2017 16:45:57 +1100, James
wrote:

On 15/03/17 16:15, Jeff Liebermann wrote:
On Wed, 15 Mar 2017 15:14:56 +1100, James
wrote:

On 15/03/17 13:43, Jeff Liebermann wrote:
On Tue, 14 Mar 2017 07:54:26 -0700, Joerg
wrote:

On 2017-03-13 20:00, Jeff Liebermann wrote:
On Mon, 13 Mar 2017 12:38:07 -0700, Joerg
wrote:
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.

Well, yeah, they just wanted to see where the limit is. I guess the
enameled copper wire inside would smoke out if you kept that speed for long.

Only the resistive part dissipates power in the wi
P = I^2 * R = 0.5^2 * 2 = 0.5 watts
So, it won't be the wire that gets hot. However, the cores in
saturation are going to get warm. Offhand, I don't know how to
calculate how hot.


Do you mean eddy currents in the core?


Nope. I meant hysteresis losses. Eddy currents do contribute to
losses by "bucking" the build up and collapse of the magnetic field,
but most of the heat is produced by hysteresis losses:
https://www.quora.com/What-is-hysteresis-loss-Where-does-the-loss-actually-occur
See an induction heater or stove for an extreme case of heat being
generated by eddy and hysteresis currents:
https://en.wikipedia.org/wiki/Induction_heating


Hysteresis losses are different from saturation. Saturation shouldn't
occur if the core has been adequately designed to accommodate all the
permanent magnet flux & MMF.


Most (not all) dynamos are designed to provide some form of
self-regulation. This made sense back in the days when the load was
just a simple 6v incandescent light bulb. It wouldn't do to have
Kamakazi downhill speeders producing enough revolutions to have the
dynamo belch 12VAC and burn out the bulb.

Fast forward to today, and we no longer use incandescent lights on
dynamos. Most (not all) LED lamps have built in regulators and really
don't need to have the dynamo perform any additional regulation.
However, the industry is conservative, and things change very slowly.
Kinda like the automobile industry requiring 25 years to get rid of
the buggy whip socket. So, we still have dynamos that intentionally
designed to NOT produce a linear increase in output for high RPMs.

Fortunately, the problem is not universal.
http://www.pilom.com/BicycleElectronics/HubDynamo.htm
Notice the 2nd graph of Hub vs Bottle Power. The Shimano DH-3D71 hub
dynamo produces a linear increase in output power with no saturation
visible. (However, at my cruising speed of 15 km/hr, it only produces
4 watts and is therefore only a slight improvement over the common
bottle dynamo).

Hystersis loss is core saturation loss. What happens is that at some
point, adding additional current to the coil and core does produce an
increase in the magnetic field. Magnetic domains will change
direction when current is applied, but are not terribly thrilled with
the idea. Their resistance to this change in current and direction is
hysteresis loss. This additional current (and power) has to go
somewhere since it can't be used to build a changing magnetic field.
So, it gets converted into heat.

Eddy current losses are the result of changes in magnetic field, not
changes in applied current. When the magnetic field finally decides
to change direction and AFTER hysteresis losses are produced, the
resultant magnetic field breaks up into small magnetic loops or eddys.
Adjacent eddys fight each other resulting in repulsion. The energy
required to overcome this repulsive force are the eddy current losses.

As I understand it, the favored core material is some form of mu-metal
or permalloy which saturate nicely at low currents:
https://en.wikipedia.org/wiki/Mu-metal
I'm not sure this is the material as some description suggest that
it's "cold rolled dynamo silicon sheet steel" or the same stuff used
in the E/I laminations of a common AC power transformer.

It's after midnight. I give up for tonite.









--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
  #134  
Old March 15th 17, 12:47 PM posted to rec.bicycles.tech
Sir Ridesalot
external usenet poster
 
Posts: 5,270
Default More About Lights

On Wednesday, March 15, 2017 at 3:07:41 AM UTC-4, Jeff Liebermann wrote:
On Wed, 15 Mar 2017 16:45:57 +1100, James
wrote:

On 15/03/17 16:15, Jeff Liebermann wrote:
On Wed, 15 Mar 2017 15:14:56 +1100, James
wrote:

On 15/03/17 13:43, Jeff Liebermann wrote:
On Tue, 14 Mar 2017 07:54:26 -0700, Joerg
wrote:

On 2017-03-13 20:00, Jeff Liebermann wrote:
On Mon, 13 Mar 2017 12:38:07 -0700, Joerg
wrote:
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.

Well, yeah, they just wanted to see where the limit is. I guess the
enameled copper wire inside would smoke out if you kept that speed for long.

Only the resistive part dissipates power in the wi
P = I^2 * R = 0.5^2 * 2 = 0.5 watts
So, it won't be the wire that gets hot. However, the cores in
saturation are going to get warm. Offhand, I don't know how to
calculate how hot.

Do you mean eddy currents in the core?

Nope. I meant hysteresis losses. Eddy currents do contribute to
losses by "bucking" the build up and collapse of the magnetic field,
but most of the heat is produced by hysteresis losses:
https://www.quora.com/What-is-hysteresis-loss-Where-does-the-loss-actually-occur
See an induction heater or stove for an extreme case of heat being
generated by eddy and hysteresis currents:
https://en.wikipedia.org/wiki/Induction_heating


Hysteresis losses are different from saturation. Saturation shouldn't
occur if the core has been adequately designed to accommodate all the
permanent magnet flux & MMF.


Most (not all) dynamos are designed to provide some form of
self-regulation. This made sense back in the days when the load was
just a simple 6v incandescent light bulb. It wouldn't do to have
Kamakazi downhill speeders producing enough revolutions to have the
dynamo belch 12VAC and burn out the bulb.

Fast forward to today, and we no longer use incandescent lights on
dynamos. Most (not all) LED lamps have built in regulators and really
don't need to have the dynamo perform any additional regulation.
However, the industry is conservative, and things change very slowly.
Kinda like the automobile industry requiring 25 years to get rid of
the buggy whip socket. So, we still have dynamos that intentionally
designed to NOT produce a linear increase in output for high RPMs.

Fortunately, the problem is not universal.
http://www.pilom.com/BicycleElectronics/HubDynamo.htm
Notice the 2nd graph of Hub vs Bottle Power. The Shimano DH-3D71 hub
dynamo produces a linear increase in output power with no saturation
visible. (However, at my cruising speed of 15 km/hr, it only produces
4 watts and is therefore only a slight improvement over the common
bottle dynamo).

Snipped

--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558


I remember burning out bulbs with my bottle dynamo if I rode really fast. I also remember the slipping problems when the wheels were wet even when I used the rubber boot sold to go on the bottle dynamo roller. Hub dynamos today really seem to fall down at slow speeds.

Cheers
  #135  
Old March 15th 17, 03:53 PM posted to rec.bicycles.tech
David Scheidt
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Posts: 1,346
Default More About Lights

Sir Ridesalot wrote:

:I remember burning out bulbs with my bottle dynamo if I rode really
:fast. I also remember the slipping problems when the wheels were wet even
:when I used the rubber boot sold to go on the bottle dynamo roller. Hub
:dynamos today really seem to fall down at slow speeds.

Mine work fine from walking speeds. They produce more light at higher
speeds, but at slow speeds you don't need it, because you're not
moving fast.


--
sig 85
  #136  
Old March 15th 17, 05:45 PM posted to rec.bicycles.tech
JBeattie
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Posts: 5,870
Default More About Lights

On Wednesday, March 15, 2017 at 7:53:52 AM UTC-7, David Scheidt wrote:
Sir Ridesalot wrote:

:I remember burning out bulbs with my bottle dynamo if I rode really
:fast. I also remember the slipping problems when the wheels were wet even
:when I used the rubber boot sold to go on the bottle dynamo roller. Hub
:dynamos today really seem to fall down at slow speeds.

Mine work fine from walking speeds. They produce more light at higher
speeds, but at slow speeds you don't need it, because you're not
moving fast.


I sometimes need light most at slow speeds, when I'm creeping up hills and trying not to fall into giant pot holes.

-- Jay Beattie.
  #137  
Old March 15th 17, 06:20 PM posted to rec.bicycles.tech
Doug Landau
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Posts: 1,424
Default More About Lights

On Wednesday, March 15, 2017 at 9:45:34 AM UTC-7, jbeattie wrote:
On Wednesday, March 15, 2017 at 7:53:52 AM UTC-7, David Scheidt wrote:
Sir Ridesalot wrote:

:I remember burning out bulbs with my bottle dynamo if I rode really
:fast. I also remember the slipping problems when the wheels were wet even
:when I used the rubber boot sold to go on the bottle dynamo roller. Hub
:dynamos today really seem to fall down at slow speeds.

Mine work fine from walking speeds. They produce more light at higher
speeds, but at slow speeds you don't need it, because you're not
moving fast.


I sometimes need light most at slow speeds, when I'm creeping up hills and trying not to fall into giant pot holes.

-- Jay Beattie.


Where are you on Strava
  #138  
Old March 15th 17, 06:28 PM posted to rec.bicycles.tech
Sir Ridesalot
external usenet poster
 
Posts: 5,270
Default More About Lights

On Wednesday, March 15, 2017 at 12:45:34 PM UTC-4, jbeattie wrote:
On Wednesday, March 15, 2017 at 7:53:52 AM UTC-7, David Scheidt wrote:
Sir Ridesalot wrote:

:I remember burning out bulbs with my bottle dynamo if I rode really
:fast. I also remember the slipping problems when the wheels were wet even
:when I used the rubber boot sold to go on the bottle dynamo roller. Hub
:dynamos today really seem to fall down at slow speeds.

Mine work fine from walking speeds. They produce more light at higher
speeds, but at slow speeds you don't need it, because you're not
moving fast.


I sometimes need light most at slow speeds, when I'm creeping up hills and trying not to fall into giant pot holes.

-- Jay Beattie.


Ditto. Or ride off the edge of the trail and down the side into the river.

Chers
  #139  
Old March 15th 17, 06:36 PM posted to rec.bicycles.tech
Doug Landau
external usenet poster
 
Posts: 1,424
Default More About Lights

On Wednesday, March 15, 2017 at 10:28:52 AM UTC-7, Sir Ridesalot wrote:
On Wednesday, March 15, 2017 at 12:45:34 PM UTC-4, jbeattie wrote:
On Wednesday, March 15, 2017 at 7:53:52 AM UTC-7, David Scheidt wrote:
Sir Ridesalot wrote:

:I remember burning out bulbs with my bottle dynamo if I rode really
:fast. I also remember the slipping problems when the wheels were wet even
:when I used the rubber boot sold to go on the bottle dynamo roller. Hub
:dynamos today really seem to fall down at slow speeds.

Mine work fine from walking speeds. They produce more light at higher
speeds, but at slow speeds you don't need it, because you're not
moving fast.


I sometimes need light most at slow speeds, when I'm creeping up hills and trying not to fall into giant pot holes.

-- Jay Beattie.


Ditto. Or ride off the edge of the trail and down the side into the river.


You mean like this, except at night?
https://www.youtube.com/watch?v=Fmb6OvejAC0

  #140  
Old March 15th 17, 06:45 PM posted to rec.bicycles.tech
Frank Krygowski[_4_]
external usenet poster
 
Posts: 10,538
Default More About Lights

On 3/14/2017 9:35 PM, Jeff Liebermann wrote:
On Tue, 14 Mar 2017 10:46:19 -0400, Frank Krygowski
wrote:

On 3/13/2017 11:00 PM, Jeff Liebermann wrote:
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?


Ideally, overall efficiency of the lighting system and verification of
the simulation and dynamo model.

Mechanical power (watts) in, as simulated by an electric motor vs
optical power out, measured in lumens or lux. The main exercise would
be calibrating the major components so that the measurements would be
accurate and meaningful. It would be something like the
Friction-Facts chain and lubricant test fixture in:
http://www.friction-facts.com/equipment-overview


OK. You may be aware of Andreas Oehler's approach, but in case you're
not, what he built was essentially a big flywheel that could be used to
stand in for a bike wheel and drive a bike dynamo of any design. He
used a data acquisition system to record dyno electrical output as well
as angular deceleration of the flywheel. That allowed computing
retarding torque resulting from the dynamo, thus (coupled with angular
velocity) the power consumption.

I used a much simpler method. I mounted dynamos in a frame that pivoted
on the dyno's rotational axis, and used a lever arm of known length
pressing on a scale. Force on the scale gave torque, and known rpm
enabled calculation of power. But my method didn't include losses from
the friction drive. Andreas's method does.

Output power was measured electrically, in Watts. If you try to measure
lumens, you'll have a much harder job, and the efficiency (lumens/Watt)
of the LED will enter into things. I'm not sure you want that or not.
And lux isn't a power measurement, of course, so you can't get a true
efficiency that way.

--
- Frank Krygowski
 




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