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On 06/03/17 10:22, Barry Beams wrote:


Burn time: What if you had five or ten hours battery time at your
generator's brightness? My Oculus gives at least that much
brightness, and a quickly field replaceable battery so you can put in
a fresh battery. Other rechargeables leave you out of light and out
of luck when the battery drains. Oculus also comes with a spare
battery included.


What if I don't want to play with batteries?


--
JS

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On 06/03/17 12:26, Jeff Liebermann wrote:

Well, let's do some arithmetic. If your dynamo is rated at 3 watts,
and your lighting is rated at 70 lumens/watt, then the most you can
perhaps deliver is 210 lumens. 6 watts will get perhaps 420 lumens.
Usually, it's less as the losses accumulate. Rectification losses,
optical losses, heat degradation, and connector losses all conspire to
produce lower output.

We know that a 3W dynamo is quite capable of delivering more power than
3W, once the bicycle speed increases. 6W from a 3W dynamo is quite
achievable, and the retardation torque drops off as speed increases too.

--
JS

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Assumptions or measured ?

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On Mon, 6 Mar 2017 17:04:13 +1100, James
wrote:

On 06/03/17 12:26, Jeff Liebermann wrote:

Well, let's do some arithmetic. If your dynamo is rated at 3 watts,
and your lighting is rated at 70 lumens/watt, then the most you can
perhaps deliver is 210 lumens. 6 watts will get perhaps 420 lumens.
Usually, it's less as the losses accumulate. Rectification losses,
optical losses, heat degradation, and connector losses all conspire to
produce lower output.

We know that a 3W dynamo is quite capable of delivering more power than
3W, once the bicycle speed increases. 6W from a 3W dynamo is quite
achievable, and the retardation torque drops off as speed increases too.

Maybe:
http://www.myra-simon.com/bike/dynotest.html
See "Electrical Output" graph.

Kinda looks like all of them will sorta deliver 2.5 watts before the
core saturates (to provide some level of voltage regulation). Further
down the page is a "Low Speed Power" graph, which shows that most can
produce 2.0-2.5 watts at 10km/hr. One could assume that the dynamo
will deliver 4.0 watts, but that would require buying one of the few
better (hub) dynamos listed, and riding at 25-30km/hr (15-19mph).

If I were designing or sizing a lighting system suitable for my slow
style of "cruising", I would use the worst case 10km/hr (6mph) and 2.0
watt figures.


--
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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On 3/6/2017 11:22 AM, Jeff Liebermann wrote:
On Mon, 6 Mar 2017 17:04:13 +1100, James
wrote:

On 06/03/17 12:26, Jeff Liebermann wrote:

Well, let's do some arithmetic. If your dynamo is rated at 3 watts,
and your lighting is rated at 70 lumens/watt, then the most you can
perhaps deliver is 210 lumens. 6 watts will get perhaps 420 lumens.
Usually, it's less as the losses accumulate. Rectification losses,
optical losses, heat degradation, and connector losses all conspire to
produce lower output.

We know that a 3W dynamo is quite capable of delivering more power than
3W, once the bicycle speed increases. 6W from a 3W dynamo is quite
achievable, and the retardation torque drops off as speed increases too.

Maybe:
http://www.myra-simon.com/bike/dynotest.html
See "Electrical Output" graph.

Kinda looks like all of them will sorta deliver 2.5 watts before the
core saturates (to provide some level of voltage regulation). Further
down the page is a "Low Speed Power" graph, which shows that most can
produce 2.0-2.5 watts at 10km/hr. One could assume that the dynamo
will deliver 4.0 watts, but that would require buying one of the few
better (hub) dynamos listed, and riding at 25-30km/hr (15-19mph).

If I were designing or sizing a lighting system suitable for my slow
style of "cruising", I would use the worst case 10km/hr (6mph) and 2.0
watt figures.



I don't know about currents but 6V 4W bulbs for standard
dynamo systems have been around for twenty years and some
customers like them. I don't know if the dynamo drag is
noticeably greater.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

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On Sunday, March 5, 2017 at 5:26:18 PM UTC-8, Jeff Liebermann wrote:
On Sun, 5 Mar 2017 16:03:30 -0800 (PST), wrote:

Thanks Jeff. These however all appear to be battery powered
lights. We were sort of looking for lights that operated on
the hub dynamo of 6V 3W or the Globe dynamo of 12V 6W or
four times the power.

Sorry, I thought you were still open to looking at battery powered
lights. Here's what I fished out of my bookmark dumpster. No reviews
and few tests, but some interesting dynamo graphs and numbers:
http://www.myra-simon.com/bike/dynotest.html
http://pilom.com/BicycleElectronics/DynamoCircuits.htm
http://www.eeweb.com/blog/extreme_circuits/power-mosfet-bridge-rectifier

This one is well worth reading (or skimming) and has quite a few test
results:
http://swhs.home.xs4all.nl/fiets/tests/verlichting/index_en.html

This is why the hub generator has so little drag.

Well, let's do some arithmetic. If your dynamo is rated at 3 watts,
and your lighting is rated at 70 lumens/watt, then the most you can
perhaps deliver is 210 lumens. 6 watts will get perhaps 420 lumens.
Usually, it's less as the losses accumulate. Rectification losses,
optical losses, heat degradation, and connector losses all conspire to
produce lower output.

You might find it useful to know how bright you want your light. For
that, you'll need a Lux meter. I have a Lutron LX-102 which works
nicely, and two junk meters I bought on eBay for sanity checks:
http://www.ebay.com/sch/i.html?_nkw=lux+meter
Get one that has a wide range. Lowest on mine is 1000 lux, and
highest range is 50,000 lux.

Find a dark night and an accomplice to operate the meter and send them
down the road to the farthest distance that you might want to
illuminate with your headlight. Use a headlight or flashlight to
light up that area. Have your accompli's take a reading. It will
probably be zero. Now, cut the distance in half and take a
measurement. It will be 2x as bright (lux) at half the distance or 4x
as bright at 1/4th the distance. Adjust the brightness for what it
would have been if the light meter was sufficiently sensitive.

Converting the brightness (lux) to luminous flux (lumens) requires
that you know the distance to the accomplice, and the illumination
angle. (1 lux = 1 lumen/square-meter)

The form below makes a mess of bad assumptions but is good enough for
a rough approximation:
https://www.ledrise.com/shop_content.php?coID=19
Once you know how many lumens you think you need, and have adjusted
for overly ambitious expectations, you can determine which lighting
technology is suitable.

Lets say you want to see 8 meters ahead and 20 degrees to each side
(or 40 degree conical beamwidth) at 20 lux, which is rather dim.
Plugging into the web page above, I get 485 lumens needed. You won't
be able to do that with a 3w dynamo, but might squeeze by with a 6w
and an oval shaped beam.


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

As a very occasional night rider I am interested in battery powered lights but I think that I was attempting to give a thought to a commuter that would use his light a great deal.

I notice that a large number of the people in our group have flashing red rear lights and it isn't long before these batteries run down enough that the taillight even blinking is almost entirely unnoticeable. So I don't have much respect for battery power for a great deal of use.

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On Monday, March 6, 2017 at 1:47:41 PM UTC-5, wrote:
On Sunday, March 5, 2017 at 5:26:18 PM UTC-8, Jeff Liebermann wrote:
Snipped
I notice that a large number of the people in our group have flashing red rear lights and it isn't long before these batteries run down enough that the taillight even blinking is almost entirely unnoticeable. So I don't have much respect for battery power for a great deal of use.

I have a rear red light I bought from MEC (Mountain Equipment Co-op)along with a front light that came with the five AAA batteries (2= rear, 3 = front)that were less than $15.00 for the pair and that rear light on flashing mode lasts for months and I do a LOT of night time riding.

Cheers

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On Sunday, March 5, 2017 at 9:57:44 PM UTC-8, James wrote:
On 06/03/17 10:22, Barry Beams wrote:


Burn time: What if you had five or ten hours battery time at your
generator's brightness? My Oculus gives at least that much
brightness, and a quickly field replaceable battery so you can put in
a fresh battery. Other rechargeables leave you out of light and out
of luck when the battery drains. Oculus also comes with a spare
battery included.


What if I don't want to play with batteries?

Then you're done with the battery light discussion and may move on to helmets.

-- Jay Beattie.

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On Monday, March 6, 2017 at 2:15:56 PM UTC-5, jbeattie wrote:
On Sunday, March 5, 2017 at 9:57:44 PM UTC-8, James wrote:
On 06/03/17 10:22, Barry Beams wrote:


Burn time: What if you had five or ten hours battery time at your
generator's brightness? My Oculus gives at least that much
brightness, and a quickly field replaceable battery so you can put in
a fresh battery. Other rechargeables leave you out of light and out
of luck when the battery drains. Oculus also comes with a spare
battery included.


What if I don't want to play with batteries?

Then you're done with the battery light discussion and may move on to helmets.

-- Jay Beattie.

or carbon frames versus steel frames.

Cheers

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On Monday, March 6, 2017 at 1:37:23 PM UTC-5, AMuzi wrote:
On 3/6/2017 11:22 AM, Jeff Liebermann wrote:
On Mon, 6 Mar 2017 17:04:13 +1100, James
wrote:

On 06/03/17 12:26, Jeff Liebermann wrote:

Well, let's do some arithmetic. If your dynamo is rated at 3 watts,
and your lighting is rated at 70 lumens/watt, then the most you can
perhaps deliver is 210 lumens. 6 watts will get perhaps 420 lumens.
Usually, it's less as the losses accumulate. Rectification losses,
optical losses, heat degradation, and connector losses all conspire to
produce lower output.

We know that a 3W dynamo is quite capable of delivering more power than
3W, once the bicycle speed increases. 6W from a 3W dynamo is quite
achievable, and the retardation torque drops off as speed increases too.

Maybe:
http://www.myra-simon.com/bike/dynotest.html
See "Electrical Output" graph.

Kinda looks like all of them will sorta deliver 2.5 watts before the
core saturates (to provide some level of voltage regulation). Further
down the page is a "Low Speed Power" graph, which shows that most can
produce 2.0-2.5 watts at 10km/hr. One could assume that the dynamo
will deliver 4.0 watts, but that would require buying one of the few
better (hub) dynamos listed, and riding at 25-30km/hr (15-19mph).

If I were designing or sizing a lighting system suitable for my slow
style of "cruising", I would use the worst case 10km/hr (6mph) and 2.0
watt figures.



I don't know about currents but 6V 4W bulbs for standard
dynamo systems have been around for twenty years and some
customers like them. I don't know if the dynamo drag is
noticeably greater.

6V 4W? I'm aware of 6V 3W bulbs, which are (or were) used mostly with bottle
dyno systems when driving a headlamp but no taillamp. They were an alternative
to 2.4 W in front and 0.6W in back.

I'm not aware of any common use of 6V 4W bulbs.

- Frank Krygowski