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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 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 |
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