#151
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More About Lights
On 3/15/2017 2:57 PM, Frank Krygowski wrote:
On 3/15/2017 2:48 PM, Sir Ridesalot wrote: On Wednesday, March 15, 2017 at 2:08:49 PM UTC-4, Frank Krygowski wrote: On 3/14/2017 11:15 PM, Jeff Liebermann wrote: On Tue, 14 Mar 2017 12:09:27 -0400, Frank Krygowski wrote: But the point I was discussing was whether too brief or too dim standlights really kill or seriously injure _stationary_ bicyclists. I've never heard of such a case. I think it's yet another exaggerated danger. Bicycle lighting seems to be divided into "see where your going" and "be seen" parts. Standlights are in the "be seen" part. If so, then using a relatively narrow forward facing headlight is inadequate and a poor substitute for all around "be seen" type lighting. So far, no driver has tried to kill me while I'm stationary, but it's possible. To help prevent such a threat, I would need all around illumination because I don't know from what direction the driver might approach and I do NOT need to see where I'm going (because I'm not going anywhere). Some kind of flashing headband, flashing arm bands, or maybe downward facing flood lights to illuminate an area. Maybe an LED illuminated vest, which is now popular among highway workers: https://www.amazon.com/HIGH-VISIBILITY-VEST-COMPLIANT-REFLECTIVE/dp/B01L2US0EY https://www.amazon.com/SE-EP08L-Illuminated-Flashing-Feature/dp/B008WAE2XQ https://www.amazon.com/SE-EP07L-Flashing-Illuminated-Safety/dp/B004J663A2 I don't know which type of "be seen" lighting might be most effective, but any of the aformentioned would be better than a dim forward facing standlight. Thing is, nobody's demonstrated any need for so much stationary "be seen" light, beyond the usual "well, it _could_ happen" safety inflation mentality. We're facing the same mentality regarding our local forest preserve. Some people want to cut down every dead or dying tree within 100 feet of any trail because, well, it _could_ fall on somebody and kill them. Sheesh. -- - Frank Krygowski I remember the Soubitez (sp?) ads from the 1980s that showed a stopped bicycle without a front light at an intersection at night and another image of the Soubitez dynamo light with the standlight. The ad was about how much safer yuo were with the Soubitez dynamo because others could see the light whilst you were stopped or just starting up again. So this perceived need for a safety standlight on a dynamo powered light is nothing new. As I recall, that system failed in the marketplace. The idea might have existed in a few minds back then, but it wasn't common enough to be commercially successful. The same could be said of many present "safety" devices. You'd have gone broke trying to sell "walker safety vests" in the 1970s or 1980s. Ditto little hammers to let you break your car window if you were trapped inside. Or foam pads to put on the corner of every hard object your toddler might walk by. Or bathtub mats that say "HOT" when the water is, well, hot. But all those things have been sold recently. None anywhere near as lucrative as Pet Rocks (a product of similar utility but more trendy) Regarding Soubitez standlights of the 1980s, devastatingly unpopular. http://www.yellowjersey.org/photosfr...t/soustan1.jpg http://www.yellowjersey.org/photosfr...t/soustan2.jpg -- Andrew Muzi www.yellowjersey.org/ Open every day since 1 April, 1971 |
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#152
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More About Lights
On Wednesday, March 15, 2017 at 12:17:31 PM UTC-7, David Scheidt wrote:
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. I assure you the potholes in Chicago are as least as big as yours, and my lights are fine for finding them as slow as I can ride a bike upright. Perhaps your hub is defective. Perhaps I do have a defective hub. Unlike Chicago, though, I'm riding home up little goat roads that are between a 6-10 percent grade and that are really a collection of patch and broken pavement. http://tinyurl.com/zo6hq6e Scoll up the road. A lot of the patched sections are now holes after the snow storms. With wet pavement, it's hard to see the holes. Even when perfectly dry, it's not that great. -- Jay Beattie. |
#153
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More About Lights
On 15/03/17 18:07, 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). 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. You seem to be confusing current and magnetic flux. What is used to alter the characteristics is the inductance of the alternator coil. -- JS |
#154
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More About Lights
On 16/03/17 03:45, 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. You are an anomaly. At creeping speeds (less than 10km/h), I could see holes with a candle light. -- JS |
#155
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More About Lights
On 3/15/2017 4:45 PM, James wrote:
On 15/03/17 18:07, 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). 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. You seem to be confusing current and magnetic flux. What is used to alter the characteristics is the inductance of the alternator coil. That's how I've seen it explained, with appropriate equations. Since AC frequency increases with speed, the inductive reactance due to the coils increases with speed. That fights the tendency for more voltage from higher magnet-to-coil velocity. -- - Frank Krygowski |
#156
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More About Lights
On Wed, 15 Mar 2017 14:08:44 -0400, Frank Krygowski
wrote: On 3/14/2017 11:15 PM, Jeff Liebermann wrote: On Tue, 14 Mar 2017 12:09:27 -0400, Frank Krygowski wrote: But the point I was discussing was whether too brief or too dim standlights really kill or seriously injure _stationary_ bicyclists. I've never heard of such a case. I think it's yet another exaggerated danger. Bicycle lighting seems to be divided into "see where your going" and "be seen" parts. Standlights are in the "be seen" part. If so, then using a relatively narrow forward facing headlight is inadequate and a poor substitute for all around "be seen" type lighting. So far, no driver has tried to kill me while I'm stationary, but it's possible. To help prevent such a threat, I would need all around illumination because I don't know from what direction the driver might approach and I do NOT need to see where I'm going (because I'm not going anywhere). Some kind of flashing headband, flashing arm bands, or maybe downward facing flood lights to illuminate an area. Maybe an LED illuminated vest, which is now popular among highway workers: https://www.amazon.com/HIGH-VISIBILITY-VEST-COMPLIANT-REFLECTIVE/dp/B01L2US0EY https://www.amazon.com/SE-EP08L-Illuminated-Flashing-Feature/dp/B008WAE2XQ https://www.amazon.com/SE-EP07L-Flashing-Illuminated-Safety/dp/B004J663A2 I don't know which type of "be seen" lighting might be most effective, but any of the aformentioned would be better than a dim forward facing standlight. Thing is, nobody's demonstrated any need for so much stationary "be seen" light, beyond the usual "well, it _could_ happen" safety inflation mentality. We're facing the same mentality regarding our local forest preserve. Some people want to cut down every dead or dying tree within 100 feet of any trail because, well, it _could_ fall on somebody and kill them. Sheesh. I have worked in area where it is probable that no one has ever cut down a tree until we arrived and there never was a problem with dead or diseased trees falling down. One problem with cutting down trees that "could" fall down is that in a hurricane many perfectly healthy trees get blown down. Perhaps the cutting of all trees taller than the average human "could" lives. And, of course, banning the ownership of bicycles "could" save ~900 lives a year. -- Cheers, John B. |
#157
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More About Lights
On 3/15/2017 7:39 PM, John B. wrote:
On Wed, 15 Mar 2017 14:08:44 -0400, Frank Krygowski wrote: On 3/14/2017 11:15 PM, Jeff Liebermann wrote: On Tue, 14 Mar 2017 12:09:27 -0400, Frank Krygowski wrote: But the point I was discussing was whether too brief or too dim standlights really kill or seriously injure _stationary_ bicyclists. I've never heard of such a case. I think it's yet another exaggerated danger. Bicycle lighting seems to be divided into "see where your going" and "be seen" parts. Standlights are in the "be seen" part. If so, then using a relatively narrow forward facing headlight is inadequate and a poor substitute for all around "be seen" type lighting. So far, no driver has tried to kill me while I'm stationary, but it's possible. To help prevent such a threat, I would need all around illumination because I don't know from what direction the driver might approach and I do NOT need to see where I'm going (because I'm not going anywhere). Some kind of flashing headband, flashing arm bands, or maybe downward facing flood lights to illuminate an area. Maybe an LED illuminated vest, which is now popular among highway workers: https://www.amazon.com/HIGH-VISIBILITY-VEST-COMPLIANT-REFLECTIVE/dp/B01L2US0EY https://www.amazon.com/SE-EP08L-Illuminated-Flashing-Feature/dp/B008WAE2XQ https://www.amazon.com/SE-EP07L-Flashing-Illuminated-Safety/dp/B004J663A2 I don't know which type of "be seen" lighting might be most effective, but any of the aformentioned would be better than a dim forward facing standlight. Thing is, nobody's demonstrated any need for so much stationary "be seen" light, beyond the usual "well, it _could_ happen" safety inflation mentality. We're facing the same mentality regarding our local forest preserve. Some people want to cut down every dead or dying tree within 100 feet of any trail because, well, it _could_ fall on somebody and kill them. Sheesh. I have worked in area where it is probable that no one has ever cut down a tree until we arrived and there never was a problem with dead or diseased trees falling down. One problem with cutting down trees that "could" fall down is that in a hurricane many perfectly healthy trees get blown down. Perhaps the cutting of all trees taller than the average human "could" lives. And, of course, banning the ownership of bicycles "could" save ~900 lives a year. A bicycle ban? How's that 100-year worldwide Heroin ban working? -- Andrew Muzi www.yellowjersey.org/ Open every day since 1 April, 1971 |
#158
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More About Lights
On Wed, 15 Mar 2017 19:46:28 -0500, AMuzi wrote:
On 3/15/2017 7:39 PM, John B. wrote: On Wed, 15 Mar 2017 14:08:44 -0400, Frank Krygowski wrote: On 3/14/2017 11:15 PM, Jeff Liebermann wrote: On Tue, 14 Mar 2017 12:09:27 -0400, Frank Krygowski wrote: But the point I was discussing was whether too brief or too dim standlights really kill or seriously injure _stationary_ bicyclists. I've never heard of such a case. I think it's yet another exaggerated danger. Bicycle lighting seems to be divided into "see where your going" and "be seen" parts. Standlights are in the "be seen" part. If so, then using a relatively narrow forward facing headlight is inadequate and a poor substitute for all around "be seen" type lighting. So far, no driver has tried to kill me while I'm stationary, but it's possible. To help prevent such a threat, I would need all around illumination because I don't know from what direction the driver might approach and I do NOT need to see where I'm going (because I'm not going anywhere). Some kind of flashing headband, flashing arm bands, or maybe downward facing flood lights to illuminate an area. Maybe an LED illuminated vest, which is now popular among highway workers: https://www.amazon.com/HIGH-VISIBILITY-VEST-COMPLIANT-REFLECTIVE/dp/B01L2US0EY https://www.amazon.com/SE-EP08L-Illuminated-Flashing-Feature/dp/B008WAE2XQ https://www.amazon.com/SE-EP07L-Flashing-Illuminated-Safety/dp/B004J663A2 I don't know which type of "be seen" lighting might be most effective, but any of the aformentioned would be better than a dim forward facing standlight. Thing is, nobody's demonstrated any need for so much stationary "be seen" light, beyond the usual "well, it _could_ happen" safety inflation mentality. We're facing the same mentality regarding our local forest preserve. Some people want to cut down every dead or dying tree within 100 feet of any trail because, well, it _could_ fall on somebody and kill them. Sheesh. I have worked in area where it is probable that no one has ever cut down a tree until we arrived and there never was a problem with dead or diseased trees falling down. One problem with cutting down trees that "could" fall down is that in a hurricane many perfectly healthy trees get blown down. Perhaps the cutting of all trees taller than the average human "could" lives. And, of course, banning the ownership of bicycles "could" save ~900 lives a year. A bicycle ban? How's that 100-year worldwide Heroin ban working? Works great! Allows a considerable number of common ordinary people to make a "decent" living. True the demand does seems to be decreasing but the widening the demand for amphetamines, which can be made at home rather than waiting for a crop to ripen and getting all bound up with buying futures and warehousing raw materials. As an aside, do you think anyone wants the "war on drugs" to be won? Examples: U.S. Coastguard budget (numbers adjusted to 2013 dollars): 1950 - $1,439,312,446 2013 - $ 7,051,054,000 The total DEA budget is difficult to ascertain but: The total budget of the DEA from 1972 to 2014, according to the agency website, was $50.6 billion. The agency had 11,055 employees in 2014. For the year 2014 the average cost per arrest made was $97,325. An estimate by The Cato Institute, in 2010, states that the legalizing of drugs would save roughly $41.3 billion per year in government expenditure. Or to put it a different way, The War on Drugs is costing the U.S. an estimated $41.3 billion dollars a year. Do you think that anyone wants all that lovely lolly to disappear? -- Cheers, John B. |
#159
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More About Lights
On 3/15/2017 11:05 PM, John B. wrote:
On Wed, 15 Mar 2017 19:46:28 -0500, AMuzi wrote: On 3/15/2017 7:39 PM, John B. wrote: On Wed, 15 Mar 2017 14:08:44 -0400, Frank Krygowski wrote: On 3/14/2017 11:15 PM, Jeff Liebermann wrote: On Tue, 14 Mar 2017 12:09:27 -0400, Frank Krygowski wrote: But the point I was discussing was whether too brief or too dim standlights really kill or seriously injure _stationary_ bicyclists. I've never heard of such a case. I think it's yet another exaggerated danger. Bicycle lighting seems to be divided into "see where your going" and "be seen" parts. Standlights are in the "be seen" part. If so, then using a relatively narrow forward facing headlight is inadequate and a poor substitute for all around "be seen" type lighting. So far, no driver has tried to kill me while I'm stationary, but it's possible. To help prevent such a threat, I would need all around illumination because I don't know from what direction the driver might approach and I do NOT need to see where I'm going (because I'm not going anywhere). Some kind of flashing headband, flashing arm bands, or maybe downward facing flood lights to illuminate an area. Maybe an LED illuminated vest, which is now popular among highway workers: https://www.amazon.com/HIGH-VISIBILITY-VEST-COMPLIANT-REFLECTIVE/dp/B01L2US0EY https://www.amazon.com/SE-EP08L-Illuminated-Flashing-Feature/dp/B008WAE2XQ https://www.amazon.com/SE-EP07L-Flashing-Illuminated-Safety/dp/B004J663A2 I don't know which type of "be seen" lighting might be most effective, but any of the aformentioned would be better than a dim forward facing standlight. Thing is, nobody's demonstrated any need for so much stationary "be seen" light, beyond the usual "well, it _could_ happen" safety inflation mentality. We're facing the same mentality regarding our local forest preserve. Some people want to cut down every dead or dying tree within 100 feet of any trail because, well, it _could_ fall on somebody and kill them. Sheesh. I have worked in area where it is probable that no one has ever cut down a tree until we arrived and there never was a problem with dead or diseased trees falling down. One problem with cutting down trees that "could" fall down is that in a hurricane many perfectly healthy trees get blown down. Perhaps the cutting of all trees taller than the average human "could" lives. And, of course, banning the ownership of bicycles "could" save ~900 lives a year. A bicycle ban? How's that 100-year worldwide Heroin ban working? Works great! Allows a considerable number of common ordinary people to make a "decent" living. True the demand does seems to be decreasing but the widening the demand for amphetamines, which can be made at home rather than waiting for a crop to ripen and getting all bound up with buying futures and warehousing raw materials. As an aside, do you think anyone wants the "war on drugs" to be won? Examples: U.S. Coastguard budget (numbers adjusted to 2013 dollars): 1950 - $1,439,312,446 2013 - $ 7,051,054,000 The total DEA budget is difficult to ascertain but: The total budget of the DEA from 1972 to 2014, according to the agency website, was $50.6 billion. The agency had 11,055 employees in 2014. For the year 2014 the average cost per arrest made was $97,325. An estimate by The Cato Institute, in 2010, states that the legalizing of drugs would save roughly $41.3 billion per year in government expenditure. Or to put it a different way, The War on Drugs is costing the U.S. an estimated $41.3 billion dollars a year. Do you think that anyone wants all that lovely lolly to disappear? To make a sort of meta-point: People often claim that the discussions here are worthless. In particular, because nobody here ever changes their mind. But it's partly because of information I've gotten here (corroborated elsewhere) that I now believe most drugs should be legalized. I think the U.S. should more or less follow the Portugal strategy, with perhaps some minor modifications. -- - Frank Krygowski |
#160
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More About Lights
On Wednesday, March 15, 2017 at 5:40:55 PM UTC-4, James wrote:
On 16/03/17 03:45, 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. You are an anomaly. At creeping speeds (less than 10km/h), I could see holes with a candle light. -- JS Must be nice to be blessed with such perfect vision! many of us find that we need a prety bright light in order to see where we're going and the obstacles to avoid at night. that's not to mention that it's nice to be able to see critters on theroads or trails in time to slow or stop to avoid running over them. Personally, I like a supplemental High beam light so that ican see a longer way down an unlit very dark road on a moonless night so I can see the skunks at the side of the road or on the road well BEFORE I startle them. YMMV Cheers |
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