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Woodturning (rec.crafts.woodturning) To discuss tools, techniques, styles, materials, shows and competitions, education and educational materials related to woodturning. All skill levels are welcome, from art turners to production turners, beginners to masters. |
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#1
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This is somewhat OT, but you appear to be the biggest suppository of
knowledge when it comes to NiChrome. I want to build a Hot Wire to bend some Acrylic. The wire in question is #22 and approximately 1 ohm per foot. Most of the temperature tables I've seen for NiChrome wire show the relationship between Amps and Temperature. But shouldn't this really be Watts? For example the tables show that I need about 3 Amps for the 400°F that I require. The tables I've seen don't actually show temps that low. But assuming the tables are referring to 120V, that would mean 360 Watts or 15 Amps at 24 Volts? This can't be right? The second problem is the power supply. Assuming I'm confused about the Watts and 3 amps at 24 Volts will suffice. The average light dimmer will only handle about 500 Watts, but if I short out (2 Ohms) the transformer secondary I will fry the dimmer and/or transformer (DAMHIKT). I've seen the light bulb in series trick, but even a 200 Watt bulb on the Transformer secondary would not give me enough Amps to reach my temperature. Although I suppose a 200 Watt bulb on the Transformer primary would give me 8 Amps at 24V? There's obviously something I don't understand here. I would appreciate it if someone could lead me out of the darkness. |
#2
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Bill Stock wrote:
This is somewhat OT, but you appear to be the biggest suppository of knowledge when it comes to NiChrome. We do? Maybe this is why my woodturning seems so difficult... PK PS: I am not sure about those RC guys either...are they NiChrome experts for some reason? |
#3
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![]() "Bill Stock" writes: This is somewhat OT, but you appear to be the biggest suppository of knowledge when it comes to NiChrome. REpository. I want to build a Hot Wire to bend some Acrylic. The wire in question is #22 and approximately 1 ohm per foot. Let's assume you need 3 feet for the sake of the math below Most of the temperature tables I've seen for NiChrome wire show the relationship between Amps and Temperature. But shouldn't this really be Watts? When resistance is fixed per foot, and the manufacturer doesn't know how many feet you have, they can't use watts. They could use watts per foot, but that's essentially amps. Constant amps gives a predictable watts/foot regardless of the length of the wire. For the same amps (and thus temperature), and twice longer wire uses twice the watts (and needs twice the voltage). For example the tables show that I need about 3 Amps for the 400°F that I require. The tables I've seen don't actually show temps that low. But assuming the tables are referring to 120V, that would mean 360 Watts or 15 Amps at 24 Volts? This can't be right? 3 amps for a 3 ohm (3 foot) wire is 9 volts (E=IR). You choose the voltage in order to create the appropriate current. If you put a 3 ohm wire on a 120VAC outlet, you'll get 40 amps (4800 watts) for a few seconds. If you try this, use a movie camera so we can all share the excitement ;-) The second problem is the power supply. Assuming I'm confused about the Watts and 3 amps at 24 Volts will suffice. You want a variable voltage power supply rated at, say, twice the amperage you'll actually need, and high enough volts to generate the amperage your project will call for. You adjust the voltage to result in the current needed. Make sure the supply has an ammeter on it, or use your own. The average light dimmer will only handle about 500 Watts, The average light dimmer is a pulse width modulator suitable only for 120VAC circuits. If you want 3 amps across 3 ohms, with a 120VAC circuit, 3 amps at 120VAC is 360 watts. You'd need a couple lightbulbs in parallel to get that, or a floodlight. I suppose you could build a box with, say, 3-6 100W bulbs each with their own light switch, to provide variable current. Each bulb adds ~ 0.8 amps. |
#4
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![]() Paul Kierstead writes: PS: I am not sure about those RC guys either...are they NiChrome experts for some reason? RC aircraft wings are often cut with hot wires through foam. |
#6
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![]() "DJ Delorie" wrote in message ... "Bill Stock" writes: This is somewhat OT, but you appear to be the biggest suppository of knowledge when it comes to NiChrome. REpository. ![]() I want to build a Hot Wire to bend some Acrylic. The wire in question is #22 and approximately 1 ohm per foot. Let's assume you need 3 feet for the sake of the math below Most of the temperature tables I've seen for NiChrome wire show the relationship between Amps and Temperature. But shouldn't this really be Watts? When resistance is fixed per foot, and the manufacturer doesn't know how many feet you have, they can't use watts. They could use watts per foot, but that's essentially amps. Constant amps gives a predictable watts/foot regardless of the length of the wire. For the same amps (and thus temperature), and twice longer wire uses twice the watts (and needs twice the voltage). For example the tables show that I need about 3 Amps for the 400°F that I require. The tables I've seen don't actually show temps that low. But assuming the tables are referring to 120V, that would mean 360 Watts or 15 Amps at 24 Volts? This can't be right? 3 amps for a 3 ohm (3 foot) wire is 9 volts (E=IR). You choose the voltage in order to create the appropriate current. If you put a 3 ohm wire on a 120VAC outlet, you'll get 40 amps (4800 watts) for a few seconds. If you try this, use a movie camera so we can all share the excitement ;-) No plans to try this any time soon. The second problem is the power supply. Assuming I'm confused about the Watts and 3 amps at 24 Volts will suffice. You want a variable voltage power supply rated at, say, twice the amperage you'll actually need, and high enough volts to generate the amperage your project will call for. You adjust the voltage to result in the current needed. Make sure the supply has an ammeter on it, or use your own. Yep. Priced the Variacs. ![]() (3A/37V) that I built 20 years ago. I smoked the PS before the wire got hot. Fortunately I only fried the output caps and not the transformer. (I love the smell of burning Tantalum in the morning.) The average light dimmer will only handle about 500 Watts, The average light dimmer is a pulse width modulator suitable only for 120VAC circuits. If you want 3 amps across 3 ohms, with a 120VAC circuit, 3 amps at 120VAC is 360 watts. You'd need a couple lightbulbs in parallel to get that, or a floodlight. I suppose you could build a box with, say, 3-6 100W bulbs each with their own light switch, to provide variable current. Each bulb adds ~ 0.8 amps. Thanks. This may be the easiest solution. |
#7
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Bill Stock wrote:
This is somewhat OT, but you appear to be the biggest suppository of knowledge when it comes to NiChrome. I want to build a Hot Wire to bend some Acrylic. The wire in question is #22 and approximately 1 ohm per foot. Most of the temperature tables I've seen for NiChrome wire show the relationship between Amps and Temperature. But shouldn't this really be Watts? For example the tables show that I need about 3 Amps for the 400°F that I require. The tables I've seen don't actually show temps that low. But assuming the tables are referring to 120V, that would mean 360 Watts or 15 Amps at 24 Volts? This can't be right? Watts ? No. The required wattage for 3Amps (400F) depends on the length of the wire. Fir example 1 foot (1 ohm) would need 3 V to drive 3A through the wire - Watts = I^2 * R or Watts = E * I Wattage needed would 9 Watts at 3V to give you 400F for 1 Foot. For longer pieces of wire work the math: Given: Current (I) 3A Length of wi Whatever you need Resistance: 1 ohm/foot Voltage (or Electromotive force E) R = 1 (ohm /foot) * Length needed (in feet) E = I * R Power = E * I The second problem is the power supply. Assuming I'm confused about the Watts and 3 amps at 24 Volts will suffice. The average light dimmer will only handle about 500 Watts, but if I short out (2 Ohms) the transformer secondary I will fry the dimmer and/or transformer (DAMHIKT). If you're using 2' of wire with 1 ohm/foot then you're getting you've got 12A with a 24V transformer, and drawing 288 watts, and the 500w lamp dimmer should be ok. You'd need to bring the voltage down to 6V for 3A with a power of 9W. These currents are on the secondary side of the transformer - the primary (120V side) the currents would be approximately 1/6 as much. I've seen the light bulb in series trick, but even a 200 Watt bulb on the Transformer secondary would not give me enough Amps to reach my temperature. Although I suppose a 200 Watt bulb on the Transformer primary would give me 8 Amps at 24V? There's obviously something I don't understand here. I would appreciate it if someone could lead me out of the darkness. |
#8
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![]() "Bill Stock" writes: Thanks. This may be the easiest solution. It's also the most dangerous, because you have exposed metal with 120VAC on it. If ANYTHING happens, you get electrocuted. DO NOT USE WITHOUT A GROUND FAULT INTERRUPTER. And rubber gloves. And make out your will first. And have someone nearby ready to pull the plug. I'm not kidding. Better yet, just don't do it. |
#9
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DJ Delorie wrote:
Paul Kierstead writes: PS: I am not sure about those RC guys either...are they NiChrome experts for some reason? RC aircraft wings are often cut with hot wires through foam. Ahhh...I am just old enough that I only know of tissue covered balsa wood planes; didn't know ppl were fabricating their own foam ones, but of course it makes perfect sense. Also old enough to have used djgcc a fair bit; many many thanks for rescuing me from the perils of the crap commercial compliers of the day (not that things are so much better today). PK |
#10
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![]() Paul Kierstead writes: Ahhh...I am just old enough that I only know of tissue covered balsa wood planes; didn't know ppl were fabricating their own foam ones, but of course it makes perfect sense. It depends on the plane. WHen I was doing it, foam cores and carbon fiber spars were used for gliders and covered spar-n-rib was used for powered and/or high performance planes. Also old enough to have used djgcc a fair bit; many many thanks for rescuing me from the perils of the crap commercial compliers of the day (not that things are so much better today). Well, djgpp is much better today :-) |
#11
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"Leo Lichtman" wrote:
"DJ Delorie" wrote: (clip) REpository. (clip) ^^^^^^^^^^^^ SUPpository is funnier. A nichrome suppository is funny?? |
#12
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Think about it. Cut and cauterize....
"Lobby Dosser" wrote in message news:sOmwd.7661$E_6.2438@trnddc04... "Leo Lichtman" wrote: "DJ Delorie" wrote: (clip) REpository. (clip) ^^^^^^^^^^^^ SUPpository is funnier. A nichrome suppository is funny?? |
#13
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"George" george@least wrote:
Think about it. Cut and cauterize.... High Pucker Factor! "Lobby Dosser" wrote in message news:sOmwd.7661$E_6.2438@trnddc04... "Leo Lichtman" wrote: "DJ Delorie" wrote: (clip) REpository. (clip) ^^^^^^^^^^^^ SUPpository is funnier. A nichrome suppository is funny?? |
#14
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On Thu, 16 Dec 2004 11:19:13 -0500, "Bill Stock"
wrote: rec.crafts.woodturning is a knowledge base for NiChrome?? I must have NiCHrome filtered out.. never seen it mentioned here.. This is somewhat OT, but you appear to be the biggest suppository of knowledge when it comes to NiChrome. I want to build a Hot Wire to bend some Acrylic. The wire in question is #22 and approximately 1 ohm per foot. Most of the temperature tables I've seen for NiChrome wire show the relationship between Amps and Temperature. But shouldn't this really be Watts? For example the tables show that I need about 3 Amps for the 400°F that I require. The tables I've seen don't actually show temps that low. But assuming the tables are referring to 120V, that would mean 360 Watts or 15 Amps at 24 Volts? This can't be right? The second problem is the power supply. Assuming I'm confused about the Watts and 3 amps at 24 Volts will suffice. The average light dimmer will only handle about 500 Watts, but if I short out (2 Ohms) the transformer secondary I will fry the dimmer and/or transformer (DAMHIKT). I've seen the light bulb in series trick, but even a 200 Watt bulb on the Transformer secondary would not give me enough Amps to reach my temperature. Although I suppose a 200 Watt bulb on the Transformer primary would give me 8 Amps at 24V? There's obviously something I don't understand here. I would appreciate it if someone could lead me out of the darkness. |
#15
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Bill,
See comments interspersed: "Bill Stock" wrote in message ... This is somewhat OT, but you appear to be the biggest suppository of knowledge when it comes to NiChrome. I want to build a Hot Wire to bend some Acrylic. The wire in question is #22 and approximately 1 ohm per foot. ============================== Is that at room temperature or at 400 degrees? Nichrome, as all metals, change resistance as temperature rises. Therefore, you'll have higher currents (Amps) at lower temps, so your supply needs to have adequate reserve to heat the wire. As it reaches the higher temps, the current will self limit according to voltage available. ================================ Most of the temperature tables I've seen for NiChrome wire show the relationship between Amps and Temperature. But shouldn't this really be Watts? For example the tables show that I need about 3 Amps for the 400°F that I require. The tables I've seen don't actually show temps that low. But assuming the tables are referring to 120V, that would mean 360 Watts or 15 Amps at 24 Volts? This can't be right? ================================ The normal Ohms law rules won't work here since the resistance is variable as well as the Voltage. (Ohm's law is valid, just not as you'd normally think of it in linear terms). ================================ The second problem is the power supply. Assuming I'm confused about the Watts and 3 amps at 24 Volts will suffice. The average light dimmer will only handle about 500 Watts, but if I short out (2 Ohms) the transformer secondary I will fry the dimmer and/or transformer (DAMHIKT). I've seen the light bulb in series trick, but even a 200 Watt bulb on the Transformer secondary would not give me enough Amps to reach my temperature. Although I suppose a 200 Watt bulb on the Transformer primary would give me 8 Amps at 24V? There's obviously something I don't understand here. I would appreciate it if someone could lead me out of the darkness. =================================== If you could find an old filament transformer like used in old tube type radios, etc., it would probably get you into the desired range, but you'd need to find out more about the cold to hot characteristics of the Nichrome. |
#16
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![]() "Ken Moon" wrote in message nk.net... Bill, See comments interspersed: "Bill Stock" wrote in message ... This is somewhat OT, but you appear to be the biggest suppository of knowledge when it comes to NiChrome. I want to build a Hot Wire to bend some Acrylic. The wire in question is #22 and approximately 1 ohm per foot. ============================== Is that at room temperature or at 400 degrees? 25°C. Nichrome, as all metals, change resistance as temperature rises. Therefore, you'll have higher currents (Amps) at lower temps, so your supply needs to have adequate reserve to heat the wire. As it reaches the higher temps, the current will self limit according to voltage available. ================================ Most of the temperature tables I've seen for NiChrome wire show the relationship between Amps and Temperature. But shouldn't this really be Watts? For example the tables show that I need about 3 Amps for the 400°F that I require. The tables I've seen don't actually show temps that low. But assuming the tables are referring to 120V, that would mean 360 Watts or 15 Amps at 24 Volts? This can't be right? ================================ The normal Ohms law rules won't work here since the resistance is variable as well as the Voltage. (Ohm's law is valid, just not as you'd normally think of it in linear terms). ================================ The second problem is the power supply. Assuming I'm confused about the Watts and 3 amps at 24 Volts will suffice. The average light dimmer will only handle about 500 Watts, but if I short out (2 Ohms) the transformer secondary I will fry the dimmer and/or transformer (DAMHIKT). I've seen the light bulb in series trick, but even a 200 Watt bulb on the Transformer secondary would not give me enough Amps to reach my temperature. Although I suppose a 200 Watt bulb on the Transformer primary would give me 8 Amps at 24V? There's obviously something I don't understand here. I would appreciate it if someone could lead me out of the darkness. =================================== If you could find an old filament transformer like used in old tube type radios, etc., it would probably get you into the desired range, but you'd need to find out more about the cold to hot characteristics of the Nichrome. The adjustment factor is only 1.037 for the temp I want. |
#17
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![]() "mac davis" wrote in message ... On Thu, 16 Dec 2004 11:19:13 -0500, "Bill Stock" wrote: rec.crafts.woodturning is a knowledge base for NiChrome?? I must have NiCHrome filtered out.. never seen it mentioned here.. Probably not as frequently as the RC group. I believe you guys use it to make "hot pens" to sign your work. This is somewhat OT, but you appear to be the biggest suppository of knowledge when it comes to NiChrome. I want to build a Hot Wire to bend some Acrylic. The wire in question is #22 and approximately 1 ohm per foot. Most of the temperature tables I've seen for NiChrome wire show the relationship between Amps and Temperature. But shouldn't this really be Watts? For example the tables show that I need about 3 Amps for the 400°F that I require. The tables I've seen don't actually show temps that low. But assuming the tables are referring to 120V, that would mean 360 Watts or 15 Amps at 24 Volts? This can't be right? The second problem is the power supply. Assuming I'm confused about the Watts and 3 amps at 24 Volts will suffice. The average light dimmer will only handle about 500 Watts, but if I short out (2 Ohms) the transformer secondary I will fry the dimmer and/or transformer (DAMHIKT). I've seen the light bulb in series trick, but even a 200 Watt bulb on the Transformer secondary would not give me enough Amps to reach my temperature. Although I suppose a 200 Watt bulb on the Transformer primary would give me 8 Amps at 24V? There's obviously something I don't understand here. I would appreciate it if someone could lead me out of the darkness. |
#18
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![]() "Mike" wrote in message nk.net... Bill Stock wrote: This is somewhat OT, but you appear to be the biggest suppository of knowledge when it comes to NiChrome. I want to build a Hot Wire to bend some Acrylic. The wire in question is #22 and approximately 1 ohm per foot. Most of the temperature tables I've seen for NiChrome wire show the relationship between Amps and Temperature. But shouldn't this really be Watts? For example the tables show that I need about 3 Amps for the 400°F that I require. The tables I've seen don't actually show temps that low. But assuming the tables are referring to 120V, that would mean 360 Watts or 15 Amps at 24 Volts? This can't be right? Watts ? No. The required wattage for 3Amps (400F) depends on the length of the wire. Fir example 1 foot (1 ohm) would need 3 V to drive 3A through the wire - Watts = I^2 * R or Watts = E * I Wattage needed would 9 Watts at 3V to give you 400F for 1 Foot. Thanks Mike, I get the V=I*R. Although it's been a good number of years (decades) since my basic electronics course. It just surprises me that the amperage specified per foot, would not be for a given voltage. For example: I tried to test my wire using a variable power supply (3A/35V) a built a number of years ago. But the wire never did start to glow before the PS smoked itself. Everything past the regulators got fried. The regulators have thermal protection and there is a fuse on the mains side, so I guess the parts (diodes/caps) were underrated. It should not be a big deal to fix these components. But I'm surprised I did not get some colour out of the wire at 3A/35V. Thanks. For longer pieces of wire work the math: Given: Current (I) 3A Length of wi Whatever you need Resistance: 1 ohm/foot Voltage (or Electromotive force E) R = 1 (ohm /foot) * Length needed (in feet) E = I * R Power = E * I The second problem is the power supply. Assuming I'm confused about the Watts and 3 amps at 24 Volts will suffice. The average light dimmer will only handle about 500 Watts, but if I short out (2 Ohms) the transformer secondary I will fry the dimmer and/or transformer (DAMHIKT). If you're using 2' of wire with 1 ohm/foot then you're getting you've got 12A with a 24V transformer, and drawing 288 watts, and the 500w lamp dimmer should be ok. You'd need to bring the voltage down to 6V for 3A with a power of 9W. These currents are on the secondary side of the transformer - the primary (120V side) the currents would be approximately 1/6 as much. I've seen the light bulb in series trick, but even a 200 Watt bulb on the Transformer secondary would not give me enough Amps to reach my temperature. Although I suppose a 200 Watt bulb on the Transformer primary would give me 8 Amps at 24V? There's obviously something I don't understand here. I would appreciate it if someone could lead me out of the darkness. |
#19
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why the heck do you want to use a nicrome wire for this purpose? How sharp
a bend do you need? is a 1/2 inch radius OK - if yes, use coper pipe with a halogen bulb inside. Or take apart a toaster or something and use that heating element. If you use either a lamp or a 115V element, you can put a lamp dimmer in series and control the power with the dimmer. measure temp with a thermometer and adjust as requred. "Bill Stock" wrote in message ... This is somewhat OT, but you appear to be the biggest suppository of knowledge when it comes to NiChrome. I want to build a Hot Wire to bend some Acrylic. The wire in question is #22 and approximately 1 ohm per foot. Most of the temperature tables I've seen for NiChrome wire show the relationship between Amps and Temperature. But shouldn't this really be Watts? For example the tables show that I need about 3 Amps for the 400°F that I require. The tables I've seen don't actually show temps that low. But assuming the tables are referring to 120V, that would mean 360 Watts or 15 Amps at 24 Volts? This can't be right? The second problem is the power supply. Assuming I'm confused about the Watts and 3 amps at 24 Volts will suffice. The average light dimmer will only handle about 500 Watts, but if I short out (2 Ohms) the transformer secondary I will fry the dimmer and/or transformer (DAMHIKT). I've seen the light bulb in series trick, but even a 200 Watt bulb on the Transformer secondary would not give me enough Amps to reach my temperature. Although I suppose a 200 Watt bulb on the Transformer primary would give me 8 Amps at 24V? There's obviously something I don't understand here. I would appreciate it if someone could lead me out of the darkness. |
#20
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![]() There are 3413 BTU's per kilowatt. A BTU will heat one pound of water, one degree F. A BTU will raise the temp of one cubic foot of air about one degree F. Bill in WNC mountains |
#21
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On Thu, 16 Dec 2004 18:30:32 -0800, "william_b_noble"
wrote: or a heat gun... you can bend plexi almost double with a good heat gun and patience... wouldn't your light sabre be more effective?? (posted only to the REC to hopefully slow down this dumb ass cross posting) why the heck do you want to use a nicrome wire for this purpose? How sharp a bend do you need? is a 1/2 inch radius OK - if yes, use coper pipe with a halogen bulb inside. Or take apart a toaster or something and use that heating element. If you use either a lamp or a 115V element, you can put a lamp dimmer in series and control the power with the dimmer. measure temp with a thermometer and adjust as requred. "Bill Stock" wrote in message ... This is somewhat OT, but you appear to be the biggest suppository of knowledge when it comes to NiChrome. I want to build a Hot Wire to bend some Acrylic. The wire in question is #22 and approximately 1 ohm per foot. Most of the temperature tables I've seen for NiChrome wire show the relationship between Amps and Temperature. But shouldn't this really be Watts? For example the tables show that I need about 3 Amps for the 400°F that I require. The tables I've seen don't actually show temps that low. But assuming the tables are referring to 120V, that would mean 360 Watts or 15 Amps at 24 Volts? This can't be right? The second problem is the power supply. Assuming I'm confused about the Watts and 3 amps at 24 Volts will suffice. The average light dimmer will only handle about 500 Watts, but if I short out (2 Ohms) the transformer secondary I will fry the dimmer and/or transformer (DAMHIKT). I've seen the light bulb in series trick, but even a 200 Watt bulb on the Transformer secondary would not give me enough Amps to reach my temperature. Although I suppose a 200 Watt bulb on the Transformer primary would give me 8 Amps at 24V? There's obviously something I don't understand here. I would appreciate it if someone could lead me out of the darkness. |
#22
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I want to build a Hot Wire to bend some Acrylic. The wire in question is
#22 and approximately 1 ohm per foot. Tons if info at this website: http://www.infraredheaters.com/ |
#23
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Bill Stock wrote:
Thanks Mike, I get the V=I*R. Although it's been a good number of years (decades) since my basic electronics course. It just surprises me that the amperage specified per foot, would not be for a given voltage. For example: I tried to test my wire using a variable power supply (3A/35V) a built a number of years ago. But the wire never did start to glow before the PS smoked itself. Everything past the regulators got fried. The regulators have thermal protection and there is a fuse on the mains side, so I guess the parts (diodes/caps) were underrated. It should not be a big deal to fix these components. But I'm surprised I did not get some colour out of the wire at 3A/35V. 400F is pretty dark, as an example - look in your oven set to 450F - it doesn't glow (visible) red. 35V would have tried to drive lots more than 3A through the wire - more like 12 if I remember your numbers (in the bit bucket now) that would fry a 3A supply. mike |
#24
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Bill Stock wrote:
Thanks Mike, I get the V=I*R. Although it's been a good number of years (decades) since my basic electronics course. It just surprises me that the amperage specified per foot, would not be for a given voltage. For example: I tried to test my wire using a variable power supply (3A/35V) a built a number of years ago. But the wire never did start to glow before the PS smoked itself. Everything past the regulators got fried. The regulators have thermal protection and there is a fuse on the mains side, so I guess the parts (diodes/caps) were underrated. It should not be a big deal to fix these components. But I'm surprised I did not get some colour out of the wire at 3A/35V. 400F is pretty dark, as an example - look in your oven set to 450F - it doesn't glow (visible) red. 35V would have tried to drive lots more than 3A through the wire - more like 12 if I remember your numbers (in the bit bucket now) that would fry a 3A supply. mike |
#25
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Bill Stock wrote:
Thanks Mike, I get the V=I*R. Although it's been a good number of years (decades) since my basic electronics course. It just surprises me that the amperage specified per foot, would not be for a given voltage. For example: I tried to test my wire using a variable power supply (3A/35V) a built a number of years ago. But the wire never did start to glow before the PS smoked itself. Everything past the regulators got fried. The regulators have thermal protection and there is a fuse on the mains side, so I guess the parts (diodes/caps) were underrated. It should not be a big deal to fix these components. But I'm surprised I did not get some colour out of the wire at 3A/35V. 400F is pretty dark, as an example - look in your oven set to 450F - it doesn't glow (visible) red. 35V would have tried to drive lots more than 3A through the wire - more like 12 if I remember your numbers (in the bit bucket now) that would fry a 3A supply. mike |
#26
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![]() "Mike" wrote in message ... Bill Stock wrote: Thanks Mike, I get the V=I*R. Although it's been a good number of years (decades) since my basic electronics course. It just surprises me that the amperage specified per foot, would not be for a given voltage. For example: I tried to test my wire using a variable power supply (3A/35V) a built a number of years ago. But the wire never did start to glow before the PS smoked itself. Everything past the regulators got fried. The regulators have thermal protection and there is a fuse on the mains side, so I guess the parts (diodes/caps) were underrated. It should not be a big deal to fix these components. But I'm surprised I did not get some colour out of the wire at 3A/35V. 400F is pretty dark, as an example - look in your oven set to 450F - it doesn't glow (visible) red. 35V would have tried to drive lots more than 3A through the wire - more like 12 if I remember your numbers (in the bit bucket now) that would fry a 3A supply. mike Thanks Mike. I think I solved the mystery yesterday. I picked up a cheap switching PSU at the surplus store to continue my experimenting. But I still wasn't getting much heating. So I decided to check the resistance of my test wire and it was 3+ x what I expected. It turns out that the vendor shipped me the wrong wire, 3.5 ohms/ft, not the 1 ohm/ft I ordered. They're shipping the correct wire, so this should solve my problem. |
#27
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![]() "Dan Bollinger" wrote in message news:brIwd.516931$wV.403584@attbi_s54... I want to build a Hot Wire to bend some Acrylic. The wire in question is #22 and approximately 1 ohm per foot. Tons if info at this website: http://www.infraredheaters.com/ Thanks, good site. |
#28
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Bill Stock wrote:
This is somewhat OT, but you appear to be the biggest suppository of knowledge when it comes to NiChrome. I want to build a Hot Wire to bend some Acrylic. The wire in question is #22 and approximately 1 ohm per foot. I did a lot of acrylic bending years ago making picture keyframes and the like. I used a coiled nichrome wire inside a heatproof channel, lined with asbestos paper (!) connected to full house current. It was about 18" long, and the element, which was about an inch below the channel's 1/2" opening, glowed a dark red. Turning a piece over once, it took about 15 seconds to get the acrylic up to bending temp. and it worked really well. I would use a coiled element sized to give a much higher temp than 400 degrees at 115v, and with a lamp dimmer (no stepdown transformer). If your element is only at 400 degrees, you could be waiting forever to reach bending temp. Ken Grunke La Farge, WI US ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- -----------== Posted via Newsfeed.Com - Uncensored Usenet News ==---------- http://www.newsfeed.com The #1 Newsgroup Service in the World! -----= Over 100,000 Newsgroups - Unlimited Fast Downloads - 19 Servers =----- |
#29
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![]() "Ken Grunke" wrote in message ... Bill Stock wrote: This is somewhat OT, but you appear to be the biggest suppository of knowledge when it comes to NiChrome. I want to build a Hot Wire to bend some Acrylic. The wire in question is #22 and approximately 1 ohm per foot. I did a lot of acrylic bending years ago making picture keyframes and the like. I used a coiled nichrome wire inside a heatproof channel, lined with asbestos paper (!) connected to full house current. Thanks Ken. Did you make your own coils of buy then ready made? Do you remember the gauge/resistance? Did you use an insulator on the coil or let it hang free in the channel? How did you construct your channel? I was thinking of MDF base, reflective aluminum, masonite (channel sides), covered with some heat resistant material, perhap fiberglass. It was about 18" long, and the element, which was about an inch below the channel's 1/2" opening, glowed a dark red. Turning a piece over once, it took about 15 seconds to get the acrylic up to bending temp. and it worked really well. I would use a coiled element sized to give a much higher temp than 400 degrees at 115v, and with a lamp dimmer (no stepdown transformer). If your element is only at 400 degrees, you could be waiting forever to reach bending temp. Thanks again Ken, useful info. Ken Grunke La Farge, WI US ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- -----------== Posted via Newsfeed.Com - Uncensored Usenet News ==---------- http://www.newsfeed.com The #1 Newsgroup Service in the World! -----= Over 100,000 Newsgroups - Unlimited Fast Downloads - 19 Servers =----- |
#30
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Bill Stock wrote:
I did a lot of acrylic bending years ago making picture keyframes and the like. I used a coiled nichrome wire inside a heatproof channel, lined with asbestos paper (!) connected to full house current. Thanks Ken. Did you make your own coils of buy then ready made? Do you remember the gauge/resistance? Did you use an insulator on the coil or let it hang free in the channel? How did you construct your channel? I was thinking of MDF base, reflective aluminum, masonite (channel sides), covered with some heat resistant material, perhap fiberglass. It was about 18" long, and the element, which was about an inch below the channel's 1/2" opening, glowed a dark red. Turning a piece over once, it took about 15 seconds to get the acrylic up to bending temp. and it worked really well. I would use a coiled element sized to give a much higher temp than 400 degrees at 115v, and with a lamp dimmer (no stepdown transformer). If your element is only at 400 degrees, you could be waiting forever to reach bending temp. Thanks again Ken, useful info. Bill, the way I made my bender jig I wouldn't recommend doing it the same way to you, it was pretty cobbled up and not very safe. I would use a ready-made coiled element or take one out of a milkhouse heater whose element might be broken, but at least half of it's length usable. The dimmer will take care of having a shorter length (I think--see disclaimer below). Make a U-shape from steel sheet (NOT aluminum) and get some ceramic insulators from an appliance store to hold the element in the channel. I think the old Maytag dryers used ceramic thimbles that the element threaded through, that might be just the thing. A quartz heater element would be even better, it's self-supporting so you don't have to worry about shorting a coiled element to the sheet metal. Won't go too much further into the design, except to recommend that the channel be a seperate piece from the top surface where you lay the acrylic--you only want heat to come out of the slot. I would not use any flamable material, but fabricate the whole thing from sheet metal probably pop-riveted together, with an enclosed box at one end to hold the dimmer and protect the connections from fingers (and vis versa!) I am NOT an electrical engineer, so I don't wanna tell you how to wire it and get blamed for your demise--just be safe and find the correct way to do it! If for some reason the dimmer is not appropriate, you could use a limiter control from an electric stove, one of the burner controls which cycles the heater on and off in short periods. Think I'd better stop here before I *really* get into trouble from those who ARE electrical engineers! Ken Grunke ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- -----------== Posted via Newsfeed.Com - Uncensored Usenet News ==---------- http://www.newsfeed.com The #1 Newsgroup Service in the World! -----= Over 100,000 Newsgroups - Unlimited Fast Downloads - 19 Servers =----- |
#31
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I would not use any flamable material, but fabricate the whole thing
from sheet metal Good thinking, I wouldn't use flammable materials like lacquer thinner or gasoline to build the thing either. Come to think of it, I wouldn't use any combustible materials like wood, either. ![]() Get your ceramic grommets at: http://www.infraredheaters.com/ Dan |
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