Fred, I have several meters of Nichrome 60 and Nichrome 80; 28 and 18 gauge. Can send up, or bring to you.?
?Did some estimates- looks like you will need 2 watts to warm paddles 25-40F above ambient. That would take about 8 cm of wire at 1.5V at a max discharge of 1.5-2 amps. ?Could refine estimate with more detailed data about the key, ?but the ?estimate shows it might be feasible-experimental verification on a surrogate set of paddles would be mandatory before assembling.?
That much wire could be wound into a 1-5 -2 cm dia circular spiral or 1.5-2cm wide square spiral that would lay on back of paddles held by epoxy or Silicone RTV. ?Would probably want a potentiometer in there to adjust power to wire.?
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On Jan 4, 2025, at 19:27, David Fuller via groups.io <nn5k@...> wrote:
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There are heated garments for motorcycling and snow mobiling. ?Deb has used that a lot on her long distance rides. ? I currently have a pair of gloves and a vest that I wear on the tractor when snow plowing. ?That stuff really works! ??
My other go to game changer for hunting particularly holding up cold binoculars ?for hours and hours are the chemical hand warmers called hot hands. ?
I also remember Mike built a pair of cw gloves that worked for him!
-Dave
On Jan 4, 2025, at 18:44, Fred Maas via groups.io <just.one.hill@...> wrote:
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What is the material to be heated? What is its mass. What would be the ambient temp? ?From that I can calculate Watts required for a desired temp rise above ambient. ?
K6TAA?
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That¡¯s an interesting step¡? talking about less than a square inch paddle surface, maybe even half that.? Ambient is wide ranging, call it 20F.? If it could raise the temperature of the surface by perhaps 20 degrees, that would be right in there.? I don¡¯t know what the material might be.? Wire or resistance could be sandwiched between layers of something, plastic perhaps?? Or imbedded in a bit of colorful epoxy?
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Wonder how much resistance an inch of it might have?
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Maybe nichrome 60 or80? ?Or Kapton film elements?
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I have a resistive surface that has been used for a paddle¡
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But.?
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It isn¡¯t a specific resistance.? It is open when not being touched.? When touched it changes with the amount of pressure.? At a very light pressure it might be 50K.? with high pressure it is just 1K.
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Doesn¡¯t seem to me this is the sort of thing that would meet the need.? What is needed is a surface that has a fixed resistance that can be fed a little power and warm and in itself have nothing to do with the keying.
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The paddle already has ground on it, so it would call for one additional wire for a plus power source.? It would need to warm, not be hot, at say five volts, and ideally, not consume a lot of power.? Would seem a fraction of a watt would be adequate.
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If there exists a highly resistive wire I can imagine imbedding it in something that can handle a little warmth and make it into a paddle surface.
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Any ideas being stimulated?
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fd
