DrummerJonny Posted February 5, 2011 Share Posted February 5, 2011 Thanks Ynot, Not seen that method before at all! Edit: Just tried it out, that's great! though I feel pretty sad for noticing the difference in cable quality after throwing it across a room... well, 3 rooms, my house is tiny... Link to comment Share on other sites More sharing options...
J Pearce Posted February 5, 2011 Share Posted February 5, 2011 Depends on cable diameter. 5 core 16mm gets a bigger coil than mic cable! Link to comment Share on other sites More sharing options...
Matthew Robinson Posted February 5, 2011 Share Posted February 5, 2011 Depends on cable diameter. 5 core 16mm gets a bigger coil than mic cable! Yep, sorry, forgot to specify that I meant mainly mic cable. Link to comment Share on other sites More sharing options...
adam2 Posted February 5, 2011 Share Posted February 5, 2011 Power cables if loaded whilst wound on a drum, or coiled up in a heap, or run in close proximity to other cables, are liable to get warm, and possibly dangerously hot.This is because the passage of current causes voltage drop, and the loss turns into heat.Under normal conditions, this heat escapes into the air with only a modest increase in temperature, if however the heat cant easily escape because the cable is wound on a drum, then greater temperatures will be reached, perhaps to the point of danger.Consider 100M of cable, loaded to 12 amps, and with a voltage drop of 20 volts. That is a loss of 240 watts, which is not that noticeable spread over 100M of cable, it is only 2.4 watts per M and would result in the cable becoming slightly warm.If however the cable is wound on a drum or piled in a heap, then the 240 watts of heat cant so readily escape and the temperature rise would be much greater, perhaps dangerously so. Nothing to do with transformer action, just simple resistance losses. The same result would occur with DC. It takes a while for the heat to build up, I would not worry about a brief test useing a long coiled lead, but normal use, no way, unless very lightly loaded. Link to comment Share on other sites More sharing options...
Ynot Posted February 5, 2011 Share Posted February 5, 2011 If however the cable is wound on a drum or piled in a heap, then the 240 watts of heat cant so readily escape and the temperature rise would be much greater, perhaps dangerously so.Add to that the fact that as heat rises the resistance is affected also meaning more current flow, and more heat, etc etc etc - that's how heat can build up to dangerous proportions... Link to comment Share on other sites More sharing options...
Simon Lewis Posted February 5, 2011 Share Posted February 5, 2011 Add to that the fact that as heat rises the resistance is affected also meaning more current flow, and more heat, etc etc etc - that's how heat can build up to dangerous proportions... The temperature coeffcient of copper is +0.393 percent per degree C. As it get warmer, the resistance increases. I'm struggling to see where the 'extra' current flow comes from? Granted, as the resistance increases, more heat is likely to be produced... Link to comment Share on other sites More sharing options...
Matthew Robinson Posted February 5, 2011 Share Posted February 5, 2011 The temperature coeffcient of copper is +0.393 percent per degree C. As it get warmer, the resistance increases. I'm struggling to see where the 'extra' current flow comes from? It'd be interesting- free energy! Link to comment Share on other sites More sharing options...
Ashley R Posted February 6, 2011 Share Posted February 6, 2011 Personally, I'm a fan of over/under coiling, especially when it comes to the cheap DMX cable I've got - coiling all one way tends to mean that the cable doesn't lay flat, where over/under coiled cable has no net twist, and sits flatter. Not so much of an issue with better cables. Knowing how the particular crew you are working with likes cables coiled is a really important bit of information to avoid getting into trouble! Revbob, can you clarify this method for me(over/under coiling)? Not sure I've seen this done / called this... Thanks Ive always heard this method called 'reverse rolling' never really head it called over/under coiling Link to comment Share on other sites More sharing options...
Ynot Posted February 6, 2011 Share Posted February 6, 2011 Add to that the fact that as heat rises the resistance is affected also meaning more current flow, and more heat, etc etc etc - that's how heat can build up to dangerous proportions... The temperature coeffcient of copper is +0.393 percent per degree C. As it get warmer, the resistance increases. I'm struggling to see where the 'extra' current flow comes from? Granted, as the resistance increases, more heat is likely to be produced...Whoops!My error! That'll teach me to type too quickly. Didn't check what I'd written!!Doh! ( Homer) Link to comment Share on other sites More sharing options...
Yorkie Posted February 6, 2011 Share Posted February 6, 2011 OT, but what size do people make their coils? I make mine about 1' in diameter when laid down on the floor in a circle and use the over/under coiling method. If I'm coiling Mic, DMX, VGA, 3x1.5 or 3x2.5, each up to about 25m I tend to coil about 1' diameter, firstly I store cables in 60x40cm crates (2 piles per crate) and secondly I don't have length codes on my mic cables so if the coils are about the same size it means I can quickly differentiate between 5's and 10's. Link to comment Share on other sites More sharing options...
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