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Post by Deleted on Dec 12, 2006 16:25:18 GMT
How does thermit welding work?
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Post by Deleted on Dec 12, 2006 16:30:06 GMT
I think it has something to do with aluminum parts, and iron oxide mixed together through a funnel with a lot of heat. When the two mix at the right temperature at the bottom of the funnel (where the rail join is) the 'Thermit Reaction' takes place and welds the rails together. I could be wrong, as this is memories I have of school lessons about 10 years ago.
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Post by Deleted on Dec 12, 2006 16:30:47 GMT
BTW it is very impressive - like a small fireworks display!!!
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Post by Deleted on Dec 12, 2006 16:36:35 GMT
Interesting - I do know that the welding process is caused by a violent exothermic reaction catalysed by a few ingredients, but what is the actual reaction?
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Post by amershamsi on Dec 12, 2006 16:57:35 GMT
it's a simple reduction/oxidation reaction. As said above, Iron Oxide (rust) and Aluminium. Al, as much more reactive steals the oxygen off the iron, and the heat given out melts the iron, which falls between the tracks and welds them together. A fuse needs to get it going, often magnesium, but a sparkler can be used. Wikipedia has a good page on the reaction. |
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Post by Deleted on Dec 12, 2006 17:04:37 GMT
Ahhhh, now I see.
What is the infraco's favourite method for initiating the reaction, given the confined spaces of the deep-level tunnels?
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Post by Deleted on Dec 12, 2006 17:13:10 GMT
Ahhhh, now I see. What is the infraco's favourite method for initiating the reaction, given the confined spaces of the deep-level tunnels? I don't know a lot about the track itself, but I have memories of continuous welded rail being dragged about on trains from Ruislip Depot - does this take care of deep - level thermit reactions? The photo I saw of this CWR train was very very old and I'm not even sure if it still is used these days. |
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Post by Deleted on Dec 12, 2006 17:20:21 GMT
I've heard stories of the things falling over... Aparently it's very impressive as long as you're quite far away! ;D
I've also heard stories of welders refusing to work without a fire extinguisher nearby, to prompt replies of "That aint gunna do you much good mate..."
Sam
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Phil
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Post by Phil on Dec 12, 2006 23:08:45 GMT
it's a simple reduction/oxidation reaction. As said above, Iron Oxide (rust) and Aluminium. Al, as much more reactive steals the oxygen off the iron, and the heat given out melts the iron, which falls between the tracks and welds them together. A fuse needs to get it going, often magnesium, but a sparkler can be used. Wikipedia has a good page on the reaction. So far so good: Iron oxide + Aluminium > Aluminium Oxide + Iron. Can be started by just Magnesium, but often Sodium Borate (Borax) is added since that gets it started at a lower temperature it adds more oxygen). Do you guys mean you never saw it at school? You must have had very boring safety-conscious chemistry teachers. We always had great fun with it (outside...) and it didn't often go off unpredictably, causing the kids to run....... |
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Post by Deleted on Dec 12, 2006 23:10:29 GMT
Phil, I've seen it about 20 times....  Mind you, we have a very non-HSE conscious teacher! |
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Phil
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Post by Phil on Dec 12, 2006 23:13:06 GMT
Phil, I've seen it about 20 times.... Thank goodness there are still some prepared to do the fun stuff! Most are afraid to these days. |
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Post by Deleted on Dec 13, 2006 12:03:27 GMT
Does anyone know if this train of continuous welded rail still operates? After posting about it yesterday it did make me think.
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Post by Chris M on Dec 13, 2006 23:55:38 GMT
Phil, I've seen it about 20 times.... Thank goodness there are still some prepared to do the fun stuff! Most are afraid to these days. Alas I didn't get one of those chemistry teachers, so I've never seen it |
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Phil
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Post by Phil on Dec 14, 2006 8:03:28 GMT
Thank goodness there are still some prepared to do the fun stuff! Most are afraid to these days. Alas I didn't get one of those chemistry teachers, so I've never seen it Unfortunately I can't bring the stuff to the next forum meet, but if I could..................  |
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Post by compsci on Dec 14, 2006 9:33:08 GMT
My Chemistry teacher once made something supposedly equivalent to Napalm (phosphorus somethingorother) in a gas jar. It certainly burned brightly.
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Post by Chris M on Dec 14, 2006 10:00:58 GMT
Unfortunately I can't bring the stuff to the next forum meet, but if I could.................. I don't think the Met Bar would be too hapy with a demonstration of a thermic reaction on their premesis! Neither were the police too happy when some chap to some to a speed camera. Unfortunately for him, he parked his car in the field of view of the camera and as part of its death throws the camera took a photograph... |
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Post by CSLR on Dec 14, 2006 10:20:26 GMT
I don't think the Met Bar would be too hapy with a demonstration of a thermic reaction on their premesis! Surely the heat that is generated by the process will raise the overall temperature in the room thus encouraging their customers to drink more? In addition, many people may need to drink to stop themselves coughing after inhaling the smoke and fumes. However, there is the problem that the demonstration may be considered a public performance and I am uncertain whether these premises are licensed for entertainment. |
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