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Gas bottle furnace


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Seen on youtube of people taking old propane or butane bottles, cutting the top off, drilling a hole for an air pipe and using the shell for a furnace. Has anyone made one of these and are they any good? There are videos of melting aluminium in them but I was wondering about the longevity of them and how quickly and efficiently they melt.

Also when is it safe to start taking grinding disks to the bottle? Will getting the valve off a filling it with water suffice to get rid of the fuel?

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I would over the valve all they way like you would be turning the bottle on to use. Open the valve all the way and make sure you get out any pressure in it. Once you do that then unscrew the nozzle off the tank then fill it with water. I have not ever done it myself though so I wouldn't take my advice  haha. I think the method would make sense though, but you might want to get more opinions.

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From what I read on other forums that is what others do. Remove the valve, fill with water ( soap and water if you want to get rid of smell). You can let it sit for a bit. You are the only one liable for you actions so do what you feel and know is safe. People of been injured doing it before. I am not telling you "yeah go do it, it will be fine", I am just saying how people have done it before. 

 Here are some other people talking about this topic on other sites. http://www.thesmokering.com/forum/viewtopic.php?t=47602 and also on this one http://www.millerwelds.com/resources/communities/mboard/showthread.php?7059-Cutting-Open-Old-Propane-Tanks&highlight=cutting+propane+tank.

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apparently the local scrapyard doesn't like stocking them too much, got a nearly empty one for £2. Vented the gas, got the valve off and it is now on its second fill of water and it can soak with fairy liquid in for the night. For that money I thought I might as well have a go at making one.

Hope 27L is big enough

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Making the hole for the airpipe and so far no disastrous explosions. fudged the angle grinding the top off a bit so their is some gaps between the lid and base. Scrap yards didn't have anything for crucibles though I might be overly playing it on the safe side for wanting 5mm thick walls on tubes.

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What did you use for insulation? On youtube some had no lining and others used cement (which I believe will crack under any amount of heat). The plan was to have a solid fuel based furnace so I guess the crucible or lining has to be smaller to compensate for space taken up by coke.

 

Also how big should the hole in the top be? My air pipe is ~25mm dia and the hole in the top is 18mm dia and some will probably vent out the sides where the two parts meet (gonna try and get a sheet metal lip welding on the lid to create a better seal). I suppose the hot air will expand so the outlet needs to be >25mm but at the same time less hole means more insulation I suppose.

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Straight cement is no good, absolutely.

 

But the backyardmetalcasting recipe has portland in it, and is good well up to brass casting temps. It definitely holds up at aluminum temps. When you get into the forging range it does start to slag near the heart of the fire though.  My avatar pic has a lawnmower forge at its heart that uses their recipe, poured and used for 3 yrs, and has needed minor patching exactly once.

 

Caveat - it does NOT insulate as well as professional refractory, so you usually end up putting a fairly thick layer in. Use professional products, get professional results. (and wayne's has an excellent reputation btw) With casting, I find you'll also end up patching more often than real refractory.  Use amateur supplies.......well, I'm cheap, but you don't have to be. Strongly recommend you don't cheap out on the crucible, and read up on preheating.

 

My casting furnace....hmmmm, it's been a little bit. Maybe fire it up tonight. And no, I didn't cast in those shoes.

 

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I have been casually looking around for fire clay, with the plan to make the backyardmetalcasting refractory, in nearby places cause I don't want to pay postage for bulk stuff like that but to no avail. In one place that was half DIY/half boiler components they directed me to fire cement which gets used on flues and boilers and such. Rated up to 1250 C. For use as refractory should I add perlite and sand or since it is ready mixed do I apply as is or is it unsuitable for the job?

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I am not using it as a foundry it's just a blacksmith forge and not a foundry. I've used it plenty of times as a forge to make tools and knives i know it works for bladesmithing and blacksmithing. I will not be smelting metals or casting i don't care to try that right now.

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