[q]We have some good discussions running concerning small wood stoves. These are really neat, and simple to make, from a couple of old coffee cans. Ideal for mucking about with evenings or weekends. Don’t be afraid to experiment. The blue flame, which Carl spoke of, occurs when the volatiles are all used up and the charcoal starts incomplete combustion. This should be carefully monitored, because the blue flame is carbon monoxide – toxic gas. Do not allow the stove to smoulder with no air at this stage in the burn. Another stove I heard of consisted of rammed saw-dust in a cat food can, with both ends removed, but with a broomstick down the middle before you start compaction. This leaves a 1″ or so diameter hole down the centre. Lift the can gently onto some supporting pebbles or wood blocks to raise it 1/2″ off the ground and light the top. The sawdust should burn from the inside outwards and from top to bottom with a clean, deep orange, wood -gas flame.[/q]
[a]
Another thought on tin can stoves. As a kid, my dad helped me make a steam turbine from an old cocoa tin, with an 8 bladed turbine made from a circular disc of tinplate, cut into sectors and each sector given a gentle twist to make a propellor kind of thing. This turbine disc had a nail through the centre, sharpened at both ends to make a couple of bearing points and a bent metal bracket held the whole thing onto the centre of the press fit removable lid of a cocoa tin. A small jet was made from the underside of the lid – punched through using a nail, so that when water was boiled in the can below, it would turn to steam, come out of the tin at a few psi and turn the turbine. Now it occurred to me that the turbine could be used to turn a small blower fan to create a forced draught – again made from tinplate, set in the base of the can, mounted on the same shaft, a bit of welding rod, running through the centre of the tin can stove.
The the hot gases rising upwards from the flames could be used to turn the turbine and thus turn the forced draught fan. The fan could be started either by blowing on the turbine (and fire) until it self sustained, or possibly with a bit of string wrapped around the cold end of the fan shaft – and pulled like a starting cord. It all needs some more thought to get things working together correctly – but basically you have a wood-fired turbocharged gas stove![/a]
[a]
This is actually a good idea. And any “Yo Yo” could build one! I would start with a squirrel cage fan and a draw string or even a simple sprag ( one way ) clutch and a bow string moving back and forth to keep the fan turning. As you say, one might be able to get the whole thing to work on its own, but if one couldn’t, a little help from the bow string driven fan wouldn’t take much energy out of the person starting the fire. That way damp wood could be burned, etc. For stationary set ups a bicycle could provide the power to the fan. Quite a forge you could have with a bicycle driven blower! Almost a tenth of a horsepower at your disposal for fairly long periods of time. And with more than one guy on the bike, you could go for hours to melt bronze, etc. Blades of plastic or aluminum could be “woven” into the wheel spokes and the rear wheel aimed at a big cone leading to the fire or forge. Axial vane fan, human powered. [/a]
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