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Thread: pot belly wood heater design
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3rd Jul 2011, 09:53 PM #31
Stainless and cast iron. What else can be used? Mild steel is no good and copper is too easily damaged. What does that leave that is readily available and affordable and workable. After all you can weld stainless with an arc welder. How much easier can you get?
When I mentioned stainless water jackets I was talking about after market jackets for wood stoves which are stocked by dealers and can be ordered to suit.
Dean
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3rd Jul 2011, 10:17 PM #32Diamond Member
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Actually cast iron is very good material for a fire-box, and I would expect that for similar thickness of material, cast iron would outlast steel plate, You would just have to bolt up to it or perhaps braze if the part didn't get too hot. One thought I did have, which may have legs for you would be to make the opening for re-fueling in the top, with a removable hot plate like some pot belly heaters have. You could also incorporate a removable funnel like duct below the hot-plate, a bit like the ones in the old bathroom chip heaters. That might work well with the need to keep it to around 320 mm dia., and still be able to handle longer pieces of wood. There have been lots of good ideas here, from all contributors, I hope you have every success in sorting the different ideas, and coming up with your working solution. Keep us posted,
Rob.
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4th Jul 2011, 06:47 PM #33
Why cant mild steel be used?
We use it in a blast furnace and many other furnaces, there is refectory lining to protect it from the molten metal, but were talking 1000°c+.
In the refinery the molten lead is held in pans from 450~660°c, the setting/chamber they sit in are gas fired the cutout is set at 800°... all mild steel!....................................................................
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4th Jul 2011, 08:30 PM #34
Good question. I was thinking of rust in hot water system. Combination of water and heating. It may be feasible but would not last as long. I keep thinking about steel fittings and welsh plugs in car cooling systems and wishing that brass or copper was used instead.
It wasn't the heat I was concerned about. You can melt lead in an aluminiun saucepan. I was more concerned about corrosion.
What do others think? Is mild steel feasible as a hot water jacket?
Dean
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4th Jul 2011, 09:43 PM #35Diamond Member
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It is not so much that you can't use mild steel, but more that Cast Iron will last longer I am led to believe. C.I. won't last forever either, but it is what they use for replaceable fire grates in many stoves or heaters, and stoves such as Warmray, Aga, Rayburn were all constructed of C.I., and they had the hot spots refractory lined as well, except for the grates. These days plenty of wood fired heaters are fabricated from steel plate, and most use linings as well, and for home made ones, steel will generally be easier, as not many of us have foundry skills and equipment, whereas metal cutting and welding is well within the capabilities of most forum members I would think.
If the steel is protected in the hotter areas, it can last for years, - witness the various form of barrel heaters which use either a whole or a part of a 44 gallon drum as the firebox. they usually are part lined AFIK, and as long as you keep the rainwater out, they can have a long life.
On the other hand, using mild steel to make a heat exchanger is likely to cause you grief I would think, unless you used an automotive coolant or similar anti-corrosive fluid to transfer the heat to another heat exchanger where the heat was transferred to water or air or whatever you wanted to heat. Stainless steel is probably the easiest material to make a box or you could use stainless tube, or even copper tube as long as you protected it behind refractory or even behind a thickish steel plate. If covering with refractory, it may be an idea to wrap it first in insulating wool so that the refractory wasn't stressing directly against it with the heating and cooling cycles. My two cents worth anyway,
Regards,
Rob.
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31st Oct 2020, 11:49 PM #36
Truck Drums
Best small heater I've seen was made from a few big old truck brakedrums. Really efficient it was too, and... lovely heavy cast iron!
300mm will only take kindling size wood, you'll forever be feeding it! Copper water pipe will melt in no time.
Have a look at a water jacket from a Rayburn or similar... THICK stuff, - copper waterpipe won't cut it.
There's an art to designing these things to burn efficiently.
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1st Nov 2020, 10:23 AM #37Most Valued Member
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You probably didn’t notice but the thread has had no activity for 9 years...
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8th Nov 2020, 10:57 AM #38