tjdaggett Posted November 3, 2020 Share Posted November 3, 2020 Smiths, Good morning! I fired up the forge with my brother-in-law last Saturday. We're burning charcoal in an old bottom-blast rivet forge. We were testing the limits on the hand-crank, as it has a bad gear. At full blast there was a fountain of sparks issuing forth that went well over my head, 4-5' up from the forge. We need to reduce that fountain. My plan for right now is to go buy some coal through the Guild as I know a bottom-blast setup produces less sparks and burns less fuel when burning coal instead of charcoal. That should get me through the winter, giving my BIL and I time to put together a side-blast to use with charcoal. Good excuse to take a day off and visit the farrier school too. Any other thoughts? I'm looking for tricks I could use to make the current setup less of a fire hazard/hair burner. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted November 3, 2020 Share Posted November 3, 2020 Don't crank so much! Rivet forges often have inefficient blowers on them that have to be cranked hard and fast. Moving to a larger handcrank blower that can be cranked much slower can help keep the air flow steady and sufficient but not "erruptive". Quote Link to comment Share on other sites More sharing options...
Frosty Posted November 3, 2020 Share Posted November 3, 2020 Uh. . . don't crank so hard? Turning a rivet forge into a side blast is as easy as as laying a 90* elbow with a 1" pipe nipple over the air grate and covering it with clay. The nipple is now your tuyere, build the trench forge around it. Viola! Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
tjdaggett Posted November 3, 2020 Author Share Posted November 3, 2020 Frosty, I'll take a look and see if the conversion is a possibility for mine. Sounds pretty straightforward. We're finding that if we don't crank with a little oomph the steel heats up sluggishly. This is something I would learn in a good class, which is on my to-do list, but how long should it take to heat up a piece of 3/8" round at full blast? I need to time it. Perhaps YouTube has given me unrealistic expectations! Quote Link to comment Share on other sites More sharing options...
Frosty Posted November 5, 2020 Share Posted November 5, 2020 I should hope so! The worst it does is shift your fire towards one side of the pan by a few inches at most. If you can't deal with that you need help, maybe the maille is clogging your brain waves. It's just fire management, every fuel has a character you need to get to know. Once you know your fire it's predictable and loyal. Fire never lies or tries to trick you. Heating 3/8" round at full blast in a bottom blast charcoal fire will take longer than necessary. That much blast is blowing the heat through and out of the fire. A gentle blast will develop a screaming HOT heart and heat your stock reasonably quickly. How quickly depends on a number of factors you don't include with your question. When I've burned charcoal, usually in a camp fire I rake it down to as small as practical, say 3/4" and smaller. In my admittedly bottom blast rivet forge I screen it on my #3 screen, that's 3 openings per inch which isn't really 1/3". Don't ask me why, it's complicated and an old tyme thing. Anyway, the smaller the fuel the greater the surface ratio to volume so the fuel burns faster, consuming oxy in a shorter distance and more fuel+oxy+heat/time. I'm hardly turning my blower, maybe 15sec/rev and that's my full blast. 3/8" square comes to welding temp in under a minute easily. Remember a given size round stock is only .7854 the volume of the same dimension square. However square has significantly more surface area/ dimension and volume. For simpleness. 1" round has a curcumference of 3.146" (surface/linear dimension) where 1" square has 4" (linear) and the corners are thin and absorb heat faster. Make sense? Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
tjdaggett Posted November 5, 2020 Author Share Posted November 5, 2020 Frosty, Good afternoon! The surface area of the steel bit makes mathematical sense, yes, as it does for the coal. I think I will take a very simple step first: sizing down my charcoal. Right now it's mostly in chunks slightly smaller than what you'd get in a bag of grill charcoal, some of it larger. I'll break it into something a little closer to a peanut M&M and see how that burns. From there, we'll try the forge modification. Quote Link to comment Share on other sites More sharing options...
Frosty Posted November 5, 2020 Share Posted November 5, 2020 That'll make a big difference, try for walnut size first, that might do it and there will be fewer fines to blow around. Large pieces have too much space between them for air to blow through carrying heat with it. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
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