Coffee roaster (more brazing than welding) (prototype)

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I just finished making a coffee roaster. It's a drum roaster, meant to be used over a burner on the stove. You put green coffee inside, put it over a low flame, and slowly turn the handle until the coffee sounds and smells right. Then the beans are air cooled and poured out the hole (around the spindle). Most of the parts are brazed, but but the spindles are welded on because they're big enough, and they need strength with a small attachment surface area.Problems:I had a lot of trouble with this because the drum is thin and perforated--I don't think it's possible to weld this without burning right through, except maybe with an automated precision process. Brazing is the only option, but that's hard because the drum warps and doesn't want to make good contact with the other piece. The parts that I successfully welded are the spindles and the metal plates that hold them--these plates are then easy to braze to the drum. The spindle's contact area is so small that brazing would be unacceptable. (Fillet brazing would work, but I don't have a O/A torch to make a fillet braze.)I have some ideas about how to weld onto perforated sheet metal, but it's really thinking outside the box, and I don't know if there's a more standard technique--I'm thinking along the lines of welding a thin rod to the thicker part, then threading the rods through the perforations, bending them, then brazing them to the other side of the drum to anchor them. Are there any good ways to do this? The metal is incredibly thin, and the perforations mean the heat can't escape, so I don't think any normal type of welding will work.
Reply:going with food grade silver solder might've been another option.i.u.o.e. # 15queens, ny and sunny fla
Reply:Interesting thought, thanks. That's worth a try (except that I can't buy silver braze without cadmium).
Reply:Originally Posted by tackitWhat's the benefit of roasting your own compared to buying beans roasted in a gazilion dollar commercial roaster?
Reply:All this effort for DECAF?30+ yrs Army Infantry & Field Artillery, 25 yrs agoMiller 350LX Tig Runner TA 210, spool gunLincoln 250/250 IdealArcESAB PCM 500i PlasmaKazoo 30"  vert BSKazoo 9x16 horiz BSClausing 12x24 lathe20T Air Press
Reply:Welding thin with control has tig written all over it. Down side ( besides needing a tig welder) is that welding thin material with tig requires a lot of skill. Something most people don't have, and it takes probably several thousand hours to acquire, if you are lucky..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Originally Posted by storemanAll this effort for DECAF?
Reply:Originally Posted by piojoInteresting thought, thanks. That's worth a try (except that I can't buy silver braze without cadmium).
Reply:Bend 4 to 6 tabs for each end so they fit into your screen and rivet them to the screen and the (bowl) end plates. Pop rivets will do.---MeltedmetalIf you want it stiffer extend them to the other end, each in one piece. That is maybe even 3 bars attached with pop rivets to the 2 bowls with the screen over them. It will help to agitate the beans as a side bonus.---MeltedmetalLast edited by Meltedmetal; 08-21-2014 at 07:13 PM.
Reply:I like it! Are you pleased with the results so far? I have had really good results(no warpage, clean, etc...) with a pencil torch and silver solder. I have gone down to .015 brass shims with no problem using this method. It does melt at a pretty low temperature though, I think it should be fine since it is rotating vs. just sitting over the low flame.Not to jack the thread but, how do you brew your coffee? French press, vac-pot, siphon? I am a bit of a coffee addict.
Reply:Originally Posted by MeltedmetalBend 4 to 6 tabs for each end so they fit into your screen and rivet them to the screen and the (bowl) end plates. Pop rivets will do.---MeltedmetalIf you want it stiffer extend them to the other end, each in one piece. That is maybe even 3 bars attached with pop rivets to the 2 bowls with the screen over them. It will help to agitate the beans as a side bonus.---Meltedmetal
Reply:Originally Posted by piojoI've read a little about riveting, and this metal isn't doesn't have the recommended margin width around the holes. Could I solve this by using a rivet that's too thin (doesn't actually press at the edges of the drum holes), or will it just not work at all? Also, I've never drilled metal. I'm sort of afraid of this. Would it be easy to drill thin sheet (0.7 mm) with a small vice, or will the drill bit grip the metal and bend it? And yes, perturbing the beans is a plus. It's hard to see in the photos, but there are fins made of wire extending into the drum. There's no fin on the inside of the bowl where it's most needed, though. The beans that end up touching the bowl slide around but don't get perturbed. I need to fix it, or probably just make a prototype #2 with a removable lid instead of a cut-up bowl.Thanks for the tip about the torch--I probably would have just tried to lower the flame on my propylene torch, but butane or LPG is really what I need for silver brazing.As for the results, the first roast (about 1/2 pound) tastes great. I'm having trouble with temperature control (my stove goes from low to medium with very little control), so I plan to keep the stove on low and provide a "hat" of sheet metal or aluminum foil which I'll move to allow more or less heat to escape. When I turned the stove up to medium the coffee started roasting too fast--I'm not sure about the separation of first and second crack, and when I turned the temp back down, I don't know whether I interrupted one of these stages or whether first crack was just finished. Though I think I got into the full swing of second crack, which would make this roast darker than usual. I'm drinking it with a Vietnamese-style coffee dripper, and since I'm lazy, I also use an Aeropress (though I think the AP taste is merely "acceptable").Have you ever used your fabrication skills for coffee or food?
Reply:Originally Posted by Sheyda36I am actually working on a cold-brew similar to a Yama drip system but more "modern". Here is a link to the look I am going for: http://propercoffee.co/ Although I am having trouble getting my glassware, wrong package and items. I hate ordering from china! Between all the returns it has been a couple months of back and forth! I have also made a vacuum/siphon pot that works really well.
Reply:Originally Posted by piojoThat looks really cool. If I were you, I would have considered making a prototype out of metal--instead of a perfectly shaped carafe, you could make an inverted pyramid shape from three long triangles of metal. Getting the inside well-coated with coffee oils would protect it from potentially changing the taste. When it works well, you would order the glass. (Though there's no way you could have known it would be so hard or time consuming to order source the glass.)
Reply:Quote  "I've read a little about riveting, and this metal isn't doesn't have the recommended margin width around the holes. Could I solve this by using a rivet that's too thin (doesn't actually press at the edges of the drum holes), or will it just not work at all? Also, I've never drilled metal. I'm sort of afraid of this. Would it be easy to drill thin sheet (0.7 mm) with a small vice, or will the drill bit grip the metal and bend it? And yes, perturbing the beans is a plus. It's hard to see in the photos, but there are fins made of wire extending into the drum. There's no fin on the inside of the bowl where it's most needed, though. The beans that end up touching the bowl slide around but don't get perturbed. I need to fix it, or probably just make a prototype #2 with a removable lid instead of a cut-up bowl."You could probably get away with 3 angles fabricated out of thin sheet metal. Make each one long enough to pass from one end plate to the other with enough length to allow for attachment at each end. If you are careful you can cut the vertical leg wide and form the horizontal leg from the vertical for the end pieces where you have to cut the straight horizontal leg away to fit the shape of the end plates and then trim the vertical leg in the center to the height you want. Pop rivet them in to both the screen and the end plates. You will probably want 2 rivets in each end plate for each angle to overcome torsional forces but it may not be necessary if the assembly is tight. The vertical legs will agitate the beans as it rolls. I hope you can make sense of the description if not I can demonstrate in pictures with paper. To drill thin sheet metal use a steady pressure on the drill but not too much and ease up the pressure as the drill is about to break though. If you are concerned that the rivets will pull though you can rivet though washers to support the surrounding metal.This type of tool and the appropriate rivets should do the job. http://www.harborfreight.com/hand-ri...set-38353.html ---Meltedmetal