Gas & burner control for homemade roaster

Discuss roast levels and profiles for espresso, equipment for roasting coffee.
DanoM
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#1: Post by DanoM »

Here in Japan I threw together a little roaster for roasting beans at home. Over the year I've used this thing one of the hardest things to control has been the stove I use to drive it. After several attempts at making something work I finally have what seems a stable heat control method, so maybe this will be of use to others.

The easiest gas to get in Japan is those butane/propane mixed gas cans for tabletop stoves. It's cheap enough, and I can get about 8 roasts from a single can which comes to under ¥10/US$0.10 per roast.

I use a small camp stove that cost about ¥1700/US$15 and an adapter for the butane cans that was very inexpensive. That stove is placed under a small stainless plate that converts the flame into a sort of IR burner setup. Above that plate I have a thermoprobe that I use to monitor the "stove" temperature during the roast.



The recent addition of a gas flow meter has helped tremendously in controlling the stove in a meaningful way. It's designed for oxygen flow, but works fine with my butane so far. Typically, I have gas flow less than 0.5 liter per minute once the roaster is heated up, so getting a flow meter than handles that range is important.


My roasts have been typically using ranges in the 0.3-0.4 range, but recently on a hotter day I was running in the 0.2 range. (I think this might have something to do with how wet the gas is coming through the flow meter. I always use the cans upright, but sometimes there is a tiny amount of liquid butane clinging to the float bead when it's cooler.) Monitoring the temperature in Artisan and making meaningful adjustments has made heat control so much easier than the previous guesswork. If the stove is running hot or cold I adjust flow a little, and can make adjustments as fine as 0.025 liter per min increments.

It's not beautiful, but it does work well. The flow meter cost me about ¥1000/US$10 on eBay.
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gtemkin
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#2: Post by gtemkin »

Nice job! Love the home built stuff.

Marcelnl
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#3: Post by Marcelnl »

Nice, great idea to use a good old flow meter...never thought they are so cheap on ebay...
In what do you roast? The perforated bowl, or in a rotating drum ?
Your burner appears far better than mine, so does the pressure regulator...can seems the same. I'll check out the web for parts and pieces, have to rethink the burner anyway as I'll be building a 500g roaster soon and will then likely switch to bigger propane tanks.
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DanoM (original poster)
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#4: Post by DanoM (original poster) »

Marcelnl wrote:In what do you roast? The perforated bowl, or in a rotating drum ?
My roaster is a modified, crank-style, flour sifter. It's capable of roasting 300-400g. Here are a couple introductory videos I shot a while ago, although the roaster has been modified a little since then it's essentially the same.
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Marcelnl
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#5: Post by Marcelnl »

nice! Like the mixing, looks very thorough...an electric drill is hard to beat :D
thanks for sharing,
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EddyQ
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#6: Post by EddyQ »

Nice roaster! I've seen a few heat gun versions of the flour sifter roaster. I'm curious how quick you can roast without getting any scorching or tipping? Heat guns have blowers, which I would assume would help reduce MET temps and scorching. But maybe with the nice quick agitation you have the beans are not getting much for scorching.
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DanoM (original poster)
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#7: Post by DanoM (original poster) »

I'm able to roast dense Ethiopian beans, 300g, to first crack in under 7 minutes without tipping or scorching. I usually stretch it out just a bit beyond that, but haven't tried it any faster. The key is speeding up the drill agitation for denser beans that may need more heat from the stove.

For American beans I run the agitation slower for 300g. With 400g of American beans turn up the speed and it works fine too.
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EddyQ
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#8: Post by EddyQ »

DanoM wrote:I'm able to roast dense Ethiopian beans, 300g, to first crack in under 7 minutes without tipping or scorching. I usually stretch it out just a bit beyond that, but haven't tried it any faster. The key is speeding up the drill agitation for denser beans that may need more heat from the stove.
Thats great. Thanks DanoM. Far better than my DIY heat gun dog bowl contraption. This tells me my fixed agitation needs an upgrade to something quicker and variable.
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DanoM (original poster)
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#9: Post by DanoM (original poster) »

I have a single white line painted on the chuck of my drill, and when adjusting the speed I use that as a rough reference.
Originally I ran the drill at about 60rpm, but lately it's usually 90-120rpm I'm guessing. Keeps the beans tossing about and makes it far less likely I have burning or tipping. The smaller the bean the faster the stir since the agitator doesn't actually touch the bottom layer of beans and uses other beans to keep them moving.

I think of this roaster setup as a kind of "air roaster" with the air agitation replaced by mechanical agitation. Nearly 100% of the heat from the stove goes up through the roaster, and I can keep my bare hand just on the outside edge of the roaster indefinitely without any danger of burning due to the chimney effect. (When my roasting room is cold I place the butane can right next to the roaster so it stays warm enough to maintain pressure. Checking the bottom and side of the can constantly throughout the roast shows it never reaches body temp. !!!Not something I recommend due to the dangers of explosion involved, but it does stabilize pressure for me!!!)

ByTheWay... I started this setup with a heatgun, and when that died I knew I needed something more powerful.
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Marcelnl
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#10: Post by Marcelnl »

I just did some roasting using a plating ring as chimney, as the flame and heat often wander. The result seems more even than sometimes is the case, simple things like this can make a large difference. Thanks again for sharimg your method.
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