Hi!

I've been wok roasting beans for 10+ years. I now want small roaster than can do 200-500grams batch. Having looked at what's available online, nothing seems to fit what I want (gas operated - electricity is frightfully expensive in Manila, will last practically forever - especially if imported, good, simple design - even if it requires manual fiddling, can do reasonably sized batches). My wife works with several metal fabricators for her kitchen business, so I've decided to try my hand at building a small roaster.

The design that's appealed to me the most comes from this blog: http://iicoffee.blogspot.com/2011/04/co ... roast.html



I tried to search for it so I can just buy it since we're going to Osaka in a couple of weeks, but haven't seen it anywhere for sale.

It's the size i like, it's simple. I can probably build it from stainless sheets probably for around $300 including the labor. Can be fired from a small gas burner which is easy to get here. The housing seems to make it more efficient. There are not too many moving parts. I plan to use it out doors, so I am not so concerned about the smoke. If I don't add the motor, I think it will still be a big improvement.

The design features I am thinking of adopting:

1) Stainless steel drum and housing. I like also that you can just lift the drum out and pour the beans. 8 inch drum diameter.
2) The drum will be perforated (drill press), but not to the same extent as the mesh in the Japanese roaster. Maybe 100 holes? I can't get that mesh here. From the design, the drum is tilted, I am not sure why (to prevent spilling and a clear flow of hot air?). I plan to have 2-4 metal strips in the drum angled so that the beans at the lower end of the cylinder will slide to the top to help distribute the beans .
3) A stainless plate/flame tamer with slits right over the burner so flames don't touch the beans
4) Bearings on front and back. If it's easy to put a motor in the back, some kind of gear.
5) Drum will be more conical at the exit end so easy to dump the beans
6) Burner will probably go up to 12,000 btu (from what's easily and cheaply bought here - $20). I can also buy a nice single burner that goes to 25,000 btu for $90 but I think that's overkill.
7) I am not sure of the sheet thickness for the drum, but maybe 1-1.5mm. The housing can be thinner. The flame tamer will be 1.5mm or more so it will last longer.
I have extra copper sheeting (my wife built a custom copper kitchen hood for a project). Is copper safe to use for the drum? It will conduct heat better and look cool, but I am concerned it will react with the acid in the coffee.
9) Most of the construction probably will be riveted, with some welding

I would really appreciate any advice from the experts here. Is the design ok? Is the flame tamer necessary? It looks like the Japan one has it. Should I bother with a motor? Should I build a prototype with just galvanized sheet steel first and then tweak the design? Is the size ok 8 inch diameter, seems like 9-10 inch length.

Anyway, my wife and I are more or less comfortable with building projects. I've built a couple of brick ovens and we did a lot of the supervision work for our house. I also don't mind if it's not too automated as I enjoy cooking.

Thanks!

Hi Eric!

Here's a site where coffee roaster builders hang out.

http://www.homeroasters.org/php/news.php

Do you have any tips or advice on wok roasting coffee?

Hey thanks Hankua. That's a useful link.

On wok roasting, we have a live-in cook (it's not expensive in Manila). I showed her how to wok roast and she does it weekly.

We use a preheated All-clad stainless wok and cook about 150-200 gms per batch on top of a 15,000 btu burner which is probably at 60-70% power. During the first few minutes, I cover the pan to help the beans warm up and try to swirl/flip the beans inside the wok. We try to complete the roasting to just after the second crack (FC to FC +) within 12-15 minutes. If it's longer than that it tastes grassy and baked. If it's shorter, it's probably partially scorched. A wok is better than a flat pan because it's easier to move the beans around. The all clad distributes heat very well vs a carbon steel wok. After cooking we toss it on to a aluminum baking pan to cool. The failures typically are cooking time, over or under, mainly due to havng too many beans.

Our cook, while quite good, botches it up once in a while which makes me question my beans. If she does it two weeks in a row, I will cook a batch and normally it's pretty good.

I buy imported green beans (kenya, mandheling, ethiopia etc) but also use locally grown mountain arabica (benguet and sagada). The local beans are not as complex, but not bad and cost about 60%-70% less and still far better than what I can buy from local coffee shops.

Thanks!