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Joris wrote:The other problem is less easy to solve. I have noticed a defect in all the coffees I roasted, a smokey/ashy taste. I think this has something to do with the smoke trapped in the roasting chamber and drum. I could try to add a extractor fan but since the temperature of the air is quite high i doubt any fan would be able to take that heat without breaking down....
Anyone any thoughts on this one ??
GreenBean wrote:As shown in the photos there would be a very large flow of hot air out of the open front of the machine (and cold air in at the bottom to replace it. This would require a large heat input and large temperature gradient over the roaster. The ashy taste could be simply charing of the beans due to the high heat input.
bruceb wrote:I have a question to the basic design. You are using a catalytic heating element whereas commercial gas-powered roasters usually use open flame heating. Have you noticed that chaff falls onto the catalytic elements and burns up, possibly producing more smoke? Or does the chaff all get carried up and away by the current of hot air?
Joris wrote:Another thing, the previous vanes in the drum had a couple of gaps in which beans got stuck (a total of 15 / 20 beans). Those beans were complety charred, might that be a possible cause (e.g it "tainted the entire batch through the smoke released by burning up) ?.
bruceb wrote:You know, Joris, old Breako may have hit on something worth thinking about...
espressomattic wrote:bruceb wrote:You know, Joris, old Breako may have hit on something worth thinking about...
Well it was bound to happen at some point
espressomattic wrote:bruceb wrote:You know, Joris, old Breako may have hit on something worth thinking about...
Well it was bound to happen at some point
GreenBean wrote:3. Experiment with natural convection through a flue with a flap to control the flow of air.
I would try 3 first I would expect that a 25 - 40 mm dia flue approx 300 mm long would provide more than enough flow and you would end up throttling it to reduce the flow.
Joris wrote:Thanks mate
If the smoke problem exists in the roasting chamber and drum (e.g. smoke does not leave roasting chamber so the drum stays filled up with it as well) then option 3 sounds like a plan (and even easier to implement).
espressomattic wrote:Some of the really old probats have this strange flue system that allows you to 'Profile' the smokey taste. From what I have seen it is a simple flue that traps hot air and smoke. To quote one of the guys here 'Ireally freaked me out so I don't use it'.
bruceb wrote:You know, Joris, old Breako may have hit on something worth thinking about, namely putting a chimney on the housing. You will need to put a damper in it so you can control the heat loss, but you may get a better heat distribution and get rid of the smoke as well. I've been studying steam engine boiler design recently (don't ask) and the effect of a flu or chimney on a fired heating chamber of any kind is decisive.
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