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Building a drum roaster out of my grill
BetterCoffee
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Posted on 07/04/2017 9:08 PM
Hi everyone!
I've recently been getting into roasting coffee. I've done a few pan roasts and I want better results so I want to build a drum roaster out of my current grill that isn't getting much use. I've found a roasting basket on Amazon for about 30 bucks that will hold 900 grams. I think I will use a drill or an old standing fan to rotate my drum. I also want to cut some holes in the bottom of the grill and use a fan to blow air up through the flames to provide good air flow on the beans.

Anyways, since I don't have much experience in roasting I want to know:

Will this design give me decent results and is there anything that I can easily do to improve the design?
 
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renatoa
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Posted on 07/05/2017 10:59 AM
I have a mesh drum of 14Dx23L 3l volume, suitable for 600-700g roast, according the computations posted in several places in this forum and others.
Placed this drum in a 32Dx16H (cm) stainless steel pot, that is the oven of a turbo halogen heater, rotated with either 10 or 30 RPM, I have two units, and this is the best roaster I have built to date for the least money someone can could expect.
Much more controllable and reproductibile than a barbecue.
Roasters: DIY: TO based IR 200-640g
Commercial, moded: Skywalker, Dieckmann RoestMeister, Nesco, popper(s).
Electronics: TC4ESP (author), MS6514, USB/Artisan/Apps (contributor), PID controllers
Grinders: Potu ghost burrs, Arco, Xeoleo ghost burrs, Krinder, vintage PeDe Dienes, MBK Feldgrind, Kinu M38
Brew/presso: ALM pour over, Arin lever, Staresso Mirage, Hario Cafeor dripper, Flair Signature, Kompresso, Aeropress, Gaggia Mini
 
allenb
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Posted on 07/05/2017 7:36 PM
Welcome BC!
A few things to consider. Blowing air up through holes in the bottom of the grill will be pushing non-heated air across the beans (heating and cooling at the same time) which is bad. Better to add a (small) exhaust blower somewhere in the upper region of the grill off to one side.

For consistency from roast to roast you've got to find a way to read bean temperature, control the gas via needle valve and be able to see the gas pressure going to the burner.

Is it possible to nail a great roast now and then without the above changes to a grill? Of course but you'll never know how you nailed it and will most likely take a long time before ever accomplishing it again.

Allen
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
BetterCoffee
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Posted on 07/06/2017 10:49 AM
Thank you for the replies! They are much appreciated. I have seen a video where they used a halogen heater on top of a pot before. I was concerned about air flow with that design. Do you think that's a big deal?But I can see how that would give you more consistent results since you are dealing with less variables compared to a gas grill.

Great advice Allen, I didn't even think about blowing cool air up into the grill for some reason. Im sure they sell exhaust fans that can handle the heat but I'm not sure what to look for. Any advice there?

Would a grill thermometer do the trick? I would be able to get the ambient temperature of the grill not really the beans temperature.

Also, a needle valve seems like a pretty simple addition that will give me more control.Do you think a simple propane tank level gague(one that tells you how full your tank is) in conjunction with a needle valve will give me enough data to get repetable results?
 
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coffeeroastersclub
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Posted on 07/06/2017 1:35 PM

Quote

BetterCoffee wrote:

Hi everyone!
I've recently been getting into roasting coffee. I've done a few pan roasts and I want better results so I want to build a drum roaster out of my current grill that isn't getting much use. I've found a roasting basket on Amazon for about 30 bucks that will hold 900 grams. I think I will use a drill or an old standing fan to rotate my drum. I also want to cut some holes in the bottom of the grill and use a fan to blow air up through the flames to provide good air flow on the beans.

Anyways, since I don't have much experience in roasting I want to know:

Will this design give me decent results and is there anything that I can easily do to improve the design?


Don't worry about augmenting anything in the grill to increase air flow. Totally unnecessary. The spinning drum agitates the air inside the grill more than sufficiently for a great roast.ThumbsUp

Doing otherwise only injects cooler air into the already agitated mixture which is NOT GOOD. thumbdown

Len
"If this is coffee, please bring me some tea but if this is tea, please bring me some coffee." ~Abraham Lincoln
 
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BetterCoffee
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Posted on 07/06/2017 8:07 PM
Thanks for the advice Len. I may be over thinking it. Instead of blowing air in what do you think about an exhaust on the top? Too much? The only reason I was wanting to add air flow to the mix is because professional roasters control air flow when roasting.
 
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coffeeroastersclub
Top  #7 Print Post
Posted on 07/07/2017 3:46 PM

Quote

BetterCoffee wrote:

Thanks for the advice Len. I may be over thinking it. Instead of blowing air in what do you think about an exhaust on the top? Too much? The only reason I was wanting to add air flow to the mix is because professional roasters control air flow when roasting.


The drum in a professional roaster is pretty much an air tight environment if it were not for the induced air flow. A grill has plenty of natural air flow due to its loose fitting lid and lots of gaps here and there around the bottom, in back, etc. No need to augment. In fact it would be a detriment to augment because of the fact that the grill is so non-airtight. You would be sucking out much needed heat required for the roasting process, way over and above what naturally leaks out due to the above natural air flow I mentioned.

Len

Len
"If this is coffee, please bring me some tea but if this is tea, please bring me some coffee." ~Abraham Lincoln
 
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