Ok, maybe I won't be able to close it. If my plan works out for the glass, I should have a great view of the beans. I use the Gene Cafe now so I'm used to watching the color and volume change, it should an easier transition to this roaster that way.

Hi, what a great project, I am thinking about something on the same design.if I understand gas convection means there won't be any gas fumes exposed to the beans. Also how would you mount and sample bean temp probe, maybe threw the front plate into the roasting drum. Did you install a large bushing around the outer perimeter of the drum so you can load and dump the beans,so many things to consider before starting a project like this.I think I have enough shop tools to start. My uncle next door has a milling machine and a lathe so I think I got that covered, I have a Mig welder to fab things up. Can't wait to see your finished roaster.I have seen 2 to 5 LBS commercial roaster out there for 6 to 7K, I think I can build out for less then half that cost, just need to get the design issues clear in my head before I start,air flow,BTUs,chaff removal,temp control, ramp rate,soak,cool.For the last year I have been buying parts for this project,Fuji PID loop controller TCs for mounting, DC drive motor for the drum 0 to 100 rpms , 1/2 HP dc drive controller decided on dc for its high torq value.Any input on the the drum and propane heating system to fabrication would be greatly Richappreciated

Rich, I think you are way over thinking the project. First, have you done a lot of roasting yet? If not, I highly suggest using the heat gun approach for 200 or 300 batches. After that you will have a real feeling for what is happening and when to stop it (which is the most important thing). In my opinion the heat gun approach is the best learning tool. If your needs are small, it never needs to be upgraded.

Once you have the roasting down, it will become obvious what is and isn't important. Avoiding gas fumes isn't important, in my opinion. PIDing (ramp soak cool) the machine before you understand its thermal properties is premature. A variable speed motor is totally unnecessary, but you could use it to build something else, like a knife sharpener.

Chaff collection may or may not be important depending on your design. Kendall's closed design needs it, I guess, but I'll be interested to see if the final design makes a good roaster. I have some reservations, though I applaud Kendall and everyone who is tinkering away.

I think the most important part of the design (assuming you have enough heat to heat the beans and rotation to keep them heating evenly and avoid burning) is not a temp probe, fan, chaff collector, dumping mechanism etc., but the ability to be as close to the roast as you were when you were using a bowl and heat gun. Then you can really be on top of what needs to be done. The more steps you are away from the beans, the more likely you will not have good control. If you need to wait seconds to use a tryer, you are waiting too long.

The Sumatra I've been roasting has a very short window going from C+ to C++-- less than a minute. I want to pull it at C+ and stop the roast at that point, not let it coast all the way past 2d crack. So I need to be able to see what's going on and dump it in a few seconds and cool it in a few more seconds.

Sorry for the lecture. I'm not an expert yet, but after 300 heat gun roasts and more than 300 using my "2 pound" homemade roaster (that costs way less than $200 in materials), I've learned that for me, at least, it is better to get a feeling about the properties of the machine before making decisions on cosmetics, automation, instrumentation, etc. (I use an infrared thermometer as one data point -- smoke and smell as another and elapsed time as another).

I'm now toying with the idea of not a PID, but using an Arguino to control the roast. The thought would be to allow a semi-interactive user interface that allowed changing ramps on the fly. If the roaster is to be able to respond to this sort of control, however, it has to have thermal characteristics that allow it to do so. For me, this means the machine should not be a heat sink, that it should have enough power to drive like a car -- put your foot on the gas-- it goes. Take it off, it slows down fast. If you don't have this, you can still do ramps, but they still might not match the profile you want. I might not go ahead with the Arguino project. It isn't keeping me up thinking about it...

Good luck with your roaster. I really suggest you take an incremental approach and let it evolve. You could spend 80% of your effort on stuff that you don't use or doesn't work or you don't like if you try to design it all at once. Or you could if you really want to do that, just knock off a commercial roaster. Nothing wrong with that.

Here is some progress: I fabbed up the chute and front plate. Its all welded from sheet steel. The back of the chute has a one inch hole for exhaust extraction. You can see the large holes in the front for the TCs. They are 1/8"NPT threaded. The smaller ones in pairs are for the discharge door hinges. They may be in the wrong place, we shall see. The paint is high temp grill paint good to 2100*F or so.

You're really doing a nice job. I examined a 10 pound Probat roaster carefully yesterday. It has a shaft that runs all the way through it. The sides are made of 5mm steel plate. The interface between the open drum and the front is simple, just proper alignment. I give up on trying to get these $%&^ iPhone pictures rotated correctly, even with Photoshop. Thanks Apple.

That round silver handle is a counter weight to keep the door closed. It probably weighs 30 pounds. The tryer is only 4 inches or so and the internal baffles have an interesting complicated pattern to make the beans evenly distributed.

I don't think the owner, (very nice guy) knows what he's doing. He bragged how he does his roasts in less than seven minutes and by then they are "nice and oily".... He drops ten pounds into a 400 degree drum and the rest is history. Second crack follows immediately on the heels of First, or maybe he skips first altogether.



I think my own roaster needs a shroud. It was windy the other day and it greatly increased my roast times. I'm going to do something 'good enough' since that is the basic idea of the roaster.

Keep it up!

DJR wrote:...and the internal baffles have an interesting complicated pattern to make the beans evenly distributed.

The drum mixer paddles are meant to maximise the convective heating of the beans. It keeps the beans in the air and maximises the surface area that is exposed to the hot air stream. Of course it does help the mixing of the beans to even out the roast as well.

with that metal shiny surface on the drum, most (if not all) of the radiant heat will be reflected out. If for example the roaster uses a electric heater (mostly radiant), it will not be efficient. But if you were to sand or paint(?) the drum, the heat in the drum would transfer better.

Cheers

Thanks, that had not occured to me yet. It would be interesting if you could actively contol the balance of convective and conductive heat! Not much progress since my last post, but i'll keep everyone updated as I go along.