Hello fellow Roasters

I have decided to make my own roaster. I had, for a very short time, an iRost 2. But the noise and the fact that it could not roast a lot of beans at the time and the problem getting a good result every time, I went and ordered a 45 liter Mini oven.
The oven is from amazon.de and an electric motor with 50 RPM from China.
I still need some bits and pieces, like insulation, homemade drum, contacts and so on.

The oven already comes with rotisserie, but the motor is way too slow to get an even roast. My plan for the rotisserie motor is to build it under a pan with holes and then connect it together with a fan underneath. Then place the pan and fan, in a bucket/container which then has some holes in the bottom, so the cold air will travel from the top down through the beans. Hope it makes sense.
Hopefully it will look a bit like a Hottop cooling pan when complete.

I will update my progress, so stay tuned.

Here are a few pictures of the things that are on the way:

Here is a little update on how the project is coming along.

The slow motor came out, and the new 50 RPM is ready to be installed.



This is how the lock on the drum will look like.



The drum. I still need to make the end pieces for it.



I found a contact from a old pc power supply, so I can start/stop the drum when it needs to come out and when it needs to be loaded with beans.

I made one like that years ago. I took the shell off and wrapped the oven inner chamber with a high temperature wood stove fiberglass insulation to keep the heat in. I replaced the rotisserie motor with a 60RPM motor mounted on the outside of the roaster to keep it away from heat and welded an extension onto the spit pole and put a bearing in the side of the roaster for the shaft to go through. The little oven itself would not get got enough so I added an electric burner in the base (I think it was a charcoal or smoker burner) so I could get more heat. That one I would leave plugged in during the roast and turn up/down the roaster burners to change temps. I could get up to 500F inside the oven with the auxiliary burner. The drum I made from stainless steel, around 16 gauge. One end was solid, the other end I made a solid cap for, cut it just under the spit bar and welded on 2 hinges and put a pin/catch on it to hold it closed. I had 4 or 5 agitation veins welded into the drum. Then when my roast was finished I would open it up, grab it with my welding glove, pull the pin with pliers and dump the roast into a colander that I would put over a fan to cool. Worked pretty good. Took a lot of work to get working correctly. Probably a photo of it around here somewhere.

Year, would love to see a few pictures of it, if you have.

I still need to buy insulation and a few things, before I can start the first roast. Maybe I need to move the heating elements in the front a bit more to the back, but that is very easy done. This 45 liter oven has LOTS of space around the oven for insulation, so I don't think there will be a problem with heat escaping when proper insulated.
My plan is to make a pipe go down from the top, and inside the oven, to the drum so I won't have to open the front door, when loading the beans. I got the idea from the Ceroffee CRF-800, but instead of moving around the funnel, I just want to put a plug in the actual funnel, put beans in and lift up the plug so the beans will fall down the pipe.

Did you make a hole in the top for smoke to get out?

Right now, I am working out how to get some ventilation going. The idea is to put a voltage regulator with adjustment to the fan, so I have better contol.

I have been busy with my project and here is a little update:

This is the drum all finish.



Looking into the hole where the beans will be loaded from the top of the oven.



And the exit chute.



I also made a damper with a fan, so the smoke can come out or if I want to do some temperature changes after first crack. There is a LOT of holes and cracks in an oven like this, so I got some black oven seal paste, with a tolerance of 1500 c. celsius so its nice and closed.



I dont have digital temp. reading yet, but got this analog temp. reader, close to the beans.



Yesterday I did a first test run and the oven really heats up nice and fast. Set the temp. on the oven on 190 c. Celsius, and after just 8 minutes the temp. came up to 200 c. Celsius, but it did not stop there...it continued to clime to 250 c. celsius even when the oven says max 230.
Then I turned it down to 100 c. Celsius, and the temp. start going down. I have to play around with the temperatures before I start loading any beans, but I am very satisfied with the high temp and I dont think it needs a lot of extra insulation. It won't be long until the first real test.

Good luck on your project. Be aware of bean ignition and chaff fire. Keep a fire extinguisher handy.

Maybe I missed it, but how do you plan on maintaining a consistent ET?

Oven thermostats have notoriously wide temperature ranges. For example, when setting the thermostat to 200*, the oven might get as high as 250 before it shuts off and then drop to 175 before it kicks back on. That is not good. If this is the case, I would suggest adding a PID controller to run the temperature automatically, or a variac to do it manually.

Very true, mini ovens have tendencies to jump over the mark. The reason for this is that there is a wall between the thermostat and the oven and it will always be cooler than inside the oven.
In a regular oven the temperature is very stabile because the temp. probe is inside the oven.
I was planning to make a cover for the thermostat and then make some holes in the wall going to the oven so the temp. is the same.
Hope that will work, otherwise I will need to build in some temp. sensors, but I will give this a try first.

I could be wrong (although it happens much less frequently since the divorce) but I have a feeling the stock thermostat will be useless. Even completely insulated, they are just not designed to roast coffee. They are designed to cook something. Temperature fluctuations will likely be wide. I hope I'm wrong, but be prepared.

I started by using a turbo oven and Westbend stir crazy for my first roaster:



and ended up with this monstrosity:



From left to right:

The Stir Crazy base has a thermocouple in the bottom to track bean temp.



There was another T/C in the aluminum ring to track ET. Temp to the base was maintained manually with the Variac to its right.

Next to the Variac is a PID which controls the Turbo Oven. I found the stat on the TO had a 75* swing which was just unacceptable to getting a good roast. The PID is programmable and let me run the temp (+/- 2*) at 300*F for the first 4 minutes during the dry phase and then automatically ramp up to 450* from 4 minutes to end of roast.

On top of the PID is a Phidget 1048 which allows the T/Cs to talk to Artisan data logging software installed on my laptop.

The point is, roasting coffee is a slippery slope. At least it was for me. A cast iron pan and wooden spoon will roast coffee, but if you want to roast really good coffee and be able to repeat to results, then you need a bit more control.

Oh, and you will also need something to cool the beans. That's what the small shop vac and bucket are for.