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Second attempt, TO this time.
Billy Bean
Top  #1 Print Post
Posted on 01/27/2025 7:15 PM
Some of you might have followed my (failed) attempt to convert an air popper into a roaster, and this will be a more serious (I WAS serious) build. But before to start working immediately without thinking (and buying) a lot ahead, as I did before, I want to prepare better before to start.

Don’t need a large roaster (I am alone) but something that is reliable, repeatable roasts, at, for me reasonable cost as I will do “small” batches, probably 150 – 200 grams.

The initial idea was to use a Stir Crazy as bottom and stirrer but after reading a lot of treads on this forum, I returned the Stir Crazy and decided to go a better route.

So as preparation I wanted to pick this idea that I have for the outer bowl. I found a (thin) SSteel bowl, 13” the one they sell at the dollar store and Walmart. This bowl fits my TO perfectly and to insulate this bowl I wanted to do a double wall version, as seen in the image, after all air is a good insulator.

I lift the inner bowl with 5 mm silicone (in red), that gives me 5 – 18 mm inner space. (I could go more with thicker silicone)

I did not find this on the forum so I wanted to ask you, what do you think?

infento.design/TO/1.jpg
Edited by Billy Bean on 01/29/2025 11:45 AM
Never delay what you can do today....
 
renatoa
Top  #2 Print Post
Posted on 01/28/2025 3:36 AM
Where is the chaff escape path in your design?
It's a critical part of any coffee roaster design, to not let chaff stay in the roast chamber more than the peeling moment, then evacuate asap.
Chaff burning it's the most awful sensorial aggression that can't be imagined until you experience it...

Pressure, which pressure ?
The TO lid is not closed, it has own opening to exhaust smoke and steam while cooking.
Never noticed the slots just above the glass ? In that compartment there is a second fan, the sibling of the internal turbine lamp, serving as lamp plate cooler. Check the exhaust slots in the image attached.
The lamp plate has enough openings to allow some smoke/steam going outside, and also replacing them with clean air from outside.

I am roasting using such machine for the most years as a coffee roaster, after trying almost every build, except a serious drum roaster. Started with a popper, as usual... seems a rite of passage pain... Grin
My final take on this machine is a wok style pan, like yours, but perforated !!!
Also is not insulated against the walls... conversely... that space is the chaff escape I wrote above... allowing also the air travel under the pan and return through the holes.
You can see it in action turning 250-300g of greens below:



I have also a second pan, for larger loads, 5-600 grams, it an Ikea Stabil steam insert, part no 90163525
It really needs at least 400 grams load, else the beans will not mix good, because is flat bottom, unlike the wok style pan, there is not return to the center gravitational action.

To better understand why this design is the best, you should understand the air path in a TO roaster.
It starts with the turbine sucking a central column of the air, and centrifugate it to the lamp, then to the walls.
On the walls the air descends in a spiral to the bottom, returning to the center through the holes in the roasting pan, and closing the circuit. This way all the coffee layers are in most uniform mass of hot air, without hotter or cooler layers along the beans pile.
The descending spiral along the walls is the chaff path evacuation, on the bottom corner of the oven there is a chaff trap driving the air-chaff flow to the cyclone.
~~~
renatoa attached the following image:
image_2025-01-28_112039193.png
Edited by renatoa on 01/28/2025 5:58 AM
 
Billy Bean
Top  #3 Print Post
Posted on 01/28/2025 8:06 AM
Pressure, which pressure ?

I know the TO lid is not closed, I was only talking (and showing) about the pressure between the 2 outer bowls, the YELLOW area. You know as well as I do that the inner wall is exposed to the heating of the TO, so the yellow area will heat up and the air will expand, thus building up pressure. In order to prevent any deformation because of the pressure I have put 2 small holes in the outer bowl. (c)

Where is the chaff escape path in your design?

For the escape I have options;

A – I use the spring form that came with the TO and cut a hole in the side to let the chaff escape. I don’t really like this option as I need to make a chaff collector outside of the TO.

B – I attach a few downward pointed wings to make use of the airflow created by the TO (as you mention) that will guide the chaff between the perforated pan and the bottom. I’ve seen this already many times on the forum. I would not have to make a chaff collector AND the beans get more evenly heated because of the perforated pan. I would prefer this option.

infento.design/TO/2.jpg

I am not a “know it all” but I do have some understanding how the TO works, and I am happy for you that you made a (for you) successful roaster by trying out many things. Basically, the drawing attached shows no new things, most (except the double walled bowl) I have seen on this forum is in there, maybe not all like you have done.
I did not show the perforated pan in the first drawing, nor the stir arm or motor attachment. Form and shape are still optional so no need to discuss that now, but I have a pretty good idea how it is going to be.

Last but not least, English is not my mother tongue, after all the years spent in Canada I still translate from Dutch to English in my head before to write something down and I know it doesn't have always the exact same meaning.

That still leaves me with the question what people think of the double walled bowl.....
Edited by Billy Bean on 01/28/2025 10:48 AM
Never delay what you can do today....
 
Billy Bean
Top  #4 Print Post
Posted on 01/28/2025 4:17 PM
First shopping spree for the new TO roaster, 2x 13” bowl and 1 perforated colander, all stainless for $6.50 (Canadian, taxes included) This evening I will order the motor and coupling and it will take a few days to put it all together on paper. I am excited…..

infento.design/TO/3.jpg
Never delay what you can do today....
 
Billy Bean
Top  #5 Print Post
Posted on 01/29/2025 10:49 AM
I am waiting for stuff to arrive (tomorrow hopefully) so I focussed on what more has to be done.

The 32” bowl fits perfect in the frame of the TO, just luck but hey, I’ll take it.

On the bottom however, between the bottom of the bowl and the table, there was a space of 58 mm, not enough as the motor will take 60 mm. So I extended the 4 corners with legs of 20 mm. I 3D printed them (because I have one) but you could do it simple with some plywood or so, no big deal.

infento.design/TO/4.jpg

I am very happy with my choices and plan so far, hope it stays that way. Cheers.
Never delay what you can do today....
 
allenb
Top  #6 Print Post
Posted on 01/29/2025 6:34 PM
Wow, you move quickly! Amazing progress. Keep the progress posts coming! ThumbsUp
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
Billy Bean
Top  #7 Print Post
Posted on 01/29/2025 7:41 PM

Quote

allenb wrote:

Wow, you move quickly! Amazing progress. Keep the progress posts coming! ThumbsUp


Thanks allanb, yes it is going very well. Once I have something in my mind (and it is going well) I can hardly stop to do something else.
Below is the plan as I have it in my mind, if someone sees something wrong, now is the time, don’t be shy.
The only thing I haven’t figured out yet is how to put the perforated basket in, in such a way that I can take it out if needed.

infento.design/TO/5.jpg

The black seal is heat resistant silicone from Amazon, the green is liquid silicone that I have to process myself.
Never delay what you can do today....
 
Billy Bean
Top  #8 Print Post
Posted on 01/30/2025 2:18 PM
Hi all, this time I REALLY need your opinion.

The TO I am making is for myself to roast small batches, like 150 – 200 grams. I have a small perforated bowl, 20 cm diameter, it’s om the shelf at the Dollar Store for $1.50 (see image below)
infento.design/TO/4.jpg

So this morning 2 friends came over to see my progress and told me to make the capacity bigger. I don’t want to skip my little perforated bowl but I still had a similar, smaller bowl as the outside bowls, see image below.
infento.design/TO/6.jpg

I like the perforated idea but I was not willing to drill 600 holes in that bowl, so I thought I might cut some slots in it with the grinder. Terrible job, burrs on the inside and outside, I made only 1 row of slots instead of 2.
infento.design/TO/7.jpg

BUT HERE IS MY QUESTION:
If I open the slots a bit (2 mm or so) like a louvre door, the beans would “hop” over the slot, but some air from the outside would come back into the roast chamber.
Anyone think this re-directed airflow can add something positive?
Edited by Billy Bean on 01/30/2025 2:27 PM
Never delay what you can do today....
 
Billy Bean
Top  #9 Print Post
Posted on 01/31/2025 7:31 AM
This is the mold with the silicone in it to use as a spacer between the 2 outer bowls. The 4 holes fit the holes for the motor base.
It is a one piece mold, that means I have to destroy it in order to demold the silicone but that is easy and I can print another one if needed in the future. I went for 2 part molds in the past but that is much more work and they can leak easy, making a mess. And after all, it is only 24 cents plastic material.

BTW, if someone ever needs a stl file to print something like this, just let me know.

infento.design/TO/8.jpg

This is how it looks with the silicone ring between the 2 bowls. In the center is a 12 mm socket over a hex coupling attached to the motor shaft. I am planning to glue a small stainless dome on the bowl, sliding over the socket.

infento.design/TO/9.jpg

Today, the thrift store where I bought the TO gives 40% rebate on kitchen appliances and no taxes. They still have 2 TO’s like mine for @$15.00 each. I will pick them up as they will cost me now $18.00 for the 2. One as a spare for me and one to make another roaster for a good friend. Provided this one works of course. Grin
BTW, I will not be using the bowl with the slots in it as pictured. It will be the same bowl but without the slots.
Edited by Billy Bean on 01/31/2025 8:12 AM
Never delay what you can do today....
 
Billy Bean
Top  #10 Print Post
Posted on 02/02/2025 10:24 AM
Struggling a bit and some disappointments the last few days.

My motor got lost in shipping, it was supposed to come in 2 days ago, Amazon has refunded me and I ordered a new one this morning. Same motor with same company, hope it will go well this time.

I’ve been struggling with placing the roast pan(s) into the TO. I wanted to put them on legs but it was not a success, at the end the pans looked like Swiss cheese and it was hard to keep them nice in the center. I lost 2 pans with that, the price to pay for stupidity, I guess.
So I glued a (light green) silicone ring at the bottom of the roast pan with 4 holes in it. These holes slide over the 4 bolts from the motor attachment. In this way the roast pan is perfectly centered towards the shaft with the stir arms. I hope the result is as great as it sounds lol.

I will also have a smaller roast pan for test batches, I will do the same with that pan.

infento.design/TO/10.jpg
Never delay what you can do today....
 
Billy Bean
Top  #11 Print Post
Posted on 02/06/2025 1:54 PM
Finally, I have something to show you, not finished yet but I am getting there.

In the middle, under the roaster I have a 3 channel counter up/down. The idea is to set the top channel for like 2 minutes warming up, the 2nd channel (in the middle) will be set for when to expect the FC, this I will know only after several roasts of course. The 3rd channel (bottom) will be set for the amount of time after the FC. Basically I will roast only 1 sort of DECAF greens, so hopefully that is something I can rely on. Time will tell.

Next to the counter is a temperature data logger, it logs the data to my phone. The probe is under the lid of the TO, I am not sure what I can do with that, at least I could see the increments in temperature when I increase the temperature on the TO.

There is in this video ½ lb. of (scrap) beans in the TO and I am convinced I could do 1 lb. if necessary. But the stir arms need work, I’ve been struggling with that a bit. It was a bit of a forgotten thing which I underestimated.



I also made a smaller roast pan for smaller or test batches. I haven’t done the stir arms as first I want to have them good on the bigger pan.
Here you can see how the pans are connected inside the bowl. Under each pan I have glued a silicone ring with 4 holes in it that slide over the bolts for the motor under the bowl. In this way I am reasonable aligned with the shaft for the stirrer.

All in all it’s not perfect but for a first build from scratch without even having roasted myself before I am happy, as from here I can only improve.



infento.design/TO/11.jpg

I've spent around CAD$100.00 on it, not counting the timer and thermometer. If it works well after some modifications I will sell one locally here on Facebook to cut my own cost. I always try to be self sufficient with my projects.
Edited by Billy Bean on 02/06/2025 5:34 PM
Never delay what you can do today....
 
HarryDog
Top  #12 Print Post
Posted on 02/06/2025 3:09 PM
It might be hard to see on my test unit but one side is shorter and it pulls from one side to the other so beans are not just stirred in the middle (More of a Mix). Just a suggestion.
 
Billy Bean
Top  #13 Print Post
Posted on 02/06/2025 3:39 PM

Quote

HarryDog wrote:

It might be hard to see on my test unit but one side is shorter and it pulls from one side to the other so beans are not just stirred in the middle (More of a Mix). Just a suggestion.


I am sure my final stirrer will look differently, but for now, on the short term I was thinking of putting a (low) stainless dome over the center of the stirrer. As far as I can see now in the video, all beans are flipped/moved except in the middle. It would not be a final solution but at least I could give people some beans that I promised. And if that looks OK, I could maybe use that in the small roast pan. Cheers.
Never delay what you can do today....
 
Koffee Kosmo
Top  #14 Print Post
Posted on 02/06/2025 5:37 PM
Your idea is similar to Version 1 of the KKTO from 2008
I still have that roaster and use it occasionally for small batches

If you haven’t read that thread you can see it here https://homeroast...ad_id=1142

The reason I changed the design to a simpler 2 pot system was safety and to prevent burns to hands also its overall an easier roaster for enthusiasts to copy the build

The main points to consider are
1) Volume - the turbo oven is limited in heat performance when the volume is over 9 litres
2) Agitation must mix the beans in a rolling fashion Note that the beans increase in size / volume and become lighter as the roast progresses
3) Remove chaff as much as possible during the roast

Good luck with your roaster

KK
I home roast and I like it. Designer of the KKTO
Roaster Build information
https://homeroast...ad_id=1142

https://docs.goog...lide=id.i0
Blog - http://koffeekosm...gspot.com/

Bezzera Strega, Mazzer Robur Grinder, Pullman Tamper Convex,
(KKTO) Turbo Oven Home Roaster.
 
Web
Billy Bean
Top  #15 Print Post
Posted on 02/06/2025 7:10 PM

Quote

Koffee Kosmo wrote:

Your idea is similar to Version 1 of the KKTO from 2008
I still have that roaster and use it occasionally for small batches

If you haven’t read that thread you can see it here https://homeroast...ad_id=1142

The reason I changed the design to a simpler 2 pot system was safety and to prevent burns to hands also its overall an easier roaster for enthusiasts to copy the build

The main points to consider are
1) Volume - the turbo oven is limited in heat performance when the volume is over 9 litres
2) Agitation must mix the beans in a rolling fashion Note that the beans increase in size / volume and become lighter as the roast progresses
3) Remove chaff as much as possible during the roast

Good luck with your roaster

KK


You were basically my inspiration after reading the tread of your first build. And even though they don’t really look similar, they are.

This is also a simple 2 pot system; however, my outer pot consists in 2 bowls in sandwich with trapped air inside as insulation to prevent burning hands.

Volume-wise I decreased the volume of the TO although that was not really necessary in my case as I will do limited sized batches.
The agitation is still a concern and not finished but I am working on it.

You did a terrific job with developing the first TO. I know what it is to work into the unknown as the first one, it is trial and error and only the right amount of determination is the road to success, so thank you for that. You made life so much easier for many here on the forum and on the Internet.

Thank you for your best wishes. / Marcel
Never delay what you can do today....
 
Koffee Kosmo
Top  #16 Print Post
Posted on 02/06/2025 9:22 PM
You may not be aware of this extra modification that most don’t mention about the 2 pot design

The pasta pot set is actually a 3 set of components
The lower pot
The perforated insert
And the colander

The colander can be used as a small batch roaster as an addition to the original design. I think I mentioned that at some point in the build thread?

However I did not pursue it - but in principle it works the same by swapping the inserts for roasting duties

Here is some extra reading
https://docs.goog...lide=id.i0

KK
I home roast and I like it. Designer of the KKTO
Roaster Build information
https://homeroast...ad_id=1142

https://docs.goog...lide=id.i0
Blog - http://koffeekosm...gspot.com/

Bezzera Strega, Mazzer Robur Grinder, Pullman Tamper Convex,
(KKTO) Turbo Oven Home Roaster.
 
Web
Billy Bean
Top  #17 Print Post
Posted on 02/07/2025 11:33 AM
First real test with the TO, only 100 gram in the big roast pan to see how small of a batch it could handle. Below are all very small video fragments, sorry about that but I had to do too much at the same time.

Negatives:

I need a perforated roast pan (what was I thinking) as the beans just slide over the bottom of the pan, it’s doable so this should be resolved.
The “chaff catcher” works but at least 50% of the catch is coming back up at the back lol. I have an idea about that, have to try it out though.
The chaff that was under the roast pan was about 50%, I guess. The rest of chaff was still locked up in the beans as the beans don’t really move, they just slide. With a perforated roast pan I hope that will be much better.

Positives:

I could hear the FC (at 400F air temperature) and I aimed for a light medium roast (for my coming DECAF beans) so after the FC I let it go for 2 minutes (on the timer). It was a medium light roast, it looks darker in the video.
Even though I don’t have a temp. sensor in the beans, I could measure the air temperature in the pan and I could see the increased temperature when I increased the temperature with the dial of the TO.

I think it is not too difficult to control to get consistent batches.

There I still a lot to learn but I am optimistic, despite the video.



A few typos in the video I see now, so be it lol.
Edited by Billy Bean on 02/07/2025 12:25 PM
Never delay what you can do today....
 
Billy Bean
Top  #18 Print Post
Posted on 02/07/2025 8:53 PM
Test no 2.
I used the smaller perforated basket. As a coupling I used a ½” copper pipe which I pushed a bolt/head of 12 mm with the vise. On the other side (top side) I grinded 2 slots and used a flat stainless skewer which I locked up with UV epoxy resin. I covered the head with aluminium foil which worked great.

I started with ½ lb. of greens which was too much, I took out 90 grams as the holes in the colander are on the small side, the beans still slide a bit. I will have to increase the holes, I guess.
CHAFF; the chaff problem does not exist any more, remarkable. I had to do nothing for it, all the chaff (and I mean ALL the chaff) went between the roast pan and the outer bowl by itself. Probably because there is so much space in-between.
Both tests had FC at exactly the same air temperature, happy with that.
So, leaves me with optimizing the roast pan, probably bigger holes and some adjustment on the stirrers.



The coming days I am going to take it easy, I feel that my body is rejecting such a busy schedule.
Never delay what you can do today....
 
Koffee Kosmo
Top  #19 Print Post
Posted on 02/07/2025 9:33 PM
For some reason those 2 videos above are private and not available to me/us ?
I home roast and I like it. Designer of the KKTO
Roaster Build information
https://homeroast...ad_id=1142

https://docs.goog...lide=id.i0
Blog - http://koffeekosm...gspot.com/

Bezzera Strega, Mazzer Robur Grinder, Pullman Tamper Convex,
(KKTO) Turbo Oven Home Roaster.
 
Web
Billy Bean
Top  #20 Print Post
Posted on 02/07/2025 10:27 PM

Quote

Koffee Kosmo wrote:

For some reason those 2 videos above are private and not available to me/us ?


Sorry about that, I made the same settings as all the other videos, and I see them in my post on the forum, but here are the links again:

Test 1


Test 2


I see them in this reply also, if you don't see them I could message you the YouTube links. Let me know.
Never delay what you can do today....
 
Billy Bean
Top  #21 Print Post
Posted on 02/08/2025 9:08 AM
Yesterday evening I started to drill bigger holes in the perforated roast pan, but after 5 holes I knew that was an impossible task, at least for me.

So, this morning I started to overthink the situation and I wondered why I was not able to get a good bean distribution and I started to compare what I have compared to others. And then it hit me, everyone has a flat roast pan bottom and I haven’t.

It couldn’t be the perforation as all Stir Crazy roasters have a flat bottom and NO perforation. I will admit that perforation will ad some heat to a certain extent, which might be an advantage, but with the Stir Crazy roasters it has no influence on the distribution of the beans as long as the stirring is done good.

And as far as I searched on this forum, every TO roaster has a flat roast pan bottom.

So, I will “dump” my parabolic colander and will go for a flat bottom version. Last week I already picked up a perforated flat pan, same size as the parabolic one for $2 at the thrift store.

infento.design/TO/12.jpg
Never delay what you can do today....
 
Koffee Kosmo
Top  #22 Print Post
Posted on 02/09/2025 1:30 AM
That is a a good move

If you want me to send you a template of the actual bends of my agitator blade I am happy to do so
Just send me a PM with your email and I will reply with the template and instructions

For some reason I can’t add a photo from the iPad

KK
I home roast and I like it. Designer of the KKTO
Roaster Build information
https://homeroast...ad_id=1142

https://docs.goog...lide=id.i0
Blog - http://koffeekosm...gspot.com/

Bezzera Strega, Mazzer Robur Grinder, Pullman Tamper Convex,
(KKTO) Turbo Oven Home Roaster.
 
Web
Billy Bean
Top  #23 Print Post
Posted on 02/09/2025 10:45 AM
A lot has happened since yesterday.

So, the flat bottom is NOT the cause of bad distribution, it is the low rpm of the motor (20 – 24 rpm). So what I was trying to do is using a low speed motor with a more high speed agitator.

I have a new agitator (flat bottom pan), I got my inspiration on YouTube. It looks a bit Star Trek I guess, I bended a soft copper wire first and then replicated it with a stainless 2 mm wire.

infento.design/TO/13.jpg

For the little dome in the center I used a cheap small Dollar Store cup, I did not have to grind it.

infento.design/TO/14.jpg

Here you see the distribution of old, already roasted beans.
There are a few beans on the agitator in the middle but that will be resolved.
I like it, looks like a Stir Crazy, doesn’t it?

Never delay what you can do today....
 
Billy Bean
Top  #24 Print Post
Posted on 02/09/2025 3:59 PM
I am a happy man……

Did my first test with the TO as it is now and tried my DECAF beans for the first time.
These are sugar cane washed and pleasant surprise…..NO CHAFF!
I could hear the FC very well; I was a bit afraid as I read with DECAF it is difficult to hear.

FC was 40F higher as with my normal greens and I let it go only 1 minute after FC.
This is a medium roast as that is supposed to be with these beans and they smell DELICIOUS!, much better than my El Salvador Bourbon Natural that I have used. Can’t wait for tomorrow.
They might look darker for you but DECAF beans are darker to start with.
No video as I am tired of editing all the time.

I did 1/2 lb. it was a 13 minute roast and had 14% weight loss.
Never delay what you can do today....
 
Billy Bean
Top  #25 Print Post
Posted on 02/12/2025 11:42 AM
I’ve been playing around to get more familiar using my TO. The problem, well at least I thought it was a problem is, that I don’t have a probe in the beans, as I measure the air temperature under the lid of the TO.
All in all, the measured temperature in the air is higher than the temperature set with the dial of the TO, but nevertheless it is very predictable and always the same.

FC is ALWAYS at set temperature of 440F with all my test roasts and I have to dial in the temperature, I increase every minute 20F. So, I could extend the roast by increasing temperature slower

Graph on the left shows drop 1 minute after FC, which was too short and on the right drop 3 minutes after FC, which was great.

Funny story, this morning someone came to pick something up, his wife was with him and she saw the 2 pyrex glass bowls from the TO’s that I bought and she offered $20 for the 2……

infento.design/TO/17.jpg
Never delay what you can do today....
 
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