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Baby George Foreman Roaster
coffeeismagick
The size of the drum is 7 inch diameter by 8.5 inch long, or 17.78 CM (Dia) x 21.59 CM (Long). the volume will be 4.71 imperial gallon, or 21431 cubic centimeter.

I will be roasting 500g batches mostly, up to 750g batch, won't risk catching fire by pushing it to 1000g.
Edited by coffeeismagick on 09/19/2017 3:20 PM
 
renatoa
My volume computation give 5.375 l, so good for 900 grams.

Fire hazard could occur especially when beans occupy more than half volume (touch the shaft), the agitation almost cease in the inner layers if no vanes on the drum wall.
 
coffeeismagick
This factory GF drum has excellent vanes which enabled the beans to be roasted very uniformly even at such low RPM
 
coffeeismagick

Quote

renatoa wrote:
Regarding temperature monitoring, you can do it using just air temperature, no need for BT to have a good roast, will detail more if you want to add a temperature control.


the air temperature inside GF never get hard enough for beans to reach 1C, only the beans closest to the heating element received enough radiant heat to cause them to reach 1C temperature, therefore, it is very tricky to monitor air temperature for this oven for the purpose of controlling the coffee roasting process.

the reason for the low air temperature inside GF is because it not only has zero insulation, but also has way too many hole, gaps, openings that it is impossible for the hot air to stay inside long enough to be heated sufficiently (meaning the air temp should be greater than 2C temp). thus, in order to raise the air temp sufficiently, I need to seal most hole s, gaps and openings, except for exhaust outlet, then I need to insulate the entire metal body to prevent rapid heat losses. Can that be done without extensive labors and expenses? I believe so, I am working on design plans.
 
stuie25
I have the same oven, i added a second set of heating elements out of a toaster oven, i can hit 500 in a short time on pre heat, im running a watlow compact pid with the temp sensor drilled in just above the drum.

My biggest issue is the thing catching fire from the chaff, i have started cracking the door about two inches now and i have a bathroom fan ducted outside that i place infront of the door with a bit of tinfoil over the rest f the open door that sucks out a bit of chaff and most of the smoke.

I also went nuts with the tinfoil to help keep the heat in but with 4 elements im not as worried about lag time on my heating curve.

I can post some pics if anyone is interested, my system is down right now as i have to get a biger ssr heatsink i keep melting them down.
 
coffeeismagick

Quote

stuie25 wrote:

I have the same oven, i added a second set of heating elements out of a toaster oven, i can hit 500 in a short time on pre heat, im running a watlow compact pid with the temp sensor drilled in just above the drum.

My biggest issue is the thing catching fire from the chaff, i have started cracking the door about two inches now and i have a bathroom fan ducted outside that i place infront of the door with a bit of tinfoil over the rest f the open door that sucks out a bit of chaff and most of the smoke.

I also went nuts with the tinfoil to help keep the heat in but with 4 elements im not as worried about lag time on my heating curve.

I can post some pics if anyone is interested, my system is down right now as i have to get a biger ssr heatsink i keep melting them down.


Thanks so much for sharing! Yes, I am definitely interested in seeing your MOD pics, especially how you added the 2nd heating element.

I have purchased an original heating element for this oven from eBay, but had not put it in yet, partly because after some simple mods/tweaks I have been getting very consistent roasting time for 250g batches, at 14-15 minutes (not counting pre-heating the oven for 10-15 minutes before I start roasting), so it is no longer necessary for me to add that 2nd heating element, and partly because I had not been able to get any response from the guy on this forum who is supposed to sell a TC4 kit, he doesn't respond to emails and not posting any updates on the forum either, I had all the parts for the temperature controller MOD ready but no TC4, sad!

BTW, your measuring temperature at a location above the drum may be a little off from the temperature inside the drum, at least that had been my own experience and I had given up using any temperature probes/gauges for that reason. I am replacing the center rod for the drum (left side only) with a 6mm OD stainless steel tube with a 4mm diameter hole, and will then use a rigid 2mm diameter K-type probe through the center hole of the tube to measure the temperature inside the drum with beans constantly hitting the probe, this temperature data will then be fed to the TC4+UNO unit for controlling the roasting profiles using Artisan program, but unfortunately, TC4 is not available for purchasing any more, at least for the time being.

I am also working on replacing the motor with one that would rotate at 8 RPM to 16 RPM, with a separate power supply and voltage control for speed (possibly be integrated into the Artisan software for voltage control for both heat and motor speed).
 
renatoa
I did this trick, I mean empty shaft for drum, for other oven than GF, and indeed, inside drum temperature is significantly different than hot air outside, even 30C lower in some places near the lateral drum walls.
Adding some vanes also change temperature distribution inside a lot.
You can go even further and add a single big vane, middle drum, as in Gene roaster. The difference will be that the drum will be horizontal and paddle oblique, but the mixing will have same dynamics as in Gene.

Instead all this unobtainum TC4 quest, preferred to go simpler, cheaper and more efficient, imo, using a Mastech dual thermometer, that connects to Artisan instantly via USB, and perform manual heat adjustments until I found the machine best natural curve.
 
coffeeismagick

Quote

renatoa wrote:

I did this trick, I mean empty shaft for drum, for other oven than GF, and indeed, inside drum temperature is significantly different than hot air outside, even 30C lower in some places near the lateral drum walls.
Adding some vanes also change temperature distribution inside a lot.
You can go even further and add a single big vane, middle drum, as in Gene roaster. The difference will be that the drum will be horizontal and paddle oblique, but the mixing will have same dynamics as in Gene.

Instead all this unobtainum TC4 quest, preferred to go simpler, cheaper and more efficient, imo, using a Mastech dual thermometer, that connects to Artisan instantly via USB, and perform manual heat adjustments until I found the machine best natural curve.


Right now my highest priority is to replace the motor/gearbox that turns the drum at only 2.5 RPM speed.

The motor itself does not contain any reduction gear, it runs at synchronous motor speed, likely 60Hz (60 RPM?), but I don't know how to determine that motor speed precisely. I was thinking to get a replacement synchronous motor that runs at higher than 200 RPM speed, but they are not easy to find, or are outrageously expensive, so I am still working on finding one on ebay that is reasonably priced.

Another thought is to modify the gearbox, this would require some detail knowledge on how to calculate gear reduction ratios, design the new gear set layout within the existing gearbox with existing holes to insert the new gears, and to source the exact diameter and teeth-number plastic gears from ebay or from an online hobby supply web store, I am sure it is DOABLE, but I just have not have the required knowledge for that yet, am working on it loosely now, not a priority for now, since the motor replacement method is a much simpler solution for this problem.
 
renatoa
For the other readers here, this is the assembly we are debating:

i.ebayimg.com/images/g/XP4AAOSwqVxZha9i/s-l300.jpg

Running faster means replacing that gearwheel we see with one proportionally bigger, same tooth profile/pitch.
Double diameter = double teeth = double RPM

And alternative would be to direct drive the drum shaft with a 30-60 RPM $15 motor how I am using for my roasters, I can post link if interested.
Roasters: DIY: TO based IR 200-640g
Moded commercial: Skywalker, Dieckmann RoestMeister, Nesco, popper(s).
Electrics: TC4ESP, MS6514, USB/Artisan/Apps, PID controllers
Grinders: Arco, Xeoleo ghost burrs, Krinder, vintage PeDe Dienes, MBK Feldgrind
Brew/presso: ALM pour over, Arin lever, Staresso Mirage, Hario Cafeor dripper, Flair, Kompresso, Rota Aeropress, Gaggia Mini
 
coffeeismagick

Quote



Running faster means replacing that gearwheel we see with one proportionally bigger, same tooth profile/pitch.
Double diameter = double teeth = double RPM



If I were to double the diameter of driver gear, I also must half the driven gear, in order to keep the existing gearbox structure. This will result in 2x2=4 time higher speed.

Unfortunately, these gears are not standard, and the driver gear is part of the motor shaft, so that option is now dead.

I can still replace the motor with one that has higher speed (300 RPM is what I am looking for), and in fact I have been able to locate them on ebay (same size motor body), but the problem is: I don't know how to attach the driver gear to the new motor, the driver gear is plastic with a 2mm hole in the center, none of the motor of this size has a 2mm diameter shaft.

Another option is to remove the existing gearbox and motor, then add a new gear motor (6Watt minimum) with 16 RPM speed to drive the drum shaft directly by coupling the drum shaft to the motor shaft, I will need to do some substantial mod to the roaster housing to attach the new motor to the exact location to drive the drum shaft.

Why 16 RPM? because the medium drum speed is 8 to 12 RPM, or 10 RPM, I want to use a motor speed controller to control the motor/drum speed (both manually and automatically via Artizian).
 
renatoa
In this video I see the drum speed is close to the motor speed, one rotation is about 20 seconds, from 1:30 to 1:50
https://www.youtu...P0tHdsYd00
This means the gear ratio is 1:1 or very close.

If the gear is plastic, should be easy to enlarge the hole to 3-4 mm as you can find other motors on eBay. Much easier than mod direct drive the drum shaft.

About speed rotation, from my experience 10 RPM is the minimum acceptable, IF adding a lot of vanes inside drum, like Behmor.
Else, without additional agitators 30 RPM is a minimum, 60 RPM is desirable.
Gene roaster turns also by 10 RPM, but it has inside a big paddle !
You can also have a look at a Dieckmann Roestmesister drum, to have an idea about the movement of 300 grams at 20 RPM in a drum without any vanes.

Speed control for this design is a gimmick, not waste your time and resources, this is not a real drum roaster, to worry about drum speed, or hope you see any effect from only 20% change.
Roasters: DIY: TO based IR 200-640g
Moded commercial: Skywalker, Dieckmann RoestMeister, Nesco, popper(s).
Electrics: TC4ESP, MS6514, USB/Artisan/Apps, PID controllers
Grinders: Arco, Xeoleo ghost burrs, Krinder, vintage PeDe Dienes, MBK Feldgrind
Brew/presso: ALM pour over, Arin lever, Staresso Mirage, Hario Cafeor dripper, Flair, Kompresso, Rota Aeropress, Gaggia Mini
 
coffeeismagick

Quote

renatoa wrote:

In this video I see the drum speed is close to the motor speed, one rotation is about 20 seconds, from 1:30 to 1:50
https://www.youtu...P0tHdsYd00
This means the gear ratio is 1:1 or very close.

If the gear is plastic, should be easy to enlarge the hole to 3-4 mm as you can find other motors on eBay. Much easier than mod direct drive the drum shaft.

About speed rotation, from my experience 10 RPM is the minimum acceptable, IF adding a lot of vanes inside drum, like Behmor.
Else, without additional agitators 30 RPM is a minimum, 60 RPM is desirable.
Gene roaster turns also by 10 RPM, but it has inside a big paddle !
You can also have a look at a Dieckmann Roestmesister drum, to have an idea about the movement of 300 grams at 20 RPM in a drum without any vanes.

Speed control for this design is a gimmick, not waste your time and resources, this is not a real drum roaster, to worry about drum speed, or hope you see any effect from only 20% change.


Thanks for the suggestions. I had completely dissembled the gearbox and took out the motor and the gears for examination. The motor shaft is driving a planetary gear that rotates at 11 RPM based on the gear ratio calculation. The driver gear has 12 teeth, the driven gear has 44 teeth, the ratio is 1:3.666, so with the drum speed at 3 RPM, the motor speed is exactly 11RPM, which is very common for this type of motor.

If my above observation and calculation is correct, all that I need to do to increase the drum speed to 10-16 RPM is to replace the motor with one that runs at 35-60 RPM, this is better than what I originally thought that I would need a 300 RPM motor based on the assumption that that the existing motor speed is 60 RPM. I was not able to find a 300RPM motor at this size, but 60RPM motors at this size (5CM D x 2CM H) is much easier to get on ebay.
 
renatoa
A crazy idea... is there any chance to mechanically swap the wheels, turning the 1:3.67 reduction ratio into the same ratio but reversed=multiplication !
Will result 3*3.67*3.67 = 40 RPM, a nice speed, but beware, proportionally less torque... worth a try though :)
Roasters: DIY: TO based IR 200-640g
Moded commercial: Skywalker, Dieckmann RoestMeister, Nesco, popper(s).
Electrics: TC4ESP, MS6514, USB/Artisan/Apps, PID controllers
Grinders: Arco, Xeoleo ghost burrs, Krinder, vintage PeDe Dienes, MBK Feldgrind
Brew/presso: ALM pour over, Arin lever, Staresso Mirage, Hario Cafeor dripper, Flair, Kompresso, Rota Aeropress, Gaggia Mini
 
coffeeismagick
In theory I can replace gears and get whatever ratios I want; in practice, it is almost impossible to to find the gears that would fit the existing holes and the gearbox layout.

Changing the motor appears to be the easiest option, but I was still unable to find a motor that is the same size as the existing one and with the centered shaft layout, most gear motors have the shaft off center. The hardest part is to find a 12 teeth pinion gear that would fit the motor shaft, I had not been able to find one.
 
coffeeismagick
One year after my last post.

I was not able to find a suitable motor to replace the original motor, nor was I able to figure out how to modify the gearbox, therefore I have been using this roaster at 3 RPM drum rotation speed, beans have been consistently evenly roasted, so 3 RPM drum rotation speed is actually perfectly acceptable for this type of steel mesh drum roaster.

I have not performed any additional modification to this roaster since my last post, because it works exactly as it is expected to: I can roast 230g in under 11 minutes or 250g under 15 minutes, FC occurs at around 7 - 9 minutes depends on the load size (230g to 250g).

I am using the roasting time as my main roasting control, while I also use cracking sounds and smoke as confirmation to terminate the roasting. Right before the 1st crack, I remove the vent cover, which immediately causes a slight environment temperature drop, to lengthen the development time, since I don't have means to control the temperature of the heating element. I could also open the glass door slightly to let some cool air in, but so far I have not had the need for doing so.

All that has been accomplished with a $53 roaster without any major mod except for adding tin foil to cover the glass door and some insulation tape to cover up some holes and gaps. This has been a great learning experience, turning a cheap rotisserie oven into a perfectly functioning "drum" roaster with just two little tricks (that cost less than $5)!

Would my coffee tastes better if I had spent thousands of dollars on a 500g or 1-kilo real drum roaster that I can run automated profiles using Artisan? Perhaps so, but I think I am perfectly happy with this cheap, simple but very capable "drum" roaster. If I ever need to roast a 500g or larger batch, I can always add that spare heating element that I purchased for $15 last year, it serves as a spare heating element for the peace of mind as well.
Edited by coffeeismagick on 12/12/2018 10:58 PM
 
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