So all is going well with my Turbo Oven/Stir Crazy roaster. With the PID controlling the TO, the variac manually controlling the heating element in the SC and Artisan monitoring what's going on, I can roast 1# of coffee pretty much any way I like:



But people have been asking me to roast for them, and a 1# capacity per 15 minutes is just not going to cut it. So I've been noodling over a way to keep the same system basics, but upgrade the capacity. I need more volume and more wattage. The SC claims 1000W, but I doubt it can generate that much.

While walking through my local supermarket, I noticed some cheap aluminum stock pots left over from Easter and it got me thinking. So in the spirit of not leaving well enough alone, I bought one and am working on a replacement for the Stir Crazy bottom.



I guess the stars were aligned just right, because the TO fits inside like it was made for it.



There is even a small lip inside that would act as a support:



3# of beans leaves plenty of room:



And the turbo oven fits down snug. If it's too close I can always raise it.



For $29, I picked up a used glass stove top heating element for lower heat.



The SC element is 1000W but the variac is never above 70% and that's only for warm up. It cruises around 50% during the roast. So I figure I'm only using 500W.

The new element is rated at 2700W, but that's at 240V. My variac can do 140V max so I figure I can get 1575 watts out of it. That should give me enough juice to heat things up from the bottom...I hope, and coupled with the 1200W of the TO on top, I should have plenty of heat.

I ordered an upgraded motor for $13.95 that will supply more than enough torque to turn 20# of beans:



http://www.herbach.com/Merchant2/mercha ... y_Code=MTR

So once I figure out a way to cobble all this together, I'm hoping to have increased my capacity to 3, maybe even 4# at a time for an $82 investment. We'll see...

I'd have a look at what Krazy Kosmo does to boost volume. His design evolution led to the inclusion of an inserted colander type of pot within a larger pot like the one you picked up. This adds the benefit of chaff collection in the empty space below the colander, as well as having the ability to wrap the insert in insulation. As an additional benefit, the insert can be quickly lifted out for dumping the finished hot beans into an external cooler.
http://koffeekosmo.com.au/shop/basic-ki ... 1lA3_ldV8E

I looked at the motor you bought, but couldn't see an RPM spec, that would have me trying to determine if it needed extra arms to assist in the mixing of the beans. Just a thought, but alot could be done to them to assist in the roasting, again, this is another area kosmo spent some time prototyping.

I would also try to increase the SC fan strength, only so as to be assured that hot air was being well circulated through the new larger pot volume, as it looks to be pretty deep and large in diameter.

I don't doubt that you can achieve the results you desire, my comments are only to help motivate your pulling it off. So continue on, I say, and if you can't produce the heat to roast in the time frame, well, step back and rethink of how to get there. Maybe a heat gun duct on the side of the pot would be a necessary booster.

sprint jinx wrote:I looked at the motor you bought, but couldn't see an RPM spec, that would have me trying to determine if it needed extra arms to assist in the mixing of the beans. Just a thought, but alot could be done to them to assist in the roasting, again, this is another area kosmo spent some time prototyping.

I would also try to increase the SC fan strength, only so as to be assured that hot air was being well circulated through the new larger pot volume, as it looks to be pretty deep and large in diameter.

Thanks for the link. I hadn't seen KKs site. I like the colander idea.

I was actually thinking or drilling small holes in the bottom of the pot which would facilitate heat transfer as well as allowing me to remove it from the heat source and attach a lid with a shopvac hose installed in the top which would draw air up through the bottom to cool the beans while removing chaff simultaneously.

The motor on my SC is 12RPM. The new motor is 16RPM, but very powerful @ 25 lb-in of torque. I could just stir or lift and fold the beans if I wanted. I could run 2 blades or 4 or more.

As far as the pot volume vs fan speed, I am planning on cutting down the pot to maybe 6-8" high and have the TO only 2" above the beans.

Thinking about a stirring system to circulate the beans. While I do enjoy a good project, I sometimes get an equal thrill from a simple solution. A 12" antique brass fan blade with proper blade orientation for my CCW motor...

So parts are coming in fast and furious for this project. The pot fits nicely on top of the lower heating element:



The plan is going something like this:



I plan on cutting the pot in half and using the top for the base, where the lower heating element and motor will be mounted. A hole will be drilled into the pot bottom (now on top) and heating element to facilitate the motor shaft.

The fan will be mounted into the top. Many venting holes will also be drilled into the bottom to allow heat to flow up during the roasting phase and cool air during the cool down phase. The top section where the fan is located and beans are roasted will simply rest on the lower base. A drive shaft receiving mechanism has yet to be concocted.

So the process will be to insert the turbo oven, turn on lower heat and roast the beans. Fan will rotate at 16RPM to circulate beans. When the roast is over, kill the power to the lower heat, remove the TO and place the lid with shop vac attached on top drawing cool air up, cooling the whole rig off and hopefully sucking out the chaff. Fan will continue to rotate during the cooling process to agitate beans and release chaff. Yes, venting holes will also be drilled into the base and ceramic heating element so air could pass through.

When cooling is done, the top can be lifted off to dump beans. It should be well cooled by this time.

My Phidget has 4 inputs. I plan on using an upper ET measuring the TO output, a lower one installed into the existing heat sensor in ceramic heating element, another in the roasting chamber making contact with the beans for BT and the fourth measuring ambient temp.

Well that's Plan A. Stay tunes for plans B, C, D etc.

Quick question: what size holes should I drill in the bottom of the top (roasting chamber) so as to allow air, yet not let beans for through? Maybe 3/16"? Can I go a little larger?

Fan blade seems a good fit...

So work is proceeding slowly on the new roaster. Question: my old SC/TO had a chaff vent so smoke and chaff could escape.

On the new one, the bean compartment is the top pot and with the TO on top will not have an air vent. I'm planning on vacuuming out chaff during cool down, but should I drill some holes in the side to vent some smoke?

Ideally, you want to remove smoke and chaff as quick as possible.

Good luck with your project!

Thanks! It's almost done...assuming all works as planned! I was hoping to have it done over the weekend, but life got in the way.

I made a vent mechanism to allow smoke an chaff to exit. I'll attach a pick tonight. It's pretty clever, if I say so myself, but easier to show than explain.

More progress.

I'm running into a snag with the lower heating element. Those ceramic stove radiant heating elements are very hard to work with. The ceramic clay hold the element wire just crumbles at the slightest touch.

In the mean time I got the motor and fan blade mounted. Here's a vid of 4# of beans twirling around. I hope this is enough circulation:

https://www.youtube.com/watch?v=Mp-ogsDiipo