SC/TO Profiles / Q&A / Tips & Tricks

[David (PalateOfAnAardvark)]

The turbo oven

[Ascholten]

but does it blow enough air to cause bean movement, if they just sit there, it won't do well for us, unless we add some sort of manual stir thingie to them.

Aaron

[David (PalateOfAnAardvark)]

but does it blow enough air to cause bean movement, if they just sit there, it won't do well for us, unless we add some sort of manual stir thingie to them.

Aaron

That's my previous post, using the Baumann popcorn machine as the 220v StirCrazy substitute. Here is a view of the stirrer.

[David (PalateOfAnAardvark)]

Using these 2 components, a 220v popcorn maker with bed and stirrer, and a 1400w turbo oven, I can, hopefully, start the construction of a SC/TO hybrid.

[Ascholten]

Ok let me potentially save you some money.,
I had almost exactly the same idea several years ago, I got one of those stir wand popcorn machines, took the thermostat clicker out of the circuit and PID'd it for better temp control.  anyways...

The main problem you are going to have is, the stirr arms, will NOT really rotate the beans, it will just slide them along the bottom.  They will pile up in a pattern and kind of just slide, this causes a problem with even roasting.  If you put enough beans on there that they do start to tumble over it, the ones on the very bottom may not get caught up enough to do that with.  Maybe you can figure something out but that was a major drawback that I seen / experienced on setups like that.

Aaron

[peter]

You can use a coat hanger to make a new stirring arm, one that will ride along the bottom.  It kind of depends on what batch size you want to have.  I had a bunch of pics of my build, but google decided to delete them.  If you think it would help, I'll re-take them.

I would suggest sourcing a 220v motor for the stirrer and adapting it, something with 30-60 rpm.

My two SC/TO's have a 1" aluminum spacer, with a 1/2" slot cut into the top and that's where my thermocouple sits.  It rides in the beans and when it's time to dump it simply slides up and out of the way.

[David (PalateOfAnAardvark)]

Um, thank you. I am having trouble visualizing the spacer and thermocouple you mentioned. If you could supply a pic of that part of the build, I'd be grateful.

[David (PalateOfAnAardvark)]

Ok let me potentially save you some money.,
I had almost exactly the same idea several years ago, I got one of those stir wand popcorn machines, took the thermostat clicker out of the circuit and PID'd it for better temp control.  anyways...

The main problem you are going to have is, the stirr arms, will NOT really rotate the beans, it will just slide them along the bottom.  They will pile up in a pattern and kind of just slide, this causes a problem with even roasting.  If you put enough beans on there that they do start to tumble over it, the ones on the very bottom may not get caught up enough to do that with.  Maybe you can figure something out but that was a major drawback that I seen / experienced on setups like that.

Aaron

In terms of saving money, you mean the whole PID circuit thing? I hope you are not saying to abandon the whole SC/TO idea.

The Chinese flatbed I have now is nothing more than the working part of a popcorn maker. Heating element under the bed, and two stirrer arms.

Nothing I've seen about the whole stircrazy idea does anything different about the stirrer/bean interaction, yes, the beans slide along until they reach a high enough point to tumble over the arm. And yes, I get a somewhat uneven roast.

The bed heater also takes a long time to heat up, and for anything approaching or exceeding 500 grams, it takes 30 minutes to roast, unless I stay at the top temperature from the beginning, which tends to scorch the beans.

The advantage I see over what I have now is the heating/blower action of the turbo roaster.

[Ascholten]

No, im saying, just using the stirrer as it is, may not do what you want it to,  as Peter mentioned, you will have to mod the arm to get it to work right.
As for the entire PID thing, no that sounds great, Id like to see it.

Heat input and retention is important.  If it heats too slow then you are more cooking or baking your beans than roasting them and besides for taking forever, the flavor will be ehh.  Too fast and you scorch, tip, and other problems.

If the blower one could actually dance the beans that'd be perfect I think.   One thing on thermostats, you have a pid .. thats good.  you may need to take out the Thermo's they have built into those things, they may have one control, which is really just a very crude bimetallic clicker generally, and one overtemp to cut the whole thing off if it overheats. control it with your pid and you are good,  be mindful of the power you pull through that pid controller, it may only like am amp or so,  use external relays or I find that I like ssr's a lot better for power control.

Aaron

[David (PalateOfAnAardvark)]

This is the PID I'll use.

[David (PalateOfAnAardvark)]

There are a couple of ways this could be wired up, but this is what I'll probably use. I originally envisioned it to control a fan/blower in the smoker, but I think I will experiment with using it to control the turbo oven. Not sure if this will work or even if it is needed, but I'm stuck in the house, so what the hell.

[ptrmorton]

Fun project!  My experience was that allowing air to escape the roasting bed (along with chaff via an adjustable gap in the aluminum spacer that Peter mentioned) was the most controllable way to adjust ET and thus BT.  The PID could be fast enough to make that unnecessary for temperature control and improve duplication of roasts.  Chaff ejection during the roast is still going to be an issue however - especially with naturals.


I modified my stir crazy with a 50 RPM, 220V motor and "cat whiskers" (2 slightly wavy arms separated by about 3/4 of an inch at the tips at slightly different heights off the roasting bed floor)  and it worked excellent for larger batches.  The torque of the 220v motor was a huge plus and allowed for the dual arms. Good luck!

[Ascholten]

You can get motors that do from 6 to probably 30 rpm etc at many BBQ sites too.  They use them for rotisseries.   Most r's go slow like 2 or 3 rpm but some are geared faster depending on what you need.  I even seen one that had a motor with pretty much 'snap on' gear boxes.  You get the motor then buy a gearbox for whatever RPM you are looking for slap it on and then stick the rod into the output and viola you are good.

Aaron

[David (PalateOfAnAardvark)]

I can get 50rpm 220v motors from China (AliExpress), but shipping is expensive and time-consuming. I think you can get reasonable torque (depends on the motor build and subsequent $$$) for larger roasts. Do you know the specs on your motor?

I was hoping you (or someone would reply on this subject). I timed my flatbed, and the new flatbed popcorn popper I just bought and they are 8-10 rpm, seems slow.

The current setup takes 30 minutes to roast 1/2 kg, 12-15 minutes to roast 300g. I'm hoping to reduce that or get even bigger roasts. Spending 3 hours in the garage roasting 7 300g roasts is kinda boring.

[ptrmorton]

I can get 50rpm 220v motors from China (AliExpress), but shipping is expensive and time-consuming. I think you can get reasonable torque (depends on the motor build and subsequent $$$) for larger roasts. Do you know the specs on your motor?

I was hoping you (or someone would reply on this subject). I timed my flatbed, and the new flatbed popcorn popper I just bought and they are 8-10 rpm, seems slow.

The current setup takes 30 minutes to roast 1/2 kg, 12-15 minutes to roast 300g. I'm hoping to reduce that or get even bigger roasts. Spending 3 hours in the garage roasting 7 300g roasts is kinda boring.

I'm able to roast about 450g in 13 minutes.  The motor will handle more, but I can't get a fast enough temperature ramp up to make for a good roast.  In the summer (Arizona 40 degrees C) I could roast 500g with adequate preheat in less than 14 minutes. 


The roaster is at my neighbors, but I'll stop by later today and get the specs on the motor and take a picture.