Build a stirring roaster from scratch.

[Tex]

This is as far as I've gotten in designing a roaster. It uses a 16" S/S steep-sided skillet, a BBQ rotisserie motor, and a Turbo Oven top (for heat). I've gotten as far as drilling a 5/16" hole in the center of the skillet; now I've got to fabricate a mount for the motor. Then I'll need to refine the ideas shown in the drawing and figure out how to fabricate a stirrer that's tilted enough to ensure sufficient bean motion.

Thoughts? :icon_scratch:

[grinderz]

How are you going to get the beans out when they're done? Just dump them out like a StirCrazy?

If you make a casing of some sort to set the motor and vessel inside of, you could insulate the underside of the pan pretty well to increase the efficiency of the HT...

That gives me an idea... anybody tried taking apart a StirCrazy and insulating the bottom? You might be able to speed up the ramp in the early part of the roast that way. The SC might last longer, too.

[Tex]

How are you going to get the beans out when they're done? Just dump them out like a StirCrazy?

If you make a casing of some sort to set the motor and vessel inside of, you could insulate the underside of the pan pretty well to increase the efficiency of the HT...

That gives me an idea... anybody tried taking apart a StirCrazy and insulating the bottom? You might be able to speed up the ramp in the early part of the roast that way. The SC might last longer, too.

I'm going to have this mounted in a box, with the skillet on a pivot (locked in place while roasting). When the roast is done I'll flip rotate the skillet and the beans will dump into a large sieve, which will be transferred to a fan.

It all looks pretty good on paper. I'd planned on adding insulation at some point - if everything works as planned (which it seldom does).

 

[grinderz]

Like with a hinge on one side and a clamp on the other? Sounds good.

You could attach another box to it and make a really similar stirring cooler, too. Roast -> dump -> cool -> dump. The cooler could swing up and dump into a chute of some sort for bagging.

[John F]

Then I'll need to refine the ideas shown in the drawing and figure out how to fabricate a stirrer that's tilted enough to ensure sufficient bean motion.

What is your expected batch size?

[Tex]

Like with a hinge on one side and a clamp on the other? Sounds good.

You could attach another box to it and make a really similar stirring cooler, too. Roast -> dump -> cool -> dump. The cooler could swing up and dump into a chute of some sort for bagging.

This is a top view. The skillet pivots on the pins (right & left) and is locked into place while roasting (pin at the bottom).

[Tex]

Then I'll need to refine the ideas shown in the drawing and figure out how to fabricate a stirrer that's tilted enough to ensure sufficient bean motion.

What is your expected batch size?

If I can get enough action from the stirrer, I'd think 1-kilo should be workable. Of course, this also assumes that a TurboOven puts out enough heat?

[John F]

Hmmmm.... 1kilo makes it interesting.


I have more questions than answers at this point but with the Cast iron (heat sink) I think  you might consider supplemental heat or face possible lag times that will cause baking.

Pop a heat gun in the spacer?

Small gas burner under the skillet?

Pictures are now mandatory of any progress. 

Edit - I see on re-read you said SS not  Cast iron....but you might still be in the same boat.

[Tex]

...I think  you might consider supplemental heat or face possible lag times that will cause baking.

At one point I was considering using a round electric skillet for the bottom, but all I could find was non-stick coated and at these temps I don't want to use non-stick. I'm hoping that the 500?F capacity of the TO will suffice.

Pictures are now mandatory of any progress. 

Most of my projects go a lot faster in the planning stage than they do in execution. I've got a couple of Bunn ES-1A's to finish rebuilding, a garage to clean, a handful of Gaggia's to do something with, ♪ and a partridge in a pear tree ♪.

[peter]

The roasters people have built with a TO sitting on top of a bread machine, make it appear that faster stirring allows greater batch sizes.  Based on that, I think the rotisserie motor is slower than you want.  The TO has enough heat for a kilo.

Your stirring arms will be the limiting factor with a slow motor.  If you design the arms to move a large amount you'll be stuck doing large batches.  Then, because the TO circulates the heated air around the outside and sucks it back up at the center, the outside beans roast faster and darker.  Faster, flying beans overcome that air circulation because the beans move from inside to outside as they're being flung around.  You may be able to come up with stirring arms so that one pushes beans out and the other scoops them back toward the center.

[grinderz]

What would you estimate would be the right speed?

[peter]

I should have known trying to come off like I know what I'm talking about in that last post would come back to bite me...

It would be really hard to guess what the right rpm would be.  The bread machine has less bottom area, so the shape and size would enter into the calculation.  For a flat-bottomed thing like Tex is dreaming up, faster may just pile up the beans around the perimeter.

[ButtWhiskers]

There are a couple of things you need to consider, Tex...

1) A turbocrazy will do about 1# at an acceptable rate if the stircrazy unit is not heated, and about 1.5# if the stircrazy heat is left on (of course you can go higher, but the rate will be too slow).  If your stirring mechanism is not heated, your heat transfer to the beans might be too slow.

2)  I would seriously insulate the bottom if I was taking your route for the above reason.  Ceramic fiberboard insulation will help contain the heat and greatly increase your potential load.

3)  Turbo ovens are not created equal.  While many of them may have a 500?F setting, to actually get there it takes a balance of how much air is flowing through the system (not recirculating), true 120V power supply, and in some cases how new the oven is.  The Sunpentown analog model seems to have more oomph for the first 20 or 30 hours, then tapers off to a slightly lower level.  Some Galloping Gourmet ovens are beasts compared to others.  The backpressure can have some effect, as well.  You will also need to blow the thing out frequently with compressed air to keep it working efficiently if you are after a larger roast payload.

4)  Removing the thermostat and thermal fuse in the turbo oven might be necessary for such a large payload. 

[John F]

1) A turbocrazy will do about 1# at an acceptable rate if the stircrazy unit is not heated, and about 1.5# if the stircrazy heat is left on (of course you can go higher, but the rate will be too slow). 

My concern as well because his SS pan has no heat source and the batch is 2.2#s.

[rasqual]

If that's insulated, a good pre-heat might top off the accommodations needed to make it work for the large amount.

Agitation will be key.