That's not a popper. THIS, is a popper!

[MrJack]

So, after a failed attempt to boost the capacity of my popper by wiring a seond fan in series and adding a central cone to the chamber for spouting (see the RHS), I decided I need more air!

Enter an 800W motor from a hand held vacuum cleaner, some PVC fittings, a custom built pine enclosure, and a heap of mica insulation sheets, and voila (see LHS)

This baby will easily move as many beans as will fit in the chamber before it overflows (ca. 200g), even when green and without the heat on!! I've fitted it with my osPID, measuring the roast chamber inlet air temperature with a bead k-type thermocouple.

This prototype is not 100% finished, but close enough to use in anger. The final version will probably feature a conical roasting chamber (for spouting) with a glass top, a ceramic tube to contain a higher power heating element, and some other features.

Hoping the popper element will put out enough heat, otherwise it's back to the workshop!

Itching to do a roast.

Only drawback is I've just finished it, it's 7:30pm, and its a bit noisy.

[fg1972]

Nice. Hope the maiden roast goes well.

[Pete39]

Looks good. Where did you get the insulation?

[MrJack]

Cheers. Got it from the bay of evil.

First roast... Well let's just say I put a colander on top to contain the beans after it reach 100°C or so, and then spent the last minute trying to work out how to unplug it without letting the collander fly away.

Worked in principle though. Very pleased about that.

Certainly not low on flow. Also managed to reach an air temp of 230°C, so no problems there either. Seems the outlet temperature of the air from the fan is 70°C or so, which supplements the heating element. It does raise some concerns over the PVC I've use to house the fan on the 'cold side' though.

If anyone knows a supplier of ceramic tube (mallite, alumina or similar), please let me know.

[marcism]

Does your cone in the chamber help much? I'm trying to get a uniform circulation of my beans without tilting the whole thing to the side.

[MrJack]

Yes and no. It circulates better, but it requires more airflow; as the bed depth increases for the same mass of beans, while the flow area reduces. The intent was to remove the "dead zone" of beans in the centre of the popper where the air velocity (and thus heat transfer) is lower.

My attempt to increase capacity, with a second fan, was more than counteracted by the reduction in capacity from the cone (with the net effect bein 70g batches instead of 90g).

It was a little frustrating, as my aim was 150g!

The cone is a piece of pure Aluminium flashing - you could cut it with scissors almost.

[thewpguy]

Great project I love the intensity of it all and I'm all for a popper to get closer to coretto output.

Could you join a 425g Atlantic salmon tin on top that has the bottom removed and some removable mesh in its place so you could have beans flying everywhere but contained?

[MrJack]

I could, but it would not be enough. My first attempt at retaining the beans was to hold a piece of mica sheet over the top. The air caused the sheet to bend, and fired greens all over the garage through the small gap!

Like I said, plenty of flow

In light of that, I am going to order a spun cone section and have a crack at building a 250g spouted bed roaster from it. In the mean time I will find a way to direct some of the air away from the chamber.

I was going to try restricting the intake, but I think that may increase the discharge pressure by reducing the flow through the compressor (there is typically an inverse relationship, like in a centrifugal pump).

Better I just redirect some of the air and put it to use in a cyclonic chaff collector instead

[Pete39]

I use a 240V leaf blower for my popper roaster. Got sick of replacing the little motors - have done nearly 500 roasts now. Usual charge mass is 120g. I have restricted the input (just goes through the cooling fins for the motor now), added some vents just before the air goes into the popper and control it with a triac-based voltage controller. Try to keep the airflow to just enough to keep things even. Works well. Good luck with your system - I'm sure you'll get there in the end.

[MrJack]

Just completed my first successful roast. All that was required was a 200mm chimney. A bit over 120g of ethiopian sidamo, no problems with heat or airflow. Could probably go up to 200g if the chimney was a cone shape.

Had a few issues with the PID settings - was a bit unstable, but generally it went well. A little uneven, but looking forqard to tasting my largest batch ever!



Might post some video later.

[chokkidog]

Not sure what you're after.........??

High Purity Alumina Ceramic products such as Crucibles, Australia made by Taylor Ceramic Engineering

[MrJack]

Cheers, I'll check them out. I'm not 100% sure what I want yet, but knowing whats available is a good start

[Dimal]

For a Blower...

Why not try a Vacuum Cleaner Motor Ass'y that uses a Variable Speed Controller. That's all I used years ago when playing around with a home-made Fluid-Bed Roaster. Worked a treat and very inexpensive...

Mal.

[MrJack]

Might do later if I think I need more control.
Picked up the current vacuum cleaner for $8 at a swap meet. The guy was a bit sad about the effort he had put into cleaning it up!