From scratch roasters - worklog

[RichardM]

Ok, so after a lengthy discussion with a gas fitter my in law knew, I have decided against direct flame, purely because of price.

I have obtained a burner to go under the pot today. It's a three ring burner that will put out around 8kW of heat: http://www.bcf.com.au/online-store/products/Primus-Triple-Ring-Burner-RB40.aspx?pid=114492#Description

The picture doesn't do it justice, it's VERY weighty and large. The centre burner will just be used as a pilot, with the other two for temp control. I will have a lot of work to do this weekend putting pretty well the whole thing together.

[Koffee Kosmo]

A suggestion
Heat applied from the outside without a barrier can be wasted

I also suggest a cowling/cover for heat retention and safety 
Doesn't need to hinder the flame ring

KK

[RichardM]

A suggestion
Heat applied from the outside without a barrier can be wasted

I also suggest a cowling/cover for heat retention and safety  
Doesn't need to hinder the flame ring

KK

Indeed. A flame diffuser will be fitted, and I'll put some metal sheeting either side to try and guide the heat up onto the pot. I think if I put 8kW out there, maybe half of it will be wasted  () so that still should be plenty to roast up to 1kg (as long as the stirring, airflow etc is good of course, which will remain to be seen).

[RichardM]

Ok, long time no post.....But I haven't been sitting on my arse, I promise!

Tonight, I bring you the first roast from this roaster...and it's one that I'm going to try and drink!

Bean: 300g Nicaragua Las Glorias
Gas roasted with a three ring burner.

Roast data (from 100^oC onwards:
6:00 - 100^oC
7:00 - 115^oC
8:00 - 129^oC
9:00 - 143^oC
10:00 - 158^oC
11:00 - 172^oC
12:00 - 184^oC
13:00 - 193^oC
14:00 - 205^oC
15:00 - 216^oC
16:00 - 226^oC - 1st Crack
17:00 - 236^oC
18:00 - 241^oC - HOLY CRAP SECOND CRACK
*STOP!!!*

And the result (ignore the yellowish bit. That is just the white balance on the camera being off)


So the information on the roaster.
The burner is a three ring burner, bought from BCF.
The roasting chamber is two pots stuck together. If doing again, of course, would just get a 30L pot instead of 2 x 16L bolted together.
The roasting chamber is attached to the ring burner with a bolt through the middle.
The motor is a wiper motor from an EF Falcon, and has a 12mm socket attached to the nut on the end with high temperature epoxy. It is powered by a car battery charger.
The Temperature probe is about 1cm below the roasting cage/drum (which is a spare drum for a Behmor).







The roast chamber got fairly smokey, because the chaff was burning on the bottom near the flame, so I need to mount a vacuum cleaner at the back of it to run during the roast and suck out the chaff.

[Koffee Kosmo]

Excellent 
Progress at last and now in working condition

I have a few ideas for the chaff but I need to see how it falls
Also have you considered a fan with speed control

Keep us in the loop with cupping & taste tests

KK

[RichardM]

Excellent 
Progress at last and now in working condition

I have a few ideas for the chaff but I need to see how it falls
Also have you considered a fan with speed control

Keep us in the loop with cupping & taste tests

KK

Will do. With the chaff, a fan would suck it out (the pot actually sits at about a 10 degree angle, but the cage is level, so it all falls to the back). I'm just concerned about how to mount a fan without melting it, but I think it will be an easy issue to solve.

[Koffee Kosmo]

Will do. With the chaff, a fan would suck it out (the pot actually sits at about a 10 degree angle, but the cage is level, so it all falls to the back). I'm just concerned about how to mount a fan without melting it, but I think it will be an easy issue to solve.

Oven fan wont melt
KK

[mycuppa]

Ok, long time no post.....But I haven't been sitting on my arse, I promise!

Tonight, I bring you the first roast from this roaster...and it's one that I'm going to try and drink!

Well done RM - and here we all were thinking you were not posting anything because you could'nt work out how to take off your wedding goggles.

Couple of things.....

Is it mounted on wood ? I know wood is a great thermal insulator and you are in the prototyping stage, but you may want to think about some safety pretty soon - flames and wood are not a good mix.

Does the gas burner/bottle have a regulator ?

Speed of the drum is less important than what a whole bunch of people may think (this applies to drum method). Many years ago I thought it was important and run a whole series of controlled experiments. Result = did'nt matter. There is way too much written on the internet about the perceived benefits of drum speed controls and this only comes into play on very large roasters with contact volume ratio and significant inertia lag. Reality is ........purpose of drum rotation is agitation and so long as you have something close that gives you reasonable turnover of product you should be fine. Reason I write this is so you can focus on your airflow and other thermal characteristics first and don't worry about drum speed - you probably knew that already.

You may have already been told, but make sure you adjust your burner flame so you have a nice small blue needle and minimal/no large yellow flame.

When designing your airflow system it only needs to be quite low pressure and of course you will need to direct the chaff and smoke somewhere.

Great start RM.

[UNM]

You definitely need to get the chaff away from the heat and airflow control will have many benefits, not just chaff removal.

You might want to set up a fan to blow rather than suck - less issues with the high  temperature.

[RichardM]

Is it mounted on wood ? I know wood is a great thermal insulator and you are in the prototyping stage, but you may want to think about some safety pretty soon - flames and wood are not a good mix.

It is on timber at the moment, but just sitting there. I will be sitting it on a metal photocopier pedestal soon (metal) and I'll probably put some masonite under it as a thermal insulator. It's actually not "Mounted" on anything as such. It all just sits there, which makes it fairly portable.

Out of the shot of the photos are two fire extinguishers within reach, just to be safe.

Does the gas burner/bottle have a regulator ?

Yep. Standard regulator. Also, before you ask, I have a CO detector mounted nearby based on your previous advice.

Speed of the drum is less important than what a whole bunch of people may think (this applies to drum method). Many years ago I thought it was important and run a whole series of controlled experiments. Result = did'nt matter. There is way too much written on the internet about the perceived benefits of drum speed controls and this only comes into play on very large roasters with contact volume ratio and significant inertia lag. Reality is ........purpose of drum rotation is agitation and so long as you have something close that gives you reasonable turnover of product you should be fine. Reason I write this is so you can focus on your airflow and other thermal characteristics first and don't worry about drum speed - you probably knew that already.

From what I've noticed, it doesn't seem to matter too much. I'm at about 60rpm at the moment, which is a bit quick, but seems to disperse the chaff well, but not break the beans (thus why the roast looks so even I think).

You may have already been told, but make sure you adjust your burner flame so you have a nice small blue needle and minimal/no large yellow flame.

Yep. CO poisoning isn't really my thing.

When designing your airflow system it only needs to be quite low pressure and of course you will need to direct the chaff and smoke somewhere.

As yet the airflow system is "whatever leaks out the lid area". I HAVE to do something about smoke and chaff though. I'm thinking a small chimney and a rearranging of my garage so it vents out a nearby window, and a vacuum for sucking chaff at the bottom. I'm impressed with a lot of the home style roasters that have minimal airflow (iRoast, KKTO), so while I'll focus on airflow soon, I'm thinking just a gentle breeze instead of a gusty wind.

It's all just a start right now, but I've got the basic hard bit nutted out, so looking forward to taking it to the next level over christmas break. I'm trying to be a minimalistic as possible for both cost, and reproduction reasons.

[RichardM]

Ok, so tasted the coffee from roast 1, and it is quite flat, nad lifeless. No acidity to speak of, and the pour was REALLY thick and syrupy, but also no bitterness. The quick 1st crack>2nd crack has definitely made it boring. Will try again with what I now know and go from there.

The biggest thing I can take from this is despite all the chaff turning to ash powder in the bottom of the roaster, there is definitely no smokeyness to speak of (which I somethign I've been struggling with in the Behmor). Might not need to exhaust it yet...

[UNM]

Just a thought - to stop the chaff falling right to the bottom, you could get a piece of metal duct, slice in half to get a curved section that can then be mounted below the roasting cage.
 Could mount on the front plate so it acts as a removable chaff tray.

Of course it would alter the heat distribution too.

[Koffee Kosmo]

Richard
I came across this roaster and thought it may be just the thing for your build

<a href="http://www.youtube.com/v/LF4pAiQ81WE&fs=1" target="_blank" class="new_win">http://www.youtube.com/v/LF4pAiQ81WE&fs=1</a>

KK

[Muscles]

Any updates RM? Just wondering if you have sourced a new motor and if you are planning on mounting it differently to prevent another melt down?

[RichardM]

For those who haven't heard, my motor melted. Also, the aluminium pot has deformed majorly since implementing, so I need to buy another stainless steel pot, but it has to be over 32cm tall to work in one piece (difficult to find at a reasonable price). I will also need to buy a motor ($20, easy).

I have however seen some great hooded BBQ's going for just over $100, so really contemplating rigging it up inside that, which would eliminate the need for the pot. It would also mean the flame was inside the roasting chamber which would mean I could have the chaff fall down beneath into a drip tray at the bottom, which would get rid of my issue of burning chaff on the bottom as well.

If i'd mounted the motor on a smaller pot at the back, and filled said pot with fiberglass, then it wouldn't have come to that, and I was super happy with the results this roaster was producing, but let this go down as a lesson to anyone wanting to do something similar: Aluminium pots melt, and windscreen wiper motors MUST be insulated.

_{Just wrote all of this through a burning eye. Another lesson: don't cut up birdseye chillis then rub your eye}

[Lacehim]

RM, just think of it as a mark 1.  Somewhere to learn and develop in to the mark 2.

Keep your eye our on ebay/gumtree, garage sales and the local classifieds.  A s/s pot will turn up cheap.

[Brett H]

I had a BBQ roaster and it did work brilliantly.  Very messy and large but the BBQ was a hooded one from eBay for $50 second hand so you may find it the cheaper option.  It also gives you the option for a larger drum for increased batch sizes.  Only drawback of mine was unloading manually with gloves.  That's why it didn't suit me in the end.