From scratch roasters - worklog

RichardM

So I had five hours in the car driving today, just me and my brain (horrible company!).

I first had the idea that I would add a third halogen heater to my Behmor, as I have access to a heap of lamps that get thrown out (photocopier tech), however they were too long to fit. I also have access to plenty of low speed DC motors.

I was in Big W this afternoon, and impulse bought two mesh 20cm garbage bins which will be perfect for making a drum out of once I've removed the no doubt toxic paint from them.

Before I get cracking, has anyone here ever built a roaster completely from scratch, and are there any tips mainly regarding airflow and heat position in relation to the cage? I will have either 6 or 8 lamps, individually hooked up to light switches. Also, any tips on how to "test" without wasting beans. I anticipate this roaster will do ~500g as the internals will be just a big bigger in size compared to a Behmor, but with an extra ~800W, and possibly better insulation. Will putting small holes in the bottom and top be enough for convection airflow, or will a fan be definitely required?

I plan on using just sheet metal and rivets to make the outside, and insulating with just an air pocket and/or fiberglass insulation.

Will get started tomorrow night if my lamp gathering goes to plan.

Koffee_Kosmo

The only one I know of is a New Zealand halogen roaster (drum type) It was presented in a competition on Home Roasters in the US You will see me there as I am an active member I wont say more except advising you to study the construction details on the link http://www.homeroasters.org/php/forum/viewthread.php?thread_id=570 Ohh and if you want a pot to start the above build I have a couple of unused ones that you can have gratis :o Regards KK

mycuppa

RM, Why don't you look into a low-power/intensity IR system - these have been known to be far more effective (e.g. Diedrich use them on their <30kg roasters). You might want to research the thermal transfer rates of halogen versus IR as my simplistic engineering understanding is that Halogen may provide too much "surface" heat that could result in the outside of the bean being cooked but the inside being medium "RARE" (if you get my drift). IR works differently via the wavelengths somewhat akin to a microwave. Mate, you are a smart boy - just bite the bullet and design your own small drum roaster using a gas source (LPG or natural). Now that I've owned a few drum roasters and pulled them all apart, rebuilt and put back together, there's no rocket science involved - all pretty simple actually when you break it down. Gas is the only way to go - just way easy to control thermals without lag.

RichardM

Thanks guys. KK - that roaster looks a touch more professional than I have the engineering skills or tools to build. Thanks for the offer though 🙂 Jeff - I am building this roaster specifically with the idea that I could do the following: a) fit a turbo oven to the lid b) Remove the lamps and put a gas stove underneath For reference, Quartz lamps are just as readily available to me, and they are in the IR range, so I will get some of those instead. I was avoiding them because they were lower wattage, but if they are just as effective, they will actually be easier to mount. This first attempt is more just about me improving my understanding of roasting technique. If successful, I'll probably take my learning onto a bigger/better roaster and try and replicate something similar to the Diedrich's. With heat sources and sheet metal costing me pretty close to $0, I should be able to have some fun 🙂

RichardM

I've started, but only cutting metal sheets etc, so nothing to show yet....but just wondering, do the commercial roasters use a design similar to the one KK linked (ie a solid drum with no airflow, and heat source inside) or is there a secondary inner chamber and heat source outside the bean holding drum, or is there a mesh drum with airflow???

mycuppa

RM, Best advice is to travel to a Roastery, beg for permission and then poke your head inside a roaster. Once you have done that, many things will start to make sense. Most commercial drums are solid with a perforated set of 3-4mm holes at the rear - somewhat similar to a cooling tray. Airflow is VERY important and typically drawn from the rear towards the front of the roaster, but there is no reason you could not reverse this approach - it depends upon accessibility as most roasters are operated from the front or side. Many use a design near the greens hopper at the top front of dual channel paths whereby greens can pass down into the drum via one channel and roast/chaff air is being pulled through, up and out of the drum via the other channel. Heat source is best when it does not make direct contact with the drum, e.g. if using flames, don't let them lick the drum ! Sometimes deflector shields are used to more evenly distribute heat. Other designs like Joper use high-powered eclipse burners and a "heat box" concept. On one of my previous roasters, I re-built some of the parts and re-designed the paddles inside the drum. I will send you some pics of the parts via email, but alas I did take many pics of everything involved in the process as it was kind of a case of "time is of the utmost essence".

Koffee_Kosmo

RichardM wrote:

I've started, but only cutting metal sheets etc, so nothing to show yet....but just wondering, do the commercial roasters use a design similar to the one KK linked (ie a solid drum with no airflow, and heat source inside) or is there a secondary inner chamber and heat source outside the bean holding drum, or is there a mesh drum with airflow???

No air flow in the design I linked The outer pot is an external rotating drum The heat source / halogen lamp is in a fixed position KK

RichardM

Right, so after much thought, I went back to the drawing board...and basically decided to essentially rip off the design that KK linked originally 😛 Jeff has sent me pictures of a stripped down Has Garanti, and some advice regarding heat sources, which has been most useful. First things first, get drum made, on a spindle. I found it easy to find a saucepan, and ended up getting this one for $15 from Kmart (mild stainless - the absolute crappiest saucepan I've ever seen. It would burn anything that you tried to cook in it....but perfect for this use 🙂 ). Big W had some for $19 which were aluminium...but I don't think they would have been quite as good. For the mount for the drum, I pulled an old stepper motor in half, and drilled the four holes, which has formed a VERY stable base for the drum to rest on. Lids are, however, much harder to come by at a reasonable price. The saucepan came with a glass lid, which is pretty much useless because a) it's too heavy and b) it's near impossible to drill holes in. I mounted the pot on the shaft of a main drive unit from a photocopier. Still need to organise a motor, and I'm just building it on wood, so then I can mark off holes, and mount onto a pedestal once I've got the basics nutted out. I have used joist hangers as bean stirrers, and will be using gas as the heat source. I'm looking at $20 camping stoves, but also thinking I might buy a BBQ and just strip the long, straight gas jets from it. I'll get a flame diffuser. I still need to mount some mesh in the back for ventilation, but will do that closer to the end of the project. Not all the bearings are heat resistant, but I figure I'll just replace them with heat proof ones as they die. I'm hoping this design will be able to do 1kg with ease. So....obligatory pictures attached. Not bad for an afternoon's work I think, considering I'm very limited with tools etc and have never done anything like this before:

Koffee_Kosmo

You can still use gas in the same way the original design uses a halogen lamp Its old school and is called direct flame Here is some info on it and how to build one http://www.homeroasters.org/php/forum/viewthread.php?thread_id=2153 It will set your roaster apart Plus I wouldn't be guiding you down this path if I did not think it would work KK

RichardM

Koffee Kosmo wrote:

You can still use gas in the same way the original design uses a halogen lamp Its old school and is called direct flame Here is some info on it and how to build one http://www.homeroasters.org/php/forum/viewthread.php?thread_id=2153 It will set your roaster apart KK

Indeed, and I'm keeping that option open. I could just get an LPG blowtorch and rig that up. I'm kind of skeptical that it would offer any benefit though, just due to the condensation from the flames inside if the ventilation wasn't high enough. Also, if there weren't enough oxygen for the flame, that could cause some dramas.

Koffee_Kosmo

RichardM wrote:

Indeed, and I'm keeping that option open. I could just get an LPG blowtorch and rig that up. I'm kind of sceptical that it would offer any benefit though, just due to the condensation from the flames inside if the ventilation wasn't high enough. Also, if there weren't enough oxygen for the flame, that could cause some dramas.

Oxygen will feed the flame via a hole outside the roaster, Edit:- on the gas probe/burner itself KK

RichardM

Koffee Kosmo wrote:

Oxygen will feed the flame via a hole outside the roaster

Ah, haven't really done that research. If that's the case, I might pop my head in to BOC Gas and Gear this week and see what my options are. Realistically, it won't change the way I do the build though, and I will be able to change my mind at the last minute if need be.

Koffee_Kosmo

On shift work at the BHP we made our own BBQ's so we could take a steak in on afternoon shift Anyway we just had a piece of pipe with may holes drilled along the top Sealed at one end A gas fitting on the other, also air adjust hole (similar to a Bunsen burner) Worked a treat KK

RichardM

Hmm, so just to make sure we are on the same page, I assume you're talking about something like this: http://www.auscrown.com/page/shop/flypage/product_id/103/a/category/e/blowtorch_blowtorchburners which would be equivalent to around 3kW electric, which should be enough direct heat to roast 1kg of beans (with the added benefit of just changing tips if it wasn't). I saw that guy on homeroasters that you linked using 26kW of heat in the two bowls - I'm amazed he didn't incinerate the bowls. The only thing I'm really concerned about is whether the beans at the back would get enough heat - which I guess comes back to whether I'm trying to heat the air, heating the drum, or heating the beans.... (why oh why didn't I just build a KKTO. That would have been pure simplicity compared to this monster that is taking on a life of its own). Just wanted to say thanks again for the help here. I really do appreciate it - couldn't do it without the community here 🙂

Koffee_Kosmo

You will only know from experiments on the best blow torch tip to use The purist direct flame roasters also had the beans quickly crossing into the flame while tumbling I help in any way that my trade experience allows It matters not what path a fellow roaster takes KK

RichardM

Today's acquisition: 1 x 24V DC 13RPM motor with worm gear Housing from an old "Fiery" - basically a big solid steel box to mount everything on Pedestal from photocopier - will form a sturdy base. No pics today, but this will give me something to work on for a while. What I am having issue with is obtaining reasonably priced metal lids for my 28cm saucepan. They all seem $50+. I might end up having to bite the bullet and just spend the money 🙁 I want something like this: http://www.nisbets.com.au/product.asp?pID=4683&cID=242 but with a flatter handle, and not for the $40 it would end up costing including shipping.

Koffee_Kosmo

Regarding the lid Go to a few second hand stores and you may get lucky Also if you have any African goods stores close by, they will have large pot sets/ lids Also I will have a look to see if I have one from my build of the original KKTO You may be lucky a second time Also 13 rpm may be a little slow KK

WotB

Did you want a glass one? Might try an asian supermarket or junk store.

RichardM

Koffee Kosmo wrote:

Regarding the lid Go to a few second hand stores and you may get lucky Also if you have any African goods stores close by, they will have large pot sets/ lids Also I will have a look to see if I have one from my build of the original KKTO You may be lucky a second time Also 13 rpm may be a little slow KK

13rpm will be too slow, for sure, but I've got a full gear assembly that I can easily change ratios on. Should get it to about 30rpm easily - it's a worm gear drive, so should handle the increased load (it's a toner stirring motor from ...a photocopier). WOTB - I have a glass one - they are a dime a dozen (even got one with the saucepan I bought) but not being able to easily drill into it is just a pain in the neck and makes things too difficult. Regarding lids, I've tried two asian stores, Big W, K Mart, Target, Myer (had them but too $$$), a kitchen catering place, and Vinnies. We have no African stores 🙁 I will have a look at some second hand stores this weekend (going to the sunshine coast, so will have a look there).

shape_shifter

Richard we're watching your progress. Our new roaster is also a start from scratch as we're keeping the smaller one for home use and making the larger one for supplying others so making it hold at least 500 grams 🙂