Feedback sought: New corretto/KKTO build

[nikko.the.scorpio]

Hi Folks,

I've been using a heavily modified Breville BB290 (with insulated sides, cover, chaff vent) on it's dough program in conjunction with an Ozito heatgun for the past couple of years. ~400-450g per batch.

Anyway as chance would have it the Roasting Gods must of gotten a tad displeased with me last week as the corretto nearly caught fire (silly mistake after some rags I'd been using as insulation down the gaps either side of the vertical pan were accidently pushed to the wrong spot & started smoking....a LOT!!!) - thus it got me thinking to totally redo my home roaster design.

Now I'm kind of stuck deciding on between the KKTO design (full credit and a tip of my hat to Koffee Kosmo for this gem of design!) (which is based around the fitting pot-colander design, classically with the heat coming from a Halogen/Turbo oven) vs a breadmaker corretto using a heatgun. Or a hybrid of each.

Now luckily or complicating my choice (depending on your view) I've got quite a lot of the parts for either roaster path already on hand. Including:

- I gutted/dismantled the Breville BB290 and have removed it's motor keeping it's connections to the control buttons etc and power supply (so worst case scenario if I can't rewire it etc I could use it on the same 'dough' program - though I'd suspect it'd be easier to remove this extra bits and just connect a 12v(?) power source into the motor. I also removed the fanbelt/gearing on the motor as I assumed it might be simpler to use in a 'direct drive' style up directly to the agitator.)
IMG_0083 by NG, on Flickr

- I also happened to have pretty much the identical Arcosteel pasta pot set thats the foundation of the KKTO

- an Ozito variable temp heat gun (unsure how this compares as a heat source vs a Halogen/Turbo oven? Any pro's or cons of each?)

- I've also got another two breadmakers (one of them a very similar Breville BB270 and the other I'd prefer not to use a newer Sunbeam BM7800)

So I like the simplicity &versatility of the KKTO design - though I'm a bit worried about being able to cobble together an adequate drive shaft & agitator. I downloaded the basicish plans that KK had kindly put up and they give you an idea of where to go with the design so thats quite handy.

Alas I've not been able to find any cheap Halogen ovens here locally, was considering the KKTO design but with a heatgun as the heat source via an inlet in an insulated roof- not sure how that would compare.

Very much like the KKTO design, especially as I have the very sought after pots already on hand.....however the driveshaft, making a suitable agitator and modifying the electric motor I have onhand (if viable) are the current obstacles I'm weighing up vs whats essentially a almost ready to go option via one of the other breadmakers.

Would welcome any feedback etc from other members with experience in this area.

Thank you in advance, Nick

PS. I should also note that I've got the extreme luxury of knowing a person who owns one of the ACTUAL made by KK KKTO's. So if I went that path I'd be able to essentially compare and take notes from the real McCoy item, which is a huge advantage as the basic design path.

[Koffee_Kosmo]

Hiya Nick
Now you have the designer answering your question

If you want a
1) Clean roaster that collects the chaff internally
2) Large capacity
3) Single unit roasting
4) Safe with electricity
5) Reliable & Modifiable roaster
6) It can be used with a heat gun for its heat source

Then a Koffee Kosmo roaster is a good choice as you have the preferred Arcosteel Pot Set
How reliable is the KKTO roaster you ask - I would be close to 3000 or so roasts on the same roaster - with a couple of TO changes in that time


This design has remained the same but as parts have depleted I have made design changes to suit
The drive section is available
Turbo ovens can be purchased from Deals Direct or Aldi and other outlets for $50 or less

Good luck with your build choice

KK

[russellb]

ALDI have a halogen turbo oven at $35 at present, I just got one to replace my original unit. They went on sale about 3 weeks ago, but I've seen a number in several stores while I made up my mind to get one.

[Dimal]

G'day KK...

How are you mate?

Mal.

[Koffee_Kosmo]

Im doing fine Mal
Back working long hours again

KK

[Dimal]

Good to hear my friend...

Don't work too hard mate, you know what they say about time and roses....

Mal.

[nikko.the.scorpio]

Thanks for the replies chaps - special thanks to KK for taking the time to give his feedback.

Yes, I think using the KKTO as the design basework is a bit of a no-brainer. It's proven to work VERY WELL and it adaptable in multiple ways. haha thankfully we very seldom use the pasta pot set, so I won't have to worry about blowback on that one - another major reason the universe is telling me to make a KKTO.

So I have downloaded KK's excellent 36 page PDF designs for the KKTO (again my sincere thanks for being such an amazing individual to not only come up with this concept but share and assist people in making one as well!).

I also stumbled across this thread at another US coffee forum, which deals with how to rewire/simplify the electrical internals of most breadmaker's motors:
Homeroasters.org - Discussion Forum: Modifying a Bread Machine 2 - Re-Wiring

This is the pasta/pot set I very fortuitously had and it's bang on 24cm in diameter:
IMG_0084 by

It appears to be a lot smaller than the initial one KK uses in the designs - however it's essentially identical to the 3 section one he details on page 32. I'M unsure if I'd use the larger inner colander or the smaller one as my roast chamber - I'd always tend to do around 400-500g batches as thats what we drink in a week-10 days and doing more just lends itself to stale beans. I like the idea of using the smaller chamber up at the top of it - as that would be closer to the radiant heat of the TO, and also obviously heat rises so makes sense that you'd have to put less heat in to get said results. And then the larger colander would be as KK has stated primarily be a chaff catcher.

One of the advantages of the smaller container is that I won't have to put the insulated false bottom in place to reduce the overall air volume - so thats a major plus.

However I do suspect chaff would find it hard to escape out of the colander as it is - dunno if that might be an issue - I don't mind just shaking it off later anyway but I'd also have to be careful that the agitator isn't too fast and this spinning the beans all over the place - might have to consider putting that gearing back on or getting a window winder motor instead i it spins too fast - will test that out in a while.

Also I found several suitable ebay listings for whats essentially,"8mm High Temperature Heat Insulation Fire Flame 10KV Protection Tubing Sleeve 1M" to place around the lips of the containers so they get a nice tight seal.

Says it's safe up to 260 (so knowing Chinese product claims prolly catches fire at 120 but anyway) - I assume this is the type of thing that KK uses? Just wondering what diameter you found suitable?

Again not sure if anyone knows of the pros vs cons of a Turbo oven as the heat source vs a heat gun? I would assume the TO might be more likely to get better results as it uses radiant heat over a wider spread - whereas the HG uses a small tight and very strong projection of hot air. The latter I would imagine tends to dry the beans out more and thus add an extra element thats somewhat undesired to roasts.

I'd figure the HG might have the advantage in the reliability stakes - as often even the Ozito ones come with 3yr warranties (which has bailed me out atleast once) but anyway alas I think I've missed out on all the Aldi ones in my area (which amazed me as they seemed like they'd never sell but sure enough as soon as I'm interested they're all gone!)

Anyway I'll have a hunt around - and also pull the scrap breadmaker body metal out of the bin as I will try to follow KK's design and fashion the agitator from that.

Much thanks, Nick

[russellb]

Nick,
I checked the "air-off" temperature on my original turbo oven, admittedly not a halogen, and at the top of the pot it was more like 360 degrees IIRC. Anyway it singed the insulation on my thermocouple. I have been using tubing rated at 250 deg and it has slowly darkened over the years. Just recently replaced my original tubing (I had a double length), but when that goes I will look for something with a higher temperature rating.

HTH

[readeral]

Hey dudes, I've been looking into the hoses for my own build. You're not likely to find hoses over 250 degrees in silicone in my anecdotal experience - I'm not sure that car spec would need it higher than that?! But if you come across any let me know! I looked up KKs recommended inner and outer diameters and found the relevant tubing on evilbay (bunch of UK stores have it cheap with good shipping too)

[nikko.the.scorpio]

@russellb, handy info - good to know.

@readeral, any chance you can post up or msg the links to the tubing you're considering? As it's not coffee related or anything sold by the sponsors I don't think it'll irk anyone. Thanks in advance.

FWIW just ordered an inline on/off power switch to mod the breadmaker motor. Also found a very cheap 19cm diameter steel baking sieve to use to make an improved bean cooler (I currently use a large sink colander/strainer with a large fan blowing on it - so the extraction fan style via bucket will be far more effective) - ~$AUD3.40 delivered from China.....crazy prices!

Anyway FWIW the dimensions of my potset (which isn't the Arcosteel one BUT is very close is)

MAIN POT (to be used as exterior)
Height to lip: 14cm
Internal diameter: 21.5cm
Nice thick and stable base around 3mm thick, all stainless steel, spotwelded handles (which I know KK insists on!)
By my calculation even if this was used as was it would have a volume of around 5.7L - so well within KK's recommendations and definitely NOT needing a false bottom etc.

LARGE INTERNAL INSERT/COLANDER
Height to lip: 14cm
Internal diameter: ~21cm
Again reasonably solid SS construction, has a lip around 6cm down from the top of it that allows it to 'sit' in the outer/exterior solid pot. All the holes are 5mm in diameter, which should be small enough to allow most of the chaff through but no beans (will test out just to make sure but optimistic).

SMALL INTERNAL INSERT/COLANDER
Height to lip: 6.5cm
Internal diameter: ~20cm
Same quality of materials, 2 wire steel handles (handy but would have to put lil extensions/holders out so they wouldn't fall down when in use and snag on the agitator). The holes in this are smaller, ~3mm.

[Koffee_Kosmo]

Nick
Both KKTO roaster designs have a false floor or insert to adjust the chamber volume to the ideal I have set

Version 1 was a large pot with a floating insert - This design was changed to the two pot system for burn safety reasons
The hoses that I use are high temp vacuum type that are used in racing or high performance cars
OD top hose is 12 mm , OD lower hose is 8mm

Cheers
KK

[nikko.the.scorpio]

Nick
Both KKTO roaster designs have a false floor or insert to adjust the chamber volume to the ideal I have set

Much thanks KK, I've been enjoying your posts over at Coffee Forum as well - so much wisdom but you've got to search out the best stuff - oh well makes it more rewarding!

I suspect my pots are quite a bit smaller than yours and unless I was using the small internal colander alone (without the larger one in as well) I'd actually not have much room for a false bottom inside the main pot. My larger pot is only 14.5cm or so in total height (vs the one in your plans being 16.5cm). By my calculations with the large insert in there's around a 4cm gap between it's base and that of the external pot.

Therefore with a total height with this on of 18cm that gives an internal volume of ~6800cm3. Which is around the ballpark of what you recommended.

Therefore I'm unsure if the false floor would provide any benefit as my concern is that it makes the already small-ish internal volume even smaller. As if I did say a 3cm total false floor and then had only 1cm clearance between the large insert and the false bottom it'd take ~1100cm3 off - I'm unsure if this is of much real benefit given the already small size - but would greatly welcome your feedback if you feel it's still essential or very recommended (even in this smaller pot/s).

Thanks again, Nick

PS. Much thanks for the confirmation of the tubing used and the diameters. :-)

[readeral]

So this is the hose for the seal between lower pot and roasting chamber (8mm hose, 4mm inner, 2mm wall) hose 1 or hose 2
And this is the hose for between the turbo-oven and the rim of your roasting chamber. You'll have to slit it to slide it over the edge of the pot (11mm hose, 6mm inner, 2.5mm wall) hose 3 or hose 4

Unfortunately somewhat mis-matched colour wise if you wanted anything other than blue or black, but it didn't matter too much to me.

All those links state they have a working temperature of 260°C - dunno how true that is, but the best you can do is take their word for it!


I've been thinking about the KKTO build for about a month now. The beta testers thread will give you a whole bunch of context into why KK has done what he's done in terms of design - the false floor seems invaluable.

[readeral]

Looks like you're all over it when it comes to searching through the forums Nick! Where you based?

[nikko.the.scorpio]

Looks like you're all over it when it comes to searching through the forums Nick! Where you based?

Ah I wouldn't say that but hey it's worth doing right and KK has done all the hard work so tracking down a few posts (and those of other KKTO builds) isn't too hard. :-)

I'm in Coffs Harbour. :-)

Oh and much thanks for those links to the silicone hoses. FWIW I don't think that silicone hose or any type of hose for the lower pot & large roasting chamber insert is actually going to be viable. Mine has a sort of a recessed lip inwards and thats what the internal insert sort of sits on. So I'd actually be better off making a sort of a gasket by sticking a thin strip of heat resistant material (silicone again seems a reasonable choice) around either the internal join point of the external pot or on the exterior same point on the roasting chamber.

To be honest it's already a pretty good seal I cannot imagine that much heat will escape from it. I might actually try and make a gasket to give a tighter 'seal/fit' by doubling up/folding some aluminium foil around the join point for the internal chamber. That might be all hard to picture haha and it's pretty much only specific to my pots but I don't think anything but some really BIG tubing/hose would work on that joint/seal. e.g 15mm

The top joint between the pot-roasting chamber and the TO however is very much perfect for the tubing you suggested and I'd say the smaller ones would be the best solution as I've got a rolled rim thats around 3mm in diameter. So as long as it's a nice even fit all the way around smaller would actually give a better seal than say a 8mm one , where there'd be a lot of play/room to move around etc.

Yes, I think the Chinese sellers have picked 260degrees as their temp mark - not sure how true that is but in theory it's ok and am happy enough to run with it & replace down the track.

Thanks again for your help, very handy as I did not see those at all!

PS Ordered the 5mm internal hose in lime green! Should fit easy and seemed the good value point. 75cm diameter so will do the top -> TO joint nicely.