New built KKTO uneven roast issues

Brett_H

Hi mate, how are you measuring your bean mass temp?

Lacehim

pisanoal wrote:

Hello, let me first start by saying I'm new to the world of home roasting, and I'm still trying to find my groove. I recently built a kkto type roaster after trying unsuccessfully to get decent roasts out of a popcorn popper. I have a 1300 watt TO that I am using, and found a pasta pot set that has the approximate internal dimensions of the suggested arcosteel after the false floor has been fitted (read mine didn't need a false floor to reduce volume). I have tried several agitator types, but my roasts always come out uneven. I am preheating on thaw for 5 minutes, then cranking the heat until 1c, I then back off to 225c until I pull the beans a few minutes after depending on color. My roasts usually have an ash taste, and will have localized uneven roasting on the beans themselves and across the roast. Not sure what else to look at to help.

I would look at the movement of the beans to check they are mixing ok. Tip from KK here. http://coffeeforum.org.au/roasters-different-roasting-equipment/kkto-finaly-completed/msg41702/#msg41702 Ash taste could be from the chaff. I put 2 slots in the side which helps the chaff escape (you'll need to look at the direction it travels in when it's on). Are you cooling the beans afterwards with a fan? That usually blows most of the excess chaff away. some beans are uneven when you roast them anyway but by the found of it your roasting lighter than me. How much are you roasting? My technique, is preheat at 250 for 5mins, drop beans in on full power set timer to 20mins. First crack snaps, drop it back to 220ish, for a minute and I usually take a look and let some of the heat out in the process. crank it back up to 250, and leave it for a few mins till just before 2nd crack or just on the first snaps of 2nd crack. I'm happy with roasting a darker roast on my roaster, than the hipster roasts (lighter) that I end up buying in coffee shops. I find it pours much better, and is easier to control (just my observations and opinion). Took me a while to get my roasts down pat and to understand the process so don't worry, it will all happen with time when you get into the swing of things.

Koffee_Kosmo

If you were in Brisbane I would gladly have a look at your roaster and sort it out for you KK

pisanoal

Brett H - I do not have a way to measure bean mass temp yet. I am going based off time/color/observations. I have been trying to devise a good way to measure bean mass temp, but I'm not sure of how to mount a thermocouple to accurately measure, but not get in the way of the agitator. Lacehim - Thank you for the comments and tips. I have indeed looked at the thread you posted a link to, but on looking at it again, it looks like KK's clearance between the wall of the chamber and agitator blades is significantly more then mine. I have tried to pull them away from the wall but I find my beans against the wall ride along the outside. This is probably my 4th agitator design. I am roasting around 1 pound. I think part of my issue with agitation is that the pot that holds the beans might have a slightly larger diameter, and therefore spreads the beans out. It is hard to get a good mixing action when the bean mass is only a few beans deep. I will try to take some pictures and videos and post them. I am not yet cooling with a fan, but I plan to build a setup for that probably today. I do have holes drilled all the way around above the bean mass to try to let chaff out. Slits would probably work much better. I have tried one darker roast but I prefer things on the lighter side. I enjoy the brighter notes and find that lighter roasts tend to have a lot more variability from origin to origin that I like to taste. KK - Thank you for the offer! I wish I lived down around your area of the world for more reasons then having your help. It has always been near the top of my list of places to visit.

pisanoal

here is a photo

pisanoal

Link to video of agitation https://youtu.be/-YihhhJx-l8

Koffee_Kosmo

Drawings attached are Pot size of Arcosteel potset and How to add a thermocouple probe in PDF Not sure if I have already sent them to you ? KK

PDF_Thermocouple_placement.pdf

borat123

I had to do some digging to find this pic... It's from when I first got a KKTO and had a go at installing a K type thermocouple (from Jaycar). I later moved the end down to the edge of the base and secured the lead to the inside of the pot with little wire ties.

pisanoal

I have not seen the drawing of the thermocouple placements. But I had my agitator arms going almost all the way to the wall so there would not have been enough room for a probe which is where my confusion came from. I have since bent them differently so there is enough room for one, but I am again finding some beans that ride along the outside wall for a while. Would you be able to take a look at the pic and video I posted and let me know what you think of my agitation? Borat123 - thank you for the picture and information

Koffee_Kosmo

Because you have 4 agitator arms you can experiment with two inner and two outer positions The outside arms should have a gap of approximately 10mm from the side That's the area where you would position the probe The main objective of the agitator is to mix the beans in a constant rolling fashion You can use a few coloured beans in your tests to see In the video I see a little pooling in the centre and a little to much pushing of the bean mass So aim and look for with your coloured beans Constant rolling Diving and surfacing Drifting from the centre to the outer and back again ( preferably in a corkscrew fashion ) I achieved all 3 with blade shape So try bending your wire to this shape KK

Brett_H

A great design KK. I used some 12mm copper pipe and flanged the ends so my bean mass is flung quite violently around the chamber. It means that I can't do smaller batches because the agitation is to violent to get the mass up to temp but the larger batches are very evenly roasted.

pisanoal

I do have a few colored beans in the video. That is how i know that i am getting some that ride around the outside. And yes, i have definitely noticed the pooling in the center and have not devised a way to fix that yet. I need to come up with some sort of convex attachment that will push the beans away from the shaft. I have experimented with quite a few agitator designs with increasing success so i will try to bend them to shape of your agitator design and see if I can come closer to how yours works. I may give up and have my machinist friend make me an agitator like your design. I tried to make one but i cut it out with an angle grinder so I couldn't do the curves. Thanks for the help, i will see what i can do with it! 🙂

Koffee_Kosmo

Be aware that the metal agitators are best used with an insert that does not flex in the bottom On some brands the insert can flex up to 5mm X 2 both directions That leaves a gap between the agitator and the base - This gap causes the beans to jamb often while roasting That's why I added the spring as even the Arcosteel post flexed approx 2mm Due to many DIY builders emails for help I came up with the wire agitator blades - They flex with the pot and eliminate bean jamming So if you are going to use a solid agitator you should also stiffen the perforated pot base with a large washer spot welded or riveted in place ( see photo )