Hi all,
I've been thinking about this for some time, and hoping I've come up with a beginning to the solution.
Before y'all tell me that you love your stock KKTO setup - that's totally fine, but this thread is specifically about trying to increase the heat stability of the system.
My setup: I've modified my Turbo Oven to be under the control of a TC4 for it's heater pulse cycles (e.g. at 50% it's on for 3 seconds, off for 3 seconds), and I use the PID of my software to set my temperatures. This has decreased my roast lengths from 25 minutes (as my stock TO was crap) to 15 minutes. This was a great start. The KKTO is also triple wrapped in a fire blanket, and has insulation under it's false floor.
What I'm finding is that the whole system is highly susceptible to changes in the TO heat level, as the fan stays at a constant temperature, and the majority of the heat that the beans receive is fan-forced convective heat. A drop in element temp is a very quick drop due to the high airflow.
I've placed a probe below my 'roasting chamber' and observed that it doesn't get above 100 degrees. The system just doesn't hold much, nor does it circulate much outside the roasting chamber. (Turn it on empty and you'll see chaff swirling around in the chamber perfectly happily without falling through.)
SO... I wanted to solve this problem without doing a complete rebuild and was doing my head in, so I tried to come up with some way of 'filling' the space below the roasting chamber with something to store heat and then support the heat stability of the system. Stored heat coming from below, not just via the fan-forced TO.
I've found a bunch of ceramic pie weights on clearance, so bought 900g of them. They're 7 or 8mm in diameter, and I'll try to come up with a way to restrain them from the driveshaft (and the driveshaft hole) and put them into the roaster below the roasting chamber. It'll be a much longer heat up and temperature stabilisation, but hopefully it'll mean that I can start the roast with a more stable environment.
I roasted today, so it'll be a week or two before I experiment with the pie weights, but I'm hoping it works! It might not make a big difference, especially given it's only 900g of ceramic, but I'm hoping it'll be enough.
Eventually the goal is to gain control of the fan in the TO too, and start with a lower heat from above and lower airflow, so I don't strip the moisture so quickly (and hopefully retain some more of the aroma of the beans). I'm also going to see if I can work out using PWM to regulate the power output of the element (sooner rather than later... but it's the same solution for controlling the fan, so they come together) so I don't need to pulse it on and off, but rather up and down.
Al
I've been thinking about this for some time, and hoping I've come up with a beginning to the solution.
Before y'all tell me that you love your stock KKTO setup - that's totally fine, but this thread is specifically about trying to increase the heat stability of the system.
My setup: I've modified my Turbo Oven to be under the control of a TC4 for it's heater pulse cycles (e.g. at 50% it's on for 3 seconds, off for 3 seconds), and I use the PID of my software to set my temperatures. This has decreased my roast lengths from 25 minutes (as my stock TO was crap) to 15 minutes. This was a great start. The KKTO is also triple wrapped in a fire blanket, and has insulation under it's false floor.
What I'm finding is that the whole system is highly susceptible to changes in the TO heat level, as the fan stays at a constant temperature, and the majority of the heat that the beans receive is fan-forced convective heat. A drop in element temp is a very quick drop due to the high airflow.
I've placed a probe below my 'roasting chamber' and observed that it doesn't get above 100 degrees. The system just doesn't hold much, nor does it circulate much outside the roasting chamber. (Turn it on empty and you'll see chaff swirling around in the chamber perfectly happily without falling through.)
SO... I wanted to solve this problem without doing a complete rebuild and was doing my head in, so I tried to come up with some way of 'filling' the space below the roasting chamber with something to store heat and then support the heat stability of the system. Stored heat coming from below, not just via the fan-forced TO.
I've found a bunch of ceramic pie weights on clearance, so bought 900g of them. They're 7 or 8mm in diameter, and I'll try to come up with a way to restrain them from the driveshaft (and the driveshaft hole) and put them into the roaster below the roasting chamber. It'll be a much longer heat up and temperature stabilisation, but hopefully it'll mean that I can start the roast with a more stable environment.
I roasted today, so it'll be a week or two before I experiment with the pie weights, but I'm hoping it works! It might not make a big difference, especially given it's only 900g of ceramic, but I'm hoping it'll be enough.
Eventually the goal is to gain control of the fan in the TO too, and start with a lower heat from above and lower airflow, so I don't strip the moisture so quickly (and hopefully retain some more of the aroma of the beans). I'm also going to see if I can work out using PWM to regulate the power output of the element (sooner rather than later... but it's the same solution for controlling the fan, so they come together) so I don't need to pulse it on and off, but rather up and down.
Al
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