Ikawa Home thermal performance - Page 7

Discuss roast levels and profiles for espresso, equipment for roasting coffee.

#61: Post by Iowa_Boy »

GDM528 wrote:Very nicely done - totally looks "Pro". Is it taped in place - what keeps it perpendicular to the chamber wall?
Yes, just Kapton tape holding it in place. It's stainless steel wire so it's easy to bend into position.

GDM528 (original poster)

#62: Post by GDM528 (original poster) »

Here's a test that shows the effects of the roaster warming up:

Ran the same profile four times, with the first run starting with a 'cold' machine that hadn't been run for at least 12 hours.

My first observation is running the machine just once is enough to warm it up, and it's remarkably consistent thereafter, like, really-really consistent. Wow. From now on, I'll be doing an empty-chamber warm-up run before loading in the greens.

The other thing I'm noting is a slow drift in chamber temperature, about 1.5 degrees/minute at first-crack temperatures. It's steeper (2.5C/min) at the 200C setpoint, but that could be because it was preceded with a pretty large initial temperature jump.

The drift effect is probably not such a big deal at lower temperatures but could be significant when trying to dial in exactly when first-crack/second-crack is supposed to happen if it's not accounted for. The drift will also flummox any rules of thumb for estimate the offset between the input setpoints and the chamber temperature. I used to think the gap was 40C, but now I'd say it's 40-30C at drying/browning temps, and 45-35C for FC/SC temps.

GDM528 (original poster)

#63: Post by GDM528 (original poster) »

Another thermal drift and offset measurement; this time with beans in the chamber:

Instant initial jump to emulate dropping beans into a preheated chamber, followed by a straight ramp to first crack, brief pullback to accommodate the beans going exothermic, and finally a slow ramp to a City roast level:

Also showing results with an empty chamber, which illustrates how the beans are largely following the shape of the empty-chamber curve after about 2-3 minutes. I theorize the slopes line up once the beans are finished drying out.

The ramp over the first 5 minutes is faster than the beans can follow, which causes the temperature offset to increase over time, but starts tracking 1:1 for the final 3 minutes. The good news is the temperature offset stays pretty close to a steady 40C over the phase of the roast where it matters the most.

GDM528 (original poster)

#64: Post by GDM528 (original poster) »

So, it turns out the glass cover on the Ikawa is optional...

Smelly and messy for sure - definitely doesn't play well indoors. But as long as the bean-loading funnel is installed, the internal electronics are blissfully unaware of the idiot at the helm. The beans still stay in the chamber and spin around as they would with the cover on. And the resulting roast looked... serviceable. I don't recommend this unless you're on some sort of quest.

With that pesky glass out of the way, an IR camera has a clear view inside the chamber. Below is a comparison between a 50g and 100g batch size. The IR camera's frame rate is only 16Hz, so the spinning beans are blurred, especially for the 50g batch size. As one might expect, the bean temperature looks more uniform for the smaller batch size.

It was also interesting to note the thermocouple I placed in the bean mass was reading within a few degrees of the camera's readings - that really demotivates me from figuring out how to install an IR probe.

★ Helpful

GDM528 (original poster)

#65: Post by GDM528 (original poster) »

Here are short clips of the beans as they're heating up.

The camera software is kinda dodgy, hence the pulsing pixeliciousness in the clips. Also switched to greyscale to show details a bit more clearly. For you IR camera nerds: Seek Thermal CompactXR with a detection range of 7-14 microns - ain't a lick of visible photons in these images. The recognizable landmarks in the image (dosing funnel, magnets, screw holes, aluminum frame) pop out due to their IR emissivity. The beans are actually well suited for thermal imaging compared to all the metal surfaces in the Ikawa.

The 50g clip shows how hot that dome at the bottom of the chamber gets - which is covered when the dose is increased to 100g. So, for larger batches there may be some 'accelerated roasting' for the beans that contact the dome, which might be why the bean temp is a bit higher in the center of the 100g batch size.

50g batch:
100g batch:

GDM528 (original poster)

#66: Post by GDM528 (original poster) »

Want the hot-air exhaust of the Ikawa to go somewhere other than straight up? Copper tubing to the rescue. I got these at a local hardware store:

Both are 1 inch (Ikawa is a British company after all); one is a 'cup x cup elbow' and the other is a 'fitting x cup street elbow'. They nest together into an articulable bend and drops neatly into the exhaust port of the Ikawa:

This allows me to redirect the airflow laterally, such that I can park the Ikawa anywhere near my range hood and point the airflow right to the intake. This could also be used to direct airflow out a window.

No discernable impact on airflow during either the roasting or ejection phases - but I wouldn't be surprised if Ikawa disapproved. After successfully roasting with the glass cover completely off (for posts #64 and #65) I'm impressed with the robustness of their design. Clearly an insult to the Ikawa's industrial design ethics, but they should have included an airflow deflector in the first place, IMHO.

Warning: it gets litigiously hot, the first clue being the reddish hue the copper picks up after the first few uses. The copper is also very good at holding and transferring heat, so, no touch!

GDM528 (original poster)

#67: Post by GDM528 (original poster) »

PSA for Ikawa Home owners: warm your machine up before roasting.

As I am sure many Ikawa owners do, I was roasting consecutive batches of greens - such is life with a small-batch roaster. Same bag of greens, same batch size, same roast program, same, same, same. Normally I run them back-to-back, but this time I got distracted for about fifteen minutes before starting the next batch. First crack timing was delayed about ten seconds from the prior runs - in the range of 10-15% lower development time. Hardly a disaster, but got me wondering if some of the variation that others observe in first-crack timing might be related to the thermal inertia of the machine...

From an earlier post in this thread, temperature readings in an empty chamber for consecutive runs, starting from cold:

The Ikawa Home is only aware of inlet temperature and is unaware of what's actually going on in the chamber. Sometimes that's really useful and other times it's a liability. My setup workflow includes running the machine empty before loading the first batch of greens. Now I'll be doing the same if the machine sits idle for more than five minutes or so, depending on how OCD I'm feeling that day.

ET-controlled Pro models should first-order correct for warmup effects. I imagine there's a longer delay before the bean-drop signal when starting from cold. A Pro user could confirm this by making consecutive empty-chamber runs (starting from cold) and comparing the curve overlap.

Team HB

#68: Post by ira »

A pro starts warmup and then when it's warm, it alerts you to drop the beans and then starts the profile when you close the bean chute. It's one of the features of the Pro that's really nice.