Cafelat Robot Temperature Tests - Page 2

A haven dedicated to manual espresso machine aficionados.
jpender (original poster)

#11: Post by jpender (original poster) »

GregoryJ wrote:Hi John, can you post a picture of how you've mounted your probe?

I first tried to route the wires through the plastic pressure tube. I had it all set up, with the wires coming out through a right angle fitting that I had purchased and drilled. I wasn't 100% sure the adhesive was going to hold but I never got to find out because the lower fitting didn't seal. I think I must have damaged it when I took it apart. I haven't been able to find a place to order a replacement so for now I have no pressure gauge. And, to be honest, I don't miss it that much.

So anyway, I just ran silicone coated wires through the damaged fitting, filled with epoxy (JB Weld is non-toxic):



That's a thermistor, coated in epoxy and then coated again in silicone. I kind of overdid the coating, worried that water would get in. I scratched off some of the silicone when I discovered that the response rate was less than I was hoping for but it still takes a little too long to go from 20°C to 90°C.


The wires run through the metal tube to protect them from the inner workings of the Robot...



...and terminate at an Arduino based board that includes a small OLED screen an an SD card.




The thermistor is supposed to be within 0.1°C up to 80°C. I "calibrated" it for 80-95°C by comparing it to two other probes in a slowly cooling pot of hot water. That's no guarantee but all three were within 0.2°C of each other so I think it's probably good enough for what I'm doing.

jpender (original poster)

#12: Post by jpender (original poster) »

Bluenoser wrote:How did you preheat the piston?

I boiled a cup of water in the microwave and set it on top of an object (a black pepper container) that positioned it so that 5-10mm of the piston was submerged. Then, after letting it sit for maybe 20 seconds or so (I wasn't methodical about the time), I tried to work as quickly as I could: Raise the arms (they stay up), remove the cup of water, get the portafilter and basket, pour in water from the kettle, lock in the portafilter, move the scale and cup into position, push the start button on my board, and start the preinfusion.

jpender (original poster)

#13: Post by jpender (original poster) »

Bluenoser wrote:If the portafilter holder had a rubber-type insulated wrap all around below the handle, the PF would remain hotter..

That's one of the things I want to try. The other is insulation for the piston face.

GregoryJ

#14: Post by GregoryJ »

Cool thank you for the pictures!

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bobpaule

#15: Post by bobpaule »

With the risk of trolling, my Flair observations are also similar. Preheating both the cylinder and the PF result in much better extractions, temps with my infrared thermometer show better stability, but still not on par with a boiler machine. I guess nothing short of building heating elements into the walls will fix that.

Anyone think about insulation? Just kidding:)
Never get between a man and his ristretto, ever!

max

#16: Post by max »

I made a cup with preheated piston and pf today. The extraction was a little lower than normally, so likely I messed something up. Nevertheless, it was much smoother. Even the normal shots with 1-2ppts higher EY% did not have that smooth quality. Will experiment further...

Just need to get a new piston gasket to see if that solves it folding outwards...
bobpaule wrote:With the risk of trolling
Either this is some next level trolling, or trolling is not the word you are looking for :) https://www.urbandictionary.com/define. ... m=Trolling

Nate42

#17: Post by Nate42 »

I would think the perfect tool to preheat the piston is the pressurized basket. Just pull a blank shot before your session and good to go. Haven't tried this since I don't own the pressurized basket, but seems like it would be ideal.

Can anyone who owns the pressurized basket verify whether it holds water (or at least leaks at a managable rate) with no coffee in it?

Bluenoser
Supporter ♡

#18: Post by Bluenoser » replying to Nate42 »

I think that is true, but the pressurized basket doesn't come with the kit ( you only get one basket).. so that would be another cost and shipping wait. I used the double-spouted and simply taped the inside.. You can test the level the boiling water needs to be so it doesn't overflow.. basically fill till it does overflow with arms down. Once overfill is done (put in sink), raise arms and look at level.. You can note, dry.. and put a little piece of black tape or something on inside of PF as a marker for future fillings.... it won't affect the basket fitting in..

I did this for my morning shot.. and I think I got the face of the piston pretty hot.. The extraction definitely tasted a bit better .. but not easy to put a probe in their to really verify. The insulation also makes the hot PF much nicer to handle..

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yakster
Supporter ♡

#19: Post by yakster »

Nate42 wrote:I would think the perfect tool to preheat the piston is the pressurized basket. Just pull a blank shot before your session and good to go. Haven't tried this since I don't own the pressurized basket, but seems like it would be ideal.

Can anyone who owns the pressurized basket verify whether it holds water (or at least leaks at a managable rate) with no coffee in it?
Yes and I've used the pressurized basket in just this fashion, it's the way that I pre-heat the piston. It holds water until you apply pressure. I just find it unnecessary for my shots, pre-heating the portafilter with the pro filter basket results in great shots so I normally won't bother pre-heating the piston. I'm not drinking very light roast coffee, though.

The results above are great, showing that you get higher temperature by pre-heating the piston, but don't really speak to what temperature results in the best tasting shots. That's going to vary by individual taste and coffees used.
-Chris

LMWDP # 272

Jonk

#20: Post by Jonk »

Bluenoser wrote:I used the double-spouted and simply taped the inside..
That's pretty neat actually as it pre-heats both the portafilter and piston at the same time.

Appreciate the measurements jpender. Perhaps you could try longer pre-infusion as well?