Cafelat Robot User Experience - Page 410

A haven dedicated to manual espresso machine aficionados.
jpender
Posts: 3860
Joined: 11 years ago

#4091: Post by jpender »

Ken5 wrote:What I do is fill the pressurized basket higher than I do the regular basket when making a shot, usually about 1/16 an inch from the top and then immediately after locking in the portafilter I loop a string from claw to claw to keep the arms up. What happens is there will be a few drips from the basket and then it stops due to the finger on a straw effect.
By filling the basket to within 1/16" (2mm) you're getting the piston closer to the water, improving the heat transfer.

The difference between pulling a dummy shot and letting the arms hang is the air gap will be a lot smaller when you apply pressure. If you fill the basket to within a 0.5cm and let the arms hang you'll have a 0.5cm gap between the water and the piston. But if you apply 6 bar of pressure that gap will instead be a fraction of a millimeter.

Ken5
Posts: 977
Joined: 4 years ago

#4092: Post by Ken5 »

I used to pull dummy shots and I found that it does work better to tie up the arms. Perhaps it is the longer time that helps, but the small gap of air does not stop seem to stop the heat from getting to the piston. Perhaps it is more efficient because the pressurized basket seals the chamber tight.

Pulling a dummy shot lasts maybe 30 seconds and after the first dummy shot the piston is not really that hot. A second dummy shot really helps, but I doubt even that is hotter that keeping the arms up.

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vladgiurgiubv
Posts: 52
Joined: 7 years ago

#4093: Post by vladgiurgiubv »

Maybe the easiest way to preheat without fiddling would be with some kind of heater: I'm thinking an induction heater (cheap ones can be found on amazon, but a bit of electrical work is needed).

It's too bad it's so much trouble to preheat (at least for me with the cup and gasket problems)... once you try a light roasted coffee extracted at the right temperature, you can't have it anyway else :D

Ken5
Posts: 977
Joined: 4 years ago

#4094: Post by Ken5 »

Hi Vlad,

If you have the pressurized basket give it a try, it really isn't that hard to preheat with it. I had it anyways and do find it easy. If I did not have it on hand I most likely would use a cup as jpender does.

Ken

vladgiurgiubv
Posts: 52
Joined: 7 years ago

#4095: Post by vladgiurgiubv »

I don't have it. I'm thinking about how to use the cup without damaging the gasket. Unfortunately when the basket is filled with coffee and water it's much harder to lock in the portafilter. Maybe I'm not leaving enough room for air above the water.

jpender
Posts: 3860
Joined: 11 years ago

#4096: Post by jpender »

Ken5 wrote:I used to pull dummy shots and I found that it does work better to tie up the arms. Perhaps it is the longer time that helps, but the small gap of air does not stop seem to stop the heat from getting to the piston.
It's both things, gap size and time. I found that about 2 minutes gave the best heat transfer. But a larger gap reduced the overall effect. Water volume also makes a difference, as does preheating the basket, or whatever you're using as a water container.

jpender
Posts: 3860
Joined: 11 years ago

#4097: Post by jpender »

vladgiurgiubv wrote:Maybe the easiest way to preheat without fiddling would be with some kind of heater: I'm thinking an induction heater (cheap ones can be found on amazon, but a bit of electrical work is needed).
I'm not exactly sure what you have in mind but the Robot piston is not magnetic.

I tried to install heaters inside the piston but there's not very much room in there.

A passive solution is the best, I think, since then there is no water, no electricity, and no wait time. I made a plastic piston for testing and found that it worked just as well as preheating a metal piston does. The only problem is that you can't buy a non-metal piston; you have to make your own.

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imp96
Posts: 55
Joined: 3 years ago

#4098: Post by imp96 »

Preheating for medium and medium light roasts is no longer a problem for me. I bought a 58mm silicone backflush disc which I put into a basket. Just fill this basket with boiling water and lock it in. In the meantime, you can do your puck prep in a second basket. By the time you are done, the piston will be preheated and the portafilter will be warm. You can re-repeat this to get the piston and the portafilter even hotter. I saw this method in one of the threads.

VoidedTea
Posts: 191
Joined: 3 years ago

#4099: Post by VoidedTea »

vladgiurgiubv wrote:
It's too bad it's so much trouble to preheat (at least for me with the cup and gasket problems)... once you try a light roasted coffee extracted at the right temperature, you can't have it anyway else :D
I've been preheating the piston and silicon gasket with hot tap water (not boiling) since I got the Robot 1.5 years ago and still on the original gasket. Never used the lube, I use oils from my fingers instead gently wiping the gasket with my fingers after preheating to make sure it is clean of coffee grinds (I suspect residual coffee grinds could be the main reason for excessive seal wear). I try keeping it simple as I am not too finicky about all those blubbery/strawberry notes I read on the label from my light roasted beans. A sweet and balanced shot without sourness or bitterness with pleasant aromas is all I need, and preheating with tap water does it for me. I start with placing the basket holder into the cup that will be used for a shot (250ml size) and fill it up with hot tap water. Then grind the beans and prepare the puck in the basket. Then I remove the basket holder from the water and place the basket with prepared puck into it. Then I take the cup that still contains hot water and use it to preheat the piston. I submerge the piston into the hot water from the coffee cup and then place the basket holder with the puck underneath the cup. I let the coffee cup sit on the basket, everything fits well under the piston. This way I don't have to hold anything, the basket gets warmed up from the holder and from the warm coffee cup above it, and the piston is warming up as well. I just wait for the kettle to boil, then remove the coffee cup from under the piston, clean the wet seal with my fingers, and then fill up the basket with boiling water, using overflow technique. This way everything gets warm without much of a hustle. Sure this method doesn't warm everything to the highest possible degree, but it does produce the results I am looking for, sweet and balanced espresso, so I can't complain.

vladgiurgiubv
Posts: 52
Joined: 7 years ago

#4100: Post by vladgiurgiubv »

Thanks for the idea. I can't seem to find any silicone disk with 58mm on Amazon.de. Where did you get yours?

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