Cafelat Robot Piston Seal Life - Page 4

A haven dedicated to manual espresso machine aficionados.
YeetSkeeterson

#31: Post by YeetSkeeterson »

I really do love it, it works so wonderfully and then I just can't get it to act as it always has but I think the seal is just goofy, I am going to have to replace it soon but I haven't checked if I have an extra, so I'll have to order. Like I said, I owned Robot #1 for months, many months of daily use, no problem, it was not my technique, nothing changed. I don't recall if Paul pulled a shot but it'd be interesting to note if the seal was not seated probably and the basket forced onto it like is happening now.

I wouldn't say I under fill... Is 68g-70g not pretty typical fill weight? It's surely about ~5mm or less away from the top but my metric eyeball isn't that good.

I sold #2 to pursue electric setups but the more research I did, the more expensive I would've had to go to feel happy with my addictive personality and preference to buy once cry once... Decent... Kafatek... Cremina... You get the picture.

So, Robot #3 came to stay, I will never sell it, doesn't matter what happens with it. What I have decided is that for future machines, which will inevitably be electric, they should be levers. I think that's all I want, ignorance is bliss. I do not have the time nor capacity to join the endless hunt on Decents, I have my toes in too many other hobbies. The soft lever profile is fine by me for the electric spring lever manuals. If I want to crank a 12 bar 30 second shot with no declining profile for some reason, my Robot can do that.

I roast organic beans, so a manual lever is fitting I think, just an aesthetic thing. I'm also not pulling 5+ shots a day, ever, maybe I will pull two back to back for the occasional guest, but 99% of the time it's one shot a day, only for me. So another point against electric, a bit overkill, like a lifted truck that looks like a Hot Wheels toy.

jpender

#32: Post by jpender »

YeetSkeeterson wrote:I wouldn't say I under fill... Is 68g-70g not pretty typical fill weight? It's surely about ~5mm or less away from the top but my metric eyeball isn't that good.
You said you were weighing out the amount of water you needed for the shot, like James Hoffmann did in his video. That pretty much guarantees that you're using less than a full fill of water. With an 18g dose you need about 100g of water to fill to within 5mm of the rim. With 70g of water and, say, 20g of coffee you'd probably filling to more than 10mm below the rim. You'd need a dose of something like 35g of coffee to fill to within 5mm. Or else a coffee that is weirdly low in density.

Underfilling means that your Robot is probably a little "spongy" feeling, which is okay. And your shots will be a little cooler because of less thermal mass, which may or may not matter, depending on your coffee. Also you have that extra time spent measuring which allows for a little more cooling to occur. And to me the extra step would be a bother. I'm always trying to figure out how to reduce the number of movements to a bare minimum. For example, I got tired of moving my scale after weighing a dose from the counter to the Robot and then back. So I got a second scale and attached it to the Robot base with some double sided tape. It's a small thing but it saves me moving and positioning the scale a hundred times each month.

YeetSkeeterson

#33: Post by YeetSkeeterson »

Thanks, I guess filling the Robot to a specific weight is pretty much useless if the grind is set so that I know at x time, roughly, I will have 40g out. I know small scales are cheap but, I'm a bit of a minimalist, to me it's just another thing to buy... I may yet though.

For today, I will try a shot with the basket filled to 100g and see how it goes, perhaps this is an unconsidered problem.

Jonk

#34: Post by Jonk »

Off topic, but I change beans often and really appreciate that extra amount of water available whenever the grind is off. If it's a gusher I think "ooh, allongé" to myself and just push everything through. Rarely end up with sink shots that way with the Robot, but quite often change the intended style during the first seconds of a shot.

Miltonedgebert

#35: Post by Miltonedgebert »

If you really want to be minimalist with the robot you can ditch the scales entirely. I have a few different sizes of scoop to dose beans, and I just stop the shot based on blonding. I'll usually have a shot that needs milk when dialing in the grind, but once I have the grind figured out for a bean the shots are surprisingly consistent.
I'll probably never be able to move to a machine other than the robot because it enables my sloppy habits and just keeps putting out solid espresso.

VoidedTea

#36: Post by VoidedTea »

YeetSkeeterson wrote:I really do love it, it works so wonderfully and then I just can't get it to act as it always has but I think the seal is just goofy, I am going to have to replace it soon but I haven't checked if I have an extra, so I'll have to order. Like I said, I owned Robot #1 for months, many months of daily use, no problem, it was not my technique, nothing changed. I don't recall if Paul pulled a shot but it'd be interesting to note if the seal was not seated probably and the basket forced onto it like is happening now.
I've been using my Robot for 2 years, 2 drinks a day, every day, still on original seal. I believe silicone can easily withstand extreme heat, this is why they make silicone spatulas and other cooking utensils that get in touch directly with burning hot surfaces. So I don't think boiling water would have any impact on it. It is just not hot enough. I always pre-heat my piston with hot water, not boiling hot though, but still. Never used lubricant.
There are two things that I do, which I think might contribute to the longevity of the seal. First, I always clean it with my fingers after soaking the piston in hot water. Even when I soak, I swoosh the cup around trying to wash off any residual grinds from previous pull and then I clean the rest with my fingers. I think leaving it dirty causes micro-scratches on silicone surface eventually wearing it down.
Second, I rarely pull at 8-9 bars, usually it is near 4-5 bars pressure. I think extra pressure could be the main contributing factor to the seal damage. I don't use the scale under the robot, only when measure the beans. When my scale broke once, I made my coffee without it for a week, and it was fine.
Not sure if any of this helps, but just wanted to share my experience. Love the Robot, never had a though about upgrading.

Antonee

#37: Post by Antonee »

VoidedTea wrote: Second, I rarely pull at 8-9 bars, usually it is near 4-5 bars pressure. I think extra pressure could be the main contributing factor to the seal damage. I don't use the scale under the robot, only when measure the beans. When my scale broke once, I made my coffee without it for a week, and it was fine.
Ive been using my robot for 3 years, and have had to change my piston seals 5 or 6 times now (I stopped keeping track). I normally pull 2-3 shots daily on it. The portafilter has just started getting difficult to install now, after changing them maybe 6 months ago, which, in my experience means they will soon start to fail to hold a seal under pressure.

I also pull 99% of my shots between 4 and 6 bars. I don't clean my seal regularly though I have never noticed grinds on them on the rare occassion I do inspect them. At one point I did lube them once in a while but stopped that a long time ago.

At this point I've just accepted that it is what it is. Given the outstanding shots I get from it, replacing the seals twice annually is a small price to pay.

YeetSkeeterson

#38: Post by YeetSkeeterson »

Eh, I just roasted 3 batches of different beans of the same weight and after roast one bean takes up significantly less volume than the other 2. I will stick with a scale for this one.

Nate42

#39: Post by Nate42 »

Latest in my second seal odyssey (riveting to you guys I know :D) The thing continues to come off frequently, and it now has very obvious stretch marks on it. But despite all that it keeps working. I went ahead and ordered a replacement for my replacement today since I only have one extra right now and want to always have one on hand. Surely the stretched one is going to fail any time now. If nothing else it is beginning to annoy me.

Speaking of which, PSA, orphan espresso is selling seals and other parts now. I ordered a seal and a new screen (I have the original screen with the metal nub, I think the silicone nub will be easier to grab).

jpender

#40: Post by jpender »

Nate42 wrote:The thing continues to come off frequently, and it now has very obvious stretch marks on it.
Stretch marks? I'd love to see a photo or two of it.


My own seal was working perfectly a month ago, as if it were brand new. I thought maybe it was doing so well because I haven't preheated the piston by soaking it in hot water since installing this latest seal. Then a few weeks ago I had a bag of coffee and thought preheating might help it. So I soaked my piston in boiling water, just a few times. And my seal started to go downhill almost immediately. I relubricated it twice but nonetheless locking-in went from silky smooth, super easy to a more strenuous affair, complete with metal-on-metal friction. And there is frequently a little hiss of air when I first start the pull. Did the soaking do this or is it a coincidence?