Decent Espresso Machine - Page 76

Need help with equipment usage or want to share your latest discovery?
anakinstoys
Posts: 83
Joined: 7 years ago

#751: Post by anakinstoys »

Yep, temporary channeling sounds way more technical. :lol: so it sounds like whats going on in your case doesn't have anything to do with the bottom of the puck- your shot could still look great coming out of the bottomless? sounds like a very odd effect!

roastini
Posts: 207
Joined: 7 years ago

#752: Post by roastini »

decent_espresso wrote:No, I'm talking about a ~4mm depression in the top of the puck, when you take it out. Doesn't happen every time though, which is confusing.
From your post on March 19th introducing this issue, I take the issue to be a series of depressions, directly below the holes in the shower. If so, I'm having problems theorizing how this could correlate with the placement of the group feed hole directly above one shower hole. If that was the cause, you'd think you'd see a single defect in the puck.

That said, you seem to be well along the way to an experimental test of this hypothesis, and if the new design consistently fixes the issue, then the experimental results will of course be more important than my personal inability to theorize an explanation for the facts.

Have you noticed a correlation between the defects and the quality of the shots? That is, are the shots poorer quality when the defects appear in the puck? Or do you notice signs (on the graph on the screen) of channeling when the defects (later) are seen in the puck?

If there is no such correlation, I wonder whether these depressions are perhaps created during evacuation at the end of the shot. At the end of the shot, the 3-way valve opens the path between the portafilter and the drip tray, allowing pressurized water to evacuate up through the shower (or at least that is the case for your typical machine with a 3-way valve). I can see that this might "pull up" some of the grounds in the puck that are below the holes in the shower.

Indeed, given the low-pressure during preinfusion, the high-pressure change during evacuation seems like a more likely candidate for causing this problem.

As for why these defects don't appear consistently, it could be the the force of the evacuation varies from shot to shot. Evacuation of pressurized water presumably involves lots of non-linear turbulent forces, so the depressurization curve is not always going to be the same. If the portafilter depressurizes at a different rate on any given shot (due to slightly different initial conditions), that could affect whether the dimples in the puck appear.

BTW, if the problem is a correlation between a hole in the shower and the hole above the shower (and, again, that seems odd to me, if there are multiple dimples in the puck rather than just one), and if the problem is caused by evacuation rather than during the shot, then moving the group entry hole is not going to fix anything, because the key will be the placement of the exit hole, from which water is evacuated at the end of the shot. In the diagram of your improved set-up, with water entering the group near the center of the shower, it appears to me that the exit hole is directly above a shower hole. So if that correlation is the problem, I would expect that there would continue to be an issue, even with the "fixed" set-up. But in that circumstance (dimples caused by evacuation), the "defect" wouldn't have an effect on shot quality, so wouldn't matter.

Hope that mess of text makes sense to someone other than me; I did my best.

anakinstoys
Posts: 83
Joined: 7 years ago

#753: Post by anakinstoys »

I too thought it might be the backflush causing the dimple. I ended up deleting what I wrote because it's probably easier to diagnose what's going on at the bottom of the puck with something strange like this, or the stats as you suggested. If it's coming out great and tastes like your baseline, then its possible this dimple is happening after the fact. The redesign simply fixes a cosmetic issue and not necessarily quality of the shot. OTOH, I bet decent will get a lot of emails about "whats this random hole in my puck" despite the shot tasting great. :lol:

jwCrema
Supporter ❤
Posts: 1097
Joined: 11 years ago

#754: Post by jwCrema »

roastini wrote:Hope that mess of text makes sense to someone other than me; I did my best.
In my best Jack Webb impersonation: My take is this issue boils down to "does it impact taste"?

User avatar
decent_espresso (original poster)
Sponsor
Posts: 1762
Joined: 9 years ago

#755: Post by decent_espresso (original poster) »

roastini wrote:As for why these defects don't appear consistently, it could be the the force of the evacuation varies from shot to shot. Evacuation of pressurized water presumably involves lots of non-linear turbulent forces, so the depressurization curve is not always going to be the same. If the portafilter depressurizes at a different rate on any given shot (due to slightly different initial conditions), that could affect whether the dimples in the puck appear. Hope that mess of text makes sense to someone other than me; I did my best.
You know, what you wrote makes a *lot* of sense, thank you very much for pushing my thinking in a different direction.

As you theorized, shots with the depressions don't seem to taste any different, and their flow and pressure curves are the same as other shots. It could just be the flush.

We have, however, checked that the water distribution is even coming out the bottom, and we've not always found it to be. Rotating things seems to help, but I also suspect that the water coming into the head quite off to one side could have been a contributing factor. That's why the new design moves the water inflow very close to the center of the shower.

Also, I've noticed that the espresso machine's group head *must* be level, or the water will preferentially pool out of the downhill side. At my demo at 49th Parallel, I was on a narrow espresso drinking bar made for walking up to, and it inclined slightly. All the shots were terrible for hours there, and it wasn't until I went home that Rao told me "duh!" and I could see in the photos the tilt on the table.

It's pretty easy to check for even water distribution out of the group, you just pull a shot without the portafilter mounted, and look at water coming through the screen.

roastini
Posts: 207
Joined: 7 years ago

#756: Post by roastini »

decent_espresso wrote:Also, I've noticed that the espresso machine's group head *must* be level, or the water will preferentially pool out of the downhill side. At my demo at 49th Parallel, I was on a narrow espresso drinking bar made for walking up to, and it inclined slightly. All the shots were terrible for hours there, and it wasn't until I went home that Rao told me "duh!" and I could see in the photos the tilt on the table.
If you can't fix this, you might want to consider height adjustable legs to let users level the machine. The other thing you could consider is including a bubble level that one could place on top of the group head while adjusting the legs.

User avatar
decent_espresso (original poster)
Sponsor
Posts: 1762
Joined: 9 years ago

#757: Post by decent_espresso (original poster) »

Finalizing the water tank design.

This week, we're finalizing the water tank design, so we can send it out for manufacturing. For at least the first 500 machines, we'll be using porcelain (ceramic). While it is heavier than other options, it's totally food safe, even quite hot water, and totally dishwasher safe : lots of other material aren't.

We've previously allowed the water tank to slide out the front and the back. However, I'm blocking the back-fill because I've now had two employees think they're being helpful and unplug the 220V power plug as another person fills the water tank. That has them holding an open electrical wire inches from pouring water. Not good.

Banning filling from the back gains us 100ml of capacity because I can get rid of the little 1cm rim on the back. It also avoids the problem of the tank sliding out when you lift the DE1.

From the front, we've always had a little rim


that you squeeze with your fingers to pull the tank out.


However, ceramics are glazed and very rounded, and it's not been very easy to grab this. If we make the rim bigger, it becomes easier, but at a significant cost in water tank capacity (100ml for 1cm). There's also a ceramic deformation problem that if we have a rim on the front, we need to have a symmetrical rim on the back or the tray will deform when drying.

So, I've decided to remove all rims from the drip tray, which gains us 200ml of water capacity (bringing us up to 2000ml) but now we need a dependable way to get the water tank out.

My favorite idea is to put the tank on runners, so you push it in, hear a click, and it stays put. Then, push it again to have it pop out. Here's a video of what I mean:
However, that's going to take some R&D to get right, and I want to kill all the R&D that I can so that we can move to shipping.

Jeffrey's low-tech-but-just-works idea is to have a metal "pull tab" like so:


placed to the left of the water tank:


a little tug of the finger:


tugs the water tank out:


We've also considered button a metal "collar" around the entire water tank, so you pull that, or a strap, but this pull tab seems the most simple.

I'm soliciting ideas now, so let me know what you think of this, and if you have any other (simple) suggestions!

leon
Posts: 133
Joined: 9 years ago

#758: Post by leon »

My suggestion is a small hole (or pair of holes) on the rim that will accommodate a small strap or loop of cordelette that can be hooked with a couple fingers to pull out the reservoir. Similar to what you might find on the zipper pull of a ski jacket, but probably a slightly bigger loop. This would be very lo tech and easy to repair or replace by the end user.

anakinstoys
Posts: 83
Joined: 7 years ago

#759: Post by anakinstoys »

in one of the early videos you were explaining that you have to push up on a latch on the back to lift a tube out in order to move the reservoir. do i have to reach around back, fiddle around with the latch and try to slide the reservoir out? it sounds complicated but hopefully not in use.

since i mention reaching around the back of the machine, are you putting a panel at the back of the reservoir to block it? If not, i'd just reach around back and push the reservoir forward enough where i could grab it. not going to be easy if i have to hold a latch too. lol

since you've been talking about silicone, how about a silicone collar with handle? you obviously dont want it to stretch while pulling, but the idea is with 5-10% tolerances in the ceramic a silicone collar will fit these variances better than a one size metal collar. or expanding on the collar idea - as long as the reservoir and silicone float you could make a "bumper" with integrated handle that adds the benefit of giving the base of your reservoir some protection from hard surfaces.

the only thing i dont like about your pull tab is the aesthetic. just looks like macgyver grabbed a coat hanger and made something magical. and please take it as a compliment, its a very DIY'er type mod. i'm probably just lacking the imagination as to how to make it look integrated with the machine.

User avatar
decent_espresso (original poster)
Sponsor
Posts: 1762
Joined: 9 years ago

#760: Post by decent_espresso (original poster) »

roastini wrote:From your post on March 19th introducing this issue, I take the issue to be a series of depressions, directly below the holes in the shower. If so, I'm having problems theorizing how this could correlate with the placement of the group feed hole directly above one shower hole. If that was the cause, you'd think you'd see a single defect in the puck.
Here is a photo of what I'm looking at, and because I'm a worrier, I want to make sure this occasional phenomena doesn't portend anything bad.



Here is the shower. The depressions look sort of like a similar pattern, but the holes don't actually line up, and there are depressions in the puck where there are no shower holes.



Given that they look like "craters" it might be that these are air bubbles ripping through the bottom of the puck during the flush cycle.

If that's so, might the upward-going air columns prefer to orient themselves near the holes in the shower as they rise up?

Post Reply