CoffeeJack: One Million Dollars of Bad Coffee

[PlainName]

not espresso

I drink gallons of coffee, but it's all instant so really just flavoured water. So, bearing that in mind...

Isn't the mark of real espresso the foam stuff that floats on the top? If so, surely the clincher for this thing is not how it works but whether that espresso marker exists in the cup at the end. I presume it doesn't (although, personally, I wouldn't really care since it's bound to be more coffee-like than the dishwater I drink )

[Cerebus]

Exactly.

Water is incompressible. So watch the video again, Cerebus.

When you let go of the lever on an espresso machine, the coffee stops coming out, right? It doesn't continuously spew coffee out like diarrhea, once you hit that 10 bars. That coffee leaving is taking the pressure with it. What is your storage medium for all this pressure? A big pressurized air tank? I don't think pressurized air and boiling water are a good mix in chintzy consumer garbage that you operate within arms reach of your face.

This is some kinda hybrid drip coffee maker thing that you can speed up a little to make extra weak coffee (or use 10x as much grounds to start), not espresso.

I'm not arguing for their design, I'm just countering the argument that you couldn't produce 10 bar odd manually without excessive effort. I'd imagine a practical working design would involve an input manual pump, with non-return values before and after, an intermediate chamber of 2-3ml to smooth out the pressure pulses from the pump with a restriction allowing water into the actual brewing chamber to permit flow and provide a pressure drop to 9 bars  - in other words something that looks a lot like the existing group head on most espresso machines.

You seem to be arguing that the old espresso machine that sits in my kitchen can't work - which it does - without some pressure storage mechanism - which it doesn't possess, it's a 'thermoblock' design that uses unpressurised brew water. It's a pump (which by its nature provides pressurization and fluid drive in pulses) some intermediate plumbing (through a heater block), a group head and a portafilter.

Similarly, my shiny new Christmas present to myself, a fancy 'dual boiler' espresso machine has an essentially unpressurised water feed on the brew side and all the water pressure comes from the pump (it has a brew 'boiler' but the set point for this is 93C, below boiling - so no pressure). I know it develops at least 10 barg, because it has an honest to goodness pressure gauge attached to the group head.

The whole point here bring that no stored pressure system is required to brew espresso, just a pump. If you can make that pump work effectively on muscle power you can make a portable espresso machine.

My shiny new dual boiler machine does have a pressure vessel in it, for the steam side of things and that operates at 135C (which equates to about 3 bar) which one can quite safely operate within arm's reach otherwise it would be pointless. Saying that you can't safely use a pressure vessel in consumer equipment smacks of FUD being used to support an unsupportable argument to me.

There's a weird dynamic going on here. I don't think CoffeeJack's design is there yet, it may never be 'there'. But some people, including a slightly hysterical rather self absorbed Thunderfoot, are making this out to be a scam and impossible to achieve "because physics". It's achievable, if it wasn't no extant espresso machine would work. It doesn't need any new physical principles it just needs engineering development.

[KL27x]

You seem to be arguing that the old espresso machine that sits in my kitchen can't work - which it does - without some pressure storage mechanism - which it doesn't possess, it's a 'thermoblock' design that uses unpressurised brew water. It's a pump (which by its nature provides pressurization and fluid drive in pulses) some intermediate plumbing (through a heater block), a group head and a portafilter.

No, I'm not.

I'm stating the fact that your machine doesn't keep squirting/dripping espresso out when you let go of the lever.

You could use some gearing to make it 10 or 20 pumps to get your shot, but the same thing would apply. You would press the lever the entire way in order to get the 1/10th or 1/20th of a shot out the machine. And when you let go of the lever halfway, the coffee would stop coming out. Even if you keep your hand on the lever to maintain just shy of the pressure to keep it moving, the coffee will stop coming out. The exit has a check vale and the pressure has to be higher than X to get the coffee to exit.

This obviously uses some kind of air pressure reservoir, and if you think it's reaching the proper pressure through this pressurized air, then it might have a liability problem. Much more likely, and even obvious to me, this place the coffee exits is not acting like a check valve at X bars. It's much lower, if it's even anything more than a drop coffee maker with a mini air pump in it.

You don't pump your espresso machine once, then sit back and watch the coffee drip out at some later time. The reason for the high pressure is so the liquid can reach super-boiling temps without boiling and turning to steam. When you let go the lever, the pressure and temp drop. If you were using pressurized air/steam to make this coffee, it would jet super-boiling stream of coffee and steam when it failed. The dingus in the video, you pump up a few times then sit back and watch the diarrhea drip out.

[Cerebus]

I'm stating the fact that your machine doesn't keep squirting/dripping espresso out when you let go of the lever.

What lever? Neither of my espresso machines has a lever.

You could use some gearing to make it 10 or 20 pumps to get your shot, but the same thing would apply. You would press the lever the entire way in order to get the 1/10th or 1/20th of a shot out the machine. And when you let go of the lever halfway, the coffee would stop coming out. Even if you keep your hand on the lever to maintain just shy of the pressure to keep it moving, the coffee will stop coming out. The exit has a check vale and the pressure has to be higher than X to get the coffee to exit.

No it doesn't - there is no check valve on the exit. You've not actually used an espresso machine have you? Or looked properly at one.

Here's where the coffee comes out of an espresso machine:



That bit clamped into the machine is the portafilter and it looks like this with lots of small (~50-100 um) filter holes in the bottom:



Without the spout on the bottom of the portafilter it looks like this (with coffee actually exiting):


Please point to the check valve.

This obviously uses some kind of air pressure reservoir, and if you think it's reaching the proper pressure through this pressurized air, then it might have a liability problem. Much more likely, and even obvious to me, this place the coffee exits is not acting like a check valve at X bars. It's much lower, if it's even anything more than a drop coffee maker with a mini air pump in it.

There is no air pressure involved, it's just a liquid pump.

You don't pump your espresso machine once, then sit back and watch the coffee squirt out. The reason for the high pressure is so the liquid can reach super-boiling temps without boiling and turning to steam. When you let go the lever, the pressure and temp drop. If you were using pressurized air/steam to make this coffee, it would jet super-boiling stream of coffee and steam when it failed.

Super-boiling temps? You really haven't a clue how this works. The (PID) thermostat on my espresso machine is set at 93ºC.

Here, watch an espresso being poured on an identical machine to mine (by some random bloke on YouTube). Watch the pressure gauge, it's measuring the pressure of the pumped water that's in contact with the coffee. The coffee has nothing between it and the outside world except for those little filter holes - specifically no check valve. 93ºC water, 9 bar of pumped pressure, ground coffee (pressure drop across a restriction), little holes - the only thing involved worth calling a pressure vessel is the portafilter mounted in the group head. One can tell that it's actually the coffee that provides the restriction (and thus the pressure drop to the outside world) because if the machine is operated without coffee in to flush the system clean the pressure gauge barely moves off the stops.

http://youtu.be/oAnUVnQHsVg?t=117

[KL27x]

I assumed you were talking about the manual lever/piston kind. Try that. Read it again.

The other machine keeps dripping out after you pump it. Unless there's some spring or compressed air in there, it is not working the same way. And most likely not working and maintaining 10 bar from the looks of it. That's 145 psi? The coffee starts coming out after a few of these tiny pumps, then it looks like the flood gates are opened and the coffee just keeps on a comin?

Not a "check valve" like a mechanical part. The block of compressed coffee is what does this. You don't meet the pressure then sit back and watch the water pour through it. You have to press it through (with the manual machine). As the liquid exits, the pressure drops. The espresso comes out only while you keep pressing and advancing the piston.

Super-boiling temps? You really haven't a clue how this works. The (PID) thermostat on my espresso machine is set at 93ºC.

This part I messed up. Liquids vs gases. I retract that part and thanks for the correction.

edit: I think you could say that I had a brain fart and misapplied Boyle's law (of ideal gases) to liquid coffee.

[PlainName]

The coffee starts coming out after a few of these tiny pumps, then it looks like the flood gates are opened and the coffee just keeps on a comin?

Might the coffee be acting as a resistor, so the water takes its time to get through it all. Hence you get a small amount to start but the bulk is working its way through and appears after a little time. Whatever pressure us built up behind eventually gets released as the water is expelled (and reduces before that as the space available increases).

Having said that, I would suspect a bit of video faking 'for illustration', though