CoffeeJack: One Million Dollars of Bad Coffee - Page 1
Forum section: electronics / general

author: m98
author_rank: Frequent Contributor
timestamp: December 30, 2019, 04:01:10 am
content: Now I haven't watched all of Thunderfoots reasoning for why that espresso maker shouldn't work, but isn't he effectively arguing that it would be impossible to inflate a regular road bike tire using a handpump? Or more general, that a pump can't increase the pressure of a medium beyond the peak force put into driving it? That's absolutely ridiculous.

author: Cyberdragon
author_rank: Super Contributor
timestamp: December 30, 2019, 05:22:13 am
content: Quote from: m98 on December 30, 2019, 04:01:10 amIt's clear that the people making the product have no idea how to make coffee, just judging from the awful demo video they put out, and there product does have design flaws (could crush the cup if you really smashed on it). HOWEVER, Thunderfoot, who usually makes rants that have a point, keeps comparing this thing to an electric coffee machine. "But you still have to boil the water!" No shit Sherlock! It wasn't until the second video that he even mentioned more than once a manual coffee maker (comparing the stresses on the container), and it seems like he has no idea of what this machine is actually trying to be...which isA FRENCH PRESS!I guarantee he has no idea how to properly use one either and would make just as bad of a coffee with a real high end press as the numpties making this thing. He really should do a proper video comparing it solely to other manuals and not complain that it doesn't boil or pump like an automatic machine does, because that's not the intended market.

author: PlainName
author_rank: Super Contributor
timestamp: December 30, 2019, 02:41:34 pm
content: QuoteThat seems to be his modus operandi - create a strawman he can burn down with spectacular ranting and job's done. But it gets him the bucks.

author: jonroger
author_rank: Regular Contributor
timestamp: December 30, 2019, 02:53:05 pm
content: He seems to believe that his machine with an 8 second extraction time is superior. But this is not even close to the Italian Espresso National Institute standard of 25 ± 5 seconds. Typed while sipping actual espresso from a direct lever espresso machine.

author: ebastler
author_rank: Super Contributor
timestamp: January 04, 2020, 07:46:40 am
content: Why would I take advice on coffee from someone who keeps calling it "expresso"?Seems clear that Thunderfoot is out of his depth here.Nevertheless, I'm not a fan of the Coffeejack design either. It is advertised as making espresso-style coffee ("barista style"), and the water temperature will certainly be too low for that by the time it has been poured into the room-temperature reservoir and worked its way through the manual pump. Also, the whole thing seems a bit shaky during the pumping process, due to its top-heavy design and relatively small footprint area.If you want a simple, low-cost way to make "somewhat simliar to espresso"-style coffee, the Italians have solved this since the 1940s with the "moka pot" stove-top coffee maker. Available in various sizes, cheap and simple, lasts forever. And yes, I know it's not espresso since the brewing pressure is much lower (just like in the CoffeeJack...)

author: PlainName
author_rank: Super Contributor
timestamp: January 04, 2020, 08:02:10 am
content: QuoteGot one. Has the disadvantage that you need a stove top. This CoffeeJack just wants hot water, so it would be conceivable to use wherever there is a kettle or one of those hot water machines. Which also kind of gives it green credentials since your stove top isn't warming up the kitchen as well as the water

author: Kilrah
author_rank: Unknown
timestamp: January 04, 2020, 12:15:24 pm
content: Quote from: m98 on December 30, 2019, 04:01:10 amNot impossible, but inflating a tire manually to 10+bar definitely would be extremely painful...

author: PlainName
author_rank: Super Contributor
timestamp: January 04, 2020, 04:03:33 pm
content: I thought he was a physicist or something. The bicycle tyre has a large volume so to compress it 10:1 you're need 10x more volume (is that right or have is it more?), which is a lot of pumping. The CoffeeJack, on the other hand, should have hardly any volume so would need relatively little pumping for the same pressure increase. And it wouldn't necessarily be harder either since there is the small matter of leverage to consider.

author: Cyberdragon
author_rank: Super Contributor
timestamp: January 06, 2020, 06:44:50 am
content: QuoteIt's not at all, any more that pouring water from the kettle into a different container to steep tea. Look up how to use a french press. Water has a relatively high specific heat.

author: Terry01
author_rank: Frequent Contributor
timestamp: January 06, 2020, 07:42:21 am
content: Eh?Handpump 10 BAR!?I inflate my wheelchair tyres to 25 ish PSI which google conversion says is only 1.7 BAR!I know when my tyres are fully pumped up properly when the pump takes my weight standing on the foot plate and it doesn't compress no more. I don't bounce to get more pressure or anything like that, just keep pumping steady till it takes my weight. When I check the dial it's always dead on.It's one of those double barrel things that pumps the tyre up pronto, it's meant for car tyres.I wouldn't like a slap on the head from the guy who can hand pump 10 BAR!! Must be Popeye's BIG brother or something!On a side note, I was in hospital quite ill a few months ago and dropped 2.5 stone in weight. It doesn't seem to affect the pumping process any, I thought it would. I still just pump till it takes my weight and the 2.5 stone weight difference doesn't seem to matter any.Oh I weight about 10 stone just now, maybe a wee bit over...

author: ebastler
author_rank: Super Contributor
timestamp: January 06, 2020, 07:49:13 am
content: Quote from: Cyberdragon on January 06, 2020, 06:44:50 amNot sure why you keep relating the Coffeejack to a French press. The similarities are superficial only -- both take hot water, have a plunger, have a glass jar.But the extraction principle in the French press is obviously very different; the coffee grinds stay in contact with the water for several minutes, floating in suspension. In contrast, the CoffeeJack claims "barista style" coffee and an extraction process similar to espresso machines.

author: Psi
author_rank: Super Contributor
timestamp: January 06, 2020, 09:38:43 am
content: Quote from: ebastler on January 06, 2020, 07:49:13 amYes, that is the key point. They claim it can do a proper espresso extraction with that level of pressure.

author: thm_w
author_rank: Super Contributor
timestamp: January 07, 2020, 12:46:55 am
content: Quote from: Terry01 on January 06, 2020, 07:42:21 amIts not unusual for a bike to use ~120psi (8 bar) rated tires. You can get small telescoping hand pumps that are capable of achieving that. It takes effort and a floor pump is way better, but, you don't want to carry those around in your bag.https://www.chainreactioncycles.com/ca/en/lifeline-performance-cnc-mini-pump/rp-prod155349(120 psi)https://www.chainreactioncycles.com/ca/en/topeak-race-rocket-hpx-master-blaster-road-pump-aw17/rp-prod165286(160 psi - 11 bar)

author: Cerebus
author_rank: Super Contributor
timestamp: January 07, 2020, 03:49:29 am
content: Quote from: Terry01 on January 06, 2020, 07:42:21 amHave ye nay heard of levers and hydraulics laddie?I can lift a side of my car (approx weight 1200kg) using a hydraulic jack with negligible effort. The actual piston that holds the car up has a diameter of 20mm, so an area of 2pi(0.01m)2= 0.000629 m2. It's holding 1/2 the car's weight, say 600 kg, say 6000N; so the pressure on the backside of that piston is 6000N/0.000629m2= 9.55 MN/m2= 9.5 MPa = 95.5 Bar.The magic that turns my minimal effort (perhaps 10-15 kgf) into almost ten times the pressure figure you think neigh impossible is a lever driving a small area piston. There's no reason that the same principle couldn't be applied to shifting the 30-40 ml of water at 10 Bar over 30 seconds that's required to make a shot of espresso.Let's work it out. Magic numbers for espresso: 9 bar brewing pressure, shot of 40 ml delivered over 30 seconds.We need 40 ml of water delivered over 30 seconds. Let's suppose a piston with a cross sectional area of 1.33 cm2, move that piston through 1 cm and it will deliver 1.33 ml of water. Do that 30 times (once a second) will deliver 40 ml. Working against a pressure of 9 Bar (900 kPa) it will need 900,000 N/m2, applied over 0.000133m2=> ~120 N applied to the piston. Connect that piston to a lever with a 10:1 ratio and you will need to apply a force of 12 N (1.2 kgf) over a distance of 10 cm. (20:1 might be a better ergonomic compromise, 20 cm movement, 6N force).If you can pump a lever through 10 cm, working against 1.2kgf, 30 times in thirty seconds then you can supply both the power and the pressure needed to brew a shot of espresso. I don't think too much of the machine from the video, but in principle it could be made to work.

author: james_s
author_rank: Super Contributor
timestamp: January 07, 2020, 04:28:37 am
content: Quote from: dunkemhigh on January 04, 2020, 08:02:10 amWe have a really old one of those at our cabin, it's been there for as long as I've been part of the family. I had no idea what it even was until last summer when we took a friend from out of town there and he was looking for coffee in the morning and found it, turns out it works just fine. My partner and I both think coffee tastes vile and never drink it but I do think many of the machines for making it are fascinating for some reason.

author: Terry01
author_rank: Frequent Contributor
timestamp: January 07, 2020, 08:47:04 am
content: Quote from: Cerebus on January 07, 2020, 03:49:29 amSo ... more brains … less brawn?

author: KL27x
author_rank: Super Contributor
timestamp: January 08, 2020, 10:57:19 am
content: You can see in the video, the coffee starts to emerge after only a couple pumps, and the flow rate appears fairly high.This reminds me of the stuff in the Skymall catalog on the seatbacks of the airplanes, back in the 90's. Wild claims. High price. Latest technology. And made to appeal to the luxury impulse purchaser.

author: thinkfat
author_rank: Unknown
timestamp: January 08, 2020, 11:17:33 am
content: You can of course pressurize any volume to 10 bar, the thing with making a decent espresso is that you need these 10 bar constantly while you force the hot water through the ground coffee. For the CoffeeJack it means you need to reach 10 bar every time you push the pump. With one hand. That's going to leave some serious dents in your palm.

author: thinkfat
author_rank: Unknown
timestamp: January 08, 2020, 11:36:51 am
content: Quote from: Cerebus on January 07, 2020, 03:49:29 amThis will work if the chamber that holds the ground espresso powder has the same cross sectional area, right? If the area is larger, the pressure will drop proportionally.

author: PlainName
author_rank: Super Contributor
timestamp: January 08, 2020, 11:55:10 am
content: QuoteAnd rise proportionately the other way?Anyone taken into account the chamber volumelessthe coffee grounds volume? Could be very small indeed.

author: Cerebus
author_rank: Super Contributor
timestamp: January 08, 2020, 12:18:48 pm
content: Quote from: thinkfat on January 08, 2020, 11:36:51 amNo, if all the chambers are directly connected they are at the same pressure. This is a basic property of all fluids (including those fluids called gasses). Pressure drops/rises can only happen under flow conditions across restrictions that are small and/or long relative to the viscosity of the fluid under consideration. Under steady state non flowing conditions the pressures equalize.

author: ebastler
author_rank: Super Contributor
timestamp: January 08, 2020, 03:20:24 pm
content: Quote from: Cerebus on January 08, 2020, 12:18:48 pmRight. You can scale upforceby driving a large piston from a small one, but that does not change the pressure inside this hydraulic system. Of course, the large piston will move correspondingly more slowly, so power (and work) are conserved.But one could then have that large piston drive another small piston (by bolting them together mechanically), and build higher pressure in a secondary fluid circuit. The primary combination of small and large piston just serves as a lever -- and could be replaced by a classical mechanical lever too.

author: Cerebus
author_rank: Super Contributor
timestamp: January 08, 2020, 04:52:53 pm
content: Quote from: ebastler on January 08, 2020, 03:20:24 pmBut the final thing we are trying to move is not another piston, it's a small quantity of water through a bed of coffee grounds at (an industry standard)pressureof 9 bar. We're just trying to pressurize water (an in-compressible fluid) and move a mere 30-40 ml through some ground coffee. You can do this with a small piston and, with the help of a short lever, very little force. If you applyXPa pressure to the surface of that small piston, then the sameXPa pressure is applied to all surfaces in all connected vessels - this is the basic magic that makes hydraulics work.We dono work, in the physics sense, in pressurising the water - we pressurise the water by applying a force to the small piston. We do noworkuntil the piston moves. Theworkthat we are trying to do is to overcome the fluid drag forces involved in moving water through (slightly compressed) ground coffee, it's not a great deal of work - based on my earlier premise it's 120N moved through 0.3m = 36 J, done over 30 seconds that's a power requirement of 1.2W (excluding losses). If it helps, think: pressure = voltage, current = water volume moved per second, the coffee puck = a resistor and the interconnected pressure chambers = a wire.QuoteYes, you could replace a small piston/short lever system by a big piston/large lever system. That's already done and indeed was the standard form of espresso machines for many years:but this (a small domestic lever machine) is not exactly pocket or shoulder bag size - heck it's not even rucksack sized. From the bottom to the top of the lever is about 500mm (height excluding the lever 320mm).

author: KL27x
author_rank: Super Contributor
timestamp: January 09, 2020, 06:33:29 pm
content: 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.

author: PlainName
author_rank: Super Contributor
timestamp: January 09, 2020, 07:10:40 pm
content: QuoteI 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)

author: Cerebus
author_rank: Super Contributor
timestamp: January 09, 2020, 08:21:52 pm
content: Quote from: KL27x on January 09, 2020, 06:33:29 pmI'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.

author: KL27x
author_rank: Super Contributor
timestamp: March 03, 2020, 06:13:16 pm
content: QuoteNo, 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.

author: Cerebus
author_rank: Super Contributor
timestamp: March 03, 2020, 06:58:17 pm
content: Quote from: KL27x on March 03, 2020, 06:13:16 pmWhat lever? Neither of my espresso machines has a lever.Quote from: KL27x on March 03, 2020, 06:13:16 pmNo it doesn't - there is no check valve on the exit. You've not actuallyusedan 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.Quote from: KL27x on March 03, 2020, 06:13:16 pmThere is no air pressure involved, it's just a liquid pump.Quote from: KL27x on March 03, 2020, 06:13:16 pmSuper-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

author: KL27x
author_rank: Super Contributor
timestamp: March 03, 2020, 07:44:33 pm
content: 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.QuoteThis 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.

author: PlainName
author_rank: Super Contributor
timestamp: March 15, 2020, 11:37:33 am
content: QuoteMight 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