Ken Fox wrote:
I don't know your machine and I don't know the curves you have produced; if you have posted them, please point me to them.
If a protocol for machines to qualify in a high profile event like the WBC excludes whole classes of machines and only allows double boilers (and I believe that Greg has posted that a HEX machine, presumably a 220v version, did fine on this test) then one would have to question the value of such a test where the winners have been pre-ordained by the chosen methodology.
I've watched parts of a couple of these competitions and although I think they probably do motivate employees in the few good cafes out there, those of us who never or almost never have a chance to go to such places really don't benefit much. If the purpose for developing the protocol was solely for choosing machines for the WBC, then I think this should be entirely divorced from marketing attempts on the part of whichever company "wins" this contest. Of course this is not going to happen because (presumably) fund raising through sponsorship is a major part of the funding for such an event as the WBC.
Since the protocol seems to have been designed to pick a certain class of machine to "win," and then the winner gets to sponsor the event and to use the fact that they "won" in advertising, I think it would be a bit (a lot) more honest to simply have a sponsor for the event, let the sponsor advertise that they are the sponsor and they are supplying the machines for the contest, and leave it at that. This seems to work well for sponsorship in Olympic events. Instead there is this mystique of a competition for choosing the most stable machine and then this machine just ends up having been more or less selected by the selection criteria and so on and so forth.
I happen to like the company that is the sponsor for the upcoming events and I admire what they are trying to make for home users; don't get me wrong on that. But I think this whole process is a bit disingenuous.
As to home users, again, I repeat, temperature stability is a very hard thing to deliver, and much harder to deliver in a low volume setting like a home. The importance of temperature stability has not been established by any sort of scientific means. Simply reading that someone claims they can taste brew temperature differences of 0.1 degree F doesn't prove that it is so. I think it will be proven by those who are conscientious enough to test it and honest enough to report the results they have found, that no machine currently existing can deliver a flat temperature profile through all the possibly good brew temperatures, even if it was true that this was desirable (and I'm not sure of that, either).
ken
OK, I gotta try to nip this misconception in the bud. The WBC procedure was designed to test machines period. None of us give a rats ass what wins or doesn't win in terms of machine configuration (hx or twin boiler) and if you read the procedure you'll see we don't say how to pick winners or losers. Testing machines without performing big cooling flushes gives lots of useful information that benefits home user or pro because you learn what is deficient in the design of the machine, and you get an idea of what is needed to compensate. The fact that a specific machine may not produce the same temperature at duty cycles shorter than a specific time may be of interest to anyone. The magnitude of correction required to make a machine achieve the same brew temperature can't be determined until you know the baseline without any flush. So you gotta start somewhere.
WRT 110V machines doing well enough on the tests, my Astra Gourmet can keep up at all duty cycles. It suffers from needing cooling flushes to get the temp down like any e-61 machine, but it can keep up with very short duty cycles just fine. I did some calculations on a perfectly efficient system a while ago that showed you needed 800W of heat to brew a double shot a minute, which is the fastest WBC duty cycle (10 sec wait, 15 sec dose / tamp, 25 second shot, 10 sec to knock out the puck and flush the screen). A 50% efficient machine would need 1600W heating element. The Astra's is 2kW, so you'd expect it to keep up. 1400W machines may not.
Also, the LM GS3 can keep up no problem. Not only can it keep up, the machine needs pretty much no flushing ritual at all, according to the data I have and that got posted on HB.
Ken, I disagree with your comment that the importance of temperature stabilty has not been proven. It most certainly has been studied and conclusions have been drawn that form the basis for various standards of espresso. The question is more properly "what is the stability requirement?" and that is a much harder question to answer. The opinion of pro baristas who are very highly regarded in the industry, that have tested the GS3 claim that they can taste the difference in 0.3 F changes in setpoint temperature. My own measurements put the reproducibility of the GS3 at around a half degree. Taking the square root of the sum of the squares of 0.3 and 0.5 gives you 0.6, which is prolly a good guess on what actually makes a meaningful difference. That doesn't mean that one shot brewed 0.6 degrees different is gonna suck compared to another one, it just means you can taste a difference. There are only a couple of machines out there that can produce that level of reproducibility and one of them is still a prototype. So we ain't there yet when it comes to reproducibility. With regard to temperature profile, the argument that flat line is good or bad is pretty meaningless really. It's a long way down the road before anyone's gonna develop a machine with variable profile that can test the argument, if one blindly assumes that we care about the temperature above the cake. The temperature inside the cake varies with time and position in the cake. It is most assuredly not constant during the brew cycle. The reason that we oughtta be concerned with flat line temperature above the cake is that given the technology that we use to pull this stuff off, a flat line is more likely to give you reproducible brew temps from shot to shot that can get within a factor of 2 of the minimum detectable difference temperature.
OK, I better go do some work now.
-Greg
