Project: PID NS Oscar: Result: Modded now Graphing/Learning

[ciordia9]

I've got two projects I'm working through. The first one is the modding of my Oscar to be tighter, the other thinking of making the Eureka (NS) MDE grinder doserless.

Nuova Simonelli Oscar:

I picked this little one up about a year and a half ago ±. It's been a trooper but I desire to learn more and understand this machine and others. The entire universe of coffee has been a fantastic voyage and this seems like an appropriate way of continuing my education. Know that I am a novice when it comes to these insides. I do not profess to have anything but a good sense of curiosity, looking for good questions and good answers to apply.

From my reading and exploring over the past few months I've found a wealth of thoughts but where they fall in difficulty, ability, and time I'm not sure, thats why I'm here. Help me sort the signal out.

Modifications possibilities:

Addition of a Vacuum Breaker
Addition of Steam & Pump Gauges
General Temperature Adjustments
Advanced Adjustments via PID installation
OPV Setting
Pressure Limiting Valve Adjustments

Ramble
Not everything is necessary; I just wanted to think without being boxed in. I think this is everything I could really do to the machine. I think some things stack. If I were to be cutting copper for a vacuum breaker then it doesn't seem so far an idea to tie in some gauges. Course I've never cut copper so if that has a large learning curve then both of those seem of vague relevance.

In the next week I'll have most of my tools at the ready. Scace, Omega therm, probes, PF gauge
Ebay has not too bad a price on the Fuji PXR3, but I don't know the extent or method for what I would require to do this fully.

Steam wand/Vacuum Breaker

At first I thought this was a definite. I've always run the unit 24x7, but I read on how people timer theirs and that sounded pretty nifty. Then I saw a number of techs writing that said that stresses the machine, seals, and wears the valve out which made me ponder the real need for such a device. I'm easily compelled but adding a breaker now doesn't sit as high as it did a few weeks ago.

Pressure Limiting Valve

I've yet to find this bit, can someone help point it out and how to modify it? I've got the classic NS Oscar that when it's got a blind in it still doesn't release the pressure.

Pressurestat

Clockwise more pressure, counter less? Once my gauge comes in I should be able to tune this right?

Temperature & PID Adjustments

Now my hunting for information really drops down.

How do I adjust the pstat?
From where do I draw my best measurement?
How do I rig a PID into this?

Lastly gauges are more neat than anything else. I have no concept of its difficulty just that it'd be tied into an intersection of pipe and need to be either brought outside the machine or cut the plastic and mount them in the wall. More food for thought than taking seriously, at least today. Gauges don't give me better shots but it might act as an easier way of catching deteriorating equipment sooner than later.

Any help, tips, resources, or ideas/things I'm forgetting are always appreciated.

-a

[ciordia9]

for tweaks, anyone added some tiger paw or some form of sound/vibration damping to these units? When that pump kicks on it can put out some noise. Wonder if it can't be mitigated somehow.

[HB]

Sorry about not responding earlier. Lots of questions in one post intimidates me...

Then I saw a number of techs writing that said that stresses the machine, seals, and wears the valve out which made me ponder the real need for such a device.

On the other hand, the pressurestat will wear out faster too if the machine is run 24/7. Components degraded by heat will also suffer (e.g., grouphead gaskets). Metals will be happier. Bottom line is that some components benefit from the constant temperature, some suffer from the additional exposure to heat, and others just plain wear out faster.

I've yet to find this bit, can someone help point it out and how to modify it? I've got the classic NS Oscar that when it's got a blind in it still doesn't release the pressure.

You should have a second return line to the tank. Some machines like the Wega have a return loop to a tee in the inlet line. Either way, a little poking around with this diagram from another thread should get you started:

Jim Schulman's Adjusting vibe pump pressure on HX machines explains the mechanics, including the diagram below:

(reproduced with permission)

You should be measuring the water exiting the over-pressure valve, which you've clearly identified. The tubing at the end of the OPV may twist when you adjust, but it's easy to remove, untwist, and replace.

Clockwise more pressure, counter less? Once my gauge comes in I should be able to tune this right?

Yes * 2. The Sirai's adjustment isn't touchy, unlike the smaller MATER / CEME pressurestats.

How do I rig a PID into this?

Ken Fox is the leading HX PID man; see threads like Should I PID my Heat Exchanger? I wonder if the great results he reports will apply to machines with lighter groups like yours. My gut reaction is "no".

I have no concept of its difficulty just that it'd be tied into an intersection of pipe and need to be either brought outside the machine or cut the plastic and mount them in the wall.

That's pretty much it, except you need some dampening agent to get a steady reading. Either a wet gauge, or snubber / coil of thin copper tubing leading to the gauge will work.

for tweaks, anyone added some tiger paw or some form of sound/vibration damping to these units?

I moved the pump outside the case into the cabinet below. That eliminated the problem at the source - reverberation of the casing.

[ciordia9]

Thanks Dan for the response, and my belated to your belated response hehe.

I've been busy, but then held up in parts acquisition for a while now. Some of these guys are hard to come by. I went ahead and learned what I could from the Pstat side of things. If I were one to sit on a temp forever I'd be happy where it is. I now have to flush at least once to get the temp I aimed for but it's on. Reducing the brew pressure was helpful as well. I now discharge a lot more water but it's improved shot tastes quite a bit.

I've been slowly moving towards the PID. Dan you say if you wonder if I'll get as good a result, is there a reason I wouldn't? In sizings I thought the Cimbali that DK works on and the Oscar were similar in size. The only reason I really wanna go PID is due to SO's & not wanting to recalibrate that pstat every time I want to experiment.

Still need to pick up a dremel so I can hack my project box in to form. Picked up the Auber PID & SSR. Ordered a 3" probe from Omega and want to turn the stock oscar T on it's side, add another T for the vac breaker & keep the OPV. Where I'm hitting a new wall is pulling these bits apart.


How to unhook these guys without ripping things apart...
First things first, counter-clockwise for removal?

If I tweak the white, then the blue (pstat) shifts & torque is added to the boiler.
If I tweak the white and counter with the red then the pstat shifts (blue).
If I tweak the red the boiler wants to move, no counterpoint evident?

What's the cleanest way for me to remove this assembly? I feel like I'm going to rip it out with the amount of force I have at my disposal and I'd much rather not damage the equipment beyond reversibility. I always like to be able to work backwards in case of an eventuality.

[barry]

the silver nut at the pstat simply holds the pstat to the mounting bracket. to loosen the brass nut where the pipe fits to the pstat, you're going to have to hold on to the pstat to counter the torque (or really really tighten down that silver nut against the bracket).

as for the other end of the pipe, you're just going to have to torque against the boiler. if you think the nut is stuck on there, then i'd suggest hitting the nut with a torch to get it hot. often these fittings are assembled at the factory with a threadlocker, so initial disassembly can be somewhat nervewracking when it comes to pulling things off the boiler.

[cannonfodder]

I made some of the same changes to my Isomac

There is more on my BLOG but you will have to go back a few months in the archives.

[HB]

What's the cleanest way for me to remove this assembly? I feel like I'm going to rip it out with the amount of force I have at my disposal and I'd much rather not damage the equipment beyond reversibility.

I friend of mine is seriously into cabinet making and woodworking. In situations like yours, he advises using iron pipes and clamps to create a crossbar and then fix the plumbing pieces you wish to secure to them. Of course it helps that he has a workshop that would make Norm Abram proud.

[ciordia9]

Of course it helps that he has a workshop that would make Norm Abram proud.

Ah, I wish I could be so lucky. I am not that tool laden, I'm a wannabe woodworker and Honey-do generalist

So I got the pstat off with not as much trouble as I had thought. With that nice step in my stride I went on to trying to get the entire T off and that.. well that's back to a pita and I want to be told nice things haha.. I first thought I'd clean up the area and remove the other compression fitting to the now defunct copper piece and when I was doing that I could see the T ever so slowly bending (in or within) the boiler. That made my stomach drop so lightly retorqued it into position and tried to get the T to unscrew. Man I never knew how soft copper was. Unfortunately I can't brace the boiler and I feel like I'll either end up stripping it, destroying the port all together, or torquing the boiler's mount beyond acceptability. I'm skurrr'd as they'd say down the road.

It looks like some form of gunk might have been applied where the screw meets the boiler.. Can anyone else comment on that discoloration around that area?

I've tried a little heat in the area and that didn't get me any distance (thought I'm not sure how much heat to apply in these situations).

Any more thoughts are appreciated.

-a

[HB]

Unfortunately I can't brace the boiler and I feel like I'll either end up stripping it, destroying the port all together, or torquing the boiler's mount beyond acceptability.

Sorry, I've forgotten what the goal was. I don't like the look of your project's current trajectory. Rather than fuss with the T pictured above, if the goal is to tap into the steam line, why not cut the copper tubing and splice in a tee? No risk of torquing a fitting off the boiler.

[ciordia9]

Sorry, I've forgotten what the goal was. I don't like the look of your project's current trajectory. Rather than fuss with the T pictured above, if the goal is to tap into the steam line, why not cut the copper tubing and splice in a tee? No risk of torquing a fitting off the boiler.

Trying to get a thermo probe installed.. I've been told a few different things.

1. Greg Lepore advised me to add an additional T and just take the steam's temp and that was "good enough" for calibrating the pid. Which twomartini's told me that it wasn't such a good thought at a cupping.
1.1. I attempted to go down this a bit but I've got an auber probe which is 5/32 and doesn't fit any compression I have and its short.. Probably good for steam but not good for distance and I have no real way to fit it.

2. Jack Denver said to turn my T on it's side and drop a probe down that way so I can get to the actual boiler water.

At this point I just want to turn the T on it's side, put the probe down into the tank, then with the showing male thread attach an all female T (which I'm still trying to source) and add the vacbreak and opv. I've got an omega 4" K probe which fits the compression fitting but I can't crack this T off easily.

It's funny how relatively easy this all sounded on paper and reading online but it's been a rather detailed and long project thus far. I guess everyone who gets nitty gritty has more kungfu belt levels than I originally thought was needed or this is just a murphy teaching me more lessons.

My wife asked me as I strained today whether or not we were about to invest in a new machine. :-/ heheh.

So I dunno.. I feel like if I can get the equipment unhooked, I've got just about everything to go forward. I never thought taking the bits off was going to be harder than building the new setup.

-a

[HB]

1. Greg Lepore advised me to add an additional T and just take the steam's temp and that was "good enough" for calibrating the pid. Which twomartini's told me that it wasn't such a good thought at a cupping.

I probably wouldn't PID an HX in the first place, but if I were going to do it, I would check if a pressure transducer would be a better choice. Sean let me borrow his portable pressure testing kit and it seems reasonable that if it can translate brew pressure into 20 readings per second graphs, controlling steam pressure would be a snap. Steam pressure is more readily measured and not subject to the vagaries of probe placement.

(The engineers / physics majors are welcome to support or shoot down my assertion.)

[cannonfodder]

I had brought up the PID of a HX discussion a few months ago at Barry's gathering of the brains. I was contemplating using a PID in the rebuild of the Faema. I was told that PID and HX machines are not the best option.

It had to do with the PID attempting to correct for carryover. The PID will switch on and off quite rapidly while steaming in an attempt to compensate. What you end up with is not a smooth and stable temperature curve you would associate with a PID brew boiler, but a very ugly looking saw tooth temperature curve. The pressurestat or pressure transducer will give you a flatter temp curve on a HX machine (unless you never plan on steaming).

I did look at transducers, but an $80 Pstat is much cheaper than several hundred for a transducer.

[ciordia9]

I went forward; whats the worst that can happen?

I've learned what the overpressure value sounds like. I've learned what the boiler emergency pop sounds like. Neat experiences *wry chuckle*

No it's not all that bad. Just a note when you switch an auberin pid from 'f - 'c it uses the old numbers as the new numbers, literally and when you're dialing by a tenths of a degree you will not win the race of the boiler vs countdown. hehehe!

TC is an Omega 3"/K, sticks about 3/4" into the boiler.

Now I get to learn about how this thing is driven, and it's driving me crazy. I followed these rules:

at least 30m sitting
50ml flush
2m wait
pull for 22s
wait 2.7m
next..

I've got to think I can tighten this up. It feels high on the surf side now, each pull can average a 7'f change to the next shot. I'm going to lower the temp a bit more since most of this series has been out of my desired range of 93.8-94.4c. If Ken's right then I'm going to see these bands continue to slide around. I'm trying to visualize these different dynamic systems and I see the boiler being feathered at temp, shot causes new water to enter, temp flutters, should restabilize for another round.. if its not then maybe I need to hand tune the pid away from auto.. but I'm not sure what the shot temperatures are indicative of.. or it could be my time between shots should be longer.. or shorter.. or.. so I ramble.

Thoughts are welcome.

-a

[Ken Fox]

Hi,

Sorry I have not had time to get into this thread beforehand, and have little time now, either. I'm in France for yet another month-long stint, mostly in language school, and have very limited internet access in an unpleasant venue (some of the McDonald's here have free WiFi, but since these places are jammed with people you don't want to spend time with most of the day, they are usable only in the morning before the lunch rush, which conflicts with my classes a lot the time).

Anyway, not responding to any particular posts or comments made before, I think that each HEX machine has its own natural temperature "behavior," and differing patterns of recovery. This is to say that my observations on my machines, although perhaps generalizable to a modest extent, are not going to work on other machines without a lot of trial and error. My 10 year old Jr. heats up its boiler water as quickly as does my newer rotary machine, but the response in the Heat exchanger as measured by shot temperatures is MUCH slower. As a result of this and perhaps other factors that I think are due to changes in materials used in the HEX by Cimbali over a 7 year period, I need both a higher boiler temperature (like 7degrees F, I think) in the older machine, combined by a 30 second longer inter-shot interval in order to get temperature stability at the same shot temperatures in both machines.

I have standardized on 50ml flushes in both machines and get good stability AS LONG AS ALL I DO IS TO PULL STRAIGHT SHOTS. If you introduce frothing into the mix, then all bets are off. I wouldn't even bother to check temps in that situation as I'm sure they are all over the map. My usage pattern is that cappas are never made after the first hour or so that the machine is used in the morning, so the machine restabilized after 10 minutes or so and it doesn't matter. For someone using a HEX machine to make a mixture of milk drinks and straight shots, who does not have a fairly long interval between shotmaking (say in excess of 10 minutes) I think that shot temperature stability is unlikely to be obtained.

As to what would work best in an Oscar, I haven't any idea. The PID does allow changes in boiler temps to be made easily, so play around with it, using various flush quantities until you find something that works. I'm assuming you will find something that "works," but of course I can't guarantee that!

Early on, don't bother to graph the results you get (unless you have software that allows that painlessly; I don't). You will become familiar with the raw data and whether it looks "good" without graphing it. Bad results can be erased from the Fluke's memory without bothering to type them out. Once you do find a regimen that "works," then you can start graphing it. Most things you try early on will NOT work; that I know from personal experience. As a general rule, the more you can reduce the boiler temperature, reducing flush size, the more you will be likely to attain stability, if my observations are any indication. How much this is machine-dependant I do not know.

Of course, if you are making a lot of milk drinks, reducing boiler temperature below the point where you can froth efficiently is a PITA, so you can decide that temp. stability isn't that important for milk drinks (my opinion) and you can bump up the temperature easily on a PID when you make milk drinks and reduce it when you make straight shots, allowing time for things to stabilize.

Good luck,

ken

[DierdreDipstick]

Hi Andy,

I have recently bought an Oscar and am still very pleased with it. I watched your photos and measurements of the oscar before I decided to buy it. They were a great help in my decision, so thanks a lot.

I have one question about your PID-work. Why are you setting the boiler temperature to around 119°C? The steam-pressure of water is approximately 1.92 bar absolute pressure then. That would relate to a pstat-setting of just around 0.9 bar which is far too low for the oscar (you can use it on an isomac). I think 125°C which means a pstat-setting of 1.3 bar would be better for the oscar and should lead to a higher brew-temperature (and thus better steaming performance).

Greetings,
Andreas

[ciordia9]

Hi Andy,

I have recently bought an Oscar and am still very pleased with it. I watched your photos and measurements of the oscar before I decided to buy it. They were a great help in my decision, so thanks a lot.

Wow, I'm glad I could help and I'm glad you're enjoying the way of the Oscar!

I have one question about your PID-work. Why are you setting the boiler temperature to around 119°C? The steam-pressure of water is approximately 1.92 bar absolute pressure then. That would relate to a pstat-setting of just around 0.9 bar which is far too low for the oscar (you can use it on an isomac). I think 125°C which means a pstat-setting of 1.3 bar would be better for the oscar and should lead to a higher brew-temperature (and thus better steaming performance).

I may or may not be grasping your question, if I miss the mark I blame the morning The boiler temp at 119.3'c equates into brewhead temp of 201-202'f. I was concerned about brewhead temps for the dialing. Since I'm not on a pstat anymore and using the pid I don't set by pressure. I was worried about how steam pressure would be affected but truthfully I haven't noticed a difference at all. I can't quite step back into the map of the pstat as the regulator as it has been a while. I just remember that the outcoming pressure of the oscar at the brewhead was amazing and had to open the flow control nut to get it to come down to 9. The pstat is amazingly stable, just not granular for those quick adjustments.

I'm sure I've muddied that up.. finagle another question and I'll see if I can mash that as well

[Ken Fox]

Hi Andy,

OK, you've had this setup for around 5 months now. The graphs you posted are from some time back and I assume you have generated some more. Obviously, you have left this PID installation in place and one has to assume that you find it on a par or better than your old pstat. Do you find that you frequently use the PID to set boiler temperature as you adjust for different types of drinks and beans? I certainly do.

The crux of my question is to try to figure out how generalizable were my own observations on my Cimbali Juniors, e.g. that one can use a PID and a consistent flushing routine to produce relatively stable shot temperatures in a Heat Exchanger machine. I don't know to what extent you have accomplished that at this point, but I'm sure that you do.

Since most people who read this who own HX machines don't own Cimbali Juniors, the generalizability of the observation might be helpful to others and certainly would be interesting to me.

Finally, reading one of your later posts in this thread, having to do with shot series, have you tried altering the intershot timing as opposed to boiler temperature and flush volume, to try to get relatively consistent shot temperatures in series, as if you had a bunch of people over for espressos? I've found considerable differences when shots are pulled at a rate of one every minute, one every 1.5 minutes, or one every 2 minutes, so standardizing on a production rate, it seems to me, could be a useful strategy in those uncommon home situations where one is pulling a lot of repetitive shots. At the same time, however, very few people (even coming to my house) request straight shots, so this observation may be of limited value in the real world, where one would have milk to soften any of the intershot temperature differences.

Best,

ken

[ciordia9]

OK, you've had this setup for around 5 months now. The graphs you posted are from some time back and I assume you have generated some more. Obviously, you have left this PID installation in place and one has to assume that you find it on a par or better than your old pstat. Do you find that you frequently use the PID to set boiler temperature as you adjust for different types of drinks and beans? I certainly do.

I've generated a few but I haven't been focused on it once I achieved results I thought were on par with expectations. As you know testing this stuff out pretty much takes your day and if you screw up a little something you just occupied another day of tests. I trip up and down the temp range only on new arrival of beans. I haven't gotten in to my own espresso blends so I don't get to take advantage of it on personal roasts. As I tour the myriad of other roastmasters though I do take advantage of listening to what they want their blends at and adjust accordingly, and if doing a review or some such will ladder up or down to see just what will occur with the blend.

The crux of my question is to try to figure out how generalizable were my own observations on my Cimbali Juniors, e.g. that one can use a PID and a consistent flushing routine to produce relatively stable shot temperatures in a Heat Exchanger machine. I don't know to what extent you have accomplished that at this point, but I'm sure that you do.

Since most people who read this who own HX machines don't own Cimbali Juniors, the generalizability of the observation might be helpful to others and certainly would be interesting to me.

I think that your observations and my own show that you can achieve at minimum singular shot stability. Where machines will differ is the amount of time till you can assure a followup shot will meet the same profile again. For the Oscar it takes about 6.5-7.5m before I would trust a shot to have the same profile. Anything less than that and the graphs are predictably out of alignment. Some weird observations were first shot clean, second shot naturally shallow in temp, third shot shows spike in temp with quick falloff. It's got some sort of rubberyness in the struggle to stabilize on shot after shot. As well walkups are so rarely different with the Oscar. I'm not sure if it's due to the way the heat bleeds off it, materials, or what, but I can have a shot in the morning and a shot in the afternoon with little (<1oz) or no flush and I'm where I should be. The only time walkup needs a flush is if you leave the machine running for a good day without pulling a shot, then you'll notice a burp in the line where I hypothesis that water has either boiled in the line and created the gap or perhaps its more simple and the system has just lost the pressure in the line due to inactivity. Regardless a quick flush after a day of nonuse and you're in line again. I don't find myself needing to flush for a duration and watch steaming water stream. I think this is machine/manufacturer dependent.

Finally, reading one of your later posts in this thread, having to do with shot series, have you tried altering the intershot timing as opposed to boiler temperature and flush volume, to try to get relatively consistent shot temperatures in series, as if you had a bunch of people over for espressos? I've found considerable differences when shots are pulled at a rate of one every minute, one every 1.5 minutes, or one every 2 minutes, so standardizing on a production rate, it seems to me, could be a useful strategy in those uncommon home situations where one is pulling a lot of repetitive shots. At the same time, however, very few people (even coming to my house) request straight shots, so this observation may be of limited value in the real world, where one would have milk to soften any of the intershot temperature differences.

By intershot timing, you mean like waiting the 7m ± for stability? That's the only thing I've found to really work. Pushing the temp up and flushing never showed a reliable multishot series. In effect it actually created more bounce in the series. Chris Keener wants to take some profiles of his machine so maybe I'll bring out the equipment and go back over this for show once I'm done with him. If I recall right though the predictability of it went out the window for me. I have much better luck just dealing with a latency than trying to force stability. These machines can't hope to compete on a professional level of one after the other shots (even then how many pro machines can?). There simply isn't a large enough boiler to take the dynamic shifts. Something is going to under or over compensate with these guys. Luckily between your use of high temp and flush and my learning what the realistic timing game is, it's about as close to perfection as we get until.......

In the real world I have one or two people who take their shots straight, and I put them in the time queue, after they have their drinks I then cycle in quick succession milk drink requests because it really takes a discerning palate to understand what is changing when you've got milk (&|| sugar).

I tell you what though, learning all of this spoiled something for me. Before doing all of this I'd take shots, make lots of drinks, and I was none the wiser. Now that I know I'm finicky on when I want to, and how I, use the machine. Even moreso knowing my grinder and how it likes to trap grinds requires me to clean it for each shot. The entire process/task has become more labor intensive because I understand what it is to achive quality. Kind of weird. Maybe I'll take a mortgage and get a versagrinder and G3! hahahah.

Thanks for the Q's Ken, you reactivated a part of my brain I haven't been using lately heheh.

-a

[Ken Fox]

By intershot timing, you mean like waiting the 7m ± for stability? That's the only thing I've found to really work. Pushing the temp up and flushing never showed a reliable multishot series. In effect it actually created more bounce in the series. Chris Keener wants to take some profiles of his machine so maybe I'll bring out the equipment and go back over this for show once I'm done with him. If I recall right though the predictability of it went out the window for me. I have much better luck just dealing with a latency than trying to force stability. These machines can't hope to compete on a professional level of one after the other shots (even then how many pro machines can?). There simply isn't a large enough boiler to take the dynamic shifts. Something is going to under or over compensate with these guys. Luckily between your use of high temp and flush and my learning what the realistic timing game is, it's about as close to perfection as we get until.......

In the real world I have one or two people who take their shots straight, and I put them in the time queue, after they have their drinks I then cycle in quick succession milk drink requests because it really takes a discerning palate to understand what is changing when you've got milk (&|| sugar).

I tell you what though, learning all of this spoiled something for me. Before doing all of this I'd take shots, make lots of drinks, and I was none the wiser. Now that I know I'm finicky on when I want to, and how I, use the machine. Even moreso knowing my grinder and how it likes to trap grinds requires me to clean it for each shot. The entire process/task has become more labor intensive because I understand what it is to achieve quality. Kind of weird. Maybe I'll take a mortgage and get a versalab grinder and G3! hahahah.

Thanks for the Q's Ken, you reactivated a part of my brain I haven't been using lately heheh.

-a

By "intershot timing", I'm referring to repetitive shot series, where you would pull 5 or 6 or 7 or however many shots in succession with only enough of a pause to get ready for the next shot, plus perhaps an intentional gap to allow your boiler and HX and element to get back into swing. I have found that if I make shots every 60 seconds (e.g. a shot takes 30 or so seconds, then there is a 30 second gap for cleaning, grinding, and preparing for the next shot) that I get declining temperatures on successive shots. On the other hand, depending on which machine, if I make one shot every 90 seconds or every 120 seconds, I get much more repeatable shot temperatures. Granted, I would have difficulty pulling one shot every 60 seconds without risking channeling and other problems due to bad technique; I've never claimed to be an exceptional barista

In reality, I almost never use my machines like this; it is very unusual for me to pull more than 2 or perhaps 3 shots in a session, before there is at least a 10 minute gap in between them. Nonetheless, it is good to know at what pace you can get your machine to work, full out, while still maintaining more or less the same shot temperatures.

ken