Rotary pump cup clarity achievable with a mod ?

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cannonfodder
Team HB

#1: Post by cannonfodder »

I may be mistaken, but Malachi's 'clarity in the cup' pointed heavily to the constant pressure that a rotary pump delivers as being one of the major contributing factors in the cup clarity? It took a few reads to wrap my novice mind around the discussion. If that is the case, wouldn't the average home user with our modest barista skills, be able to achieve a relatively comparable cup by simply replacing our vibratory pumps with a rotary? That would eliminate the need to upgrade a perfectly good 'prosumer' machine to the next level (which is essentially the exact same machine with a rotary pump).

I ask the question because I was reading the Synesso thread and the remarks about its cost. Could I theoretically get the same results by modifying my HX to a rotary? I also have to inject that I have no idea what a rotary pump would cost so in the end it may still be cheaper to upgrade to something like a Wega. I am just thinking of the 'next step' in my espresso progression, but that is a year off (or maybe a 06 swagfest article :wink:).

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malachi

#2: Post by malachi »

Actually, you need stability in pressure and stability in temp.
"Taste is the only morality." -- John Ruskin

framey

#3: Post by framey »

Just on cost of rotary pumps, here in Australia a spare part price for a typical rotary pump is $350 ish and a vibratory pump runs at about $100

I'm sure I've seen photos where someone had put a smaller than usual rotary pump into a Silvia...?

-Stephen-

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cannonfodder
Team HB

#4: Post by cannonfodder »

But assuming you could attain a serviceable temp stability, would the pump upgrade make a marked increase in the cup? Now as Framey stated, $350 for a rotary pump, plus added mods/plumbing to the existing machine quickly makes this an unwise modification. I could sell my existing machine and for the price of the upgrade, get a higher quality machine, which would address both issues.

I take it from comments and debates I have seen, that the best option for temp stability would be a dual boiler with a saturated group. That would eliminate the cooling flush, get the timing just right and I can hit my target temp, routine of a HX. You also need a boiler of adequate volume to match you duty cycle and heating elements large enough to match your shot to shot timing (recovery).

One factor that complicates the issue is constant blend changing. I rarely roast back-to-back identical blends. Different blends prefer different temps so it would be a constant temp adjustment. The only reliable, and simple, way to do that would be with a PID controller. The only system I have seen with that (in a reasonable home price range) is the Brewtus, but you sacrifice boiler size and the rotary pump. So you are back to square one. It does not look like I will be able to avoid the $2k price range when the time comes, unless someone puts out a new machine.

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malachi

#5: Post by malachi »

cannonfodder wrote:One factor that complicates the issue is constant blend changing. I rarely roast back-to-back identical blends. Different blends prefer different temps so it would be a constant temp adjustment. The only reliable, and simple, way to do that would be with a PID controller. The only system I have seen with that (in a reasonable home price range) is the Brewtus, but you sacrifice boiler size and the rotary pump. So you are back to square one. It does not look like I will be able to avoid the $2k price range when the time comes, unless someone puts out a new machine.
Actually... I disagree.
I average between 3 and 12 different coffees a week.
With a good understanding of the temp drop over time and practice, flushing is reliable and simple.
For me, the great advantage of an HX machine is the flexibility you get with brew temp. I can pull 10 shots in a row at 10 different brew temps if I want, or I can pull a couple shots of one coffee and then a couple of another - without brew temp issues.
"Taste is the only morality." -- John Ruskin

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Walter

#6: Post by Walter »

Wow, Chris jumping in with a pro HX argument... ;)

But I agree, I use different coffees on a daily base and even though I am fairly new to the business I find it quite easy to adjust my Butterfly's temperature for different roasts/blends.

Cannonfodder you know of Ken Fox's and Jim Schulman's comparison Junior vibe vs. Junior rotary? Since I first read that thread on alt.coffee I've wondered how representative this comparison was and also whether or not it's applicable to the general Vibe vs Rotary disputes. (Now don't get me wrong I don't question their results, but I wonder if such a comparison e.g. on an E61 machine would result in different conclusions)

But I've pondered too about Chris' "Elusive Clarity", where such minimal changes - IIRC, that is - in the chain as omitting the filter seemingly caused major differences in taste. Makes one wonder if such a test with a vibe-machine would produce similar results...

My own interpretations of this effect always seem to end up with what happens in the brewhead. The pump (vibe as well as rotary) generates a more or less laminar flow of hot water, but as soon as this water enters the grouphead/shower the pressure drops and the flow becomes turbulent. This not only makes the extraction process less "linear" it also should cause - significant, IMO - temperature changes on a microscopic level.

To cut the long story short, my hypothesis is, that the turbulence in the grouphead have a somewhat detrimental effect on the taste - especially to what Chris refers to as "clarity" - of the espresso and that instead a laminar flow in the cake should be able to provide this. But on the other hand, this also would probably reduce or even minimize crema...

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cannonfodder
Team HB

#7: Post by cannonfodder »

Don't misunderstand my comment about the cooling flush routine. I agree with both of you that a stable temp can be achieved. I use a HX now and am perfectly happy with it at this time. I was just thinking of taking one of the existing variables out of the mix. It is just one less thing to worry about in the morning routine (read this as lazy).

It is definitely something to contemplate when it is time for the next upgrade. But as to my original question, would a rotary pump make a significant improvement in the cup, I am leaning toward a solid maybe as an answer. It sounds like there are too many other considerations. The cost/time vs. cup improvement in modifying my existing machine does not appear to justify itself.

I did not know of Schulman's comparison on alt.coffee, I will have to look it over. I just changed my ISP and have not had time to set up the usenet account. I don't spend much time in the news groups anymore.

The more I learn, the more I realize how much more there is to learn.

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HB
Admin

#8: Post by HB »

I've not done a side-by-side comparison of rotary versus vibration pumps. But given the care Jim and Ken put towards attempting to discern a difference while finding little, I'm doubtful it's a worthwhile consideration for your average home barista except for the quiet it affords. That said, if I went through the trouble of a conversion, I would replumb to enable the E61 lever's "mid position" for preinfusion under line pressure. It's my hunch that enhancing the machine's preinfusion a la the Synesso would make a bigger improvement than the rotary conversion.
Dan Kehn

Abe Carmeli
Team HB

#9: Post by Abe Carmeli »

HB wrote: That said, if I went through the trouble of a conversion, I would replumb to enable the E61 lever's "mid position" for preinfusion under line pressure. It's my hunch that enhancing the machine's preinfusion a la the Synesso would make a bigger improvement than the rotary conversion.
This is a good point, and right on time. I'm starting my rotary conversion next week, and preinfusion was near the top on my list. Rotary ramps up pressure immediately to set pressure on a home E61. The preinfusion chamber works well with a vibe pump, but once you convert to rotary, it will go to max pressure in about 2 secs. A little too fast for real preinfusion.
Abe Carmeli

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Walter

#10: Post by Walter »

So, does that mean that preinfusion on E61 machines hasn't really worked all those decades before the E61 made it onto the prosumer machines with their petty vibe-pumps? :?