Who ya gonna call? (vibe vs. rotary pumps)

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RapidCoffee
Team HB

#1: Post by RapidCoffee »

Alan Frew "mythbusting" in his latest newsletter:
Alan Frew wrote:Yet another frequently expressed myth is that rotary pumps (as found in commercial espresso machines) produce better espresso than vibration pumps, as used in domestic machines. The arrival of my new laScala Butterfly shipment has allowed me to put this one to rest forever, because along with the Butterflys I imported a couple of laScala Eroica machines. These are identical to the Butterfly except for the rotary pump & motor replacing the tank; they are designed to be the fully plumbed in version. So I set an Eroica and a Butterfly up side by side and started pulling shots. My assistant then moved the shots while my back was turned, and I had to try and pick the differences and which machine produced which shot.

Over a dozen trials I not only couldn't pick which machine produced which shot, I couldn't detect any differences between the shots at all. Pump type appears to have no effect on shot quality whatsoever.
An interesting data point in the vibe vs. rotary pump arena (and there aren't many good comparisons available). Although I'm a big fan of rotary pumps, I've got a lot of respect for Alan's no-nonsense approach to espresso.
________
John

Ken Fox

#2: Post by Ken Fox »

Apologies for blowing our own horns, but Jim Schulman and myself have done this test, and published it online, TWICE, in a much more controlled fashion, with my two Cimbali Juniors, one a rotary and one a vibe. These two tests were well controlled, with everything we could think of including shot temperatures and pump pressures standardized. We did this twice, over a span of 3 years, with a number of different coffees.

We were unable to determine any systematic differences. Adding a delay timer to the rotary pump, allowing preinfusion at around 3 bar, which basically mimics the behavior of a vibe pump, made the two machines equally forgiving.

I would not buy an espresso machine with a rotary pump if the only reason for doing so was a perceived benefit in shot quality. They buyer in that case is apt to find his goal to be elusive.

ken
What, me worry?

Alfred E. Neuman, 1955

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another_jim
Team HB

#3: Post by another_jim »

The idea that rotaries are better came from comparing home machines to commercial ones; a comparison that confounds a lot of variables. A few people who replaced the vibe on the Silvia with a rotary also got better results, and this confirmed the idea. However, it turned out that the effect was caused by the poor quality OPV on the Silvia, which often does not do anything under about 15 bar (I've heard they are supposed to limit pressure to 11 bar, but this may be a rumor).

Once the checks were repeated with vibe pumps that could be adjusted properly, the difference between rotaries and vibes more or less vanished. Moreover, it turns out the conventional wisdom among Italian manufacturers is that vibes are equally good; although they believe they should be set at 11 bar blind pressure rather than the 9 bar of rotaries.

Vibes don't last as long as rotaries, cannot drive more than one group, and have limited duty cycles that make them inappropriate for high traffic uses. But espresso quality is not one of the considerations.

The main reasons savvy people get rotaries for the home are the convenience of having the machine plumbed in and for their quiet operation.
Jim Schulman

alsterlingcafe

#4: Post by alsterlingcafe »

John..... interesting post for me. Ken...... yes, I read your pieces on vibe v rotary

More and more, I'm of the opinion that once one gets into the "adequate equipment zone", meaning true HX machines, whether it's vibe or rotary pump, it's pretty much up to the operator/barista. I hear this from others on the forums often. I started my home espresso hobby with the Expo Pulsar Office. (I had a Krups and Gaggia Super Auto, but gave the super auto back for full credit after 2 weeks.) Once I figured out the Expobar, my shots were consistent and "per factory spec's."

Just when I thought I was hot stuff...... I sold the Expobar and got the La Spaziale S1. When I upgraded to the S1, it was for both the rotary pump and dual boiler reasons. I thought I'd be able to "buy into better quality espresso." However, it didn't happen that way. I was lost for quite awhile, trying to "dial it in." I even thought I might have made a mistake by not getting the BII with its tight temp control. One of my early "dial in" problems had absolutely nothing to do with the darn machine. I forgot all about the true "freshness" of the pre-roasted beans I was using and "chased my tail" for a couple weeks, thinking that it was adjustments to the grinder, tamping or PF filling issues. I've since put my HT roaster into service and now roast most of what I use at home. I'm a firm believer, after wasting all that time and coffee, in starting the system QC check with the beans! (....weakest link in the chain, etc.)

I've read, with interest, the many "objective-quantitative" posts that you, Jim and others have authored. It's interesting, gives me better insight into the science of espresso, (when I understand all of the graphs!) and helps me appreciate the "why's" of espresso. Again, I believe that once one buys into an HX machine and Macap-Mazzer level grinder, upgrading is more about volume, convenience and ever finite levels of quality.

Vibe pump vs Rotary? I like the "silence" of the rotary, but don't credit it with improving my espresso. Dual boiler better than HX? I keep asking myself....... if it were, why are HX machines still on the market? Personally, I love the look of the high-end Faema commercial machines. And I can't believe, with their advanced temp controls, that they're that much less a machine than the LM? Or are they??!

Best, Al in SoCal

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RapidCoffee (original poster)
Team HB

#5: Post by RapidCoffee (original poster) »

Ken Fox wrote:Jim Schulman and myself have done this test, and published it online, TWICE, in a much more controlled fashion, with my two Cimbali Juniors, one a rotary and one a vibe.
Yes - and a big THANKS! for taking the time and effort to do this. But I haven't seen other studies comparing vibe vs. rotary espresso taste on two virtually identical machines, so I thought I'd point out Alan's newsletter. His study may not "put this one to rest forever", but it's confirmatory evidence for your work, which is nice.
another_jim wrote:The main reasons savvy people get rotaries for the home are the convenience of having the machine plumbed in and for their quiet operation.
Agreed. One side benefit of quietness that impacts on taste: it's easiest for me to monitor the HX flush by ear. A rotary pump allows me to do this more effectively.
alsterlingcafe wrote:More and more, I'm of the opinion that once one gets into the "adequate equipment zone", meaning true HX machines, whether it's vibe or rotary pump, it's pretty much up to the operator/barista.
Well said. And who knows? There might be a DB machine in my future as well. But if so, it will likely be my obsession (cough, cough, I mean passion) for espresso, clamoring for attention, that drives the purchase. And it will undoubtedly have a rotary pump. :)
________
John in RC

Ken Fox

#6: Post by Ken Fox »

another_jim wrote:The idea that rotaries are better came from comparing home machines to commercial ones; a comparison that confounds a lot of variables. A few people who replaced the vibe on the Silvia with a rotary also got better results, and this confirmed the idea. However, it turned out that the effect was caused by the poor quality OPV on the Silvia, which often does not do anything under about 15 bar (I've heard they are supposed to limit pressure to 11 bar, but this may be a rumor).

Once the checks were repeated with vibe pumps that could be adjusted properly, the difference between rotaries and vibes more or less vanished. Moreover, it turns out the conventional wisdom among Italian manufacturers is that vibes are equally good; although they believe they should be set at 11 bar blind pressure rather than the 9 bar of rotaries.

Vibes don't last as long as rotaries, cannot drive more than one group, and have limited duty cycles that make them inappropriate for high traffic uses. But espresso quality is not one of the considerations.

The main reasons savvy people get rotaries for the home are the convenience of having the machine plumbed in and for their quiet operation.
I do have both of my Cimbali Juniors in the kitchen but almost never have both of them turned on (unless Jim Schulman is here for a visit, that is). The rotary machine is plumbed in and right next to the sink, the vibe machine is across on the kitchen island, and self-contained. About 75% of the time lately, I'm using the rotary, and maybe for a week a month I use the vibe. With the delay timer installed, the machines are more or less equivalent in the quality of their output, and "forgiveness factors." The rotary gets used more than the vibe because it simply is easier to use; I have the flush automated and I don't have to refill the pourover tank or empty the drip tray. It is also quieter, another real plus.

ken
What, me worry?

Alfred E. Neuman, 1955