Are there any multiple head manual lever machines? I guess more consistency might be possible with spring levers and it takes less hands on time. Any other thoughts?

farmroast wrote:Are there any multiple head manual lever machines? I guess more consistency might be possible with spring levers and it takes less hands on time. Any other thoughts?

Much less hands-on time. Barista can be steaming milk during the extraction, or preparing other drinks.

P.S. Brilliant, Bluecold.

Wow Bluecloud. great video thanks for sharing, that Barista is really cranking out the shots!

I suppose its also the fact that a commercial-size lever group brews under as much pressure as is desirable, so a manual lever would not present any advantage. At least the some of the Conti levers have coupled mechanisms that allow a manual increase in pressure by pushing up on the lever.

My miniGaggia has the same type of coupled mechanism, and it is a nice feature. Almost nice enough, among its many other nice features, for me to keep it. But I'm selling it to a coffee friend here in Sweden. "Parting is such sweet sorrow"

PC

peacecup wrote:At least the some of the Conti levers have coupled mechanisms that allow a manual increase in pressure by pushing up on the lever.

PC,

Why can you not push up a little on your PV to increase the pressure over the normal spring tension? I always assumed this would be a possibility on any spring lever. I hope you or others can clarify why your PV is different than say a Conti.

Thanks.

fantastic video! wow.

The lever on la Cimbali spring lever machines uses a cam to push the piston down. You can lift the lever to the vertical position with zero resistance.

Rob

Yes, its the design of the cam, but I don't know the terms. On the PV you can't push the piston down by pushing up on the lever - there is no linkage. The linkage only works to pull the piston up by pulling the lever down (ie its one-way).

On the MiniGaggia it is linked, so it can work both ways. As I said, I keep having second thoughts about letting that baby out of my hands....

When reading discussions of the question in the past, I believe it was Timo who offered the force calculations required to pull a shot at 9 bar using a manual lever. Due to the size of the cylinder as it was engineered way back when to produce the required shot volume the lever handle would have to be much longer to give the operator enough physical advantage to pull the shot. That was how I remember at least part of the discussion. I think that yes, consistency and freedom for the barman to do other things is logical but also that as with any machine, why make it harder to use than need be....if you can add a spring alls the better....makes it modern, almost automatic, and then of course if you can just push a button to run a pump etc etc.

and then of course if you can just push a button to run a pump etc etc.

There is, however, a fundamental difference in the physical way in which the water interacts with the coffee when brewing with a piston vs. a pump/dispersion screen. I've been suggesting for some time that the former is an inherently better way to ensure that the coffee is evenly extracted.

There's an ergonomic factor as well. Can you imagine trying to pull several hundred shots per day, 5-6 days a week on a manual lever? What kinds of overuse and strain injuries would result from such a job? Few people would be able to do it for any length of time, and fewer would even want to.

Mark

Has there ever been a 2 group non-spring lever machine?

the video provides the answer: you can see how the Barista is able to multitask while the spring is doing the work- if he had to manually pull each shot his working capacity would be severely reduced- and the entire process would be less repeatable- and more hit and miss...

Peacecup, heaven forbid you would think I of all people would be advocating pump machines over levers....I was just making the point, or trying to, that one step sometimes leads to another and it is all thought to be progress.
Every time we go through another early machine, and it is a learing experience each time, it causes me to ponder the entire issue of why the machine was designed as it was, throwing out all other ideas and gravitating to a single general design. Piston, cylinder and pf size (but for La San Marco), spring operated lever, etc....but all pretty much the same group design. Think about Achille Gaggia and his Crema Caffe idea and imagine that you are the one working out this 14 grams coffee at 94C under 9 bar pressure pulled 25 ml in 28 seconds. Pretty high degree of specificity there to just stumble upon.
The dosing and grinding had been pretty well worked out in the verticale machines as just what made for a good cup of espresso, but the 9 bar made the crema. How to deliver the 9 bar. I reject the ergonomic idea and pity the poor barman with repetitive stress injuries (such concepts asrepetitive stress injuries did not exist then.....they were a part of life), and any touchy feely ideas about ergonomics are pretty much obviated by the continual use of stoop labor to plant and harvest our fresh market crops, so I think that in 1948 there was likely not much thought of the barman who would have to pull a lever all day long since he was lucky just to have a job anyway. After all, the piston could have been foot operated, which would have done away with that argument alltogether and been very simple to kick down on a pedal linked to the piston, or use a counterweight system for compressing the piston in the cylinder. I think that Gaggia found that he needed a force multiplier of some kind to get the pressure up for crema and just had a eureka moment when he hit on the spring, even though his first machines had a clockwork type mechanism for the power.
Since this is more or less lost in the mists of time I just have to think that the spring was such a good idea at the time that it just stuck and was seen as the best way to manufacture the machine for this wonder process. Like the internal conbustion engine, it just became the way it was done.

The barista in the video is seen pulling the levers down very quickly even when there is a porta filter with coffee in the grouphead.

Does this mean that there is a mechanism to prevent rapid depressurization above the puck when the lever is pulled down? If not why doesn't the puck fracture like in most home lever machines?

Geoffrey

Sorry Doug! I didn't mean to suggest that YOU like to push buttons to run pumps.

GB, I think one can pull the lever on the PV quite quickly without damaging the puck - its a simple test to try, and see if you get worse results if you pull quickly.

Paul,

Thanks for your reply - very interesting. With my Ponte Vecchio Export water does not enter the grouphead until the lever is pulled past halfway. Consequently I have to slowly pull down the lever or risk puck fracture from the pressure differential across the puck. If these professional lever machines allow water into the grouphead at the beginning of the stroke then do they must have some sort of no-return valve? Or is it some other mechanism?

Thanks
Geoffrey

BTW. Last September I had a superb cappuccino and service at a cafe just near the Auckland airport. A delightful and welcome stopover on a long flight to Oz.