Advantage of E61 lever action semi-auto espresso machines

[stjones]

Having read the posts about lever machines, I have a question. Some time ago I remember reading that lever operated (mechanical) sem-automatic espresso machines have an advantage over espresso machines where you simply flip a switch to start the flow of water/steam. I tried to search this on H-B and CG but to no avail. What's the benefit? Chris Coffee's Vetrano is an example of such a machine (http://www.chriscoffee.com/produc...e/espresso/vetrano). I'm not considering a Vetrano so I'm really not interested in comments about the Vetrano.

Thank you.

Stephen Jones

[DaveC]

Having read the posts about lever machines, I have a question. Some time ago I remember reading that lever operated (mechanical) sem-automatic espresso machines have an advantage over espresso machines where you simply flip a switch to start the flow of water/steam.

From my on perspective the only advantage is a mechanical simplicity one. The group is basically the same except some mechanical wizardry, motors and solenoids operates the venting and movement of the group internals to direct water flow.

So less to go wrong with the mechanical lever. Also when backflushing things stiffen up for a while so a component that was going t fail might be more likely to in a "automatic system". There are also 2 types, those which replace the lever on an E61 group with motor etc. and the others (for groups that never had a lever) that work on an "E61" type group (bottom only), these usually have 3 way electrovalve of different design to the E61.

In all cases, there will be no impact on taste or shot quality in semiautomatic vs manual lever movement

[erics]

There is (I believe) an explanation of the types of machines you are trying to compare on this site. I would point you to it but I've lost a lot of writing trying that one. The Vetrano is NOT an example of what you might want to compare because it is an E-61 lever machine that also happens to have a rotary pump. All of the Quickmill machines that Chris Coffee offers are lever operated E-61 machines.

The comparison you want is between the varietals of say, the La Valentina and Vibiemme Domobar - I'm sure there are others - they just don't come to mind. The Valentina and Domobar can be purchased in either a manual configuration (lever operated group) or a semi-automatic (push button).

The lever operated group offers simplicity, full user control, and a preinfusion system that assists in the consistency of your espresso adventure. The push-button machines allow you to program a fixed flush amount and a fixed shot amount. For sure, there exists many satisfied users of both types.

[HB]

Some time ago I remember reading that lever operated (mechanical) sem-automatic espresso machines have an advantage over espresso machines where you simply flip a switch to start the flow of water/steam... What's the benefit?

To clarify for those reading along, below are the two designs in question:


E61 with expansion chamber / lever action, E61 with solenoid (please do not copy)

I agree with Dave and Eric that the difference in the pressure profiles is small, especially when comparing vibratory pumps. The next two charts are excerpted from Pressure profiles, preinfusion and the forgiveness factor. The first chart shows the difference between E61 vibe pump espresso machines having an expansion chamber (left) and solenoid (right):


E61 with expansion chamber, Elektra A3 rotary, E61 with solenoid

As shown the by gentler slope, the expansion chamber does indeed retard the rise in brew pressure. The next chart shows two E61s with expansion chambers; the left has a vibratory pump and right has a rotary pump.


Two E61s with expansion chambers (vibe, rotary)

Rotary pumps pressurize almost instantaneously, producing a sharper rise and a more distinct knee as the chamber fills up. Vibe pumps take longer to build pressure, producing a more gentle "progressive preinfusion."

I've evaluated the espresso machines above for months and didn't notice a noteworthy difference between the expansion valve / solenoid type E61 designs with respect their to forgiveness of minor errors in barista techique. One combination I haven't tried is the E61 with solenoid and rotary pump (e.g., Wega Lyra); I would expect it to have a steeper pressure rise than the E61s above, which would translate into less time for preinfusion and potentially less margin of error for channel avoidance.

[cannonfodder]

Manual lever machines...

Modern Day Lever Espresso Machines

Modern day lever piston espresso machines use three different water supply brew systems and two different piston power designs.

Spring assist and manual lever.

There are two different piston powered systems. The spring assisted lever uses a coiled spring to regulate the extraction pressure of the piston. When the lever is depressed, the piston is cocked. You simply release the lever and the spring delivers the needed pressure for your extraction. The Elektra Microcasa a Leva is one of the most popular spring assisted lever machines.

The second power system is, well, you. The full manual lever relies on the operator to supply the needed pressure to the lever for extraction. These systems require much more time to learn. The operator has to apply steady pressure to the lever during the extraction. The difficult part is training yourself to apply the same amount of pressure for every shot. The La Pavoni Europiccola and the Gaggia Achille are two of these full manual systems.

Water delivery methods.

The most common type of water delivery is the steam pressure driven. In these systems, a single large boiler supplies both brew water and steam power. The machine relies on steam pressure to force water up a brew group supply line and into the group piston chamber. In order for that to work, the water in the boiler must be hot enough to generate steam. Most of these machines operate around .8 bar, or roughly 250F.


Hydraulics diagram from the Olympia Cremina manual

Since the brew water is well beyond the target brew range (195-205F) the water must be cooled prior to the extraction. On these machines, the group acts as a heat sink, leaching heat from the brew water as it enters the piston chamber. This is not a good way to regulate the brew water. Every time you pull a shot, the group absorbs more heat. Most of these will only allow for 3-4 shots before they overheat. Extended idle time also results in an overheated group because the grouphead is directly attached to the boiler. Common machines in this category include the La Pavoni Europiccola, Olympia Cremina and Elektra Microcasa a Leva.

Gravity feed (open boiler) water delivery systems can avoid these overheating problems. A gravity system uses a boiler placed above the grouphead. When the lever is lifted, gravity pulls the water down into the group piston. Because steam pressure is not required to move the water, these systems can operate at much lower temperatures. The water in the boiler can be kept at or slightly above the target percolation temperature. The disadvantage of these systems are two fold:

1. Because the boiler is located above the grouphead, most of the machines mass is located high off the counter. That tends to make them a bit top-heavy and prone to tipping over if the base is not sufficiently large.
2. These systems generally have one boiler, the brew boiler. Because these are run at brew temperatures, there is no steam for creating milk drinks.

The La Peppina and Mini Gaggia/Minimoka are popular gravity fed open boiler machines.

Heat exchanger is the third water delivery method. A heat exchanger uses a high pressure (usually 1 bar and up) boiler with a brew water supply line running through it. Most commercial lever machines use a large steam boiler with one heat exchanger per group supplying brew water. As the cold water passes through the heat exchanger tube it is flash heated to brew temperature. The resulting brew water can be adjusted up and down in temperature by the dwell time. The longer the water sits in the heat exchanger, the hotter it gets. The majority of commercial machines use a heat exchanger system. Below is a heat exchanger hydraulics diagram for a pump-driven espresso machine:


For more on how a heat exchanger works see Espresso Machines 202

Commercial lever heat exchanger machines are plumbed into a water supply. The lever machine's heat exchanger uses the mains water pressure to force the brew water through the heat exchanger and into the brew group. This system gives the barista much more control over the brew water temperature. In the event the grouphead overheats, the barista can cool the unit by pulling a long flush of cool water through the group. These machines are intended for all day use. Our Gaggia Achille lever uses this same principle to overcome the inherent overheating problems of the steam pressure driven systems while still providing steam for milk based drinks.

So the question is, can the Gaggia Achille run all day like a commercial heat exchanger without overheating? Over the next few days, I plan to answer that question.

From the Buyers Guide to the Gaggia Achille

Then there are the pump driven machines. Of those you have a manual lever operated (lever actuated but with an electronic pump like the E-61 manual group), semi-auto (push a button to start, push a button to stop) and automatic (push a button to start, flowmeter measures how much water has passed through the plumbing and turns off the flow when the programmed amount has been dispensed). All of these are modern electrically driven pumps, either vibratory or rotary.

On a manual machine, the lever works a 3-way valve. In the down position the brew water and pressure is vented out the bottom of the group, in the middle the vent is closed and the brew path is open (on some machines). If you are plumbed into you home mains, you can use that position for preinfusion, then all the way up starts the pump for extraction. When your shot is finished, you pull the lever down to the starting position. The pressurized water vents out the bottom of the 3 way and the portafilter can be removed. The semi-auto and auto use an electronic solenoid instead of a lever to achieve the same basic function but you loose the center preinfuse position. It is on or off. If the machine is not plumbed in and running on a water tank (pour over) then the center preinfuse position gains you nothing since there is no water pressure for preinfusion. Make sense?

[gscace]

Having read the posts about lever machines, I have a question. Some time ago I remember reading that lever operated (mechanical) sem-automatic espresso machines have an advantage over espresso machines where you simply flip a switch to start the flow of water/steam. I tried to search this on H-B and CG but to no avail. What's the benefit? Chris Coffee's Vetrano is an example of such a machine (http://www.chriscoffee.com/produc...e/espresso/vetrano). I'm not considering a Vetrano so I'm really not interested in comments about the Vetrano.

Thank you.

Stephen Jones

Howdee there:

Any advantage would have to do with the difference in pre-infusion and pressure rampup. Dan's graphs illustrate that the spring loaded expansion chamber coupled with a vibe pump produce a long pre-infusion time compared to that produced by the group with electronically controlled solenoid. The electronic group is pretty much identical to what you have now on your Astra, so you should be pretty familiar with it. One thing that has not been covered here is that with the mechanical group one can further influence the pre-infusion step by lifting the lever partway, opening the water passage to the coffee and allowing hot water to percolate into the cake at a very reduced pressure. In instances where the group is fed from an internal reservoir, using either a vibe or rotary pump, the water infusion takes place at very low pressure (just above ambient), in a manner somewhat similar to a lever machine. In the case of a mechanical group fed by the water mains (no reservoir tank), the soak occurs at slightly less than the supply pressure of the mains, presuming that the pump itself doesn't restrict water pressure across the pump. I'm guessing that vibe pumps may provide such a restriction, but rotaries do not.

There is some evidence that low-pressure soaking is useful. Ken Fox and Jim Schulman performed a series of tests that suggest there is some benefit. I think that they concluded that the pressure had to be high enough to reliably soak the coffee cake within a few seconds. Very low pressure wasn't all that effective at this. Over the past couple of months I've fooled around with low-pressure soaks and various pre-infusion schemes programmed into my Marzocco. I believe that some coffees benefit from this. But not all coffees do. Terroir's very lightly roasted Brazil (forget specifically which Brazil) was best without any pre-infusion at all. My usual practice, and starting point when trying different coffees is to introduce a low pressure soak is at around 3 bars for 3 seconds, with an exponential pressure rise to 9 bars taking place over the next 2 seconds. My pressure controller has trouble producing pressures much lower - due to a combination of controller limitations and minimum pump speed. I use the bottom of the brew basket as a visual guide to required length of soak. I like to see liquid flow from the basket almost immediately on high pressure ramping. Anyhow, such games can be played with a machine that is plumbed into the water mains and a mechanical group. The pressure of the soak can be regulated by a water pressure regulator upstream of the pump. As I mentioned earlier, the pump type may also be a factor.

The flexibility of the mechanical group wrt the combination of soaking and pre-infusion could be a useful tool to have in one's arsenal when trying to maximize taste from a specific coffee or coffee blend.

-Greg