Ken Fox wrote:Lever machines don't get anywhere close to 9 bars of extraction pressure . . . .

Ken, are you sure about this? I was under the impression that common 49mm/51mm manual levers (like the Pavonis) reached ~9 bars with 30-40# of downward force on the lever (see e.g. this thread). Spring levers also appear to have no problem reaching 9 bars of pressure (see e.g. here).

You can get over 9 bars on a full manual lever, spring levers are more like 7 to 5 bar with a declining pressure profile. Boiler pressure acts as you're preinfusion albeit low at 1.3ish bar. Mains pressure could be dialed in and run up as high as the machine will allow on input pressure with a rotary or vibe pump. The big problem with a manual lever is keeping the pressure constant, and they like to overheat fast making many of them less than ideal for more than two shots unless you go to a big commercial box.

When I had my Faema hooked up I ran an adjustable delay on make relay so I could preinfuse with 3 bars of mains pressure to get a fully saturated puck then the rotary kicked in. That helped make the machine a little more forgiving. I thought about doing the same on my Elektra but have not been motivated enough to do it, I also don't have extraction problems like I did on that old two group.

AndyS wrote:Actually I believe Kees is experimenting with boiler insulation for the Speedster

It appears that it will shortly (if not already) be shipped with some silicone foam insulation.

Couldnt the pre-infusion issue be solved with a simple solution, take out the solenoid valve and replace it with a manual ball valve(or any manually activated valve), obviously the handle part would have to be fabricated on the side of the machine to gain easy access to it.
Now, pump on, eyes on the gauge and slowly start to open the valve, wait a few seconds at desired point and open fully at will.

"Manual Brew Pressure Profiling"

Total control and the barista has a hands-on effect on the outcome?

Would it work?

j7on wrote:"Manual Brew Pressure Profiling"

Very possible! Pretty darn simple, in fact

I dunno why something like this hasn't been included on some high-quality machine...

Regards, Henry

Obviously this does not end the quest to explore and come up with gadgets that can be programmed to reproduce pressure profile ramps and thus able to replicate godshot after godshot.

But this would put the barista and his skills back on the pedestal.

I havent tried this yet, the only experience i have is with swimming pool water pumps(basically the same but more powerful, more water, more pressure) and they have no problem running if you temporarily plug the outlet(dont overheat & explode immediately..., motor just runs but the water doesn't go anywhere.

Any more thoughts?

Swimming pool pumps are typically centrifugal pumps which are always best started with the shut-off valve closed. That way you are starting the motor under essentially zero load.

Espresso machine pumps would be classified as positive displacement pumps, most definitely NOT best started with the shut-off valve closed. To the best of my knowledge, all positive displacement pumps have some sort of protection (OPV, by-pass valve, relief valve, etc.) to account for this condition.

I envision a SIMPLE, user programmable "chip" installed in a variable speed motor driver such that the barista can EASILY program the pressure profile desired. Speaking from inexperience, some beans may like profile A, some profile B, some doses profile C, some doses profile D, etc., etc.

Along a similar line, could a rotary pump be adjusted during a shot? Start with low pressure and slowly build the pressure as one sees fit?

One thing that I think you'll find is that the bypass valve on a rotary pump doesn't necessarily offer a "full range" of adjustment; in particular, I don't believe it goes down to exceedingly low pressures. It'd be far more flexible to control motor speed as Eric suggested.

Hi guys,

one can always built a small PWM motor controller and add the option of saving pressure profiles. The motor will however heat up at lower speeds which might be a problem.

Regards,
dsc.