I've always felt like the lever on my machine "engages" the pressure a little to late (meaning: when the lever is pointing couple of degrees above the horizon). There seems to be too little resistance the first couple of degrees. But this could of courses be normal.

Yet, sometimes the lever engages right away, when I release it from its downwards lockdown position.

Why does this only occur rarely? And what would be normal? Could it be that pre-infusion valve (haven't messed with it yet). Maybe it's just the coffee that soakes up more/less water during pre-infusion?

Any thoughts?

Made a video.
This is normal.
19 gram

Thanks. That looks like mine. Maybe even more angled upwards.

Though, I still wonder why it sometimes (rarely) engages at almost 90 degrees. Less bubbles in the water or something?

The amount of coffee in your basket regulates the angle of attack of the lever.
You didn't want a 90 degrees engagement.It will generate a 10 bar shot or more.

Red_Donkey wrote:I've always felt like the lever on my machine "engages" the pressure a little to late (meaning: when the lever is pointing couple of degrees above the horizon). There seems to be too little resistance the first couple of degrees. But this could of courses be normal.

Yet, sometimes the lever engages right away, when I release it from its downwards lockdown position.

Why does this only occur rarely? And what would be normal? Could it be that pre-infusion valve (haven't messed with it yet). Maybe it's just the coffee that soakes up more/less water during pre-infusion?

Any thoughts?

Here's how I understand what determines the catch point of a Londinium-style group. I suppose it's the same for others as well. When the lever is down, there is a column of water above the shower head which, during preinfusion, is held in place by the coffee puck. Above the column of water is a column of air. When you release the lever, the piston first compresses the air and then the compressed air presses agains the water. The more air there is, the more time the spring will take to unwind before the now compressed air begins to press against the water column, at which point the lever catches. The amount of air above the puck is determined by the pressure of the preinfusion water, which drives more or less of the air out through the puck. In a Londinium R, preinfusion pressure is determined by pump pressure; the higher this is set, the lower will be the catch point. I've seen several videos documenting this.

[edit] P.S. Just after posting the above, I read a post from Dr Gary about his procedure in pulling shots with a Cremina. He mentions driving air out of the puck. I wrote above of air above the puck. For all I know, all of that air is in the puck; or perhaps it is both above and within. In any case, a spring lever will have to drive it out of the system before the lever catches.

Make sure the water starts running into the group as soon as you touch the lever. No air.

There are many factors which determine the catch point of the lever. From my experience these are the main ones:

• Boiler pressure/pre-infusion pressure

• Pre-infusion duration

• Flow rate (if you have a flow valve installed

• Ability of the coffee cake to resist the water

For the last point that of course depends upon the grind and dosage. Too coarse and the water will flow right through and you will have a high catch point.

Sorry - I missed the point of your last video. I noticed that you changed some setting in between engaging the lever which changed the catch point of the lever. But with no explanation or knowledge of the machine you are using (a Pompeii ?) I'm lost.

By changing the timing of the watervalve you can regulate to a certain point the catch angle of the lever.
Before adjustment the valve opens at an angle of app. 75 degrees. After adjustment at about 10 degrees.