I just saw this video about a new handheld espresso maker by Cafflano. I travel quite a bit and would love to have something like this! Thoughts?

https://www.perfectdailygrind.com/2017/ ... -pressure/

Seems too small and wide to be able to make hand-generated pressure sufficient for espresso. Reminds me of a technique I used to do with my AeroPress to generate an "espresso like" beverage, perhaps a little more successfully in this case.

No kidding. Even if the basket is just 40mm (not a 58 or 49mm)... at 9bar (about 9kg/cm^2 even when corrected for g) - the force needed to compress would by 120kg.

One can imagine an espresso machine that an obese person sits on. Not a Pacific Northwest bicycle rider type. For the latter using thumbs - it is another aeropress...

For a 58mm basket even the obese person sitting on the device would be nothing more than an aeropress (or would need a 250kg person).

One wonders about the mottled crema. However did they manage to get that crema?

AssafL wrote: One wonders about the mottled crema. However did they manage to get that crema?

Well, we can see from the video that the woman pressing out the coffee didn't get great results...
Clearly the espresso is taken in a different shot!
I am not sure where to look for errors in their or our calculations, but even if we are generous for (sex/age) combined grip strength it still means to get pressure, most of an average persons body mass has to be leant upon it.

What error in calculation? That is why Portafilters (especially 58mm ones) are so big and have such heavy duty bayonet lugs. And in the case of the GS3 held by 3 big Allen bolts.

The reason it doesn't kill you (if you even manage to release the portafilter) is that the volume is tiny and water is incompressible. The pump can only do a few hundreds of ml / min.

When you do it (I like to clean the gasket by closing the PF a bit at the edge of the bayonet - with a blind basket and release it) you absolutely feel the 100s of kg of the pressurized PF nudging you - for less than a mm that is.

Force is huge but work (energy) is minuscule as the pressure is spent immediately.

In others words - what they claim is impossible. Physiologically impossible and impossible from a physics perspective.

Yet another Kickstarter "failure to deliver"? They'll probably deliver and people will get aeropress like coffee. And when they complain the company will blame the coffee, the water, the technique, the grinder and the user. Best approach is to deflect responsibility by saying you need a 3k grinder to get crema.

I am implying the error is theirs, but I don't have their calculations to check
All the video shots they demo yield coffee that doesn't look anything like their close ups... it does seem fishy.

Yes. I assumed you had rigor at your side .

But whenever debunking a magical product* one must leave a paper trail. Perhaps someone stumbles on to this threads and avoids aggrevation.

And to those for which it is too late - give your arms a break. You are not weak. You purchased an aeropress. Enjoy it. Many here enjoy theirs.

*Edit: Obviously not a magical product - but a product originated of magical thinking.

It does seem possible to generate 9 bar static pressure using the hydraulic/Pascal's principle as force multiplier. That is assuming you have close to your entire body weight on it (~54kg force). The 'piston' diameter is about 28mm and the basket size about 49mm from the values given.

That is 9 bar static pressure so it should be lower when it's dynamic. Not to mention the presence of air may also reduce that further.

In practice, it's likely generating pressure somewhere around 2-4 bar.

For those of us who only did basic physics at uni could you or anyone describe where those numbers/units come from and how they work out?

samuellaw178 wrote:<image>

It does seem possible to generate 9 bar static pressure using the hydraulic/Pascal's principle as force multiplier. That is assuming you have close to your entire body weight on it (~54kg force). The 'piston' diameter is about 28mm and the basket size about 49mm from the values given.

That is 9 bar static pressure so it should be lower when it's dynamic. Not to mention the presence of air may also reduce that further.

In practice, it's likely generating pressure somewhere around 2-4 bar.

You would need a long tube for that (the volume has to stay the same). Look at your portapresso. How many pump pushes do you need to do with your shock pump? And the Portapresso seems to be a small basket (you'd end up in a puddle on the floor trying to pump up the volume for a 58mm basket).

You can see in the beginning there is air in there.

You are correct that had it been a fully hydraulic system with little to no adiabatic (gas) losses, you could have a smaller volume. Still needs to be the volume of the shot+ puck wetting, + losses.

Make a long thin strong tube, fill it with boiling water, and press down with full body weight. That will work. Sort of a walking stick espresso maker.

aecletec wrote:For those of us who only did basic physics at uni could you or anyone describe where those numbers/units come from and how they work out?

Water is incompressible. Hence Pascal works well on it - it is basically a lever - pressure is the same throughout the system. so:
Say I need 9 bar on a 58mm basket.
1. Area of the basket is pi*r^2 = (58/2)^2 * pi = 2642mm^2 or 26cm^2.
2. Pressure is 9bar so force is about 8.9kg/cm^2
3. Multiply: 26cm^2 * 8.9kgf/cm^2 = 231kgf

How do I generate that pressure?
Let's use Pascal's - and say I have 5kg"f in my arm. To generate 9bar:
1. Area is: 5kgf / 8.9 kgf / cm^2 = 0.56cm^2
2. Diameter of piston: D = 2*sqrt(A / pi) = 2*sqrt (0.56 / pi) = 0.8cm

Now the fun is this:
Say my espresso volume (water in puck + water in cup) is about 80ml of water.

A liter is 1000 1cm cubes of water. So 80 ml is 80cm^3.

So our piston would have to be l = 80 cm^3 / 0.56 cm^2 = 142cm. 1.5 meter piston.

Let's play some more. Lets say I want a piston of 20cm length:
The volume stays 80ml so the area is:
A= 80cm^3 / 20cm = 4cm^2

9bar on 4cm^2 is F=8.9kgf/cm^2 * 4cm^2 = 35.6kg.

Tamping at 15kg causes injury for some and is difficult for others. And it is over a distance of 1cm at most. Maintaining 36kg over a travel of 20cm is hard.

Ah gas - why not "air"? Remember the ideal gas law PV=nRT? Pressure can change because volume and temperature can change. So pushing down on the piston may not result in the pressure you expect (since the volume will decrease instead of increasing pressure). That is why "air springs" are springy.