Bosco group: double vs single spring version [video] - Page 2

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Whale

Postby Whale » Dec 08, 2017, 6:02 pm

TX, I had never seen that one.

Back on topic.

I do not understand why, if all parameters are the same except for the peak pressure, the pour would occur in the same time duration?
I understand that the yield will be the same since the coffee puck has the same composition and same saturation. The volume output will be the same as it is driven by the cylinder volume.
With a higher pressure there should be a higher flow through the puck (same composition and same saturation) that has the same resistance. Unless the pressure on the puck actually increases the resistance?
LMWDP #330

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chappcc

Postby chappcc » Dec 08, 2017, 8:39 pm

Whale wrote: Unless the pressure on the puck actually increases the resistance?


As an example, the difference between 8 and 10 bar is 29 psi.
If you are tamping a 58mm diameter puck with 30 pounds, you are only generating 7.33 psi on the dry puck.
The additional 29 psi of the water column should increase puck density / resistance.

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naked-portafilter
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Postby naked-portafilter » Dec 09, 2017, 11:49 am

Whale wrote:TX, I had never seen that one.
I do not understand why, if all parameters are the same except for the peak pressure, the pour would occur in the same time duration?


If you have a proper prepared coffee puck and you push stronger on the lever (manual) your flow will stay the same more or less (above a specific pressure of course). If the grind isn't fine enough you can play with the flow of "coarse" :-).

espressotime

Postby espressotime » Dec 28, 2017, 11:33 am

TomC wrote:Nice work! I pulled the second spring out of my LSM group long ago and never looked back.


Did that on my Pompei and put it back in real fast.
Didn' t like it.
Espresso tasted softer as if mixed with water.
Not to my liking.

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JohnB.

Postby JohnB. » replying to espressotime » Dec 28, 2017, 2:22 pm

If it's like the Pro 800 dual spring set up removing the inner spring leaves you with a spring that peaks at 7 bar. The single spring versions of the same group used on the Pro 800 use a spring that peaks at 8 bar. If someone wants to convert a dual spring group to single spring they should source the correct spring.
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naked-portafilter
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Postby naked-portafilter » Dec 29, 2017, 2:03 am

espressotime wrote:Did that on my Pompei and put it back in real fast.
Didn' t like it.
Espresso tasted softer as if mixed with water.
Not to my liking.


This is another proof for me:

1. that this discussion about the dual and single spring groups is partly a discussion about taste

2. You can not directly compare a single spring lever with 3bar pre-infusion with a double spring model with boiler pressure pre-infusion without knowing how they really work. With given setting parameters single and dual spring groups could deliver the same or at least very similar pressure profile.