Flair Classic Force vs Brew Pressure

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ray10110

Postby ray10110 » Mar 14, 2019, 12:59 pm

I was curious about force on the lever and how it equated to actual brew pressure on my Flair Classic. Using a Flair Pressure Gauge Kit and a bathroom scale I came up with these numbers. I only made two runs and the results were fairly consistent. I had been brewing coffee for some time with the Flair and I was surprised as to how much force was needed to achieve a pull in the 6 to 9 bar range. The results were:
• 5 BAR - 22.2 lb
• 6 BAR - 26.4 lb
• 7 BAR - 29.8 lb
• 8 BAR - 33.8 lb
• 9 BAR - 38.5 lb
Image
At 10 BAR the scale went above 40 lb. The gauge clearly indicates danger above 10 BAR. Danger being the possibility of a broken machine. A plot of the data shows that there is a linear relationship between force and brew pressure. The Flair "Brew Guide" recommends an average of 30 to 40 lb of force be maintained for the entire brew period. Even so, I've had some pretty good pulls in the 6 BAR range.

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another_jim
Team HB

Postby another_jim » Mar 14, 2019, 1:04 pm

Interesting. The Flair develops regular brew pressures at reasonable forces; but it requires a coarser grind than most other levers (or an underdose). That must be due to the cartridge/basket geometry rather than the brew pressure.
Jim Schulman

vit

Postby vit » Mar 14, 2019, 3:56 pm

ray10110 wrote:I was curious about force on the lever and how it equated to actual brew pressure on my Flair Classic. Using a Flair Pressure Gauge Kit and a bathroom scale I came up with these numbers. I only made two runs and the results were fairly consistent. I had been brewing coffee for some time with the Flair and I was surprised as to how much force was needed to achieve a pull in the 6 to 9 bar range. The results were:
• 5 BAR - 22.2 lb
• 6 BAR - 26.4 lb
• 7 BAR - 29.8 lb
• 8 BAR - 33.8 lb
• 9 BAR - 38.5 lb

At 10 BAR the scale went above 40 lb. The gauge clearly indicates danger above 10 BAR. Danger being the possibility of a broken machine. A plot of the data shows that there is a linear relationship between force and brew pressure. The Flair "Brew Guide" recommends an average of 30 to 40 lb of force be maintained for the entire brew period. Even so, I've had some pretty good pulls in the 6 BAR range.


Thanks. It is about 10% higher than extrapolation of my measurements with original piston, so let's say it's within tolerances of measuring devices. I usually use 14-16kg force (which is 8-9 bar according to my measurements). Result also depends on the position of the lever (higher force required under and above horizontal) and alignment of the cylinder and resulting friction between piston and cylinder due to force from the roller not being coaxial with piston (as a result of quite high friction in roller itself according to my other measurements, as there is no bearing in it). Lubing the roller axle with silicon grease helped to an extent to avoid a bit excessive piston slanting forward or backward, which resulted with very unpleasant effects on the Flair Pro reported by one of our members and recall 2-3 months ago ...

As about the grind, with lightest roast I got, I was using finest grind possible with Lido 3 which is close to turkish, dose 9-10g and about half minute preinfusion at 2-3 bar. I wouldn't say that it is underdosing, as the puck dimensions of that dose are similar to the one in LM single basket, it's just that people are usually overdosing it ...

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another_jim
Team HB

Postby another_jim » Mar 14, 2019, 4:23 pm

vit wrote: ... I wouldn't say that it is underdosing ... it's just that people are usually overdosing it ...


:D Man after my own heart
Jim Schulman

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Randy G.

Postby Randy G. » Mar 14, 2019, 5:58 pm

In my revierw of the Flair posted in 9/2017, I wrote, "Lets try some math to estimate the brewing pressure (keeping in mind I was an art major). The mechanical advantage of the lever is about 10, if a force of about 35 pounds is applied to the lever by hand, and the area of the piston's force is about 2.4 sq.in., the estimated maximum pressure below the piston's face would be about 130psi, or about 9BAR, the generally recommended pressure for brewing espresso. As I had stated, a lot of thought has gone into the design of the Flair. Yes, this is a real espresso maker!"
Espresso! My Espresso!
http://www.EspressoMyEspresso.com

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Denis

Postby Denis » Mar 14, 2019, 6:06 pm

Can the basket be drilled/changed?

I want to grind finer because on my regular machine (30-40sec preinfusion at 0 bar) I grind at 1.9 and on the Flair even with low dose (11-12g) I grind at 3.4.

Need to change basket or do something with it (had it for 2 weeks).

vit

Postby vit » Mar 14, 2019, 6:53 pm

Randy G. wrote:As I had stated, a lot of thought has gone into the design of the Flair. Yes, this is a real espresso maker!"



Well, piston diameter is quite similar to LaPavoni, so is the lever ratio (actually hard do achieve more that 1:9 on Flair) - nothing really new, except that here we don't have additional push by the steam. However, pro model has somewhat increased diameter, so higher force needed for the same pressure ...

happycat

Postby happycat » Mar 14, 2019, 8:55 pm

Denis wrote:Can the basket be drilled/changed?

I want to grind finer because on my regular machine (30-40sec preinfusion at 0 bar) I grind at 1.9 and on the Flair even with low dose (11-12g) I grind at 3.4.

Need to change basket or do something with it (had it for 2 weeks).


You can put a circle of filter paper at the bottom of your portafilter and grind as fine as you like... but you may need a long preinfusion first so you don't break the lever joint.
LMWDP #603

samuellaw178
Team HB

Postby samuellaw178 » Mar 14, 2019, 10:10 pm

Denis wrote:I want to grind finer because on my regular machine (30-40sec preinfusion at 0 bar) I grind at 1.9 and on the Flair even with low dose (11-12g) I grind at 3.4.


To use the same grind as your regular machine, you will need to use a bigger diameter basket (if you want to keep the 11-12g dose). Otherwise, use an even lower dose.

Assuming you are using 18 g coffee in your regular machine, that 18 g dose in 58 mm basket is equivalent to ~8.5 g dose in 40 mm basket on the Flair (to get the same puck thickness and thus similar flow resistance).

Conversely, with 11-12 g in the Flair, it is equivalent to dosing ~25 g coffee in your 58 mm basket. :P