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 ...