I missed the part about it being brand new. Hopefully Flair will treat you well.

This effect is present since Flair classic. Actually, with original plastic 1 seal piston it wasn't causing problems (to me at least), because there was no second seal, so the piston was freely slanting to the side. Things got worse with introduction of 2 seal piston, in order to keep it upright (Gabor's piston also exhibited same problems) - considerably higher force for the same pressure and less smooth operation (as was evident from measurements and actually even admitted by constructor of Flair). Most problematic it was on Pro 2, due to some other constructional changes, that was even resulting in spectacular dismantling of the group mid shot for some users. So I was glad to see that the new mechanism was finally introduced on Pro 58, things got considerably better, but it obviously isn't perfect yet

Problem is that force from the lever to the piston is not vertical, but the angle is slightly changing as you move the lever. And that force is 8-9 times higher than the force applied to the lever. So its horizontal component is also quite high. It is acting to the piston on the point several centimeters above the piston, causing it to slant to one or other side. As result of that, we have significant horizontal force to one direction to bottom seal and to opposite direction to top seal (assuming there is no piston to cylinder contact which may also happen in some combinations of device and piston type), preventing the piston to actually slant and as result of friction, we have some braking effect which is reducing force from the piston to the water. When the piston slants to the other side at 0:57, these forces change, resulting in change of pressure for the same force on the lever

However, due to new linkage element introduced with 58 and way how it is attached to the piston, these horizontal forces are considerably lower than on older models (where it was up to something like 300 N due to friction between the roller and top of the piston - according to my approximate measurements and calculation), but still isn't zero

On Flair classic, original piston just slants to one or other side, adjusting to applied force - doesn't look nice, but it's smooth as it usually doesn't slant that much so the plastics would come in contact with the metal (that limit is 2-3 degrees). On later versions, some things were improved, some were made even worse, some of them corrected again, some not that much, new problems introduced with every version ... just the price trend is constant ...

Some ball bearings there would be fine as I mentioned in one post a few years ago ... it's one of several flaws in Flair ... but nothing is flawless and there is always some cost optimization for desired selling price


Just my 0.02

Is there anything we could do as a user to prevent this?

Well, I have only Flair classic, so this is a kind of guesswork

Anyway, I checked the approximate dimensions of the piston from the pictures in Flair 58 manual and estimated missing data from my Flair classic stand geometry that is generally similar, just smaller. It turns out that horizontal force on the anchoring point on top of the piston for 9 bar at moment "0:57" (where it is about maximal) is around 10 kg (100 N) towards the stand - plus or minus, which results in horizontal force in opposite direction at the point of upper seal around 26 kg and force towards the stand at the point of lower seal around 16 kg - which is considerably more than I thought although considerably less than in Flair classic. And this is without taking friction into account - actual values are even higher. So it's understandable why is this

Now, as visible from the manual and also noted in above mentioned answer, upper seal is considerably smaller (unlike in flair classic metal piston), although it is taking higher force than lower seal. From the video it looks like there is a metal to metal contact at 0:57 - there is audible metal click, so upper seal might be actually too small; it looks like bigger/stronger upper seal is needed

As a temporary solution / check - you may try removing upper seal, put a narrow piece of some kind of duct tape around the bottom of grove in the piston and fit the seal back - so that its outer diameter is increased by fraction of millimeter by duct tape below it - to see does it change anything (avoid metal to metal contact if it is indeed present / reduce slanting to that side)

DISCLAIMER: I hope that I didn't make some mistake in calculation - I'm indeed a mechanical engineer, but my school times were long ago, but constructor should check this ...

ab wrote:Is there anything we could do as a user to prevent this?

After watching that video clip numerous times I would look at the following:

1) Any binding, wear or lack of smoothness in between the linkage arm and pressure valve assembly (red arrow)
2) Any binding, wear or lack of smoothness where the pressure valve assembly meets the piston. Or any defect in the o-ring on the end of the pressure valve assembly (yellow arrow).
3) Also ensure all o-rings are lubricated with a food safe product.

After about a year of use, I have never experienced this abrubt shift of the pressure valve assembly into the piston body that I see in the video. It is quite smooth on my F58 and the overall articulation is much less than on my Pro2. I generally agree with Flair's response to the OP, but not the abrupt shift, and definitely not the pressure loss during the shot. I cannot help but think these are workmanship issues versus fundamental design flaws, but then I only have my F58 to compare too. YMMV.

ab wrote:That's a disappointing response from Flair. Another reason why I'm interesting in the Meticulous.

This does seem like a design flaw. :/

Have owned and used 5 different machines since '81. F58 is far from "perfect". Not too sure about the overall customer service and marketing. Like shipping units with straight portafilter handles vs. the needed downward slanting. Not providing the "key" to those of us who purchased a F58 before it became available and hopefully included to all new buyers. Both easy "defects" to work around.

Might be more of a "defect" than design flaw. There are a few of us. Maybe hundreds, thousands of us that pulled hundreds to thousands of shots with the F58 without issues. F58 is a simple more or less mechanical machine. Relatively inexpensive, easy to maintain, and easy to pull a decent shot. The Meticulous. Yet unproven. Maybe with time for those who want or need a sensor loaded, full feature, no boiler ..... machine it will set a new "standard". Personally wouldn't touch a machine without easily sourced parts and easy diy maintenance and repair. Couple reasons content with the '03 MCal and F58.

Let's call it imperfection instead of design flaw, which in case of slightly different tolerances of its parts in combination of way of using it can lead or not to this issue

It's very similar imperfection like on old analog turntables, where the cartridge was precisely aligned with groves on the plate on only 2 positions, while elsewhere it was slightly misaligned, and most owners probably never heard of that ... The same here - linkage element between the lever and the piston is exactly vertical in only 2 positions of the lever, where horizontal forces to piston and seals are zero (assuming no friction in joints which isn't exactly true). It's not the only machine made that way. For instance, it looks like on Strietman, linkage element is never actually vertical. Just that - constructors had that in mind and placed anchoring point within the piston - unlike here, where it is well above it, and the distance between upper and lower seal is considerably higher than here - which makes a difference ...

Probably this will be improved in some further modification in this never ending Flair story ... and some new imperfections introduced ...

Another way to make this imperfection less of an issue (besides playing with thickness of the upper seal) would be slightly modifying the angle of the brewhead base - if it is possible like on Flair classic, by inserting some thin shims - that's what I did to make piston slanting about the same angle to both sides during the pull (misalignment was causing cracking of the piston plastics by the roller for some users, before top of the piston was modified to avoid this problem, which was another imperfection ... but piston of my machine was first version)

One thing I find interesting is both of you without the issue seem to have the Flair58 that doesn't have the new locking mechanism. I have that version as does OP.

I am very amazed and grateful for the amount of effort and detail you guys put into your answers! I re-read all of them.

vit, if I don't get any resolution from Flair/merchant, I will try thickening the upper seal on the piston and also shimming the brewhead. Would you put a shim at 6 o'clock (so that the brewhead is slanted towards the back of the machine) or at 12 o'clock (so that the brewhead is slanted towards the user)?

Brewzologist, I had previously lubricated all three o-rings (the one on the pressure valve and the two on the piston) with Haynes LubriFilm. I also lubricated the linkage hook and the stem on top of the pressure valve but that did not give any results - in fact when I took them out to lube I noticed sign of visible wear on the pressure valve stem (where it would come in contact with the linkage system) and call me crazy but I'm pretty sure it also feels slightly flatter on the "worn" part when I run my finger around the stem (around the reachable part at least). I will post a picture tomorrow during daylight since at night there is too much glare on the metal from the lamps and it is not well visible.

To ab's point - I still have some suspicion that all this might be due to the black guider thing being pushed by the inner wall of the brew chamber and that event providing a more abrupt "swing" of the pressure valve. The previous linkage system has that black piece detachable and on most of the videos, the piece is not there.

I am still back and forth with Flair and will see if merchant can offer me any resolution tomorrow. Meanwhile this is Flair's second and latest answer to me after expressing my disappointment that this seem to be an issue only on my and a few other units despite their claim it is "part of the normal working cycle":

Hi Vladimir,
Yeah can only judge from your video but everything is looking good. I can send a video from the two units I have here over the weekend or on Monday to ease your mind. Do be advised that by nature of the system, particularly through this inflection point, the leverage ration does change somewhat, but this is something that you get a feel for with use, and will be pulling perfectly smooth pressure shots in no time. More once I have that video for you-

Yes, I forgot there was a modification in piston mechanism and that may explain the whole difference as you said. That clicking sound may indeed also come from the joint between plunger and piston (there is also another seal there). If there is some free play there and it actually moves (hard to say from the video), it makes horizontal forces even somewhat higher. In that case I would first check is that free play outside reasonable tolerances and ask the seller what to do with it. Next step would be trying changing the angle of the brewhead base and last one playing with upper seal of the piston

As I understand this, in the middle of the pull - when both joint between lever and the stand and between lever and linkage element are at the same height - linkage element is most slanted with upper joint towards the user and goal should be to reduce angle between it and axis of the cylinder in that position by slightly slanting the base and thus cylinder - by lowering its end which is towards the user by something like a millimeter or so (if this is actually possible on Flair 58). It should reduce horizontal forces that try to rotate the plunger and piston and produce braking force. This will however increase the angle of the linkage element to the other side at the beginning and end of the pull (you can actually see the plunger being slanted slightly outwards first - at 0:40) - but force at the beginning of the pull / preinfusion phase is low and you can decrease it towards end of the pull as well (many actually do that to prevent overextraction), so this should be less of an issue and should improve overall "pulling experience"

As I said, many improvements actually introduce new problems ...