The Alicorn: Achieving Precision Alignment with the Baratza Forté/Vario - Page 3

Grinders are one of the keys to exceptional espresso. Discuss them here.
pcrussell50 (original poster)

#21: Post by pcrussell50 (original poster) »

Disclaimer, I have not done this (yet) myself...

I think what Jake is saying is something philosophically similar to this:

The way you center and align a bicycle disc brake caliper is to loosen it's mounting bolts, then clamp down in the brake lever. The caliper pistons will grip and center the caliper on the rotor. Then, while still gripping the lever, you tighten the caliper mounting bolts. Voila, centered caliper.

I think what Jake is saying is that by running the levers to full tight, with chamber screws loose, you will center one with respect to the other. Then while holding the levers at full tight, tighten your chamber screws... Or something.

If that doesn't make sense, we will have to defer to Jake. :)

-Peter
LMWDP #553

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Jake_G
Team HB

#22: Post by Jake_G »

That's pretty much the process in a nutshell.

In the case of the Forté/Vario, the lower burr carrier spins like a top with a shaft extending from beneath it. This shaft is supported by two bearings, one in the grind chamber, the other in the lower motor plate, to which the grind chamber and motor are both mounted. The drive sprocket is mounted between these bearings and the levers indirectly raise and lower the burr carrier by way of a moving (macro lever) and rotating (micro lever) cam that acts on an adjustment plate with an adjustable pivot point (calibration screw). The mounting holes that are used to secure the grind chamber to the motor plate have A LOT of slop in them. With the mounting screws loose, you can move the grind chamber several millimeters in any direction, causing the lower burr carrier to tilt in all manner or directions as you slide the grind chamber around on the motor plate. Somewhere in the midst of the slop is that sweet spot where the lower burr is perfectly aligned to the upper.

Finding the sweet spot could be quite tricky trying to use instruments to locate it, and then you're still left trying to align your upper burr to match the lower when you're done. Instead, I followed Peter's process and just let the upward pressure of the adjustment levers help the ground chamber find the spot where it needed to be to let the lower burr lie flat against the upper. Once you're there, it's just a matter of correcting any manufacturing errors in the burr carrier faces and in the Forté i worked on, these were basically non-existent. Once you have even contact on both burrs, then it's just a matter of securing them tightly without experiencing TBS. I am not a fan of leaving the screws loose and relying on Loctite, as this can lead to broken screws, stripped out threads and many other issues. Honestly, I feel like the Ditting burrs should be shipped with mounting spacers for this application as they were designed for a stepped carrier.

I with I had a nice computerized animation to show the process, but it is really as simple as Peter describes. Loosen screws, raise levers, tighten screws.

Cheers!

- Jake
LMWDP #704

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bytheway

#23: Post by bytheway »

Hi Jake,

I have a few questions if you would be so kind:

1. Does "gently tighten the grind chamber mounting screws in a crisscross pattern" mean just tightening a bit each time to ensure even tightness?
2. "I followed Peter's process and just let the upward pressure of the adjustment levers help the ground chamber find the spot where it needed to be to let the lower burr lie flat against the upper. Once you're there, it's just a matter of correcting any manufacturing errors in the burr carrier faces": do you do this with the stationary upper burr screwed in? ie you open the whole grinder up and work from the bottom? Also, in terms of manufacturing errors are you talking about runout on the burr carrier faces that would need correction on a lathe or as an inferior solution shims?
3. "drive pulley on the grinder I had the pleasure of getting to know was completely lopsided on the drive shaft. Correcting this required pressing a sleeve onto the motor shaft (it has a twisted star profile for inexplicable reasons...) and chucking the motor into a lathe to true up the motor shaft": this is where I'm completely lost...what kind of tradesperson could do this do you think?
Thanks! Ben

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Jake_G
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#24: Post by Jake_G »

bytheway wrote: 1. Does "gently tighten the grind chamber mounting screws in a crisscross pattern" mean just tightening a bit each time to ensure even tightness?
Yep!
bytheway wrote:do you do this with the stationary upper burr screwed in? ie you open the whole grinder up and work from the bottom? Also, in terms of manufacturing errors are you talking about runout on the burr carrier faces that would need correction on a lathe or as an inferior solution shims?
Yes, top burr screwed in, but NO SHIMS and just tighten the screws enough that the burrs don't wiggle. You don't wat to Taco the burrs when you do this. Lathe is always better than shims. I measured the run out on the lower burr carrier and got less than 5 microns. So I would be surprised if yours was way out of line.
bytheway wrote:this is where I'm completely lost...what kind of tradesperson could do this do you think?
When I spun the motor shaft, the pulley wobbled BADLY on the shaft. I had to fix this because the belt tension serves to hold the lower burr carrier in place within the clearances of the upper and lower plain bearings (bushings). A wobbly drive pulley means the belt tension is constantly pulsing, which means the burr carrier has the potential to rock back and forth as the belt goes tight and slack. Not good. It helps to have a friend with a lathe (FWAL) to take care of such things :mrgreen:

If your pulley spins true then you are good to go!

Cheers

- Jake
LMWDP #704

bytheway

#25: Post by bytheway »

Thanks

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Jake_G
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#26: Post by Jake_G »

I thought I should post this video as I've had some offline conversations regarding the Alicorn and I want to make sure folks understand what I did, why I did it and how to do this without hurting your beloved grinder...
Please read the description if you are interested in trying this method of alignment and realize that it is best executed by removing the grinder assembly from the grinder case. It's not hard, but not for the faint of heart, either.

You don't want to lock the the levers in place when doing this, which means getting the detent springs and pins out of play, which means separating the grind components from the case. Then you have literally just the motor, motor plate and grind chamber in your hands and the alignment becomes very simple to to do. I wouldn't imagine trying to due this with the grinder assembled as too much would be in the way and you risk hurting something jamming the levers all the way up. With everything out, you can feel in the levers as the burrs touch and just apply gentle pressure to square everything up. Likewise, you can easily access the four screws once the assembly is removed from the grinder case.

Cheers!

- Jake
LMWDP #704

baldheadracing
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#27: Post by baldheadracing »

So I tried this tonight. I improved the alignment, but I only did the process once. I am wondering whether repeating the process might improve things? ETA: nope, although I am wondering if removing the drive belt might work better ...

My Vario is calibrated so the burrs are just touching at 2(macro) and Q(micro). There was little contact at 2Q; only about 15% of the burr diameter was wiped clean: (The violet mark indicates the front of the grinder.)


After going through the process, there is much more contact; maybe 40% of the burr diameter:


This is 10 micro-steps finer, 2G, which I have used for Turkish. Before alignment:


After alignment, there is almost 100% coverage at 2G. I didn't try other settings.

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Jake_G
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#28: Post by Jake_G »

Nice work Craig,

It would seem from the pattern that the belt tension may have interfered with getting the burrs perfectly aligned. Is it particularly tight?

I would suggest easing up a bit on the belt tension and trying again. When you apply pressure with the levers, I lowered the micro lever and brought the burrs into contact with the macro, then used the micro lever to apply more pressure and gently bounce the burrs to settle them by rocking the micro lever up and down. While doing this, I checked to ensure the belt wasn't overly tight. It's tough because you need to have representative tension acting on the burr carrier when you align it using this method to ensure the carrier is loaded against the bearings lest the belt tension pull the carrier out of alignment when applied after alignment. However, too much tension simply won't allow the burrs to become parallel in the first place.

That's a wordy way if saying "check the belt tension while the grind chamber bolts are loose".

Cheers!

- Jake
LMWDP #704

baldheadracing
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#29: Post by baldheadracing »

So that was an alignment-filled afternoon ... and less tension, and no tension, made no difference.

Eventually I got frustrated and took the whole grinder apart and cleaned everything with ultrasound. That's when I discovered that my burrs aren't flat - when I put the burrs together, there was a tiny bit of light visible in some places between the burrs. (My steel burrs are quite old and well-used.)

After cleaning, I re-did the Alicorn procedure. Then I tried the three different positions for the top burr - that improved things a bit. (I have a Forte upper burr carrier so there are only three possibilities. There are nine with the Vario burr carrier; I remember doing that!)Then I tried the three positions of the bottom burr - that also improved things a bit. Then I re-did the Alicorn procedure, and that improved things a tiny bit. Then I broke out the foil and fiddled a bit with the upper burr carrier, which made the most improvement. I didn't try too many foil thicknesses because I knew that I couldn't get 100% contact.

At that point I really needed an espresso. Helpful hint: the Vario (and I assume Forte) motor is happy to run in either direction. If one disconnects the motor wires at the motor, mark the bottom of the motor. Marking the sides just rubs off. Grinding with the motor running in the reverse direction will work, but doesn't grind at all :oops: .

Unfortunately, when I took the grinder fully apart, I lost the calibration and so comparison photos aren't possible. What I can say is that before all these efforts, I was grinding for espresso at the touch point - 2Q - and was getting about a 1:5 brew ratio. Now the touch point is 1M, and grinding at 2Q gives me a 1:3 brew ratio. Ergo, improvement! Thanks for all your help! 8)

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Jake_G
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#30: Post by Jake_G »

I should have prefaced that since the Alicorn method aligns the burr carriers, it can do nothing to correct for uneven burrs. The good news is that by aligning the carriers you should be confident that you require the absolute minimum amount of shims beneath your burrs.

It is easy to get your zero point back to 2Q unless you are saying you lost the coarse calibration setting, as well. That is more tricky to adjust but it is detailed in the manual and seems intuitive. Also worth noting is that Baratza recommends grinding at 2K for espresso with the Ditting burrs when calibrated at 2Q for zero, so getting an espresso pour when you have clearance between the burrs is a noteworthy achievement! Thank you for taking the time to share and document your process. I'll be doing this to a vario in a bit and with the owner's (private) permission will do a full pictorial walkthrough from beginning to end.

Cheers!

- Jake
LMWDP #704