Arco by goat story - Page 7

Grinders are one of the keys to exceptional espresso. Discuss them here.
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#61: Post by HB »

PeterTheGoat, please review Vendor participation in the forums before posting again; it says:
...if you or the company you work for sells the product/service being discussed in a thread, you are welcome to correct factual errors, but should avoid posting opinions, product/service offerings, or critiques of competitive products.
I've edited out the parts of your post above that raised comparisons between your product and competitors'. Thanks for your understanding.
Dan Kehn


#62: Post by PeterTheGoat »

Thank you for correcting me, HB.

I was not aware of the policy, the post was not meant as a critique of anything but as an engineers' comparison of different systems of burr adjustment (with some examples that I will refrain from in the future now that I know the rules.

I am not a marketing guy and don't really care that much about the sales numbers or advertising. Just your honest engineer and coffee enthusiast over here (in that order).
I was NOT sent here by my boss or anything like that.

I hope there isn't any bad blood.



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#63: Post by renatoa »

PeterTheGoat wrote:Hey guys!

Logged on the forums today and found this debate about the clicks.
We are obviously going with 60 clicks per rotation x 3 rotations.

I don't really understand why some of you think that adjustments would be slower or more tedious with more clicks.
You don't have to count the clicks from zero on the Arco. You just have to remember or write down the number for a certain coffee and go straight to that number and you always end up at the exact same setting as you wrote down.
It takes about 2 seconds to adjust Arco to a grind setting that you wrote down/remembered.

Can someone elaborate on what kind of adjustment would be better? Also; I mostly drink pour over. You can rest assured I made sure that the espresso capability does not compromise on the pour over grind performance.
You are right and I think the main difference of Arco versus the other grinders having a multi-turn setting system is that with Arco you always know, with a quick look, which turn you are. For the others I used so far you can see only the value setting inside the current turn, but you don't know if you are in the 2 turns range, for espresso, or in the 3-4 turns range, for brew. So people needs to reset the grinder, turning until burr lock, then start counting.
When this happens two times per day, become annoying...
With Arco this issue is gone, you know always which turn you are, and straight proceed with rotating the ring to the desired setting.
Is a feature still not valued enough because didn't exist so far.


#64: Post by Jonk »

Peter, perhaps you could provide us with a close up of the actual production burr? So there's no more need for speculation.

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#65: Post by CarefreeBuzzBuzz »

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#66: Post by renatoa »

Jonk wrote:Peter, perhaps you could provide us with a close up of the actual production burr? So there's no more need for speculation.
The burr picture in the post #52, previous page, is from Goat site, so assumed it is at least from an Arco prototype.


#67: Post by malling » replying to renatoa »

A bit useless when they don't provide the date of above 1000um

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#68: Post by LObin »

I just backed the Arco Kickstarted campaign. It's a clever idea and a neat design.

A few thoughts:

I do wish they eventually offer different burrs for different brewing methods.

Smaller pitch would be neat although it might end up being overkill...

I'm hoping Goat Story will offer the same kind of after sale support successful companies like Niche, option-o or Decent offer.

My only concern, and one that I don't believe has been talked about, is the performance of the motor when grinding lightly roasted, dense beans.

Hoping the futur 110v motor noise pitch and DB are easy on the ears...

Time will tell!

Needless to say,
I'm quite pumped!
LMWDP #592


#69: Post by LObin »

180 more grind settings: Done!

LMWDP #592


#70: Post by renatoa » replying to LObin »

Ok, I see they go forward with this ludicrous claim and goal, so it's time to demolish these false claims.
Beware, the following are not guesses, but simple math and logic.

If this 3 microns per click would be true, then this means that the whole range of particle size able to be dialed will be 3 * 180 = 540 microns.
This is simply not enough for a grinder to be capable to switch from espresso to brew. You need at least 800 microns range, from 200 to 1000, for this goal.
This is the first fact.

Now the second, that demonstrate the 6 microns claim wasn't true, thus even more the 3 microns claim.
Measured the burr cone and it's slope is 73 degrees at base, so 17 degrees ar top.
Sin(17 deg) = 0.3, so the real particle resolution is 1 mm (per turn) / 30 clicks (for the first version, exhibited in the video) * 0.3 = 9.7 microns (roughly 10)
So 10 microns was the real particle resolution of the first version Arco, and the grind range was 4 turns * 30 clicks * 10 microns = 1200 microns, more than satisfying to cover the whole range from turkish to french press !
Now for the v2 it is worse, available particle size range is smaller, because some people requested more useless resolution, without thinking to side effects !
The new particle resolution is 5 microns, half of V1.
Multiplied with 180 clicks means 900 microns particle size range, only partially covering the brew scope, if the zero setting means burrs lock, thus starting zero particle size.
If the zero setting is shifted from the burrs lock position, let's say starting from 200 microns, we can hope to a more decent range, from 200 to 1100, but still not covering both ends as well as the V1.

So, the Goat / Peter, if you listen here, please reconsider your decisions, they aren't right for the goal to have the one grinder to rule the other all !
If you insist to maintain the 60 click per turn, ok, but adding back the fourth turn is mandatory, for more range in the brew.
If I were the designer, I would go with 50 clicks per turn, and 4 turns, meaning 6 microns resolution and 1200 microns range.
50, because we live in a decimal world, and to match other grinders divisions count, and 4 turns to keep unchanged the V1 particle range.

Ok, let's assume I am wrong and I don't have all the data about the real burr they are using, and the resolution is indeed 3/6 microns as their claim. This is even worse ! The particle range will be even more stretched, making the grinder optimal for only one job, either espresso, either burr... do you really want this ludicrous resolution, that is comparable with bearings play, or more range to dial ?
A last note, the burrs required for a 3/6 microns particle resolution should have, according to basic geometry, 80 degrees slope:
sin (10 deg) = 0.17 = 1mm / 30 clicks / 6 microns
So almost cylindrical. Definitely not a typical Italmill burr !