Three Mod Night, or "Taming a Titan" (Macap M7K) - Page 2

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

#11: Post by Anvan (original poster) »

Agreed, Mitch, and thanks. Yours is one of the in-depth threads on this topic that provides really useful information, plus, of course, arguments (it is an H-B thread after all) for more sides of the picture than I previously knew existed. I learned a lot from it and the others.

These discussions (regarding the effects of pop-corning, columns, weights and so forth) needed no assistance from me to continue - having already quite a life of their own - and frankly I felt unequal to the task of contributing anything meaningful to the expertise already in print. So this current thread was just about one way of modifying this one product within the context of single dosing - as opposed to replicating the arguments for or against that practice.

From your and the other discussions, however, I did come away with a few settled beliefs:
  • First, it's likely that whatever consistency is actually achievable (given the uncontrollable day-to-day age, humidity etc. variations) will take place with consistent weight.
  • Second, the ideal weight to use is the coffee beans themselves since only they can seamlessly compose both the weight and the material. Only the beans are capable of controlling pop-corning all the way into and within the burrs.
  • Third, people using columns for this task are pretty satisfied overall, and that likely stems from the gravitational pressure vectors in a column closely approximating those in a stock hopper filled to the same level. (This would also explain the preference for lighter weights upon such a replacement column, since we are trying to replicate just the weight of the column above the burrs, not that of the entire hopper contents.)
  • Fourth - and I realize I'm more out on a limb here - burrs turning slowly at fewer RPM will cause fewer pop-corning inconsistencies. I believe I recall others commenting to that effect, but also (as an admitted thought experiment) mentally reduce the RPM to near the stopping point (similar to a hand grinder turned very slowly) and picture the reduction of pop-corning in that circumstance to the vanishing point. As a corollary, a conical burr set may also "auger" the beans into and through the finer teeth with more certainty, further limiting the incidence of pop-corning. "Proof" of these influences may be hard to come by, but perhaps not so, just being "convinced."
So given this model it makes perfect sense that an inch or two of beans in a column with a weight to add relative consistency would work pretty well. For this project's rules of engagement however, the single-dosing requirement pre-empts the inch-of-beans strategy, and instead I needed to rely on a plunger/weight that would get right down to the burrs to handle most of the shot, then rely upon the slow conical design to mitigate the negative effects of pop-corning for the last few beans in the dose.

Of course that's an admitted compromise: I harbor no illusions that the result is exactly as it would be with a consistent column or hopper of actual coffee beans (see second point above). But I do believe any damage to taste in the cup has been reduced to practical insignificance, and is regardless overwhelmed by the advantage (to me anyway) of freely changing coffees shot-to-shot with zero waste.

Anvan (original poster)

#12: Post by Anvan (original poster) »

Bluecold wrote:That's not just rpms but mostly chute design. The chute of my Faema is more tangential than radial so grounds really fly out. Even at 300rpm, the tips of 8cm long vanes go roughly 7.5m/s or 27 kilometers per hour.
That's a huge factor - thanks for pointing that out. Checking the M7K, it appears to be the opposite of your Faema: the center line of the chute passes right through the burr/sweeper axis, so most of the tangential rays from the sweeper strike the left wall of the chute and sort of tumble out, instead of flying.

I'm guessing that the grinders with the least clumping are effectively using the ejection geometry to achieve that end with a nice broadcast into the hopper or chute, not unlike a really good and even rotary seed spreader for example.

Anvan (original poster)

#13: Post by Anvan (original poster) »

I've done some measurements and testing regarding replacing large hoppers with a cylinder/weight such as this, and posted them in a new thread, Replacing Titan Hoppers - Replicating Bean Weight and Behavior. As a part of this project, Danetrainer (Pat Campbell), who uses the same grinder, was a great advisor and huge help discussing these concepts.

Pat also created new weights/plungers out of a higher UHMW polyethylene rod, and used his considerable machinist skills to mill them down to perfectly fit the inside diameter of the cylinder. These new weights work much better than the original "banded" weight photo'd above - a major improvement and much nicer to use day-to-day.

I'm finding that for single dosing, I can just use the funnel base with the 1" insert, toss in the beans and top them with the short 3" weight. For grinding multiple doses, I can use one of the longer cylinders with a larger weight - not because the extra weight appears to be important to the quality of the grind, but this makes the weight easy to retrieve from the tall cylinder when the grinding is done.

As an added benefit, the fit of the new plungers is precise enough that the burst of air from a reasonably quick plunge of the weight in the cylinder will blow out and clear the grind path.

All in all, this has provided tremendous grinding consistency dose-to-dose, and I can fully endorse the M7K as a Titan that's easily modifiable and provides great usability and consistent results in single-dosing use.

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Team HB

#14: Post by TomC »

"As an added benefit, the fit of the new plungers is precise enough that the burst of air from a reasonably quick plunge of the weight in the cylinder will blow out and clear the grind path."

^ This part is way cool too. Less stale grinds hanging around.

Interesting to think, a titan level grinder, actually capable of single dosing at home. Hope to read more evaluations on this. Do you have any plans to have more made up to sell to others with this grinder?

Anvan (original poster)

#15: Post by Anvan (original poster) »

Interesting to think, a titan level grinder, actually capable of single dosing at home. Hope to read more evaluations on this. Do you have any plans to have more made up to sell to others with this grinder?
I think there are a couple other Titans - such as the Versalab - that others have praised for this application. I liked how the big Macap was so adaptable, but other grinders may work equally well.

As for the manufacturing business, I wanted to write down the process so people would be encouraged for DIY projects with their own personalized tweaks and preferences. So you're kind to ask, but I'd best leave production to others!

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Team HB

#16: Post by TomC »

I excluded the Versalab, since there appears to be some consistency issues and belt wear over time. Terranova's amazing modifications could make it the best Titan in the market though.

Anvan (original poster)

#17: Post by Anvan (original poster) »

I've added a couple photos here to show the mechanism that minimizes the amount of free-wheeling beans in the burrs at the end of a single-dose grind. The plunger weight has a bottom recess that fits over the burr bolt which enables the plunger to get all the way down to the top ledge of the outer burrs. With a typical 15g-20g single dose, ~10% or less is ground without any weight/damping (to the best of my ability to measure this).

The second picture shows the addition of a soft vinyl dome to the recessed Allen-wrench well (compare with the similar photo on the previous page of this thread without the red dome). This prevents a bean or two from lodging in the hex well. The spinning dome is offset just enough to kick beans out and away from the center, also keeping them out of the plunger/weight's recess. I used the soft vinyl so it won't damage the burrs if it comes loose. And being a real man, I displayed my masculine perogative by attaching it with a glue gun.