Spinning for distribution?

[The_Mighty_Bean]

I posted this idea over on CG, and there was a bit of debate there. In reading some of the HB threads about using a dental vibrator (or taking a quick trip to the sex toy shop), I was reminded of this intuition I had.

My goal is a practical, inexpensive way to improve distribution at home. I was thinking that centrifugal force might help. What about rigging something like a salad spinner to hold the basket- you'd dose into the basket, pop it into a mounting device, maybe you'd need to "cap" it somehow to keep grounds from flying out initially.

Thoughts?


~tMb

[Celebrian]

wouldn't that distribute the grounds around the outside of the basket? you'd have a less dense spot in the middle.
Then again, maybe I don't know what I'm talking about, and it could be good.

[The_Mighty_Bean]

wouldn't that distribute the grounds around the outside of the basket? you'd have a less dense spot in the middle.
Then again, maybe I don't know what I'm talking about, and it could be good.

This is where I need a little help with the physics.. I know centrifugal force would pull the grinds inward making it dense in the middle.And I think centripetal force pushes outward like you were talking about, and like in those carnival rides where you are on the spinning wheel.

I don't know if there's a way to balance those forces to even the distribution?

[bad physics edited out after others corrected me, thanks guys.]

If you look at the way the Versalab M3 throws the grounds, there's a bit of a dimple in the center... I think this might be similar, and you simply do a swipe or dose in a tad of extra coffee to fill it in. The density wouldn't quite be identical to the spun grounds, but possibly a lot closer than you could ever get with WDT.

[gadflea]

Celebrian is right. The grounds would go to the outer walls of the basket leaving a hole in the center.
There is no such thing as a centrifugal force. Centripetal force is that force causing a body to accelerate (change direction) in a circular motion. It is directed inwards, from the body being spun towards the center of the circular path being traveled. If you are spinning a yo yo around over your head, the string is the centripetal force that keeps the yo yo from flying off into your bay window.
The centripetal force in your thought experiment would come from the walls of the basket pushing against the grinds so that they do not fly out horizontally (in a perpendicular path to be specific). The force provided by the walls cannot push the grinds to the center, it can only prevent them from escaping. therefore the grinds would collect on the walls leaving a hole in the center of the basket.
You can google centripetal force to get some diagrams illustrating my explanation above. It is kind of hard for me to explain it without drawing pictures.
Hope this helps.

[Celebrian]

actually, there is such a thing as centrifugal force, in fact, that's what distributes the grounds around the outside of the basket. It's long and complicated, and i'm gonna simplify things waaay too much for comfort, but hopefully, it will make things a lot easier.
really dodgey diagram below:


So....the centripetal force is the force required to move the object around a circular path at a constant speed. the force is a vector (meaning it has both a magnitude and direction), which points inward at the centre of the circular path. Centrifugal force is the force directed outwards on the object, which is of equal magnitude to the centripetal force exerted on the object. But the centrifugal force isn't....real as such. i mean, it feels real, but it's all relative.

Let's say that you're in a car and it takes a sharp bend...the passengers may feel like they are thrown to one side of the car, when in reality, there is no force acting on the passengers, but reacting to the acceleration of the car....(blah blah...relativity...blah...physics).


SO.
for the simplicity of explaining stuff, we're gonna assume that centrifugal force is just the force pushing the object away from the circle centre.

Centripetal = going in
Centrifugal = out

How does this relate to coffee?

Well. Spinning the basket would cause the grounds to travel in this circular path, and both centripetal and centrifugal forces would act on them. centripetal forces is what keeps the grounds in the basket, traveling in a nice circle. the centrifugal force would push them out to the sides of the basket, therefore creating a less dense spot in the middle.

Now all of you clever baristas can explain the results. Chances are you already know what's gonna happen.

[The_Mighty_Bean]

actually, there is such a thing as centrifugal force, in fact, that's what distributes the grounds around the outside of the basket....



Now all of you clever baristas can explain the results. Chances are you already know what's gonna happen.

Thank you so much for bringing back my nightmares from the physics class in college where the class average was in the 40s. An important part of why I switched from pre-med to pre-law.


But I am picturing this spun basket with the grounds forced to the outside. I think it would take a heck of a spin to force a "ring" shape with a hole in the middle, which would be terrible distribution.

But perhaps a gentler spin might result in the most even convex tamp we've ever seen, complete with a nice side seal? As I said in my first post, maybe one could artificially help it out by slightly packing the middle, post-spin. No idea if that would be necessary.

I dunno, that's just intuition, could be way off.

~tMb

[RogerB]

actually, there is such a thing as centrifugal force, in fact, that's what distributes the grounds around the outside of the basket. It's long and complicated, and i'm gonna simplify things waaay too much for comfort, but hopefully, it will make things a lot easier...

Centrifugal force is indeed a fiction. Centripetal (from the latin, "center seeking") forces are "balanced" by acceleration, and the illusion of centifugal force is due to the tendency of any object travelling in a straight line to continue travelling in a straight line unless acted upon by an outside force (Newton's Third Law).

Centrifugal (from the latin, "center fleeing") force, if real, would portend that the yo-yo you're swinging around your head, once released, would travel away from the circle's center radially, when in fact it departs tangentially; that is, perpendicular to the radius of the circular path it was travelling only a moment before.

As for spinning the filter basket...

...I think we're overthinking it.

[Psyd]

Centrifugal force is indeed a fiction.

So is Ishmael's white whale, but I bet we all know his name. Centrifugal force is the name we give to the combination of physical circumstances that keep you alive on the spinny carnival ride.
In any case, if you were to put the entire basket on the inside of a spinning thing, with the opening of the basket facing the center of the rotation, would it distribute any better or simply be a very complicated method of 'thumping'?

[The_Mighty_Bean]

As for spinning the filter basket...

...I think we're overthinking it.

Not if it could be done simply and quickly. If it worked better and was faster than the WDT I'd do it in a heartbeat.

would it distribute any better or simply be a very complicated method of 'thumping'?

Well that is the question. There's been lots of discussion of thumping, and I think the gist of it, at least lately, is that you tend to get an uneven pack with more density towards the bottom. That's why people are talking about just uniformly agitating all the grounds sort of gently with a dental vibrator.


Now we just need a vibrator that spins.

Oh, dear.


~the Mighty innuendo

[KillerQ]

Hey all,

Cool concepts, but for now, I'll stick with sifting through the grounds with a straightened paperclip to ensure there are no clumps or pockets, then a quick shake/tap to make sure it's level before tamping (call this procedure what you will).... According to my naked PF, this works pretty well!

Later,

Matt!

[Spresso_Bean]

What about creating some sort of distributor device that works similar to the Versalab so that you dose from your grinder into a container and then dump that into the distributor with the portafilter underneath? Something like an electric sifter but one that wouldn't destroy the grounds or heat them up. I'll see what I can come up with as far as an illustration but it might be an idea, although extra bulk in the prep area.

[Celebrian]

Centrifugal force is indeed a fiction. Centripetal (from the latin, "center seeking") forces are "balanced" by acceleration, and the illusion of centifugal force is due to the tendency of any object travelling in a straight line to continue travelling in a straight line unless acted upon by an outside force (Newton's Third Law).

Centrifugal (from the latin, "center fleeing") force, if real, would portend that the yo-yo you're swinging around your head, once released, would travel away from the circle's center radially, when in fact it departs tangentially; that is, perpendicular to the radius of the circular path it was travelling only a moment before.

As for spinning the filter basket...

...I think we're overthinking it.

But the centrifugal force isn't....real as such. i mean, it feels real, but it's all relative.

Let's say that you're in a car and it takes a sharp bend...the passengers may feel like they are thrown to one side of the car, when in reality, there is no force acting on the passengers, but reacting to the acceleration of the car....(blah blah...relativity...blah...physics).

I think you explained it better than I did. There's the fictitious centrifugal force, which isn't really..a force, but merely a reaction to the change of direction, which still feels like a force. then the 'real' force is that which the object exerts on the ..container, as it changes direction (in this case a circular path)...This is a coffee forum, not a physics one. I should shut up (since there are plenty of people who probably know more than me on this subject anyway )


I think we're overthinking everything.
coffee tastes good.
hey, why doesn't someone test this spinning thing out? i mean, it wouldn't hurt to try. we just need to find something that would spin it. like a lettuce spinner with prongs. or..something. you never know unless you try.

Thank you so much for bringing back my nightmares from the physics class in college where the class average was in the 40s. An important part of why I switched from pre-med to pre-law.

you're welcome!

[The_Mighty_Bean]

What about creating some sort of distributor device that works similar to the Versalab so that you dose from your grinder into a container and then dump that into the distributor with the portafilter underneath? Something like an electric sifter but one that wouldn't destroy the grounds or heat them up. I'll see what I can come up with as far as an illustration but it might be an idea, although extra bulk in the prep area.

So, check it out. I am not crazy. Okay, I am, but in a good way.

There are many specialties that are interested in achieving even particle density, besides our own. It turns out that the term of art for particle density in airspace is called "bulk density". Then when you start settling the grounds, you get what is called "tapped density", and if the grind is even then the maximum tapped density is reproducible for individual substances.

There is a scientific device which does this, and measures the density. It's called an Autotap. Here is a quote from the brochure. http://www.quantachrome.com/density/autotap.html and click on the PDF for the brochure.

handling or vibration of particulate material causes the smaller particles to work their way into the spaces between the larger particles. The geometric space occupied by the powder decreases and its density increases; Ultimately no further natural particle packing takes place without the addition of pressure and maximum particle packing is achieved. Under controlled conditions of tapping rate, tap force drop and cylinder diameter, this condition of maximum packing efficiency is highly reproducible.

Now, check it out-- from the same brochure. Page 2:

Reading of the powder surface is facilitated by automatic rotation of cylinders during tapping which promotes a flat powder interface.

So, rotation of the powder, plus some sort of vibration action known as "tapping" will produce a distribution of maximized, even density, with a flat surface. A consistent, reproducible distribution that could be used to limit variables in comparing espresso experiences. (Hi, AndyS... you out there?).


There it is, the holy grail. Now just add something to create a side-seal- either a level tamp or preinfusion, and your extraction will have zero distribution-based flaws.

The question is, what exactly is "tapping" vibration-- EDIT- it is literally a piston "tapper" inside a cam shaft, stroking at a high speed (hush, gutter minds) to create a very steady and even agitation.


...and is it possible to create a rotating vibrating thingy that securely holds a PF basket, and is cheap enough and practical enough for the home barista

If the device costs as much as a Versalab, then there's no point. Do it for $50 or less, and I think you have a new product of the year. Ahem, all rights reserved.

Salad spinner cut down and glued to a dental vibrator?


~tMb

[popeye]

I'm interested because it seems to do to things i like:
1. Get me a good side seal
2. Get me slightly less density in the center. I always shoot for a slightly less dense center because as i tamp, most of the tamping force will be used to compress the outside of the basket, and seal the sides better. Usually this means something as little as working from the outside in when doing the WDT.

I don't think a machine could be devised to do it cheaply, quickly, and well. But hey, get Joe Behm working on it.

[RegulatorJohnson]

i wonder how many shots in a average day on the planet earth get pulled successfully, without using these types of gizmos and techniques and such.

jon

[The_Mighty_Bean]

What about creating some sort of distributor device that works similar to the Versalab so that you dose from your grinder into a container and then dump that into the distributor with the portafilter underneath? Something like an electric sifter but one that wouldn't destroy the grounds or heat them up. I'll see what I can come up with as far as an illustration but it might be an idea, although extra bulk in the prep area.

I've been looking at all sorts of strange devices on Ebay, including dental devices that spin and vibrate and apply vacuum suction from below.

I ran a quick experiment on vibration today. I dosed a double basket naked PF 3/4 full of scrap grounds in a clumpy heap. Then I applied fairly strong vibration to the bottom from a plug-in Homedics back massager, which had a flat attachment, on which I rested the basket

The grounds settled in, with fines being drawn downwards and clumps gravitating towards the top. Occasionally the mass of grounds began a rotating motion in the basket. I'm not sure what caused that kind of translation- whether it was related to the precise angle at which I was holding the basket (because the other end of the massager is rounded, it was tricky to keep it perpendicular to the floor at all times), or whether the vibration was just not quite strong enough to consistently spin the grounds.

Anyway, I found that without rotating the PF, I did not end up with a flat surface. When rotating it as far as my range of motion would allow, which was back and forth, by hand, over a range of about 270 degrees, I got closer to a flat surface. Also, even with something the strength of this plug-in massager, an unacceptable amount of clumps remained atop the settled grounds.

This leads to further questions:

If the vibration is strong enough to spin the mass of grounds, does that eliminate the need for a separate rotary mechanism?

Would even stronger vibration break up the last of the clumps (it seems like it would, having watched the process at both low and high intensity vibrations). If so, is it more practical to up the vibe power, or to have to include some sort of stirring/sifting process (as mentioned by SpressoBean) in addition to the spinning and vibration (sounds like a PITA)

It would be interesting to hear from the folks who have experimented with dental vibrators.


~tMB

P.S. I don't know Jon, why do some of the most experienced people here bother with Fluke thermologgers and Scace devices? Distribution is nearly as important as temperature, and not everyone has a Versalab, or a pocket-size Tim Wendelboe to do a consistently perfect Stockfleth's. I'm just looking for simple, cheap, practical methods to make better espresso more consistently.

[Psyd]

i wonder how many shots in a average day on the planet earth get pulled successfully, without using these types of gizmos and techniques and such.

Not that many, as a percentage. I have to get my fix at way to many coffeeshops around the country that just 'grind and pull' and don't have any tricks and treats to their coffee and their techniques, and end up serving black squirt.
I think the very reason that we get better shots amongst the HB'ers is that we're ready to try (nearly) anything and everything to get it that eensy bit better.
My mantra? "If it works, keep it." It costs me nearly nothing to try most anything that someone can come up with, and if it makes my morning coffee easier or better, I'm game.
I am not, however, building a centrifuge for my baskets. ; >

[ntwkgestapo]

I've been following this discussion for a while (and almost jumped in with the "there's no such thing as centrifugal force" bit! ), but... While I haven't tried it, I DO have one of those small dental vibrators.. Got it years ago when my dentist got a couple of new ones "thrown in" with a larger equipment purchase. I've tried it for mixing paint (watercolor [or watercolour if you're a brit! ], acrylics, etc) as it seemed like it MIGHT help with reagitating (sp?) liquid paints that had been sitting for a while (and the pigments settled out). worked, but took a LOOOOONG time to do it... 'Twas easier to just shake it! I also have an industrial ultrasonic cleaner which will agitate at about 80Khz (I seem to remember it's freq is something like 88Khz, but don't hold me to it!)... I doubt EITHER would do a good, even dispersion of coffee grinds without a LOT of assistance...

On the paint bit, I finally built a small paint shaker out of a 3volt DC motor and some small brass parts (gears, etc) with a simple vise to hold the bottle... works great and takes about 20 seconds to totally mix the paint (that way my airbrushes don't clog as often! )

[The_Mighty_Bean]

'Twas easier to just shake it!

Well then, we could just dose into the basket, slap a blind basket on top to compress the pile down, hold it in place and then shake it up! Quick levelling swipe (or tap, if underdosed), lock and load.

I wonder how that would work. It's not necessarily going to be as consistent as vibrating to max tapped density, but it still might yield a great distribution.

I can't readily try it because my blind basket is the two-dollar rubber nipple variety. Anyone want to give it a go, and see how it compares to WDT?

I doubt EITHER would do a good, even dispersion of coffee grinds without a LOT of assistance...

Bertie seemed to differ on that point. More testers needed, I guess.


Would your paint-shaker work?


~bean

[ira]

I've been reading this for a while trying to figure out if I could add anything and the last comment made me wonder if getting rid of the last few clumps would actually do anything and trying to think of a test that might answer the question. My doserless Macap clumps something awful and stirring with a needle helps, but only somewhat so I've no way to try the clumpless test. But I wonder if someone with a Versalab or a similarly clump free grinder could try this? No idea if it's meaningful, but maybe it is.

Have 2 identical baskets at hand
Measure 2 identical doses of beans into some suitable container
grind one of them into one of the baskets and tamp lightly
Hold the 2 baskets together and tap the empty one on the table so all the tamped grounds fall into the empty basket
Grind the second dose into the now empty basket

This should leave you with one almost perfect and one really badly clumped doses of identical coffee.

How do they compare?

I realize it's a badly flawed test, but it's easy to do and might answer some question or another.

Ira