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Thread: Coffee machine experiments
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17th Oct 2019, 07:59 PM #106Member: Blue and white apron brigade
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17th Oct 2019, 09:01 PM #107Philomath in training
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I'm not a coffee drinker but the mechanics (and rituals) interest me. One thing I have wondered is why a smooth tamper is used to compact the grounds. I would have though a pattern of concentric grooves (joined) would distribute water better. Another thing to try?
Michael
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17th Oct 2019, 11:08 PM #108Member: Blue and white apron brigade
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Good point but the idea is to have as uniform a path length for water to pass through as possible which grooves would seemingly contradict. Proper coffee machines have what is know as a shower screen that sits up inside the machine and the coffee makes contact with and is slightly compressed against this as the bayonet is firmed up. The shower distributes the water as a fine slow shower onto the top of the coffee. This contact is further increased as the hot water makes the ground coffee swell slightly initially. until some of the solids are dissolved (a well set up machine will dissolve about 20% of the weight of the ground coffee ground into the cup.
The vibro motors (M1 and M2)came in this arvo and I have hooked them up.
A is an accelerometer that I will hook unto a n arduino.
VT3.JPG
At at low revs (4-8V volts) without any damping load the whole thing jumps around on the bench to like a "demented mosh pit member” so it has to be clamped down
This video is at low V (4V) with the whole thing clamped down and doesn’t quite capture the smoothness of the vibe as there’s interaction between the vibe frequency and the camera frame rate
The motors are nominally meant to run between 6 and 12V and as the volts/speed increases the vibe action smooths out.
Turning it on an off from 0 to 12V and back to 9V it goes through some large amplitude resonances but at at 12V is reasonably smooth so it stays on the bench without a clamp
and generates a reasonably smooth vibe that rotates the tamper!
Endless hours of fun testing coming up.
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21st Oct 2019, 09:45 PM #109Member: Blue and white apron brigade
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We've decided to call this "thing" , "Vibraset" , as in vibration settler.
Did some testing of the older Vibraset over the weekend and was not very happy with it.
To prevent the ground coffee surfing/spilling out over the sides of the portafilter (PF) basket a tamper had to be placed on top of the loose coffee.
However, instead of levelling the coffee, the tamper kept tipping over irrespective of how level the unpacked coffee ground were to start with and produced a non-flat ground coffee top.
Came to the conclusion that the 3 point vibration geometry of the table and weight distribution of the portafiler and its handle was not the best and causing the tamper tipping over problem
So quickly knocked this one up from DWV PVC pipe, a push fit cap, a threaded coupler, and a threaded cap ($10 all up).
VT10point0.JPG
VT10point1.JPG
It only has one motor inside the base so most of the vibe is only in the two horizontal directions - its is supposed to be settling the coffee out..
The PVC threaded coupler has been bored out by 1/2mm so the PVC pipe inside it has space to vibe.
The top push fit cap has a hole in it and a thick rubber gasket glued around the top to accept the PF spouts
Preliminary testing shows:
- On the plus side the reduced up and down vibe minimises the ground coffee surfing/spilling out over the sides of the portafilter (PF) so can do a partial settle without the tamper
- Even though it has less vibe the Vibraset's much lighter weight still allows it to bounce around on the bench too much - will have to arrange a heavier base.
- Then when the tamper is placed on top of the partial settled coffee the "tamper tip” seems to be only marginally better than the previous version ie so while holding the PF with one hand the Tamper has to be held vertical with the other. Dang - I was hoping this would be unnecessary.
The tallness of the whole unit is due to the height of the motor and rotating weight, and the standard height of the DWV coupler.
Even using the current “tallish” l motor it could easily be shortened by about 70 mm.
The tall motor could be replaced by a more compact (and expensive) motor.
Can easily retrofit SMALL micro switches to get it to self actuate when pushed down instead of relying on manual switch to turn on
Meanwhile I'm the docs put me back on increased meds for the next month or so so I’m feeling increasingly mentally and physically tired so have to rest about an hour every couple of hours.
Bummer - so now have lots of time to think about designs/tests etc - much more than I have time to actually do projects.
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21st Oct 2019, 11:33 PM #110
Hi Bob,
I suspect that you are trying to move a lot of weight, hence the rather large motor you are using. Is there any way that you can make the coupling much tighter.
For instance a slightly eccentric shaft driving a plastic ring around the coffee container.Best Regards:
Baron J.
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21st Oct 2019, 11:50 PM #111Member: Blue and white apron brigade
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Thanks for that idea.
One of the reasons I have not considered direct vibe methods is that I'm worried that a direct coupling might have too high an "impact" characteristic and as well as "chattering" too much it might also knock the coffee out of the portafilter but maybe it could made of a hard rubber.
The weight of the PF (solid brass), basket and tamper (SS) is about 1kg so it is indeed a lot of weight. I think there is still plenty of vibe especially if I can stabilise (increase the weight of) the base as that will reflect vibe back up into the PF.
I'm somewhat self limited in testing in that I don't want to grind/brew/drink/waste ground coffee using coffee beans I have paid for. I might wait un till we get access to the roasters coffee lab again where we can waste top of the wazza coffee at their expense.
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22nd Oct 2019, 01:06 AM #112
Hi Bob,
Bobs_Coffee.png
This is the sort of thing that I had in mind.
A large ring that you put the container into and a hole for the driving shaft, but made the shaft eccentric.
That way you have full control over both the amplitude and frequency.
You would also get some rotational movement as well.Best Regards:
Baron J.
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22nd Oct 2019, 06:47 AM #113Philomath in training
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Wondering whether you are getting 'tamper tilt' because it's CofG is a distance above the coffee. Perhaps try with a disc without a handle or even better a disc with 3 legs and weights at the end (like a spider). I guess you could just put a guide rod on a tamper disc with a sliding bush to keep it vertical, but where's the fun in that...
Michael
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22nd Oct 2019, 09:13 AM #114Member: Blue and white apron brigade
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Thanks guys, much appreciate the feedback.
BJ, Worth a go, my concern is there would be more movement in one orientation than the other.
Michael. Good point about the COG being a potential prob but the SS Tamper base weight is about 6X the that of the handle (jarrah). I tried removing the handle and it makes no difference. I like the idea of a "spider tamper", more accessories are always "good".
So far the best performance is a 3 second vibe without the tamper which settles the coffee grounds , and then a ~3 second vibe with the tamper. That's fine for coffee nerds but less so for folks that need to do it quickly.
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22nd Oct 2019, 07:30 PM #115
Hi Bob,
BJ, Worth a go, my concern is there would be more movement in one orientation than the other.Best Regards:
Baron J.
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23rd Oct 2019, 09:21 AM #116Most Valued Member
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Bob, you should be working on free energy, you would have cracked it by now
Interesting as always, even if currently I have no intention of replacing my morning Nescafe Gold.
With the added bonus of increased complexity, would a variable speed Vibraset improve things? Start at a slower speed with the tamper in place then ramp up as you get some settling.
Failing that, how about turning up a tube that slides onto the PF and doesn't allow the tamper to move sideways or tip?
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23rd Oct 2019, 09:42 AM #117Member: Blue and white apron brigade
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That would be too practical.
Interesting as always, even if currently I have no intention of replacing my morning Nescafe Gold.
With the added bonus of increased complexity, would a variable speed Vibraset improve things? Start at a slower speed with the tamper in place then ramp up as you get some settling.
Failing that, how about turning up a tube that slides onto the PF and doesn't allow the tamper to move sideways or tip?I don't usually worry about quantifying profit.
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3rd Nov 2019, 01:56 PM #118Member: Blue and white apron brigade
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Been too third and crook to do much on this project but this is where I have got to lately.
Have ditched the hand holding the portafilter (PF) approach as it is too variable and gone back to a hands free approach
It uses the same base as previous but the top large cylinder has been replace with a 150 mm diameter x 6mm thick PVC plate (P) with a vibe motor attached to the underside and it freely floats on top of the base constrained by 3 springs (S)
"A" is a 65 mm PVC cap and inside that the accelerometer is attached. (Blue cable with Green Heat shrink)
"C" is a removable 65 mm coupler with slots machined into the sides to accomodate the port filter handle.
Luckily the portafilter fits perfectly into the coupler without any machining and holds the PF tightly while its vibrating
One of the reasons for this design is that different "C's" can be used for different PFs as their designs differ between machines
VT10point3springs.JPG
To reduce friction 3 teflon discs are attached to the user side of P so that the X-Y movement is much smoother than PVC-PVC contact.
Gutsteflon.JPG
Despite all this the tamper still tips over but I have come up with a differently designed tamper that includes a surrounding constraining device that will sit on top of the PF top and only allow the tamper to move vertically and not tip. The more I think about it the more I think this style of tamper could replace existing tamper designs
Ideally this should all be machined from SS but I will make one from Al first as I already have some suitable stock for it and would have to purchase 70 mm diameter SS rod for the job.
Hopefully the Al should last long enough for testing purposes.
I'm going to make A and B removable so that various sizes/weights of these components can be explored.
Screen Shot 2019-11-02 at 9.05.30 am.png
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4th Nov 2019, 02:59 PM #119Senior Member
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Bob, check out Eazytamp.com.au
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4th Nov 2019, 04:06 PM #120Member: Blue and white apron brigade
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