Kopi Deva
Mind if I share some of this with Brandon directly and see what he says?
ez4prez Not at all - I’m very curious to hear and learn.
CoyoteOldMan Done. Will update you when I hear back from him.
Questions are from me. Responses are from Clare who work closely with Brandon at Deva:
- People I know who have had a chance to use it tell me it retains most of the grind while grinding and starts dumping it all out after you turn it off. I’ve seen this in videos as well. That you basically just have to press the power button a few times to get all the grinds out but after that it has very little retention. Is that how it’s supposed to work? Or are you working on modifying it so you don’t have to press the power button several times to get all the grinds out?
Due to the build up of static, grounds may remain in the funnel while grinding. This static can be caused by grinding at a higher RPM, and not using the RDT method. We supply an RDT with each KOPI Deva and recommend 2-3 sprays per 18g to help reduce the static build up within the funnel. As we don’t have bellows in our grinder, we recommend pressing the power button a few times to get the remainder of the grounds out, and letting gravity do its thing by assisting with the grounds to fall into the dosing cup.
2. Do grinds start caking and getting trapped on the inner funnel and/or the wipers attached to the burrs and then lead to some grounds exchange happening every time? If so, have you measured the average amount of exchange for the machine?
After rigorous testing, the retention of our grinder is within 0-0.2g of remaining coffee grounds. This is in line with a low retention grinder and it can be further assisted by using the RDT method and pulsing the side button a few times to help let the remaining grounds fall out of the funnel. There may be some grounds left on the walls of the funnel and the wipers, but it’s minimal and again, within the 0-0.2g of coffee grounds that may remain in the grinder.
3. On the website you talk about a patent pending design which creates a small pressure differential. I asked some people who know physics more than I do and here’s what they told me: "It looks to be impossible for a pressure differential to be created given what we know about the design of Deva. The funnel at the top and the chute at the bottom are open, at atmospheric - thus equal - pressure. As far as I can tell, there is no ‘pressure-retaining’ mechanism or device inside the grind path, just the axle and its supports, and the burrs. This means that - including the “fluid” that is the coffee-and-air mix in its various states of grind - all of the grind path is at the same pressure when the motor is not running. When the motor runs, there will be some ‘pressure’ (air speed) generated by the burrs (they can look a bit like turbine vanes, if you think about it), centrifugal forces that push the coffee/air mix, and some viscous drag around the axle - not different from any other flat-burr grinder."Without giving away any of your secret sauce given that the design is patent-pending and not fully patented, would you nevertheless be able to enlighten us on how a pressure differential is created?
As the lower burr spins, and the wipers spin with it, it creates a pressure difference between the grinding chamber and the funnel. Another way of wording this is; when the lower burr spins, there is a pressure difference between the area above the lower burr, and the area below the lower burr.
Where this differs from other grinders;
In grinders where coffee grounds exit horizontally from the burrs, this difference in pressure is only realised at that exit chute, which is usually a circular or rectangular hole.
In the KOPI Deva, the pressure difference acts uniformly around the lower burr, which is also the exit chute, which helps to lower retention and prevent coffee grounds from being stuck to surfaces within the grinding chamber, or in the funnel.
There are no pumps, or anything secret in the patent pending design which creates this pressure difference. It’s true that it is a phenomenon created by a spinning burr, but in the case of the KOPI Deva, the phenomenon is utilised to help minimise retention.
Thanks for sharing - seems like nothing special about the pressure difference - all grinders would have this aspect. I guess the vertical exit chute of the Deva is the unique part then? Hmmm…
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ez4prez Thank you for asking - and reporting back! So in reality the pressure differential has nothing to do with lowering retention. Read between the lines, and what they say is that because the exit chute is all around the lower burr, unlike in ‘traditional’ grinders where the grinding chamber has a floor and an exit hole, there is no (or lower) retention.
Is that patentable? I doubt it - there is plenty of prior art in terms of grinders that have no grinding chamber floor (the Weber EG-1 for example). Does it matter? Not in the least, as long as it works.
So as I predicted, what people are experiencing is caused by static. Thanks for clarifying.
“…the retention of our grinder is within 0-0.2g of remaining coffee grounds. This is in line with a low retention grinder…”
It would be close to a miracle if it were true.
There isn’t a hard definition of ‘zero retention’ but Mark Prince suggested it was within +/-0.5g and this seems reasonable enough.
Otaibimn 0.3g is more than 0.2g.
Do it another 6 times and post the weights for each of the 10 samples.
I tend to think that dose consistency (every time you use the grinder) is the more useful measurement than retention (only when you clean the grinder) and that is seemingly very, very difficult to get below +/-0.2g.
MWJB There is retention and there is exchange.
Retention is basically how much the grinder will hold each time it grinds… but this is subjective.
Since some will be exchanged with the current grind.
You find grinders having 0.2g worth of retention each time… but in reality you are exchanging 1-2gs worth of coffee and that will be effecting the flavor.
So when I say the grinder holds only 0.3g worth of grounds in it’s assembly… the exchange will be much less than that and the retention will be lower.
This is impressive gentlemen.
Otaibimn You find grinders having 0.2g worth of retention each time… but in reality you are exchanging 1-2gs worth of coffee and that will be effecting the flavor.
You’re forgetting the third parameter, dose consistency…which this is…….
mackerel I think if you get within 0.2g it’s very good and even within 0.4g is more than acceptable.
It’s worth noting that a lot of 0.1g resolution scales don’t actually go up/down in 0.1g increments, so if you have 0.1g scales and beans in and grounds out weights match up, I wouldn’t go looking for a problem.
But to measure consistency to 0.1g you rally need another decimal point on the scales.
Me, I just check in an extra bean or two anyway, trim the dose, then I don’t need to have those last few 0.1g’s of chaff in each grind. But if you just want to weigh once & brew high dose consistency makes for an easy life.
So, the button replacement finally arrived. Was simple to swap it in for the old one, which was bent. Here are a couple pix. Not sure how it got bent, apparently in shipping, that zip tie is suspect…
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Meanwhile, bigger problems. My touch point is 6.2 - I can’t get the grinder to grind beans at less than 7. Honestly, it’s pretty hard at 7, takes 20 seconds at least to get the first grinds. Grinds great at 10, but even 7 is way too coarse for espresso. I’ve put about 450g through it so far, but still looking for my first cup. Have tried misting but no improvement. Any tips for first time user? And at 7, it will grind through about 9g, and then stop. I have to start and stop the grinder about 6 times to knock out the remaining 9g. Hoping this is just lack of seasoning. Appreciate your advice.
Wow, that’s not the best is it.
Wondering if you just got a Friday grinder.
I’d be tempted to ask for an exchange unit.
Decent De1pro v1.45 - Niche Duo - Niche Zero - Decent is the best machine ever made -
