Cooling Cooling an espresso coffee grinder?

Discussion in 'Hardware' started by murky, 15 Jul 2005.

  1. murky

    murky What's a Dremel?

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    Ok... I've been searching and searching for some 'expert advice,' and I'm hoping that folks here might have some good ideas.

    Here's the background in a nutshell: I'm part of what I'll just call (for brevity's sake) the high-end/cutting-edge coffee and espresso community. We're involved in barista (espresso bartender) competitions and stuff like that. I run a group-blog and podcast at www.portafilter.net .

    The way that folks like us use an espresso coffee grinder is pretty different from the 'normal' way they're used, and for that matter, different from the way that they're designed to be used (sound familiar, overclockers?). They're designed to kick on for like 3 minutes and fill up the 'dosing chamber' (the stainless-steel part in the pic below), and then pull the lever once or twice, depending on how much coffee is to be used.

    [​IMG]


    The way that WE use it is to grind fresh for every shot of espresso. This makes a huge difference for many reasons that I won't get into right now. The problem with this is that the motors are pretty large, about the size of a Coke can if not a little bigger, and the start-stop work cycle ends up generating a tremendous amount of heat in the motors (friction, etc), which in turn rises up the grinder body (heavy and thick cast iron) and heat is bad news for grind quality, which effects coffee quality.

    [​IMG]

    The natural design change that would help a lot of this is to put the motor on a separate axle and belt or chain drive it somehow. However, there's no such thing right now, and I've been thinking about trying to use proc coolers to maybe try to keep these grinders cool. The motor itself can't be cooled directly (at least not the moving parts of the motor), but the grinder body perhaps could. So here are my questions:

    1) Do you think that a good proc cooler (let's say price no option for now) could cool down something like this?

    2) If so, is there a thermostat-type system that will be able to cool this thing, while not cooling so much that condensation is an issue?

    3) Any other thoughts?

    We have espresso machines that are really modified to get the temperature of the brewing water really stable, but the weak-link right now is the grinder. So... thoughts?
     
  2. tetleyex

    tetleyex What's a Dremel?

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    Could you tell us what the motor looks like, or how big it is etc. Perhapse you could take some photos.

    I think simple heatsinks might be most appropriate.

    I doubt condensation would be an issue, unless your using a peltier or something, wich might be overkill for an overclocked coffee machine.

    Oh, and you should put a window in that coffee machine, I'm thinking pink 6 inch cold cathodes! :naughty:

    Umm... cool hobby.
     
  3. zackbass

    zackbass What's a Dremel?

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    It's very hard to tell what you're up against without a picture of the actual motor, the diagram doesn't do a whole lot for me. Exactly how hot does the motor get, and what kind of clearances do you have to work in a heatsink?

    My plan of attack would be to make a motor body fitting copper heatsink out of some copper blocks. Like you said, the real solution is to get the motor away from the beans. I would focus my efforts there, good results are more definite that way.
     
    Last edited: 15 Jul 2005
  4. Firehed

    Firehed Why not? I own a domain to match.

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    As you said it's a cast iron body, I don't see why you couldn't just thermal epoxy something like a couple 1U copper heatsinks onto the body in the bean reservoir (if that's what it would be called) area.
     
  5. phuzz

    phuzz This is a title

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    Like firehed said, the best place for cooling is probably that handy piece of cast iron you mentioned. What shape is it, or which part is it in that exploded diagram? Large flat areas will probably lend themselves to attaching cooling devices. And to get in there before anyone else does;
    Water cool it! Does make *some* sense, it won't get cold enough for condensation, and with big radiator atached, you could get rid of quite a lot of heat and keep the grinder body not far above room temp, which I'm presuming is ok.
    As I said before, if you have flat surfaces any type of cpu cooler (air or water or whatever) should be pretty easy to attach (duct tape! cable ties!), if it's all curved sections then yuo're looking at a a bigger job. Can you post a pic maybe?

    (still not quite sure that this isn't a piss take, but most 'normal' people look pretty suprised at the idea of watercooling a PC, so I guess a coffee grinder isn't so wierd)
     
  6. padair

    padair Inebriated

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    The fact that there's competitions on how to make coffee IS wierd.

    I think I'll start a competition on how to make tea properly, none of those rubbish bags for me.
     
  7. P2D

    P2D 99.999% Pure Spam!

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    Seriously, People say i need to get out more? lol only kidding, one of the more unusual hobbies methinks :confused:

    I dont like coffee
    `P2D
     
  8. nick01

    nick01 What's a Dremel?

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    (1) Go with the watercooling. Use thermally conductive epoxy to attach copper lines to the iron body for water cooling. http://www.epoxies.com/therm.htm

    (2) Try to find a brushless replacement motor (motors often come in NEMA sizes, so there are fairly few standard flanges). Brushless motors are more efficient anyway and stay cooler, and in addition then the driver modules can have dynamic braking resistors that dump the kinetic energy of the motor into the air (or water) instead of the motor windings.

    Do any belt driven systems exist at all? With the type of load attached (crunching beans) I would expect random vibration and lots of noise.

    I am not an espresso expert, but could pre-chilling the beans do the job? Beans from the freezer start at -18C and grinding heats them up to just to the right temperature for brewing. Again, I'm not an expert.
     
  9. Nexxo

    Nexxo * Prefab Sprout – The King of Rock 'n' Roll

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    being a coffee afficionado myself, I think the whole excersise is a bit futile.

    I mean, you are suggesting that you do not want to fill the whole dosing chamber, presumably because you want every shot to be fresh-ground. This logic would only apply if there is a large time interval between shots. If you make a new shot every few minutes or so, you may as well fill the dosing chamber up and use that, as frequent dispensing of shots will empty the chamber before the coffee gets a chance to go stale.

    If, however, you make a shot so infrequently that the coffee in the dosing chamber going stale becomes an issue, you will not be using the grinder all that frequently in the first place. We're talking, what, three or four shots per day? I'm sure that gives the grinder motor plenty of time to cool down inbetween shots. I think you are just making things too complicated for yourself.
     
  10. ralph.pickering

    ralph.pickering What's a Dremel?

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    I'd look at one of the small bore external water cooling systems, such as the Koolance Exos, Thermaltake Aquarius III or perhaps the Kailon Silencer, which would be a good match for the grinder's styling. Of course the problem is what to cool. If there's a good thermal interface between the motor and the cast iron body, you could attach water blocks there with thermal epoxy, but if the cast iron is getting hot because of heat radiating from the motor, and is not in direct contact with it, then water cooling the grinder body won't do much good.

    Another idea would be to look at the heatsinks used by RC car enthusiasts. Their motors are probably a lot smaller, but you might be able to get a similar HS CNC'd to fit your motor. A bit of adaptation of the grinder body to fit a 40mm fan to pass air over the heatsink, and voila. Cool coffee grinder action.

    And don't forget to do a project log. Everyone needs a bit of cheering up, and a water cooled coffee grinder would be just the thing to do it.
     
  11. murky

    murky What's a Dremel?

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    Thanks all for your input thus far.

    I'll take some pictures of the innards of the grinder for your perusal. I'll also take my Fluke thermocouple thingie and play around with some temp readings here and there to see where the heat is really coming from.

    The brushless-motor thing is very intriguing... I'll have to look in to that.

    I hear ya, but I guess I forgot to mention in my original post, I own two coffee bars. I'm on the Executive Council of the Barista Guild of America, and I do some freelance writing as well. For those who may be interested, www.home-barista.com is a good site for those interested in getting really serious about geeking out on some home coffee equipment.

    Naw, not three or four shots per day... more like 1,000.

    We grind fresh per shot (as does anyone else doing their espresso at the highest-level) because our target margin for error is so narrow that a slight variation in ambient temperature and/or humidity can throw off the extraction rate too far for our liking.

    Nexxo, what I will give you is that your first recommendation, to fill up the dosing chamber, is frankly the way that these grinders are designed to be used. However, for the reasons I gave, high-end shops don't fill up the doser. The sad thing is, though we have commercial espresso machines now that are super-stable in their coffee-brewing-water temperatures (within 0.25*F), nobody's made a grinder that can: a) grind with high precision, b) have infinite particle-size adjustments, c) has a dosing mechanism that works WITH baristas of this level, d) can handle a typical busy-shop's duty cycle of an "on 8 seconds, off for 20 seconds" without overheating. There are other things, but that's what's generally missing from a good grinder.

    We have grinders with "a" and "b," OR that do a better-than-average job with "c" and "d," but not together in the same grinder.

    The photo (not the exploded diagram) above is a Mazzer Robur. It is a fully conical-burr commercial espresso grinder (retails for $3500, I think), and it's what we use in barista competitions, as well as in many of the high-end espresso bars. The conical burr set (as opposed to flat burrs) has more precise cutting surfaces than other designs, which gives us better espresso extractions. The problem is, the motor on this sucker is larger than most, which puts out even more heat than flat burr (like the Mazzer Normale in the exploded diagram) grinders.

    Just thought I'd give y'all more info, since you guys went through the trouble of responding.

    I'll be back in a couple of days with better images and some measurements.

    Thanks!
     
  12. fivecheebs

    fivecheebs Dont panic!

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    I'm finding this thread really really interesting. I never new there was so much to a cup of espresso, and i am a coffee lover, just not as much as i thought! :thumb:

    FWIW, i think you would be better removing the heat from the source, rather than from the cast iron casing. Looking forward to seeing the pics of the internals, and some temp measurements would be good when its getting too hot to work well.
     
  13. Flibblebot

    Flibblebot Smile with me

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    Another thing to think of is to try is to wrap small-bore copper pipe around the motor several times, and pump cool water through it - the only problem being whether or not you'd have enough room for the motor and the pipes?
     
  14. phuzz

    phuzz This is a title

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    Personally I prefer a nice cup of tea, but I wouldn't be a modder if I didn't appreciate taking something beyond the extremes just for the sake of it...
     
  15. Nexxo

    Nexxo * Prefab Sprout – The King of Rock 'n' Roll

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    I'd say kill the heat at the source, and go aircooled. The conventional appraoch would be to mount a fan on the motor so that it cools itself as it goes along.
     
  16. Zidane

    Zidane What's a Dremel?

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    thats possibly the coolest coffee machine ive ever seen.

    as for cooling it.... is the motor in contact with the iron case? if enough of the motor casing is in contact with a nice solid iron case, you could always get someone to bore some nice holes in the cast iron, and fit some barbs, and have watercooling built in.

    if the case is seperate from the motor... brushless motor, maybe wrap some copper pipe around it as a liquid cooling heatsink.... im sure the guys can come up with something once they see some piccies of the actual unit.

    im dying to know how this works out.
     
  17. Risky

    Risky Modder

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    I'm wondering if Aircooling might be the way here. Is it possibel to vest the casign and maybe force air in from the bottom to cool the motor?
     
  18. ConKbot of Doom

    ConKbot of Doom Minimodder

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    With motors, especially brushed motors, the main problem is that it is hard to get rid of the heat. Your windings, (which are what heats up) are on a spinning shaft, and the only thing touching the shaft is the bearings, and the commutator(the brush). Cooling the casing wont do that much good, because by time the casing of the motor gets warm, the rotor is allready pretty hot (and therefore the shaft and the blade)

    See if you can force more air through the motor to cool it. If it is a motor with a fan in allready, leave that in, and put a big ducted 120mm 120VAC (or 220...) fan to force air through the motor all the time. If you want to get exotic, have a Pelt, attached to 2 heatsinks, 1 in the duct (the cold side) and the other is the hot side, outside the duct. If you get any condensation, it will be on the heatsink fins, so just design around that.
     
  19. Tulatin

    Tulatin The Froggy Poster

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    erm, why not just get a solid copper block, mill out a motor sized hole in the center, grease her up with thermal grease, and slip her on after making some waterchannels in it's exterior?
     
  20. woodshop

    woodshop UnSeenly

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    Why not seal the entire base where the motor is then just fill it up with some of that non conductive liquide maybe setup a jug of it under a counter and pupm it into the upper part of the bases and let it run down into jug... could be bactirea issues though unless you seal teh loop
     
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