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Thread: Rotary vs Vibrating pump

  1. #1
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    Rotary vs Vibrating pump

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    First post - so go easy on me if this has been covered elsewhere *:)

    Some long range research for a machine upgrade. What is the difference between rotary vs vibrating pumps ?

    - Does one develop "better" pressure ? (Putting this another way when they quote 15 bar pressure on most machines is this against a given load ? I vaguely remember pump volume/load curves from a past life...)
    - Do rotary pumps just get used on high end machines because they are plumbed ?
    - Is there any real difference in most machines or is there some kind of check valve (i have heard OPV bandied around in literature) which is the limiting factor ?
    - Does pump type/quality influence shot quality at the end of the day ?

    Ive only cracked open my via venezia a couple of times, and dont really know the inner workings of many machines - so if anybody out there does it would be great to know.

  2. #2
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    Re: Rotary vs Vibrating pump

    I reckon rotary is the go, but then you get this issue

    http://www.youtube.com/watch?v=t0D-qiPxCG4

    that said i dont know why this vid has that screaming wail. my pump is external on my HX machine and it is quieter than a sunbeam 6900 anyway and it is sitting out on the kitchen bench (the rotary pump) the wail must be the opv valve or something?

    but you can see the size of it

    its a size thing and $$$ for small machines i think, they just dont fit and cost 400+. And a rotary maybe has a better life span in a commercial environment?

    this is a can o worm / piece of string question it all depends on your usage and preference

    Leeham

  3. #3
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    Re: Rotary vs Vibrating pump

    As soon as you have more then 1 group you have to use a rotary pump. A rotary will always give 9 bars (or whatever it is set to) no matter the flow through not so for vibratory. That means if a vibe pump was on a two group if two groups were used at the same time it would be 14 bar (maximum of pump)/2 = 7bar extractions.

  4. #4
    Mal Dimal's Avatar
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    Re: Rotary vs Vibrating pump

    Quote Originally Posted by 6A4655534E464B786A48494C425E270 link=1250045599/2#2 date=1250056558
    As soon as you have more then 1 group you have to use a rotary pump. A rotary will always give 9 bars (or whatever it is set to) no matter the flow through not so for vibratory. That means if a vibe pump was on a two group if two groups were used at the same time it would be 14 bar (maximum of pump)/2 = 7bar extractions.
    Probably even worse than that MM as the Vibe Pump pressure/flow curve is not linear... :(

    That noise being heard in the linked you-tube video above is not the pump but the pressure or flow regulator on the discharge of the pump. The pumps are actually very quiet while running and do facilitate the option of plumbing-in a little better than a vibe pump but there are some machines on the market today that offer a plumb-in kit for a vibe-pump kitted machine.

    Cheers,
    Mal.

  5. #5
    borat123
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    Re: Rotary vs Vibrating pump

    Re the pressure drop - is that assuming that both groups are being fed by only one vibratory pump?

    How about the M27 2 group, with 2x vibratory pumps, one for each group?

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    Re: Rotary vs Vibrating pump

    Thanks all. Food for thought in all those replies. I only just get away with a noisy grinder - not sure how that pressure regulator would go. Will have to trial some rotary machines and listen out.

    I think this is a good set of reasons about what might mandate a rotary or vibrating pump - total pressure, size - but whether one makes a better coffee is unanswered - maybe youve been into this can of worms before ?

    If i am going to fork out big bucks for new machine i want it to make a damn good ristretto - something i really struggle with on the home machine. It could be any of the usual parameters - grind, dose, beans, my machines pump condition, basket shape (?) - but I really struggle to get a slow pour. I can get a drip start - but it will either continue to drip, or break throughand run quickly - and you can usually see channels in the puck. If i crack the steam wand in the middle of a pour i get a burst of pressure (the pump vibration kicks in), but it will resettle at the same rate (and this probably does horrible things to the shot temperature). Id speculate that pump pressure/load/flow **may** also be involved i.e on commercial machines the rotary pump can deliver enough flow at the high end of its load curve.

    Mal - your comment is interesting - non-linear pressure/flow curve. Do you have any charts for them ? Or do you know any pump brands - vibrating or otherwise that are commonly in machines ? I know your pretty busy in the forums so Ill do some more googling if youve got other things to do *:)

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    Re: Rotary vs Vibrating pump

    Quote Originally Posted by 7D70756F68796E6F1C0 link=1250045599/5#5 date=1250132330
    If i am going to fork out big bucks for new machine i want it to make a damn good ristretto


    If i crack the steam wand in the middle of a pour i get a burst of pressure (the pump vibration kicks in), but it will resettle at the same rate (and this probably does horrible things to the shot temperature).
    I agree for the price of some of those shiny topend vibes you could source a very solid rotary machine 2nd hand, but which makes a better shot is always debatable. IMO so many variables are not related to the machines at all.

    The "crack steam" comment *R U using a single boiler machine, cracking the steam wand mid pour might not be a good idea?
    My HX machine does not get bothered by opening the steam mid pour that i can tell, maybe if the boiler need to fill but hardly ever happens in my home use. (if at all) its a 7L boiler

    whats your machine now and what are you looking at?

    i was thinking of buying a smaller HX but would prefer rotary pump, and was thinking what smaller motor could be sourced that could drive the pump? The electric bit is really the bigger end of the pump and I would prefer it was all in one case.

    it an interesting discussion, i got nothing against vibes really, but they seem louder from the few i have heard. Sure the noise may not effect the coffee but i like it quite :)

    Leeham

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    Mal Dimal's Avatar
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    Re: Rotary vs Vibrating pump

    Quote Originally Posted by 3E33362C2B3A2D2C5F0 link=1250045599/5#5 date=1250132330
    Mal - your comment is interesting - non-linear pressure/flow curve. Do you have any charts for them ? Or do you know any pump brands - vibrating or otherwise that are commonly in machines ? I know your pretty busy in the forums so Ill do some more googling if youve got other things to do *:)
    Gday alisters...

    Here you go mate... http://www.ulka.it/admin/moduli/m003...g_ULKA_web.pdf This link leads to the Ulka Products PDF file and includes performance charts for the various pumps they manufacture. Most espresso machines use the Ulka E5 or a very similar design...

    Regarding the effect of using a Vibe Pump or a Rotary Pump on the flavour of the final brews.... I have both types here at home and for my money, I dont believe the pump type adds or subtracts anything to/from the brew. More important is the overall design of the machine, the quality of the coffee, the quality of the grinder and the technique of the operator.

    Rotary pumps, if installed properly, will be quieter in operation than a vibe pump and if its the noise that detracts from the overall espresso experience for you, then maybe its a worthwhile thing to substitute a rotary pump for a vibe pump. Big difference in cost of course and should only be attempted by knowledgeable and experienced technical/engineering type people or you risk causing early failure; and maybe not to just the pump and motor... :o

    Cheers,
    Mal.

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    Re: Rotary vs Vibrating pump

    Mal, Leeham, and err Borat, MM - thanks.

    Leeham - Ive got a Saeco via Venezia - single boiler - thermoblock i think (?). The cracking the steam wand is not a technique - just something ive observed when ive made the grind or dose just a bit too much for the machine to handle.

    I found some pump pages as well - and some general info on pumps - for posterity in this thread
    http://www.engineersedge.com/pumps/pump_characteristics.htm
    http://www.fluidotech.com/Contents/Documents/MONO%200109%20Ed.pdf
    Probably not as good as your link Mal - but the first link offers a general explanation.

    On the noise - personally its not a problem - but the pressure valve in the utube vid was pretty obnoxious. Good to know that its not a characteristic of rotary pumps.

    I probably have all the theory I need now - and your combined experience seems to suggest that its not a short coming of vibrating pumps. From Borats machine, and i guess others, vibrating pumps may be on commercial machines too.

    I could have phrased this question as "whats the best pump" - but that would have been far too broad - i.e could be assessed on pressure, flow, maintenance, life, noise, and quality of shot. But short of emailing a lot of machine designers this seemed like a better way of seeing whether it was a legitimate point for either the next machine purchase, or my current issue. For my own ristretto issues i think i can perform a few more controlled experiments - more combinations of grind/dose/bean. There is so much talk on which is the best machine - most centres around thermal stability/pid - its interesting that there arent any stronger opinions on the mechanical aspect - the pump !

    So for the next machine ill keep an open mind on pump type :)

  10. #10
    Mal Dimal's Avatar
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    Re: Rotary vs Vibrating pump

    Good stuff mate.... 8-)

    For what its worth, I dont believe that there is any such thing as a "Best Machine". There are just too many variables not the least of which is the person hanging on to the Group Handle. Its more a matter of which set of compromises best suits your particular requirements and circumstances, i.e. your specification. Once youve got that nailed down, it should be a lot easier to assemble a short-list of hardware that is going to best match this Spec; which has to include items such as ergonomics, aesthetics and budget too.

    You sound like a guy who should be able to assemble a pretty reasonable specification and that should go a long way to assisting your making the best decision... For you.

    As with everything, you quickly run into the law of diminishing returns, where a fixed budget no longer carries as much weight as other factors, and a nice to have becomes a must have. Thats only something you can decide Im afraid... ;)

    All the best,
    Mal.

  11. #11
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    Re: Rotary vs Vibrating pump

    tbh cracking the steam wand will do little but cause the heating element in the boiler to kick in, possibly raising your shot temp by a couple of degrees. if the shot aint right, forcing it wont help - have you got a naked portafilter?

    could also doser lower/grind finer or dose higher/grind coarser - sounds like you may have chanelling issues. my guess is that you can exclude your machines pump condition from problems with your machine, though youll find a good HX or dual boiler machine easier to use. specifically a HX is more likely to give you the kind of pours you describe by default. three questions kick in from there - budget, # groups wanted, and grinder pairing.

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    Re: Rotary vs Vibrating pump

    Coffeehorse - late reply but:

    I was debating as to whether or not to put in the "crack the steam wand" comment - thought it may mislead people. As mentioned above its an observation rather than a technique. Apologies if the paragraph below is obvious - but ill further clarify what i meant:

    When i pull water through the steam wand, or when i run a "blank shot" - I hear a loud vibrating from the pump. I guess this corresponds to a high volume/long stroke on the pump. When there is significant resistance this gets quieter and higher frequency - the flow is down and the stroke is smaller/pressure higher. This becomes almost in audible when a pour has "stalled". If i crack the steam wand the pressure in the boiler is released. As this is a single boiler this is also the pressure against the group/coffee. When i do this i get some loud vibration - my guess is the pump is able to refill the boiler temporarily. Mostly this increases flow through the coffee temporarily. You eluded to channelling issues - maybe this flow increase only occurs by forcing channels to be created ? I cant say - another feature of my machine is that there is often a fair amount of water left on top of the puck - especially when this has happened - so i cant tell very well the state of the puck when this happens.

    So to link this comment to the main thread here - I was trying to indicate the pump behaviour at high pressure. If a vibrating pump is less linear than a rotary one then this sharp drop off in volume over a narrow band of pressure could make it harder to dial in the grind - and hence there could be some mechanical benefit to an rotary pump.

    I note your comment "specifically a HX is more likely to give you the kind of pours you describe by default". Think that risks going off topic but if you can justify it id be interested in your reasoning. Are you suggesting that by better thermal stability = more consistent pour - i.e temperature is a significant parameter in quality or pour ? Interesting point .... if thats what you meant :)

    Dont know what you mean by a naked group handle ?

    Thanks.

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    Re: Rotary vs Vibrating pump

    Naked group handle has the bottom cut out so you can see all of the basket, lets you "watch" the extraction and look for channeling etc.

    your wet puck is due to no 3way valve on the Via, (i think they dont).
    the 3way lets of the pressure after a shot is run, "better" machines have them. Many let the Ghandle sit a little after a shot on non-3wat to allow any residuale pressure to bleed off on its own. Or get the dreaded SNEEZE when you remove the Ghandle.

    this got me thinking a little about small single boilers and the amount of "free air space" in the top. when the pump runs will it pressurize the boiler to 15 bar prior to pushing water through the puck?

    If there is more "free space" does it take longer? 1-2-3 secs? and what effect may this have on the shot? Good ? Bad? some tiny amount of Pre-infusion?

    could doing a crack of the steam wand as soon as shot is started fill the (or have it open) boiler a bit more and effect the shot in a positive way?

    interesting .......

    Leeham

    interesting

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    Re: Rotary vs Vibrating pump

    Just a quick question regarding rotary pumps, and specifically procon pumps. If I was to replace a series 1 or 2 procon pump, could I do so with a series 4 which has a higher flow (115-330gph as compared to series1,2 at 15-140gph)? Would I encounter any problems? It will be used in a 2 group San Marino SME-2.

    Thanks,
    Sooty

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    Re: Rotary vs Vibrating pump

    Quote Originally Posted by 404C45454646504F4C41230 link=1250045599/13#13 date=1250763415
    Just a quick question regarding rotary pumps, and specifically procon pumps. If I was to replace a series 1 or 2 procon pump, could I do so with a series 4 which has a higher flow (115-330gph as compared to series1,2 at 15-140gph)? Would I encounter any problems? It will be used in a 2 group San Marino SME-2.

    Thanks,
    Sooty
    Answered your PM Sooty... :)

    Mal.

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    Re: Rotary vs Vibrating pump

    Behmor Brazen - $249 - Free Freight
    The Expobar Minore III comes standard with a vibration pump but does come with a rotary pump kit.

    Has anyone tried them side by side to see the difference in the cup?



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