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Andreja Rotary Pump
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Discussions > Espresso > Espresso Mods > Andreja Rotary...  
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Frosted
Senior Member


Joined: 1 Jun 2008
Posts: 20
Location: Seattle
Expertise: I like coffee

Espresso: Dalla Corte Supermini, La...
Grinder: Mazzer Mini, Super Jolly,...
Posted Sun Jun 22, 2008, 12:35am
Subject: Re: Andreja Rotary Pump
 

Thanks! With this mod, the two machines have about the same performance. Their internal components are almost identical, so there would really be no practical reason for their performance to differ.
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cgardnerma
Senior Member


Joined: 3 May 2008
Posts: 11
Location: Boston
Expertise: I love coffee

Posted Sat Aug 9, 2008, 6:51pm
Subject: Re: Andreja Rotary Pump
 

Hey Frosted,

I am also searching for te elusive 3/8 m x 1/8 m BSP fitting for my project. Who was that "source" you mentioned for BSP fittings? Thanks!

cgardnerma
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Frosted
Senior Member


Joined: 1 Jun 2008
Posts: 20
Location: Seattle
Expertise: I like coffee

Espresso: Dalla Corte Supermini, La...
Grinder: Mazzer Mini, Super Jolly,...
Posted Sat Aug 9, 2008, 11:19pm
Subject: Re: Andreja Rotary Pump
 

www.hoseandfittings.com
They have a great selection and were very reasonably priced.  If you are not familiar with the sizing numbers, an 02=1/8; 04=1/4; 06=3/8; 08=1/2. Also you will find that there are BSPP and BSPT. P=parallel and T=tapered. I found that most of the existing fittings on my machines were tapered male into parallel female and sealed with some sort of liquid pipe sealant. I used teflon tape. I was under the impression that if you do use parallel male into parallel female that an internal seal is necessary. Good luck.
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Spaceman323
Senior Member


Joined: 13 Jan 2008
Posts: 3
Location: Ohio
Expertise: I like coffee

Espresso: Krups 964
Grinder: Sterbucks Barista Burr...
Posted Mon Oct 13, 2008, 8:44am
Subject: Re: Andreja Rotary Pump
 

Maybe you can help me.  I have a QM Vetrano and I would like to know what the pressure is at the filter basket when I am drawing a shot of espresso.  My pressure gauge gives pump pressure but it does not give the actual pressure at the filter basket.  It always reads 9 bar when I pull the lever on the group head.  It reads 9 bar when I am drawing a shot. It reads 9 bar when I have the blank filter basket installed. And it reads 9 bar when the filter basket is removed!  It seems that I should be able to install a pressure gauge at the connection on the group head where I presently have my temperature gauge installed.  Any suggestions?
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DavecUK
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Joined: 21 Sep 2005
Posts: 1,383
Location: UK
Expertise: I love coffee

Posted Mon Oct 13, 2008, 9:43am
Subject: Re: Andreja Rotary Pump
 

The flow rate of the rotary pump is so high that the restriction of the Gicleur (pinhole) within the E61 group is enough to allow the pump to reach it's maximum output (in your case 9 bar), before the balanced bypass cuts in and shunts the excess around the pump again. This is going to happen with/without blind filter and with/without coffee, or portafilter loaded. You don't need to install a gauge anywhere else, as the right place to measure the pressure is between the pump and the anti backflow (one way) valve and is precisely what your machine is doing. Sounds like you have no brew pressure issues at all and an extra gauge will just be additional work/cost for no benefit to you.

The only reason for even bothering with a portafilter mounted pressuring gauge, would be to check the accuracy of your machines gauge, should you have any reason to believe it may not be reading correctly, or on a machine that does not have its own gauge..
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Spaceman323
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Joined: 13 Jan 2008
Posts: 3
Location: Ohio
Expertise: I like coffee

Espresso: Krups 964
Grinder: Sterbucks Barista Burr...
Posted Mon Oct 13, 2008, 2:07pm
Subject: Re: Andreja Rotary Pump
 

Thank you for helping me on this but I am not sure I follow what you are telling me.  

I can understand that a flow restriction will maintain a certain back pressure between the flow restriction and the pump.  But it is also my understanding that I want to have 9 bar back pressure at the portafilter and it seems that I have some control over the back pressure at the portafilter by adjusting my grind and tamp. Course grind and loose tamp will result in low back pressure.  Fine grind and heavy tamp will result in high back pressure.

I don't think I am having any problems with my espresso machine but I find that I am not able to get the rich dark brown espresso drinks that I get at a few top espresso shops, even when using the same espresso roasts of these excellent coffee shops and I am searching for an explaination.  I am controlling temperature to best of my ability, timing my brew cycle, and pulling short shots but I just can't reach perfection and I would feel better if I knew for sure that I am maintaining the proper pressure at the portafilter.  

Maybe I am mistaken about my understanding of how pressure is maintained at the portafilter.
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DavecUK
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Joined: 21 Sep 2005
Posts: 1,383
Location: UK
Expertise: I love coffee

Posted Mon Oct 13, 2008, 3:06pm
Subject: Re: Andreja Rotary Pump
 

Perhaps it will help to think about the whole thing differently (its hard to explain, so apologies for the long post)

If the flow rate is at maximum during a double shot, say 2oz (60ml) in 25 seconds, this is a flow rate of only 8.6 lt per hour, your rotary pump is capable of a flow rate many times that through the group and depending on the size of Gicleur around 30 litres per hour..This means that any reasonable coffee puck is still going to have 9 bar pressure behind it, because the pressures either side of the Gicleur in the group will be equal (laws of physics)  as long as the pump can maintain a flow rate higher than the puck passes water (ignoring the effect of fast moving fluids at very high flow rates). So unless you got a 3-4 second gusher for a single or a 6-8 second gusher for a double....no problem.

I have also seen it stated on a few occasions that the OPV on a vibe pump machine set to run at say 9 bar, is there to release pressure when the coffee is ground too fine and that it doesn't matter if the pressure of the machine is too high, because it's the fineness of grind in the coffee puck that regulates the pressure to 9 bar....which of course is not true. An unregulated Ulka E5 will give a flow rate of 260ml per minute at 9 bar, but for a double you only need to pass 60 ml in 25 seconds, however if you want to keep the pressure down to 9 bar, you would be having to pass more than 130ml in 25 seconds.  So on unregulated machines you would have to grind so much finer, in fact fine enough to maintain a pressure of around 11 bar behind the puck at which time the ulka pumps flow rate will have dropped to around 60ml in 25 seconds.

It gets worse, if that Ulka is then replaced by a pump with a higher flow rate....then you need to grind even finer to maintain a 60ml pour in 25 seconds.

See here for the Ulka pump graph: Click Here (coffeetime.wikidot.com)

  • Imagine a machine set to deliver 50 bar pressure, if you could grind fine enough, then you could extract a 55ml double in 25 seconds....you'd have to grind pretty fine though
  • Now Imagine a machine set to deliver 3 bar pressure, you would have to grind pretty coarse, but then you still  then you could extract a 55ml double in 25 seconds.

In each case the taste would be totally different, partly due to the pressure dynamics and partly due to the fineness of grind exposing a larger area of coffee to the water flow.

Setting the machine to 9 bar, I suppose has been found to be the right pressure for the extraction on 2 front's, firstly any effect of pressure on extraction of solubles and secondly the fineness of grind required to maintain a volume of approx 2oz in 25 seconds for a double. Of course because the flow rates are so low, the pressure behind the puck is going to be the same as the pump head pressure (9 bar).

So...no you don't really have much control over the pressure behind the puck by varying grind (unless you get a very fast gusher), as below a certain flow rate (or finness of grind), you will always get 9 bar behind the puck no matter how fine you grind. If your machine pressure gauge is showing 9 bar and it is reasonably accurate (which is quite likely)....then the differences in your shots are liable to be down to 3 factors.

  • Bean type/freshness
  • Brew Temperature
  • Tamp and Grind (possibly even grinder or burrs)

Spending some time investigating the above 3 areas should help you achieve the same shots as in the shops. Different factors can be eliminated, e.g. for the beans, if you get a particularly good shot, ask the barista if you can buy 250g of the beans and try them in your machine. Borrow someones grinder and even their beans (if they are getting better shots than you), or try your beans on someone else's machine .
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Spaceman323
Senior Member


Joined: 13 Jan 2008
Posts: 3
Location: Ohio
Expertise: I like coffee

Espresso: Krups 964
Grinder: Sterbucks Barista Burr...
Posted Tue Oct 14, 2008, 8:58pm
Subject: Re: Andreja Rotary Pump
 

First let me say that I appreciate your help on this subject.  But I hate it when I can't seem to grasp something that must be so obvious to others.

I did check the flow rate of my system with the portafilter removed and and based on a 25 second test I found that it was passing water at a rate of 32 liters per hour which confirms that you know a lot more about this machine than I do.  Now I know the water is leaving the machine at zero pressure when the portafilter is removed and I know the pressure upstream of the OPV is 9 bar because that is what the gauge tells me.  I don't know how the pressure drops off between the OPV and the discharge from the open group head but I suspect that devices like the Gicleur are acting like an oriface (flow restrictor) and there is some pressure differential across it.  On the other hand, I believe that the pressure at the blank portafilter is probably 9 bar when I raise the brew lever as there is no flow downstream from the OPV so there is no pressure lose with devices such as the Gicleur.  

But the problem comes when I try to visualize what's happening when I am making espresso.  If, in fact, the devices (Gicleur, etc.) in the water path from the OPV to the portafilter can pass water at 8.6 liters per hour without measureable pressure drop then it must be true that there is 9 bar at the puck.  

As I write this the fog seems to be lifting and I am getting more comfortable with the idea that the pressure at the puck must be close to 9 bar when I am brewing my shot of espresso as the puck itself is the most significant flow restrictior in the system, with the pressure at the puck more or less constant while the flow rate varies as a function of the grind and packing of the puck.

Thank you for taking the time to work with me on this.  I can now continue with my quest for the perfect shot of espresso not worrying about my machines brew pressure at the puck.
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TomC
Senior Member


Joined: 22 Oct 2008
Posts: 2
Location: Vancouver, BC
Expertise: I like coffee

Espresso: Andreja Premium
Grinder: MACAP M4
Posted Wed Oct 22, 2008, 7:57am
Subject: Re: Andreja Rotary Pump
 

I have been wanting to do this conversion for quite some time now. Your modification looks very nice. Can you give me some information about your suppliers (pump, motor, etc.). Also, why did you choose to move the tank from one side to the other, was there not enough room on the right (looking from the front) for the motor/pump?
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Frosted
Senior Member


Joined: 1 Jun 2008
Posts: 20
Location: Seattle
Expertise: I like coffee

Espresso: Dalla Corte Supermini, La...
Grinder: Mazzer Mini, Super Jolly,...
Posted Sat Oct 25, 2008, 10:35am
Subject: Re: Andreja Rotary Pump
 

I got parts from several suppliers. Fittings were mostly from hoseandfittings.com(a really great source for BSP fittings); the 6/4mm hose fittings we from Cafe Parts; the hose from McMaster-Carr; you can get the motor and pump from either Chris's Coffee or Espresso Parts NW. The pump motor has to be a compact model (RPM was the brand) and the pump needs to be a short flange model (Fluid-O-Tech makes one and maybe Procon too, but both sources stocked the Fluid-O-Tech). The rubber vibration mounts to isolate the pump/motor came from Reid Supply.

I made the pump/motor base plate (if anyone was actually thinking of doing this, I could email you the pattern) from a sheet of scrap stainless I got from a local supplier. I spot welded stainless threaded inserts purchased from Lowes to the base plate I made, to firmly attach it to the machine base.

The pour-over water tank was removed completely, not moved. It is replaced by the pump/motor assembly. There is not enough room to put the rotary pump system where the vibe pump was. So this system needs to be plumbed in. If you get the plumb-in kit for the Andreja, it is designed to attach the hose to the back plate of the machine. I moved that attachment point to the bottom of the machine (much like the Vetrano) by using some new fittings not supplied in the kit. The kit does help by supplying some necessary hose and wiring, but those parts could also be fabricated and/or purchased separately, since you do not need everything supplied in the kit.

Hope this helps.
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