Flow rate of a rotary pump espresso machine - Page 4

#31: Post by **erics** » April 18th, 2006, 11:55 am

The "orifice" in Silvia is located in the small 3-way valve adaptor that bolts to the grouphead. The reason I call it an orifice is that it receives the water from the, IIRC, 6.0-6.5 mm ID standpipe inside the boiler. Water from the "orifice" fills the small volume associated with this adaptor and 3-way valve, makes an abrupt U-turn, and heads towards the grouphead passageways.

IIRC, the size of this opening is about 1.0 mm (or less) and forms the seat for the 3-way valve in the de-energized position. I can say that there is no reasonably measurable resistance (pressure gage reads 0) under normal Silvia water debit flowrates (9.5 to 11.5 ml/sec) because of this "orifice."

The link to the lengthy AC posting which Jim Schulman provided before provides for some interesting reading. Not the least of which would be the posting from Barry J. that revealed he found NO difference "in the cup" on a pro machine with/without orifices and multiple operators.

Eric S.

#32: Post by **steffen** » April 18th, 2006, 12:40 pm

Thank you, Eric!

Without having read the AC thread, I think that there is a difference, if the machine is operated with a vibration pump or a rotary pump. In the latter case, an gicleur is in my opinion needed because of the greater flow rate of this type of pump.

Steffen

#33: Post by **erics** » April 22nd, 2006, 7:10 pm

FWIW, here are the unregulated flowrates of the common Ulka vibe pump and the Procon rotary pump. I edited the Ulka graph from their website to lengthen the flowrate scale to accommodate the rotary pump. Data for the rotary pump is from the Procon website.

Eric S.

#34: Post by **dsc** » June 19th, 2009, 7:55 am

Hi guys,

the first 10 second's flow from the group, including the boiling, bubbling water, should be between 60 to 90 mL, with 75 mL optimal.

anyone care to share where did the 60 - 90ml/10s value come from (especially the 75ml optimal)? I know someone once did a basic calculation which showed how much water is absorbed by the coffee, how much ends in the cup and so on, but I can't find it now.

Regards,
dsc.

http://users.rcn.com/erics/ · #35: Post by **erics** » June 19th, 2009, 8:37 am

. . . care to share where did the 60 - 90ml/10s value come from . . .

http://groups.google.com/group/alt.coff ... ater+debit

. . . how much water is absorbed by the coffee, how much ends in the cup and so on . . .

See section 4.3 of this: WBC Procedure for Measurement of Brewing Water Temperature

#36: Post by **dsc** » June 19th, 2009, 8:51 am

Hi Eric,

thanks for the links!

Regards,
dsc.

#37: Post by **nixter** » June 28th, 2010, 12:41 pm

I've got a Giotto Evo with a rotary and a reservoir that is giving me 125ml/10sec from idle. I'm having extractions identical to those with the dead spots in the photos. I'm using 19g in a triple basket so head space isn't an issue unless too much head space is a problem. Is it worth looking into reducing this? The fussiest WDT only seems to help a little.

http://users.rcn.com/erics/ · #38: Post by **erics** » June 28th, 2010, 12:49 pm

And your pump pressure is?

You would be much better off measuring the flow in 30 seconds or 60 seconds and dividing appropriately.

#39: Post by **nixter** » June 28th, 2010, 1:10 pm

9bar on the button. I'll measure longer tonight.

#40: Post by **Grant** » June 28th, 2010, 4:24 pm

Reading this thread with great interest, I went home and measured the flow rate on my Elektra A3 and it was a whopping 300ml+ per 10 seconds. The hole in the gicleur is pretty big - has to be close to 1mm. Running at 9bar pressure with a blind basket.

So (without having a smaller gicleur to test with), I stripped some different small diameter solid core copper wires I have around (I do a lot of electronics) until I found some that looked like they would go through the existing hole in the gicleur without blocking it. Inserted different wires about 1cm through the hole and then carefully wrapped about 2 inches or so around the gicleur a few time to secure it well in place. The existing "filter" (is that what it is?) in the group head still fits around the gicleur properly.

A couple tries and I found one wire that gives me pretty well 75ml per 10 seconds exactly. All I can say is wow...THAT sure slows the pressure ramp...instead of a 1 seconds pressure ramp...take about 7 seconds before espresso starts to bead up all over the screen. It was almost instantaneous before.

Have to GREATLY increase the flush time I notice...but that makes perfect sense I guess.

So....where can I find a "real" gicleur for the Elektra with this flow rate? (....not that I see any reason why my copper wire restrictor will not work for some time.)

Grant