Vibiemme Domobar Super + Rancilio Rocky = Impossible?

Need help with equipment usage or want to share your latest discovery?
mlc85

#1: Post by mlc85 »

Hello all,

I just got a nice shiny VBM, but i cannot get a decent shot at all, period. I have a Rancilio rocky grinder, found it's zero point, cleaned it, and I am at the finest grind possible: one step away from the high pitch chirp noise when the two burrs are going against each other.

My beans were roasted 3 days ago.

No matter what I do, the shot gets pulled in 10 seconds, the pressure reading from the VBM is only 4 bar at max. Is this normal and I have to get a new grinder, or is there anything else I can do with the rocky?

Thanks,
Mason

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cafeIKE
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#2: Post by cafeIKE »

Time to update the profile :wink:

How old are the Rocky burrs?
Double?
Single?
How much coffee are you using?

What does the coffee feel like? At the finest setting it should be almost powder. It's possible that the burrs are not seated properly, i.e. they have some coffee under them. Cleaning a grinder is a surgical operation. Always vacuum out the chamber before re-assembling the burrs. When tightening the burr holding screws, seat each one lightly and then tighten sequentially.

Espresso adjustment is measured in a few tenths, i.e. 0.0003 inches. Any misalignment of the burrs renders such adjustment impossible.

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dynamiteid

#3: Post by dynamiteid »

Hi Mason. This is my first post after lurking for several months, but thought I should share my experience.

I have the same set-up, and do not have this problem. It does sound to me like the something might be wrong with your grinder. If I set mine near the zero point and tried to pull a shot, I would choke my machine for sure.

My typical setting is about 5-6 clicks above the zero point (my zero point is at 5 on my Rocky) so I am set at 10-11. At this setting, with most freshly roasted coffee, I get ~9 bars of pressure and about a 27 second pour to reach ~2oz.
My particular method is as follows:
1. I dose about 17g of coffee into the portafilter by moving the portafilter around under the chute while I grind to help get an even distribution. I also gently tap the portafilter down on the portafilter holder about halfway through the fill to help settle the coffee and allow space for a little more coffee.
2. I then use the WDT method to break up the clumps and even out the distribution. (one of the biggest improvements for me.)
3. I then use the back of my pinky finger to gently level the coffee. I move my finger top to bottom, and then side to side. Being careful not to compress the coffee too much and striving for a level surface.
4. I tamp gently to set the puck.
5. I then tap the side of the portafilter with the tamper to knock down any grinds clinging to the side.
6. Then I apply a final tamp with about 30lbs of pressure followed by a polishing turn.
7. I put the portafilter in the machine and start the extraction.

The things that have really helped me have been:
Use freshly roasted coffee.
Use a consitent process every time.
Only vary one thing at a time if you are experimenting.
Use the WDT method to improve distribution.
I had to adjust my pressurestat down to about .8 bar (the stock setting was 1 bar)
I also have to adjust the grind up or down 1 or 2 notches depending on the coffee (and I guess humidity etc.)

Having said all of this. I think I get some pretty good results. Some even bordering on great, but I am still learning and experimenting. I hope that helps.

Dave

mlc85 (original poster)

#4: Post by mlc85 (original poster) »

Hi Dave and Ike,

Thanks a lot for the help. I reset the burrs on my grinder, and screwed them in sequentially. I tried a single shot to not waste as much coffee (expensive practice), and I had some mild success. About a 15 second shot with 7 bars of pressure, and some crema! Still overly bitter, but a major step up. A few important questions though:

I'm 3 clicks away from 0 point, and when the hopper is empty, I still hear a clicking noise. Is this normal?
When you are putting the portafilter in, how much force should you use? Do you pull it to the right until the portafilter is front and center of the machine or at a slight left angle?

If my starbucks barista could do pretty decent shots with my rocky, should the E61 be able to do the same? Is the grind a big enough difference between the two machines?

Thanks,
Mason

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cafeIKE
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#5: Post by cafeIKE »

When mounting the portafilter, just enough force to snug it to the gasket. A gentle tug past the contact position is all that's needed. The handle position will vary slightly over time as the gasket wears.

Can't stress strongly enough that grinding coffee is the key to success. If you are grinding single shots, that's like grinding coarser. Quite a bit of stale coffee remains in the grinder after a shot. Grind for a few seconds to clear this stale coffee.

A Rocky in good order should be adequate.

What is the gauge pressure on the blind basket?

mlc85 (original poster)

#6: Post by mlc85 (original poster) »

The blind basket reports a pressure of about ~10-10.5 BAR. Is that too low? I was able to hit about 9.5 BAR on a single shot, which produced an almost drinkable shot in 15 seconds.

I'm still unclear as to what you mean by grinding single shots is like grinding coarser. So a double shot/naked PF should be able to pull on a coarser grind than a single shot? How does that work or is there some reading you can point me to? I've read the espresso diagnosing espresso extraction and WDT.

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cannonfodder
Team HB

#7: Post by cannonfodder »

That blind pressure is around where it should be. The onboard gauge reads about one bar high with a blank basket. I had someone over a few weeks ago and he brought over his Rocky. We had a similar problem, it just would not grind fine enough and we had the burrs backed down all the way. It may be time for new burrs or a grinder upgrade.

Your shot timing is real bad, once you get a 25-30 second double your cup will be much better provided you coffee is up to the test. If your coffee is old, you will also get fast shots, when was it roasted and what kind of coffee are you using? FYI A single shot often requires a finer grind than a double.
Dave Stephens

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mlc85 (original poster)

#8: Post by mlc85 (original poster) »

Hmm, Dave, what did your friend do with his rocky? Did he have to return it and get a better grinder or did new burrs fix his problems?

I'm using a light espresso blend that was roasted four days ago from Kean Coffee (http://www.keancoffee.com/), a local roaster here in Orange County.

Hmm interesting, I wonder why I can get a 15 second shot from a single but a 5 second one from the double. There shouldn't be any difference between using the double PF and a naked PF.

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Randy G.

#9: Post by Randy G. »

I went from:
Silvia + Rocky to VBM Domobar Super + Rocky to VBM + Kony

So I can say that yes, the Rocky should work with the VBM. If you had been buying a grinder I would never recommend it as there are other grinders that work far better with the VBM, but it should work.

Before assuming that the grinder is at fault, be sure that your technique is correct. A quick test is to prepare a double as you normally would, lock it in place, then remove it from the machine. There should be no marks or signs of disturbance on the puck. If there is, you are using too much coffee.

The next step is to use the WDT (Weiss Distribution Technique) where a straightened paper clip or equivalent is used to stir the coffee to break up any clumps before leveling and tamping. This is done before tamping, obviously.

On my website (URL in the sig) go to the "How To" section on the right and read number 12. It has a lot of tips and technique directed at what to do when things just aren't right with the espresso.
[see my post further down in this thread for dose/distribution/tamping instructions]

Once your technique has been eliminated, we have to suspect the grinder.
Did you get it new?
How old is it?
How old are the burrs?

It sounds like that Rocky may have a problem. If it is used, it may have been abused or the burrs are WAY past their useful life. I replaced my Rocky burrs about every 18 months or so. When I sold it, the grinder was about seven years old, and I had replaced the burrs at least twice. Rocky burrs are not the best and last a lot less than is generally accepted. Like shock absorbers, you don't realize how bad they are until you try new ones. Can you rock the hopper? If so, the slop in the threads my be a contributing factor, but there is probably more going on that that.

Since you are in an area with a lot of other home baristas, try getting someone to bring over their grinder and see what happens. If not, I really like my Mazzer. While I would not necessarily recommend the Kony to everyone (nor would I talk them out of it) the Super Jolly is an excellent grinder. The Mazzers in general have a really great upper burr mounting system that holds the burrs in precise and repeatable alignment. The stepless adjustment is also a plus when compared to Rocky.
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cafeIKE
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#10: Post by cafeIKE »

mlc85 wrote:The blind basket reports a pressure of about ~10-10.5 BAR. Is that too low? I was able to hit about 9.5 BAR on a single shot, which produced an almost drinkable shot in 15 seconds.

I'm still unclear as to what you mean by grinding single shots is like grinding coarser. So a double shot/naked PF should be able to pull on a coarser grind than a single shot? How does that work or is there some reading you can point me to? I've read the espresso diagnosing espresso extraction and WDT.
As Dave said, the pressure is in the ballpark.

Instead of 'grinding single shots' I should have said 'per shot' : You can either leave beans in the hopper or dose the hopper with just enough beans for a shot, be it single or double. The latter is equivalent to grinding coarser.

It's not mandatory to change the grind between double and single. For dinner parties, I just adjust the dose slightly. Milk hides a multitude of sins.

How dark is the roast? A very light roast tends to run faster than a darker roast.

How much coffee is in the basket?