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New 1 group lever from ACS - Vostok 1 group


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It's easy to explain:

more parts means more money to build something, if you add two springs you dont add just a spring, but extra parts, to make the chassis stiffer, and so on.

Now regarding the shot quality with 1 versus 2 springs. The higher the pressure the harder to dial in a shot specially when it comes to light roasts. This is why the 6 bar turbo paper was written to teach coffee shops that if they struggle with shots at high pressure better make them at 6 bar.

Yes it is harder to pull shots at 10-11 bar, way harder than 6 bar, but the shot quality at 10-11 bar has way more sweetness and fruit ripeness compared to 4-6 bar.  

The coffee I used for this test was on purpose a uganda mon cherry really light roasted, that has notes of cherry juice, pomegranate and macaruja/passion fruit. All these things are acidic and sour.

The shots at 6-7 bar max with a drop to 4 bar, lacked sweetness, to ballance out the acidity. So the overall experience was something extremely sour. Raising the temperature or grinding finer did not help.

The same coffee pulled in the two spring configuration, even at a lower temperature by 2 C produces a more balanced, pleasant shot that doesn't make you do faces.

For me this is clear already to what direction to go.  The trend of new days is to minimize the costs, the size, to everything.

A dual spring is more demanding, not only from the rigidity side but also from the user preparation, specially when it comes to filter roasts used as espresso. Since darker roasted coffee has little to no acidity, I do not think that this effect pointed out at low pressure will have any impact in the cup acidity. In the texture/mouthfeel on the other hand, probably yes.

 

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30 minutes ago, danielpugh said:

Quick question as a side - does anyone get a metal on metal chirp/screetch in the first inch of movement (pulling forward) of the lever? I've only just noticed, as it's not particularly bad and not present for the full swing/travel.  I wondered if just me and whether I need to add some grease/lube somewhere..

Yes, I had that, along with spring rubbing/skipping sounds during extraction. I took the springs out and added grease to the parts where the springs make contact with the group and the bolt (especially the small cylinder on top that holds the inside spring in place) and it's all gone now. 

Also, the little lever on the back can rub against the little nib so maybe check if it helps if you loosen that a bit.

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Strega is another machine that has two springs. Yes it has other problems that can be fixed if you are going to get your hands dirty or involved.  But even then you do not have the flexibility of the Evo.

I am more than happy with mine and really glad I got it. I would not buy anything else.

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36 minutes ago, danielpugh said:

Quick question as a side - does anyone get a metal on metal chirp/screetch in the first inch of movement (pulling forward) of the lever? I've only just noticed, as it's not particularly bad and not present for the full swing/travel.  I wondered if just me and whether I need to add some grease/lube somewhere..

I see you have had a good reply, also, can you make a video...might be a spring is wrong way round, check the outer spring doesn't have the flat area visible...look at @Denis S spring

35 minutes ago, Denis S said:

It's easy to explain:

more parts means more money to build something, if you add two springs you dont add just a spring, but extra parts, to make the chassis stiffer, and so on.

Now regarding the shot quality with 1 versus 2 springs. The higher the pressure the harder to dial in a shot specially when it comes to light roasts. This is why the 6 bar turbo paper was written to teach coffee shops that if they struggle with shots at high pressure better make them at 6 bar.

Yes it is harder to pull shots at 10-11 bar, way harder than 6 bar, but the shot quality at 10-11 bar has way more sweetness and fruit ripeness compared to 4-6 bar.  

There's a few things, most domestic machines would either have to be very long or they would tip up at the back with 2 springs, plus many don't have the strength in the chassis to support it.

Shot quality depends I guess on the coffee but IMO it's much easier to lower the pressure when you need to by slightly retarding the lever, a pressure gauge makes this easy to be consistent.

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24 minutes ago, BilliumB said:

Are any of you experienced users finding the need to (or benefit from) manipulating shots by retarding or adding pressure to the lever?

If so  how repeatable do you find it?

 

Surprisingly easy to do. You apply the lightest touch (one finger) to the lever to impede its movement during extraction. The gauge is fast reading too so if you overcompensate you can quickly correct. 

As for impact in the cup? More than happy with results I get employing full spring pressure of 10 bar and steady decline to 6 bar where I cut the shot. Maybe I should experiment more but the coffee is so good am following the dictum, 'if it isn't broke, don't fix it'. 

 

2099893675_Screenshot2021-08-18at10_18_29.png.64d72435dfb5ecf4fe98b7a7a3408e52.png

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2 hours ago, pinky said:

Yes, I had that, along with spring rubbing/skipping sounds during extraction. I took the springs out and added grease to the parts where the springs make contact with the group and the bolt (especially the small cylinder on top that holds the inside spring in place) and it's all gone now. 

Also, the little lever on the back can rub against the little nib so maybe check if it helps if you loosen that a bit.

no rubber/skipping sounds.  Just a metal scratch as the lever moves forward for the first time.  its not the little lever at the back (manually held down).  I think the springs are the right way around from looking at the side.  Its a minor thing,  i suspect easy to fix, and not affecting shots.   Ill look to take out and add grease soon (busy tomorrow, so Friday/weekend), as was loooking to check the internals etc anyway.  ill record something if i get time for general information.  Thanks All.

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@Hurzman Couple of things to try before contacting ACS...because they would have tested it before it left the factory

Remove the gauge...be careful, don't twist it by the body, you should find a small square area behind to put a spanner on. It won't be in tight at all as they use PTFE tape. Once it's out check a bit of the PTFE hasn't blocked the hole in the threaded gauge connector. If you can't see anything, put it back with PTFE and contact Paolo.

Another quick test you can do, find a rubber backflush disk, or put coffee in the portafilter and actuate the pump using the small lever at the back of the group...does water piss out of the gauge hole, if not, you have a different problem. If water does come out, put the gauge back on and it might then be working!

If you don't have any PTFE, then you won't be able to seal the gauge and won't be able to use the machine...until the gauge is back and sealed. When you put it back it doesn't need to be completely tight, there may be some slack, which you use to make sure the gauge is properly aligned.

 

Edited by DavecUK
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Pull down the lever with the machine turned off, then grease the main shaft/piston rod and then grease the sides of the metal chunks on the lever arm that will rub against the grouphead metal. Once you pull down the lever you will see what I mean.

I know someone pointed this out a few months ago, but who wants to try it first?:

https://aliexpress.com/item/1005002560205725.html

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6 hours ago, Denis S said:

Pull down the lever with the machine turned off, then grease the main shaft/piston rod and then grease the sides of the metal chunks on the lever arm that will rub against the grouphead metal. Once you pull down the lever you will see what I mean.

I know someone pointed this out a few months ago, but who wants to try it first?:

https://aliexpress.com/item/1005002560205725.html

Thanks all.  This morning i could see wear marks on the side of the lever rubbing against the rear right hand side of the caliper that holds it (i.e. the bit that rotates around the large bolt).  i gave the lever a sharp knock (from right hand side towards left), and it seems to have sorted it for now at least.  

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