Double vs single spring

#1: Post by **retireddude** » January 9th, 2022, 2:59 pm

Can anyone comment on the pros/cons of a double spring vs single spring lever? I'm wondering what the difference is likely to be in the cup between the higher initial pressure (9+ bar) of a double spring, like in the Profitec Pro 800, vs a lower pressure (8 bar) in a single spring set up, as in the Londinium Compressa.

#2: Post by **Séb** » January 9th, 2022, 6:54 pm

I have both. At home i have a Salvatore double spring lever and at my Café i have a La Pavoni Diamante 2gr single spring lever. I much prefer a single spring lever without hesitation. It require less strenght to pull the lever, it's more forgiving on the puck preparation as you have less initial pressure and i tend to prefer the overall shot attribute too. One day i will sell my Salvatore for a smaller single spring lever like the Argos or next compact Londinium.

#3: Post by **emradguy** » January 9th, 2022, 7:16 pm

Peak pressure in the Compressa is 9 bar.

#4: Post by **drgary** » January 10th, 2022, 1:29 am

thedudeabides_1 wrote:Can anyone comment on the pros/cons of a double spring vs single spring lever? I'm wondering what the difference is likely to be in the cup between the higher initial pressure (9+ bar) of a double spring, like in the Profitec Pro 800, vs a lower pressure (8 bar) in a single spring set up, as in the Londinium Compressa.

John,

Does your Robot have a pressure gauge? If so, you can partially answer your question by trying different coffees with different initial pressure. Also, are you able to pull different styles of shots that you like, from a thick, sticky ristretto to a longer shot that may suit lighter roasts? What espresso styles do you enjoy and how do different pressures relate? How do your dose and grind affect the result? Paul Pratt, in his writing about the Robot, says that:

Paul_Pratt wrote:... traditional lever machines and their spring pressure ... is actually much lower than 9 bars. Remember this is measured in the portafilter whereas a standard pump machine will take the measurement upstream. So 9 bar on an E61 gauge will be 1-1.5bar lower at the portafilter.

Back to your original question, I don't know if single versus double spring will provide your answer. Single springed levers may provide initial high pressure, depending on the specs. When I tried double and triple springs on a late 1980s Elektra Microcasa a Leva and then a single new spec spring, I preferred the new single for shot layering. One of my rare vintage machines, a Lady Duchessa, has a very weak and small spring. With a double spring it pulls shots like an Elektra Microcasa a Leva with a new spring. It needs to be double springed to perform well.

January 10th, 2022, 9:08 am

drgary wrote:John,

Does your Robot have a pressure gauge? If so, you can partially answer your question by trying different coffees with different initial pressure. Also, are you able to pull different styles of shots that you like, from a thick, sticky ristretto to a longer shot that may suit lighter roasts? What espresso styles do you enjoy and how do different pressures relate? How do your dose and grind affect the result? Paul Pratt, in his writing about the Robot, says that:

Back to your original question, I don't know if single versus double spring will provide your answer. Single springed levers may provide initial high pressure, depending on the specs. When I tried double and triple springs on a late 1980s Elektra Microcasa a Leva and then a single new spec spring, I preferred the new single for shot layering. One of my rare vintage machines, a Lady Duchessa, has a very weak and small spring. With a double spring it pulls shots like an Elektra Microcasa a Leva with a new spring. It needs to be double springed to perform well.

Thanks for your comment, I understand what you're saying ... that it's not necessarily as simple as single vs double. The real purpose of my question was trying to understand the difference in the pressure profile provided by the dual spring in the Pro 800 vs the single in the Londinium, as those are the two levers I'm most interested in.

I drink medium-dark roasts, and tend enjoy sweet, rich, thick, "comfort shots" I don't have a gauge on my Robot, but I find that I like the results when I never press especially hard and significantly let up on the pressure toward the end as the puck resistance wanes. Based on that, all things being equal, I suspect I might like shots pulled from the Londinium more than the Pro 800. But, I was surprised that it's hard to find a lot of direct comparison between pressure profiles provided by spring levers.

January 10th, 2022, 9:13 am

I did find this ... which was interesting.

Lever Machine Flow Profiles

#7: Post by **ira** » January 10th, 2022, 2:07 pm

As long as the dual or triple springs are concentric and not stacked the important numbers are spring rate(pounds/inch or kg/cm) and pressure at installed length. Those two numbers tell you everything about the pressure profile of that set of springs. Whether those numbers come from single, double or triple springs doesn't matter. If we started documenting those numbers and the tastes they provide, it would probably get a lot easier to recommend springs. And a lot easier to pick a spring from a list of stock springs without having to rely on special "espresso spring providers."

Ira