Has anyone out there replaced their spring for a custom-made one to up the pressure in a spring lever? It seems feasible, as there are spring manufacturing companies that will do many sizes, rates and materials. I've used this company before to make a custom set of springs for my Datsun 510...I think $250 for a set? But thats a car. It seems like there are enough "lever-heads" out there to order a bunch of springs to "Pimp my....(Peppina, Mcal, PV, La Rivera)" or what ever fits the most demand. Just something I thought about this morning. I know if I HAD an MCAL I would be interested in a spring that modified the brew pressure to 9 bar and I'd be willing to shell out $30-50 bucks for it! Just a thought.

yes, i did it for my faema president!
my machine has an older style grouphead, so the standard faema spring was too long. got a fitting spring from a cimbali machine, but it was not strong enough for my needs so i calculated a new spring and had it custom made by a spring manufacturer here in my town....but you have to make compromises cause to keep the spring in the elastic area u have to choose between some variables (high pretension, high pressure in the beginning of the shot and so on). my current spring gives about 12 bar when the lever is down and goes back to about 6 bar when the lever is up. if u calculate beware that the lever will go up some way before the pressure is fully applied to the coffee.
the new, stainless steel springs:

i even did some pressure test (mis-)using a three-axial testing machine:


i also did some spring modification on my elektra mcal. here i found a standard spring that fits perfectly on the piston shaft and is only very light pretensioned when lever is up. when u pull the lever it gives an additional pressure of about 2 bar to the coffee which gave me a large improvement in the cup. the additional spring was about 2 euros per piece.



cheers,
stefan

edit: i would think about the second-spring option first. the standard springs are close to what is technically possible in terms of length under full tension, keeping the spring in the elastic area and stuff like that...

Wow, Stefan, great information. I haven't thought that much about it, but upping the pressure with a different spring on the La Peppina would be interesting, but it doesn't sound so simple. Also, the flapper valves would have to be able to withstand the increase in pressure, but since I sometimes "help" my lever return, I don't think that would be a problem.

13thfloorelevators wrote:If u calculate beware that the lever will go up some way before the pressure is fully applied to the coffee.

I see this all the time with my La Peppina and I'll do a couple of Fellini pumps to prevent this. With a double, I'll load the puck with water for a ten second pre-infusion, but for a single, I just pump to the point where the lever has some resistance and go to avoid over-extraction.

yakster wrote:Wow, Stefan, great information. I haven't thought that much about it, but upping the pressure with a different spring on the La Peppina would be interesting, but it doesn't sound so simple. Also, the flapper valves would have to be able to withstand the increase in pressure, but since I sometimes "help" my lever return, I don't think that would be a problem.

i dont know the peppina so i cant say how it would work on this machine!

yakster wrote:I see this all the time with my La Peppina and I'll do a couple of Fellini pumps to prevent this. With a double, I'll load the puck with water for a ten second pre-infusion, but for a single, I just pump to the point where the lever has some resistance and go to avoid over-extraction.

yes, i do it as well..at least one pull after the extraction started (and several seconds of preinfusion), but it still goes a little bit up...just to consider when u calculate the spring...

13thfloorelevators wrote:i also did some spring modification on my elektra mcal. here i found a standard spring that fits perfectly on the piston shaft and is only very light pretensioned when lever is up. when u pull the lever it gives an additional pressure of about 2 bar to the coffee which gave me a large improvement in the cup.

Interesting! Do you have specifications for the spring or where you bought it from? Would you elaborate on the improvement?

HB wrote:Interesting! Do you have specifications for the spring or where you bought it from? Would you elaborate on the improvement?

well...basically i get more crema and the shots taste rounder....been some time since i did the mod so i cant explain the difference in detail, but i remember how satisfied i was about doing it after the first shots (even considering that the grinder is adjusted for shots on the faema, as i only use the mcal in the morning because it heats up faster)...

for the specifications: normal stainless steel 1.4310. Flat ends. Steel diameter d=2,5mm; Outer diameter De=20mm; Unloaded length l0=65mm; 8,5 turns of the steel.
i can send u details from the german spring manufacturer and article number per private message if u want. dont want to do advertisement here and i doubt they will send to the states.
better just call a local spring manufacturer and they can calculate with u the spring u need. just measure the pretensioned and the fully tensiones spring length of your machine, the diameter of the piston and then u can calculate from the needed additional pressure the spring (or let it calculate)...

How funny...I've been casually researching new springs for my MCaLs also. But I never thought about the double spring-that's brilliant. So how much energy do you think that the second spring has on its own? A few of the places that I have found do have springs that are almost an identical match, but the problem is I would have to buy at least 10 springs.....

did the calculation quick on the back of an envelope i dont have anymore. just remember that the diameter of the piston was about 40mm.
so the area is 20^2*pi=1256,64mm^2
that means that a spring force of 126 N (pulled lever) is about 1 Bar of additional pressure....dont know the length of the tensioned and pretensioned spring now, but with this u can calculate....

As far as the La Peppina goes, I think that the washers may not be an issue as they seal upon a solid surface and just hold tighter as more pressure is applied...Right?

But the MCAL, a second spring? Brilliant! It make me want one just so I can tinker more...my fear is that my wife will kill me if I get a fourth espresso machine!
-Oh well, you only live once.

Tom!

Have you found identical springs but stronger for MCAL?

I'm very interested on this too, a second spring (+ 2 bar is very nice) or a stronger. I thought about that for the Mini Gaggia too, maybe a second spring could be the way to go.

Márcio.