I had heard that a poor craftsman blames his tools but the ability angle is seldom mentioned. Like a breath of fresh air Rawman!!!

Finally I managed to get a quote for a spring for the Mini Gaggia (Elektra is next, sorry!).

Most of the manufacturer have AISI 302 in stock, it's hard to find who has 304 or 316 (and they have to buy a mininum of 20kg of steel, that could make around 300-400 springs depending on the specs!!!). Does anybody thinks there is a problem to that, considering the spring of Mini Gaggia is submerged in the boiler water? Any SS for me it's scary, considering the composition - we always hope the material get safe from corrosion, if it touches the food!

BTW, the spring will be 95mm long, 27mm diameter, 3.5mm wire, and will have 11 coils. We'll get from 2 to 0.8 bar added to the machine, and around 45 kgf max to pull the lever and let the water enter the chamber. I think more than this should be dangerous, it's a small machine. Even 45 kgf more will require 5 kgf more on the lever, from 11 kgf to 16 kgf, that's heavy!

Márcio.

Marcio,

I am not 100% sure that the frame of the Mini will take the additional force. You might want to run some tests. It is simple angle iron welded, but I can't tell if it is over engineered or close to the edge...! It is not particularly sturdy and if it bent it would probably ruin the plastic case as well. I suspect I could break it by hand if one end was in a vise.

Maybe since you seem to be an engineering sort, you should look into this. It wouldn't be hard to weld a triangle to the "L" so as to increase the strength; if it failed, that's probably where it would fail, though it would be possible to fail where the bolts attach the boiler to the "L"s.

Finally, as I noted in another thread, compressing the spring to get it onto the piston is very tricky. Keep in mind that not only do you need to compress it, but you also need to screw the piston onto the shaft, so if you are putting pressure on the end of the piston and trying to turn it a few turns, that will be very hard to do.

If I had to do it again, I would fabricate a special miniature spring compressing tool. It would be easy to make, modeled after the car spring compressing tools. Using pieces of wood or your hands is just not going to work, in my opinion, especially with an even more robust spring.

One thought that occurred to me is that a careful tuning of your grinder might get you the results you want in the cup... I don't want to discourage you, but....

Your friend,

dan

Hi, Dan! Thanks for all the tips!

I agree - just yesterday I was thinking about the iron L that hold the machine... I'll try to calculate something or test it some way.

I know the piston is hard to install back. The new spring wouldn't add to it, as it would be 95mm and there is 82mm free, so it will be compressed only when the piston starts to screw to the shaft.

The manufacturer nicely offered to make one sample spring, so I'll probably go there to show the machine and install the spring.

Marcio.

I recently had a set of springs for a Gaggia GX group wound for me by a local company, the cost was £40 (~$60US) for two springs, though I've got no doubt the cost would come down with quantity.

The springs in my machine were probably the 1970s originals and quite corroded - one spring was noticably weaker than the other, which was fun to begin with but I felt like it was time to replace them.

I disassembled the groups, took some measurements and emailed a local company for a quote. When I arrived to pick the springs up they were 2 loops wrong by my calculation, and my measurement was 2 loops short by their calculation. Fortunately I had brought an original Gaggia spring, which they then offered to copy for me there and then.

After looking at the original they selected the appropriate spindle and wound it freehand, adjusted it with a sort of press which could spread the loops individually, then ground the ends to the appropriate length. The springmaker then heat treated the spring with a blowtorch for a few help release the residual stress from the winding.

So 45 minutes after arriving I left with two hand crafted springs.

I got the groups reassembled today and the first thing I noticed was the comparative abundance of crema in my first shot. In future I'd like to test the actual pressure profile using a modified portafilter, but maybe when I have more time to do so.

I took a few photos too, if anyones interested I could post a few in this thread.