Monday, August 1, 2011

67 Cremina - Rebuild Time

So the boiler has now been removed and stripped of asbestos insulation. Now it's time to shine her up.

One thing I know for sure, I won't be using sandpaper like I've seen on other restorations. Sandpaper scars up the surface horribly (even fine grit). Instead, I'll soak the brass boiler in a ctric acid solution for a few minutes then rub it lightlly with a nylon scouring pad (NOTE: Don't use ANY citric acid on the chrome parts or it will strip off the chrome).

After the mild acid bath is complete, I buffed the surface using Simichrome paste. This stuff works like magic and creates a "gold" like mirrored surface on the boiler. The solder adds a neat "candle effect" I think.


I touched up a very small spot on the inside of the metal frame with Krylon "hammer surface" grey paint (a nice match).

All the remaining parts were removed from the frame (including every nut and bolt). All bolts were cleaned and lubed for re-assembly.

The grouphead was stripped entirely as well. The mini snap ring pliers worked really well for the c-clips!

Now time for re-assembly:

Despite the cleanliness and obvious lack of use of the machine, the rubber gaskets were all baked flat and cracked. Butyl rubber is temp rated to 250F and has a shelf life of only 15 years, so I'm WAY past due for a change! I replaced every gasket using the gasket replacement kit from Orphan Espresso. The new gaskets are silicone, rated to 500F and with unlimited shelf life . They should last MUCH longer and allow me to re-use them several times when I need to strip every 2 years or so to remove scale, etc.

Here's a picture of the old gaskets (on top) and the new ones (on bottom).


First was to install the boiler end plat gasket and reinstall all the wiring. Thank goodness I took a picture of the wiring before removing! I needed to refer to it several times. It then went back together perfectly.


Next was the most difficult part....restoring the group head. I chopped of all the old piston seals and soaked the brass portion in citric acid (NOT the chrome part though). Still, I needed to use steel wool to remove the black from the piston grooves.

On the inside walls of the group head chamber, I used steel wool, and then wet sanded with 400 grit paper in a circumferential direction to avoid and length-wise grooving that could cause slight leaking. (This is the only area where I sanded...since it cannot be seen).



I soaked the remaining chrome parts in Dusty Caf cleaner overnight. (This is a very mild soap used for cleaning portafilters and for backflushing and will not strip chrome).

Once everything was clean I installed the new piston seals with Dow 111 lube and did the upper rod cup seal as well. With a litle patience and poking, everything went together smoothly. The OE supplied rod end cap and instructions worked perfectly.

Here's how it looked when done:


The next step was install the sight glass tube and new o-rings. These worked VERY well. Only problem was trying to figure out how much torque to apply so it didn't leak but not so much that it would crush the glass. The trick seems to be to tighten it ONLY enough so it doesn't twist, then tighten more only if needed after the hot leak check.

The remaining items on the top rail, pstat, faceplate, steam faucet and grouphead all went on in about 30 minutes. The saftey OP valve was installed with a teflon gasket from OE. But for some reason the replacement copper washer for the steam faucet nut was missing (maybe they assumed mine was a post 1982 model?). In any case, I re-used the existing copper washer (which leaked but eventually sealed after some good tightening). I'm not sure why OE doesn't supply a teflon washer for this nut as well, but I suppose it is because the nut holds the steam tap from moving, so it needs to be a bit stiffer than teflon.

The new handle was installed as well. It looks great and appears totally original. (I'm very happy with that).



Not much left to do except test her out!

I pluged her in and crossed my fingers I got all the wiring right! Phew. No zap.

I added an Omega gauge to the steam wand tip with a rubber hose and checked the pressure. It was low but I increased the pstat pressure to get between 0.8 bar and 1.0 bar (quite a big deadband!).


Well that's it. Just added the back and top and here is the final result:



And another shot from inside showing the sexy boiler:


So what about the espresso you ask?

Well, I pulled a few shots and the first few were a bit hot ( I since dropped it down 0.1 bar). I also need a lot more practice. Things like warm-up time, warming shots, pre-infusion, dosing, etc, all make a huge difference. I'll report back with some espresso pictures after I've gotten a few more hours on her.

All in all, a WONDERFUL restoration experience. I can't imagine a better machine to start out with as a first project, since everything is simple, easily accessible and most parts you can get from Doug and Barb at Orphan Espresso (along with their free, excellent advice).

4 comments:

  1. Saw your youtube video on this machine; great job! Curious if you could explain how you created the wand gauge for the 67 (exact parts, size of tubing, etc.) as I'm interested in creating one myself. Thanks!

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  2. I bought my steam wand pressure gauge from Orphan Espresso for $24. Unfortunately, they now seem to be sold out. I'd try e-mailing them.

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  3. Thanks for the tip. I emailed OE and they just simply forgot to put them back in the product catalog. Also had a couple more questions: What do you have rigged up to your Mazzer SJ? It looks like some sort of power control/switch or is this part of the SJ itself? Lastly, I like the look of the cup you're using in your vid (the blue/steel look), what is it exactly?. I've been pretty fond of the Rosenthal Illy line myself.

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  4. The thing attached to my SJ is a Gralab 450 digital darkroom timer. It turns on the grinder when you hit the big button and turns it off at any time you set (in 0.1 sec increments). It basically turns any grinder into a timed dosed grinder (like the Vario). They go for about $200 new, but you can find them on E-bay for $50, since everbody is selling there old darkroom stuff since digital took over.

    The espresso cup is a fancy handmade cup from Artazza. They go for $35 each....so a bit pricey.

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