Conti Prestina Espresso Machine Restoration 101 (Completed and Indexed) - Page 38

Equipment doesn't work? Troubleshooting? If you're handy, members can help.
jedovaty

#371: Post by jedovaty »

OOOOOOOOOOoooooooooohhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh! :shock:

That's how you do it! I had a completely different picture in mind.

Imagine if you had left that spring compressed... you think it would've sproinged out?

Excellent. 8)

User avatar
drgary
Team HB

#372: Post by drgary »

I was in a seminar all weekend so didn't have time for restoration. At this point, though, the piston assembly is all taken apart and mostly cleaned up. Also McDave at Allann Brothers came through and got me a new spring and a new can (for the top of the group) within a week. The new spring is about 1/2 inch taller than the old one, so although the old one is still good the new one will give factory spec pressure and I'll keep the old one as a back-up. The new can is both thicker and lighter weight than the old one, which I'll also keep as a back-up. For tonight I just have photos of the replacement parts. I'm documenting all of these parts here so people rebuilding Prestinas have something more than old, sketchy parts diagrams for a reference. I'll show the piston assembly components soon.



Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

User avatar
drgary
Team HB

#373: Post by drgary »

Here's today's progress. I started by cleaning the lever assembly parts that are arrayed here in homage to Francesco Ceccarelli. Of course he does this for a whole machine and it looks neat and well lit. I'm not showing the piston gaskets, but I have them ready to install. Following Doug Garrott's suggestion I cleaned the old grease from the lever gaskets and pins using Coleman gasoline, which doesn't have the odor of auto fuel. I also ran over the brass parts with a wire brush on a Dremel tool. They're shinier than they look in this photo.



What you'll see won't look like much work, but as a beginner I had to check each step by searching two year old photos. I also had to deal with issues not expected by a first-timer. Still what you see will also look like a lot. :mrgreen:

To proceed I need to mount the machine and attach subassemblies to it. With the Prestina everything's mounted to the boiler or the frames holding it. When I tried to screw together the inner frame and the base frame the screws wouldn't catch. This was because the threads were blocked at the opening by powder coat. I realized I could take care of that with a small file. Those pieces screw together with the rubber feet.



I also needed to complete a touch-up of a bare spot left by the powder coater on the frame crossbar. I applied some high heat Rustoleum after this photo.



Then I attached an inner frame piece that holds the grounding wire.



I had no idea the next part would be so satisfying. It's been a year and a half to get to here. Lots of rusty parts, cleaning, like hacking my way through a junkyard. Then research, sorting through advice, parts procurement, delays. This afternoon I finally mounted the boiler back on the frame and was thrilled to see my Prestina starting to look like an espresso machine again.



After all the rust and corrosion of the tear down, I made a point of coating every screw, washer and bolt in food-grade anti-seize compound. Next I mounted the top frame to the boiler. To figure out exactly how all the bolts went in required searching old photos.



Next I slathered the studs in anti-seize compound and inserted them.



Then the group gasket.



This was fun! I got ready to secure the group cylinder to the gasket when I realized I need to source nuts that fit on those studs. And that's the way it goes, painstaking piece by painstaking piece. But now it's all coming together and I'll soon have a working Conti Prestina. Working with clean and refinished parts is a whole other feeling than the teardown, that's for sure!
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

User avatar
orphanespresso

#374: Post by orphanespresso »

Ah yes, now you are feeling that deep satisfaction...putting all of those clean parts back together. Makes it difficult to stop since there in "just one more thing" and the machine grows and takes shape. I always like to do all the plumbing and hang the pipes, then go through and tighten them all up. Once that is all done installing all of the new wiring is equally enjoyable.

It sure looks nice :D .

User avatar
drgary
Team HB

#375: Post by drgary »

Thanks, Doug.

It's hard to imagine enjoying any new machine as much as I'll enjoy the fruits of my labors on a classic like this. If I ever take on another similar project it will go faster just because of what I've been learning from how the machine works, to which projects to send out (polishing), to what materials and tools to use, and what to photograph during disassembly.

Each piece of this has a learning curve. I've never done copper tubing before. I look forward to watching your tutorials. Maybe some parts will need soldering. Some bends may require filling the tubing with fine sand. I can't be in a hurry but now it's not all parts in boxes anymore.

11/25/12: I've modified the entries in this post to offer an additional Orphan Espresso tutorial for easy access. Orphan Espresso's website offers a treasure of tutorials like this. Thanks Doug and Barb!

The first Orphan Espresso tutorial is about determining fitting sizes and bending pipe. Here's that video from the link on their great website. They've done the rest of us a great service with this. I've provided written notes below these videos so you can watch the demonstration and then refer to the notes. For this first video Barb prepared a simple chart you can reference directly on the video.
The second Orphan Espresso tutorial is about an easy and long-lasting repair to a compression fitting that has become worn.
Added notes from Doug and Barb's tutorial on fitting sizes and bending tube:

Espresso machines use metric sized pipe. The metric number refers to the pipe's outside diameter (OD, measured using a caliper). The pipe gets soldered onto a mushroom shaped "compression cap" or "cap" that seals against the male thread on a fitting (a valve or L-shaped plumbing termination part, etc.) with a "cap nut." No Teflon tape is needed when these parts are new.*

6mm pipe inserts in a ¼ inch BPP/BPT (British Parallel Pipe aka British Parallel Thread aka British Standard aka Imperial) fitting. To measure what pipe is needed from the thread, the OD is about ½ inch or 12.5 mm. The general rule for measuring Imperial sizes is for the size of pipe, add ¼ for measuring the OD of the fitting. This is the smallest size commonly used in espresso machines, although there is smaller-sized pipe available.

8mm or 10mm pipe fits on 3/8 inch cap nut (since the cap is flared it works for both sizes). The OD of the fitting is .628 = about 5/8 inch or 16.5mm. These sizes are most commonly used in espresso machines.

12mm, rarely used in espresso machines, uses ½ inch cap nut and OD of fitting is more than ¾ inch (about 13/16).

Doug then illustrates these fittings by showing a Gaggia Italcrem machine and notes that the manometer fittings often use a relatively thin pipe, in that case 6mm.

Doug then illustrates use of different bending tools, including a sophisticated mandrel bender, and two types of automotive brake line benders.


* The second video tutorial in this post shows what to do if a compression fitting starts to leak. The fitting becomes worn when people overtighten to stop the leak and distort the mushroom-shaped cap. Doug recommends wrapping that with Teflon tape as a long-lasting fix.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

User avatar
TomC
Team HB

#376: Post by TomC »

Coming along beautifully now! I'm surprised, you didn't have the nuts for the group prior to the tear down? Was it already in separate pieces?

User avatar
drgary
Team HB

#377: Post by drgary »

Hi Tom:

Yes, I'm pretty thrilled. Getting new metric size 6 nuts is pretty easy and doesn't slow the rest of the project. The major nuts, bolts and studs for the boiler and group were a rusted mess during the teardown. Much of that went into bags, some was destroyed when dealing with the rusty fasteners early on. Then what was salvageable went into acid baths and such. It's hard to keep these all organized when you try and recover them en masse. So up until now it's been lots of boxes of parts and fasteners. As I piece together each new major part, say the steam tap or lever assembly, those parts come out of the boxes and there's less left to sort through. If I had to do it over again I would document the disassembled pieces like the sections of the exploded parts diagram. Happily there's little procurement left and those are routine parts that aren't specific to this rare machine. I've been gathering new fasteners without posting about it. The exception is the drip tray grate, which will have to be fabricated because there are no spares anywhere. I'll improve on the original, which was pretty crude. I think the main value of this machine are its wonderful mechanics and compactness and not that every piece is vintage spec. You've got a group that's still being manufactured but a frame, boiler and case that are uniquely compact. As it sits on the bench I'm amazed at how small it is for a commercial lever. It's not very much bigger than my Isomac Amica.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

User avatar
drgary
Team HB

#378: Post by drgary »

Today I was able to reattach the group and install the spring. Here are the steps so others with Prestinas can have a guide. I've posted many photos with minimal comments, just so you can see what it's like to inspect the parts in place. Fitting parts and then attaching them is a great way to see what's next along with checking photos of the teardown.





Here I mount the can just to have a look.



Then I momentarily remove the can to fit the group connecting bolts before reinstalling the can.







Next I assemble the portafilter holder. Here it is with some plating worn away but clean.

Now the portafilter gasket's installed.



On the top side there's a small ring where it fits to the cylinder.



Here's the shower screen installed.



McDave provided piston gaskets prelubed with a silicone based lubricant because DOW 111 apparently breaks down these seals. They are genuine Conti parts, by the way, labeled as such, but I didn't show you a close-up. I'd thought this step would be harder than it was. A chopstick eased installation. The part of the photo that looks like a tear isn't. That's lubricant. The bottom ring has the flap faced down, the next one has the flap facing up. The top seal has the flap facing down. The empty space is meant to be there.





The lever cap has a wide, flat washer to protect against wear from the top of the spring. Here it is cleaned and installed.





Screwing the piston rod to the lever cap was only slightly challenging. I fastened the piston in a soft bench clamp. Then I pushed down with about 20 lbs force, aligning the lever rod into the threaded hole in the top of the piston. A few turns and it caught. Then I used a wrench to turn it in and align it for attaching the ratchet pieces.





At this point I've inserted the lever pins and ratchet parts. Today I'll go to the hardware store to pick up replacement c-clips because the old ones have metal fatigue and don't stay in place. I've also had the spring clamp rebuilt with plywood and will show you photos of that when I recompress the spring for installation in the group.

For now I'm using non-toxic silicone grease for the lever pins. Doug Garrott advised me to use Homelite chain saw grease, which I can't find anywhere. He said since this part doesn't touch anything for human consumption I can use such an industrial product. I wonder if silicone grease will suffice, since I have it on hand?
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

who?Me?

#379: Post by who?Me? »

looking good there, Gary. Thanks for all the photographic and detailed documentation.
It keeps me motivated to eventually restore my Prestina, that I've had for 2-3 years now,
tucked under my workbench. One of these days ..................

User avatar
drgary
Team HB

#380: Post by drgary »

Thanks, Gary. That's the point, to encourage others to bring these back from the dead! Did you write to me that you have a brass Prestina that's got a brushed finish?

Anyway, more progress today. Here are some photos. I had my clamp ends rebuilt by my contractor. He did a great job. I compressed the spring but then called Dave (aka "McDave") at Allann Brothers and he told me that for this machine I don't need to have it compressed to insert the piston assembly in the group. Well, I've now got a nice clamp! :lol:



He fastened two pieces of 3/4 inch plywood, gluing and screwing them together. This time the clamp didn't start to bend or crack when I was tightening down on the spring.



This was a fun part to do. Not hard.



Then I put crimp washers over the bolts, if "crimp washers" is what you call them. People looking closely will see a retainer clip missing. One of the other reasons I called Dave was to find out if there's a secret code to putting on retainer clips. Nope. Just bend them back into shape with a needle nose pliers. Then fit them on and spin them until you know they're in the groove. If necessary use a metal hammer and something that works as an anvil, like a vise, to flatten the large washers. I didn't need to do that.



Here's the piston assembly screwed down.



Two widely spaced ratchets weren't allowing access to the grooves in the pins for c clips to lock on. Dave suggested I use a c clamp to align that, which worked well.



Next I fastened on the water tap pipe.



Finally, following Dave's directions I used a torque wrench to tighten the boiler bolts to 15 foot pounds. He says when I heat the machine they'll tighten about 1/8 turn more. Then check again after a couple of weeks. he also suggested I similarly tighten the group onto the studs. He also offered the hint that if the machine has gotten up to pressure and turns on again to come back to pressure in two minutes or less, there's a leak somewhere.

Gary
LMWDP#308

What I WOULD do for a good cup of coffee!