Conti Prestina Espresso Machine Restoration 101 (Completed and Indexed) - Page 56

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

#551: Post by peacecup »

If you manage to fit the Conti on the counter, i'd wager that it would be easiest to get consistent results from, at least from an all-day on basis. But how many people spend all day at home, and can warrant keeping a commercial lever running? That's why several who have owned commercial levers have switched back to home levers. The Strega and Londoninum appear to bridge that gap, with their quicker warmup time. I've found the Lusso a good solution so far, not too big, but with the excellent properties of the thermosiphon.

PC
LMWDP #049
Hand-ground, hand-pulled: "hands down.."

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RayJohns

#552: Post by RayJohns »

drgary wrote:If I could actually weld the pieces of the drip grate together I would. So being able to do that with JB Weld is a good application.
Can you post a picture of that you are trying to do with the grate? JB Weld works well in some applications, but poorly in others. It just depends. It tends to work better in a filling capacity in some ways. It's not exactly like welding (as you would think of like actually welding two pieces of metal together with a TIG welder or something).

Ray

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drgary
Team HB

#553: Post by drgary »

peacecup wrote:If you manage to fit the Conti on the counter, i'd wager that it would be easiest to get consistent results from, at least from an all-day on basis. But how many people spend all day at home, and can warrant keeping a commercial lever running? That's why several who have owned commercial levers have switched back to home levers. The Strega and Londoninum appear to bridge that gap, with their quicker warmup time. I've found the Lusso a good solution so far, not too big, but with the excellent properties of the thermosiphon.
That's why a vacuum breaker is being added, so I can connect it to an appliance timer. Warm-up is about 40 minutes, I think.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

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peacecup

#554: Post by peacecup »

My Lusso takes less than 10 minutes to come up to pressure, but it has no breaker valve. If I don't release the false pressure the thermosiphon doesn't really begin to function.

Do you plan to use the Conti for AM cappas before work? I use the Lusso for this now, then all day on the weekends (and during the long vacations, like now). Even the 2-liter Lusso is really overkill for one morning cappa, however, and if it weren't so dawggone easy to pull great shots with I'd use the Export instead.

Keep us posted!

PC
LMWDP #049
Hand-ground, hand-pulled: "hands down.."

User avatar
peacecup

#555: Post by peacecup »

This was the thread I was thinking of:

A Conti-diction

Dr. Jim, who also introduced us to the Fellini move, wrote about the direct linkage of the Conti lever design. His posts were always fun to read, like this quote for example:
Taming the Isomac of its tendency to emit some truly ghastly flavor artifacts along with some very decent coffee has been a year-long process involving grinder upgrades, technique improvements, temperature profiling, and finally replacing the vibe pump with a rotary procon and experimenting with pressure profiling - all of which has ended up yielding some pretty incredible shots, but still with the occasional sour clunker thrown off to remind you of the essentially artificial and unstable method being employed.

Given this history, I'm somewhat slack-jawed that the 30-year old Conti with no tuning, tweaking, or even particularly elaborate ritual appears to not have any gross flavor vices, but instead promises to simply deliver the true and uncontaminated flavor of whatever coffees I should happen to feed it.


Perhaps that is where I first began to understand that lever machines make great espresso almost fool-proof. The resurgence of new lever machines on the market bears this out I think.

PC
LMWDP #049
Hand-ground, hand-pulled: "hands down.."

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drgary
Team HB

#556: Post by drgary »

I continue to be stunned by the effortless shot quality of the Conti Prestina and have just started to take advantage of its commercial milk texturing capabilities. To keep this thread on track for documenting how to restore one, I've started a new one where the owner experience can be explored:

Owner Experience with Conti Prestina

Tomorrow I hope to start fabricating a replacement drip tray grate.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

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drgary
Team HB

#557: Post by drgary »

Back to the Loctite discussion for a second, I found a note from Dave at Allann Brothers telling me he used Loctite 577 to fasten my plumbing parts. This created a firm hold and I was able to break it free using two large wrenches. Here's the spec sheet and a safety sheet found online. It contains some hazardous materials, but if others advise that it not contacting consumable water or steam eliminates that issue, it may not be a problem. I would use a more benign formulation. As my machine heats and cools the PTFE tape loosens, so I may use Loctite for doing the final assembly with the case on.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

User avatar
drgary
Team HB

#558: Post by drgary »

Drip Grate Fabrication Starts

Today I made a lot of progress fabricating the drip grate. Some of this went faster than expected, other steps required improvisation and painstaking work. Here's how it went. I used a Bosch jigsaw with a fast metal cutting blade. With sufficiently thick and rigid steel that cutting went quickly and was easy to keep in line. Throughout today's work I wore protective leather gloves, a face shield, and while using cutting wheels, a breathing filter. I had to change the saw blades twice when they started to catch and bend but those changes happened gradually and the saw was generally easy to control. I was fortunate to receive help selecting this tool and its blades because when I went to Home Depot the other day the factory rep was there.

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The Synesso drip grate was conveniently marked for cutting.

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The first of these cuts finished off the front so it grips the edge of the frame to securely hold the drip grate in place as if it were fitted for this machine.

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My next task was to trim the back upturned lip off the grate. This is necessary to add width. It was harder to clamp the workpiece in place for this trim so I wandered off and needed to rework the cut from the other end. My second attempt still left some upturned lip, so I carefully trimmed some more in order to have a flat surface for extending the piece back. There was a little excess that was rough so I honed it into line with my grinding wheel.

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Next I cut the piece to width. Notice that there's an unperforated edge on the left but not the right. This will be addressed with trim strips that eliminate that difference, but unfortunately the adjacent holes slightly overlap so there is no way to obscure the middle one and totally reveal with wider holes.

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Next I needed to figure out how to join the front with pieces added in back. I had originally intended to use the J-trim strip shown earlier, but the wide part I expected would be on top is actually backing with manufacturing marks and screw holes. I tried to trim that wide part off with the jigsaw but it left a mangled mess. I tried a metal shears and they weren't strong enough. So I turned to some scrap left over from the cuts already done and cut the support and edging strips you see here in the first version of my design. One of them was badly scratched in fabrication so I had my doubts. You can see these strips on the outer edges of the grate where they would be attached.

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Then I discovered I could trim the back part off the J-strip, which would leave a finished piece I could use as a border. The tool that works for this is a rotary tool with a heavy duty cutting wheel. I've seen those work effectively for cutting bolts. But they wear down very quickly when cutting steel plate. I found I could cut about 2 to 2 1/2 inches before the wheel wears down and I need to replace it. At this point I've gone through about 2/3 of a pack but am making the progress I need.

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The ability to create trimming edges means I have something finished that grips the edge of the grate. It also helps to straighten out the slight bends that occurred with cutting. In this next photo you see where my design is evolving. I'll use the thin J-trim edges to attach the main grate piece with a strip in the back that bends up slightly, which I've already edged with the same trim. I may round the front corners to go with the punched hole design. Because there will be an unmistakable meeting of two edges at the back, I'm thinking of creating a piece of rubber trim that's almost like an inlay and backing it with steel plate. The steel and trim will be attached with JB Weld. The rubber inlay with be held in place with flexible silicone seal. It will create a nice accent that goes with the color of the frame and the whole will form a grate that keeps water off the electrical connections at the front of the boiler. You'll be able to see the water inlet valve underneath, but that has no parts that would be damaged by water. I'll cut the grate at the marks you see on the left to fit the trim piece so the holes are equally overlapped left and right. Before cutting I'll use a straight edge and Sharpie marker to create a solid cutting line between those points.

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Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

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drgary
Team HB

#559: Post by drgary »

After much cutting and fitting I now have my drip grate sized and have something that will support shot making. My next step for that will be to create something more finished looking in the back. I'm finding the way the edging fits in this attempt disrupts the snug fit of the grate on the frame. I've been consulting with Ray offline on how to do this better. Cutting stainless steel using various tools is difficult because clamping and positioning must be precise, the saw I have is very powerful and can chatter and bend anything that's not well supported while clamping can get in the way. There are similar problems with a hacksaw. I also used cutting wheels on a rotary tool, but these wear out or break so fast it's very time-consuming. So I think I'll perfect the grate last. For now I'm keeping the protective film on it to avoid scratches during fabrication. I've got it set up on an appliance timer to continue the heat cycling to tighten seals but after initial start I must bleed a lot of air out of the steam wand to eliminate the measurement of air instead of steam (aka "false pressure) and allow the unit to fully heat. After this I want to improve the wiring, wire up and seat LED pilot lights, assemble the case and fit it to see where I'll finally want the Sirai PSTAT. I've sourced all of those parts and tools and will show them in the thread. I'll also install the vacuum breaker and its plumbing as soon as those parts arrive from OE.

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Added: Here's a better look at why this first version doesn't work. Notice the kludgy fit of the edging.

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Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

User avatar
RayJohns

#560: Post by RayJohns »

A thin metal die grinder cut-off wheel is usually pretty good for cutting stuff. You just have to be very careful that it doesn't get away from you while cutting. I would suggest clamping to wooden rules (or something) down on either side of where you want to cut. Also be careful of generating heat, which can warp your panel.

Ray