Did you make this? It looks amazing #jaw_drop

Does it function like you thought it would?

Man that is one cool project - hats off to you! I also love how in your profile it says you drink decaf - nothing decaf about this machine!!

Adding a few words on its performance and how I achieved it.

It can churn out virtually identical temperature shots continually with no wait between them or at any more leisurely pace.

First a bit of background. Years ago, I'd done the same thing with a Gaggia Classic by adding an active preheater. The Gaggia's small 100ml boiler being aluminum with 1360W heater is quick to recover by itself. Preheating a 28-36ml shot worth of brew water with a 1200W thermoblock made it possible, with careful PID tuning for both the thermoblock and the boiler, to be able to have remarkable shot temperature stability.

Based upon that experience, I took a similar approach but, making the system fill the group's ~80ml water volume in a few seconds and have the ability to do so every 30 seconds or so, with consistent temperatures was a higher bar.

The things I could control were:

• the water flow rate (the gear pump's control voltage)
• the brew boiler volume (by wrapping additional copper tubing around the Gaggia boiler and insulating the whole package)
• the thermoblock and brew boiler PID settings
• the temperature offsets between the group, thermoblock, and brew boiler

I achieved the performance goal by:

• running the thermoblock, brew boiler, and group at the same temperature so that the group wouldn't gain or lose temperature regardless of how many shots were done in sequence
• having the brew boiler / coil assembly have two-shots worth of water (160ml)
• running the preheat thermoblock at full wattage during water flow and using the PID and relay threshold to maintain temperature without overshooting during recovery and rest periods
• tuning the water flow rate to carefully match the thermoblock and brew boiler's recovery capacity
• tuning the water flow time to hit 80ml

When I pull the lever, it actuates the pump for 10 seconds. Because it's running at low RPMs, it's not the loud whine that gear pumps are known for. After the pump stops, I release the lever. When the shot gets to the volume I want, I release the pressure and can immediately reload another prefilled basket and start the next shot.

To make this work, and have the steam boiler work, without tripping the 20a breaker, I use the pid alarm thresholds and cutout relays to ensure that there is only one heater at full wattage at a time.

Very cool. Since you have pressure release and a gear pump and temp stability I suppose you can pull perfect pump-only shots as well?

FYI the Strega with a modified pump (not 12 bar stock) can pull good pump shots but I believe the temp increases, and you have to deal with waiting for the whole spring afterwards.

bostonbuzz wrote:Very cool. Since you have pressure release and a gear pump and temp stability I suppose you can pull perfect pump-only shots as well?
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Theoretically yes but no. There are three different size gear pumps: 4mm, 9mm, and 13mm impellers. https://www.fluidotech.it/site/assets/f ... asheet.pdf

If I'd chosen the 4mm size, I could have done that. I wasn't looking to do pump assisted or pump only shots. I was looking for the quietest way to get the flow I needed so I chose the 13mm impeller size.

Here is a link to a thread showing the water path in the machine
How Modern Hybrid Lever Espresso Machines Work

The fact that BigEric used aluminum strut and a 3D printer made it easy to iterate the location of components, the size and configuration of the case, and the effectiveness of the overall design. That and learning lessons from all the previous DIY builds and newer hybrid lever machines.

BTW, he's my twin brother so this isn't just conjecture .