Modern DIY Double Boiler Lever Build

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#1: Post by bigeric »

After many years using a heavily modified Gaggia Classic, finally trying my brother's double dipper lever, and seeing new features like the pressure release on the Nurri and ACS levers, I decided to take the plunge and build my own custom lever machine.

  • Fast heat up (I'm impatient)
  • Consistency and repeatability for multiple rapid-fire shots (to be able to serve several guests or crank out a bunch of shots for espresso martinis):
    1. shot temperature
    2. shot pressure and volume
    3. no waiting (ability to release pressure and immediately do the next shot)
  • Commercial quality steam
  • As quiet as possible even though using a reservoir
  • Compact size
  • 12" wide, 14" tall, 21" deep
  • La San Marco group, actively heated, (cartridge heaters and band heater) pid controlled
  • Adjustable shot fill volume (by timer controlled gear pump. quiet because set to low RPM)
  • Shot fill triggered by lever pull (micro-switch)
  • Brew pressure gauge
  • Shot pressure release (into drip tray)
  • Manual water flush
  • 3.5 liter tip out reservoir
  • Reservoir low water sensor and warning LED
  • Empty reservoir pump cutout
  • Double boiler with active pre-heat:
    1. Thermoblock brew boiler feed preheat, pid controlled
    2. 160ml brew boiler (twice shot volume) 1500W, pid controlled
    3. 2.5 liter stainless steam boiler, 1800w (eBay find from Cimbali M1)
    4. Electronic steam boiler pressure sensor and pressure controller
  • Steam boiler autofill with cut-out during shot fill
  • Steam boiler on/off switch
Addtional construction details:
  • 30mm x 30mm aluminum extrusion frame
  • 3d printed panels and internal brackets
  • home automation dual power relay (24v low voltage, 20 amp high voltage)
  • non-compression steam and hot water valves
  • 24v dc adjustable speed gear pump (Fluid-o-tech FG213)
  • shot fill and pressure release solenoids at group
  • three way steam boiler fill solenoid at pump
  • check valve at boiler inlet

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#2: Post by Utking »

Did you make this? It looks amazing #jaw_drop

Does it function like you thought it would?


#3: Post by LittleCoffee »

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!! :D :roll:

bigeric (original poster)

#4: Post by bigeric (original poster) »

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.

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#5: Post by bostonbuzz »

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.
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#6: Post by TenLayers »

Very big tip o the hat to you. What a big skill set you have. Impressive!

bigeric (original poster)

#7: Post by bigeric (original poster) »

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?
Theoretically yes but no. There are three different size gear pumps: 4mm, 9mm, and 13mm impellers. ... 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.

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#8: Post by pizzaman383 »

Here is a link to a thread showing the water path in the machine
How Modern Hybrid Lever Espresso Machines Work
LMWDP #551
“Taste every shot before adding milk!”

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#9: Post by pizzaman383 »

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 :) .
LMWDP #551
“Taste every shot before adding milk!”


#10: Post by LObin »

I'd love to have the skills, knowledge and toys to build something like that! Amazing work!

Is there a video showing the machine in action?
LMWDP #592