Another homemade open boiler lever

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aves
Posts: 17
Joined: 8 years ago

#1: Post by aves »

This is my first post, but I have been lurking (and learning) here for a while.

This is a documentation of my recent efforts to make my own open boiler lever single shot brewer (and a hand grinder).

Starting point was the desire to make my own simple machine (and limit expenses if ending up nowhere). Planning was done old school, scribbling on paper step by step after having a general idea. I admire people who know CAD (I don't). There are no meaningful drawings to present here. My selftaught abilities regarding metal work are pretty limited. I have a tiny 3 sq meter workshop at the end of our apartment with a small drill/lathe combo. Stainless steel was and is not an option (no liquid cooling). Choice of material for the espresso machine therefore had to be brass, stainless steel for handle and push rod only, solid aluminum for the frame (and for the hand grinder).

Influential were both the Strietman ES3 and the single shot brewer documented by deus-ex-machina here in this forum. Inspirational espresso machines! Not to forget the many Italian small open boiler machines from past decades like my Peppina.

Strietman CT1
Custom Designed and Machined Lever Machine

Hopefully my project will encourage others to show theirs or even go back to the workbench.















Details:
Inside is a brass tube with polished walls acting as cylinder with 40mm inner diameter. The piston with two v-shaped seals (Elektra MCAL) has another smaller piston inside that lets water flow through the piston when the handle is lifted up. The cylinder is surrounded by a 15mm thick brass sleeve. The upper part contains a temp sensor (a cheap LM35) and three heating cartridges (40mmx8mm, 250W each). The lower part holds the group with shower screen. Portafilter assembly is reused from a defunct small Saeco Aroma (= Starbucks Barista) type home machine with 53mm basket. The portafilter handle is machined from a dented cimbali portafilter into which I soldered the cut down Saeco parts.
The frame is made from solid aluminum that I already had. I kind of liked the raw cut metal surface and decided to leave it that way.

Heating and temperature control with 2 SSRs and an Arduino Nano is in a breakout box to keep things cool and out of reach of water. When turned on all 3 heating elements are active (750W). After reaching 2°C below the desired temperature 2 heating elements are turned off and the remaining one tries to maintain a stable temp level. Temperature is measured in the brass sleeve close to the heating cartridges, not directly in water (which would be preferable). But since the machine is a single shot brewer and has to be refilled after each shot, the sensor would hang in the air at some point, and the incorrect data would lead to overheating.

The metal is currently adjusted to 113°C, with temp change by dial on the external box. Stability of the desired water temperature appears to be excellent due to the high thermal mass. Measurements so far revealed a max. hysteresis of 0.3°C.

The Arduino solution (Chinese clone) was a lot cheaper than a fullgrown PID. I have no real clue about Arduino programming, but even I could fake it enough by trial and error. The machine needs about 8 minutes to heat up to stable level when turned on and about 2.5 minutes after each refill. Water is heated with the piston down. Maximum shot volume in the cylinder is 90ml above the piston. For a shot the piston is moved up and water flows through a 6mm hole at the bottom of the piston to the shower screen and portafilter.

Shots so far are (to me) outstanding and on par with my Cimbali Jr. This is definitely not a perfect espresso machine but as good as it gets in my tiny workshop, and I am very happy with it. I first thought about including a pressure gauge but decided against it to keep things simple and now dont miss it.

Estimated costs - all parts including numerous postage fees added up to about 280 Euros.

brass 75
aluminum 30
stainless steel rods + screws 15
shower screen 8
driptray 25
seals 24
3 heating cartridges 15 each
misc. electronics + cables 25

70-80 hours total to make the machine, but I guess an expert metal worker could make the parts in a few hours (with proper drawings).




The grinder is an earlier project machined from one solid piece of aluminum. It has two bronze bearings and a stainless steel axle holding Mazzer Kony conical burrs. The body was machined in one piece. It was meant to be used as a true hand grinder but the necessary grinding force made it impossible for me to hold it while grinding. The wooden bracket housing is just a 10 minute mockup to hold the grinder for testing. Somehow it works well and I did not have time to come up with something nicer. Grinding adjustment is done old style on the bottom with a spring fixed screw and is therefore not straightforward. Unfortunately I can't cut threads on my lathe combo since it doesn't have a lead screw - very disappointing! 14g beans need about 36 turns and grinding easily done in about 30 seconds due to the long handle and the wooden holding bracket.

The grinder was stored away for a year due to excessive electrostatic problems in the beginning, but now after a few kg beans and using RDT it is my favorite single dose grinder. No ground retention at all if knocked gently on the surface after grinding, but only with RDT. If I forget RDT the ground coffee clings to the metal for 5 minutes before letting go. Turning knob at the moment is a free golf ball.

Unfortunately I don't have a single photo of the building process because it started purely as an experiment.





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Coelacanth
Posts: 32
Joined: 8 years ago

#2: Post by Coelacanth »

Most excellent and inspiring. Well done!

Jorian
Posts: 47
Joined: 8 years ago

#3: Post by Jorian »

WOW! What a build!

I love the price point and I am super jealous of that lathe!
You seem to definitely have some skills!

Congratulations on the success!

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arcus
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Posts: 770
Joined: 11 years ago

#4: Post by arcus »

Very cool! Thanks for sharing!!

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zeb
Posts: 311
Joined: 13 years ago

#5: Post by zeb »

Sure ! Amazing !!

kwantfm
Posts: 543
Joined: 11 years ago

#6: Post by kwantfm »

Jorian wrote:I love the price point
70-80 hours to make... that changes the price point a lot!!!
LMWDP #602

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pizzaman383
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Posts: 1730
Joined: 13 years ago

#7: Post by pizzaman383 »

This is really cool!
Curtis
LMWDP #551
“Taste every shot before adding milk!”

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donn
Posts: 271
Joined: 16 years ago

#8: Post by donn »

Heck of a first post.

It would be interesting to see how much more complexity to add the water reservoir that would make it an "open boiler." Just a matter of immersing the whole thing in a tank and boring a hole in the appropriate place in the piston sleeve? Would there need to be more ports and gaskets on the piston?

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doublehelix
Posts: 470
Joined: 9 years ago

#9: Post by doublehelix »

Really neat!!!!!!!!!!!
I'm playing around with a Delonghi EC115 (inexpensive, nice parts!) that I'm hooking up to a Breville Infuser spiral heater--planning to PID the heck out of it. I really like your two-stage heating solution.

Javier
Posts: 649
Joined: 18 years ago

#10: Post by Javier »

Wow Jo ("aves"), what an amazing job!!! Is there any chance you might post videos of the machine in action?
LMWDP #115

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