(completion of thread "Playa Espresso Cart" started in 2012, with most recent post in 2013)

• Playa Espresso Cart 1 - Art Cart Concept
• Playa Espresso Cart 2 - Thermoregulation
• Playa Espresso Cart 3 - Lever Pumps
• Playa Espresso Cart 4 - Where to Measure Pressure and Temperature?
• Playa Espresso Cart 5 - Forward Progress!
• Playa Espresso Cart 6 - The other kind of grind
• Playa Espresso Cart 7 - Hot Water!

The goal was to produce a manually pumped, propane powered espresso machine that did not require a generator or "electrics", esthetically and functionally compatible with Burning Man. "Stuff Happened" in 2012 that kept the machine from getting completed for the August event (I got sick!), and in 2013 and 2014 I cheated by powering the machine off a 12 volt battery, inverter, and 120V motor and Flojet pump.

What may make this thread of interest to this crowd is that in 2015 the manual levers were completed along with a redesigned burner assembly; I now have something to show and finish off this thread.



Here is an image of the final machine setup in the shop before going to the Burning Man festival (held on a dry lake bed in Nevada, in a temporary city of 70K people). You can readily see the propane tank and the orange "Homer Bucket" with water, but if you look more closely in the upper right of the machine you will see a couple of peewee baseball bats that look a little like tap handles: those are the lever handles for the manually pumped pistons used to fill the boiler and squirt the water through the grounds to make espresso.

Playa Espresso Cart 3 - Lever Pumps

The lever design was built around the use of Bimba Stainless-Steel NSF grade pneumatic pistons that are also used in the food service industry for things like squirting goo into eclairs. Two different pistons were used: a larger one for boiler fill that did not require as great a peak pressure as a small diameter piston for pushing water at 110 PSI or so through coffee to make that delicious elixir we all so crave.

The Boiler Fill piston has an 8 inch stroke and is 1 1/2 inches in diameter, the Group piston is also an 8 inch stroke but is 1 1/16 inches in diameter.



The general problem is to optimize the amount of pull pressure and stroke length to make a triple shot with a manually controlled pressure profile (ie, you have a great big pressure gauge right in front of you that you look at while pulling down on the lever, keeping the pressure where you want it while watching the flow). It is definitely fun to see and feel the interaction between grind fineness, flow and pressure.

Amateur astronomers that build their own instruments make a big deal about "first light" - their first glimpse through the instrument that they constructed with their own hands. In that vein, here is "first dark" - the first shot that was pumped out of this monster!



It came spitting out too quickly - too much flow at about 60 PSIG. The grind needed to be adjusted... and here (once again!) Doug and Barb Garrott came to the rescue.



My Pharos has been modded to have a hopper for about half a pound of beans and a container for same. After adjusting the grind, I was getting to where I would offer a shot to a stranger.

I had to redesign the Burner completely from the earlier thread. The old design was based upon a proportional control flow valve that would decrease propane flow a little if the boiler pressure went up a little; very elegant and when operating correctly probably a dream. However, the amount of heat produced by the "stock" burner is pretty pathetic, and intended to augment the heat produced by an electric resistive element. In my revised design, the burner was too close to the boiler for optimum heating, and the lack of a safety-pilot assembly was troublesome. In 2014 I tried a redesign from the high-pressure, proportional control system that did not include a safety pilot / thermocouple to a design incorporating a low pressure regulator with safety pilot. The flame that was produced was pathetic and the machine was a failure in 2014.



Above is the current burner bar incorporating a pipe bar (82 holes each 1/8" in diameter); a venturi from Tejas Smokers, and a Robert Shaw 710-502 low pressure control valve (it has a millivolt pile that is usually used with a thermostat to control a small heater like for an RV; here the thermostat is replaced with a pressostat).


All in all, this burner worked out quite well - about as well as can be expected for a low pressure flame assembly in 12 inches of pipe burner. The new design allows about 1.5 inches between the burner bar and the bottom of the boiler; from what I read this is about right. The flame is a nice blue flame and not a lot of soot is created.



Data were collected from an Auber Instruments thermocouple in the boiler and PID controller indicate that for 2 gallons of water (my Boiler half full) water at 72 degrees will be heated to boiling in about 45 minutes. The burner consumes about 3/4 lb of propane per hour of burn time, and the effective heat transfer to the water is a little less than 3000 BTU / hour (there is a lot of heat that is wasted in propane, compared to the energy transfer of heat from a resistive element that is surrounded by water).



Off to the Playa - we called the machine "Shots Fired". Here is my bride Sarah, with the hammered copper she contributed.
It helps to have an understanding partner...



Here is a detail on the Levers and Valving Manifold. Unistrut (the stuff you hang electrical conduit off of) proved to be a wonderful material to work with for this project: There are lots of very hefty right angle brackets etc. The strutwork provided a universal selection of mounting points for the cylinder base and piston arm to "get it right" for the geometry that was required to optimize the stroke travel and mechanical advantage. The pistons are operated in Single Action mode - meaning that when you push up on the lever, suction is created that fills the pistion; when you pull down on the lever, water is forced into either the boiler or the group. The valving manifold behind the pistons have water enter the middle of the manifold, and then for each of the two pistions, a pair of flow control valves allow the water to first fill the piston, then be pushed into either the boiler or the group(s). While there are two groups, only one can be "pulled" at a time.



It was a lot of fun; the machine was simple enough that everyone could get in the act of making coffee, and for the first time many coffee lovers could actually see and feel what went into making a cup of espresso.



We had also made a Crepe Maker that was propane powered, so we had quite the little roadside attraction going.



Once started, people would grind while waiting for their shot to be pulled.



It was a great deal of fun, and I would suggest that if you want to have the pleasure of actually "pulling" your own shot, consider this simple lever setup.



All that code that controls volumetric flow rate, all the arguments about whether to control volume or control pressure or control ... - go into your hands and your eyes, when it becomes a manual interaction between grind, pressure and time.

Have fun!

PocoJoe

This is an amazing work! Congrats on crossing the finishing line!

Love that Folger and Pharos combo btw - just perfect.

Hippie flippi'n cool!! This is fantastic! I've enjoyed watching you build this machine and it's great. During the same time I re-built a much simpler propane powered machine for the playa and I must admit, I was jealous of your confidence and skill building yours. Where were you camped in 2015? My machine and I were at 4:30&D, right at the intersection. I wish I had known to seek you out this year. I would have really appreciated getting to see your machine in person! It's exactly the blend of art and engineering that makes me like the playa so much.

Well, congratulations on a successful project!
(One of our baristas serving espresso)


Hopefully you swing by next year. Naked Espresso loves making new friends!

Nice! Astoria 2 group. Do you have a pic of the front?

This shows the front reasonably well. It also shows what totally normal, average people go to Burning Man.

When I got it the machine needed a lot of love. I used this forum to guide my repair! Rebuilding an old 2 group Astoria Lever (+ propane)



Now, I don't want to hijack this great thread!

Yikes! We were right around the bend from each other, we were in BLD at 5:45 and D. I have not been active on this board for some time but read of your build after this year's burn! Congrats as well, and your machine is beautifully suited. Did you make it around the corner to Roasted Breauxs and Coffee Hoes? Another fun group!

Its a very small world! I didn't get out of camp much this year for coffee... We had a coffee roasting camp just down the street from us and would smell the process a few times a day!

Thank you for the complement on my machine. It works extremely well at Burning Man! Far better than any all-electric machine can do out there.

pocojoe wrote:Have fun! PocoJoe

D@mn, dude - that's fantastic!!