A few months ago, I published and Instructable titled:
“Pocket size Espresso Machine with integrated alcohol stove.”
I got a ton of comments on the design; a good number of them focused on my use of copper as the main build material.
Questions of material safety with food were raised and some people even went the extra mile to see if using copper in this way was food safe.
A second point was also raised, that it was not really an espresso maker but a moka pot, due to its inability to exert sufficient water pressure on the coffee grounds.
So, for all of you, I went back to the drawing board and came up with a new design that solved both the copper and the pressure problems!
And incredibly, it's also cheaper and easier to make!
BTW, it is just big enough to hold 2oz of water so you can pull a double shot :D
A short video of the machine in action:
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Step 1: Design Constraints
The espresso maker works by releasing air at high pressure into the brew chamber (I used a small bike pump to build up the air pressure).
It works just like the commercial Handpresso which is my main inspiration.
To build this, I set the following constraints:
- All water handling parts had to be either aluminum or stainless steel.
- All parts had to be easily and cheaply obtained.
- Only simple tools could be used.
- It must be safe (no exploding parts due to high pressure or hands burned by hot water)
- Must be easy to give maintenance (sometimes overlooked)
Step 2: Parts and Tools
Parts to be sized:
1 PVC reducer, sizes from 1 to 2 inches
1 PVC cap, sizes from 1.5 to 2 inches
1 PVC cap, sizes from 1 to 1.5 inches
2 O-rings that fit into the PVC union
1 small aluminum or stainless steel can
2 tubeless tire air valves
1 1inch threaded PVC plug
1 1inch threaded PVC or bronze cap
Step 3: Part Sizeing
The espresso maker’s main body is made out of the 1-2 inch PVC union.
Its size depends on the portafilter basket that you get.
When you disassemble the union, the basket should fit into the outer ring just like in the picture.
The 2 O-rings go one into the PVC ring, then the basket, then the other O-ring.
From the picture of the finished machine, you can see that the big cap has to be about the size of the union’s outer ring.
In my case, the union I used was a 1-1/4” with a 2” cap.
Since the cap is bigger than the part of the union that is screwed into it, you will need a reducer to make sure that they fit tightly together. In my case a 2” to 1-1/2” reduce did the job, but I had to sand both pieces down to make them fit.
The Small cap will be the same size as the inner diameter of the reducer.
Please see the pictures of how the machine built to better understand how the part sizes come together.
Step 4: Sanding and Fitting Together the Air Chamber
Sand down the parts until they fit together like in the pictures.
You will also have to remove the inter thread of the union part that screws with tube and outer ring, unless you can get an unthreaded one.
Glue the two parts together using PVC glue.
Step 5: The Air Chamber Dome
Remember that smaller cap?
Well, it will be to cap off the air chamber, but since caps this size also come in a nice, “dome” shape, I used one of those.
It also helps the design, because this part will be under pressure and a domed shaped one will take the pressure better than a flat one.
Just cut the cap at the top, making sure it fits tightly in place.
Just dry fit it. Don't glue it yet!
Step 6: Modify the Tubeless Tire Air Valve.
I got these two valves for free at the Walmart tire center.
I asked how much they cost, but the dude working there told me they didn’t have any barcodes, so the couldn’t sell me any but that I could take the two valves that I needed free. :D
Carefully cut out all the rubber until your left only with the brass.
I needed to cut the brass tube down a bit, so I pushed down the valve, saw how far it went inside the brass tube and cut it about 1/8” longer than the lowest the valve went.
Step 7: Aluminum Hot Water Chamber.
The thing is that the hot water will make the PVC soft and it will fail.
But not in this case, because:
- The hot water is only in there a short while.
- The machine design. In the parts that will be exposed to heat for the minute the machine is used, are PVC walls are triple thick.
I took the part I made in the previous step to the store on the corner, and looked for some can that would fit into it.
None did exactly, but one can of teen deodorant I fount did have the right diameter and the top fit snuggly into the water opening.
I cut the can in half. You don’t have to sand the outside if you don’t want to, since it will be glued to the PVC part.
I took hammer and a piece of tube I hand in my toolbox and started shaping the top of the can until it fit tightly inside the water camber.
The bottom of the can was already domed, so I used that for the domed inner part of the water chamber.
Sand and clean the inside of the can.
Drill a hole just a bit smaller than the air valve and carefully hammer it into place.
Step 8: The External Shell
Take the bit PVC plug and drill a 1/2” hole in the middle and a hole a bit smaller that the diameter of you air valve.
Screw the plug in place and glue.
Carefully hammer the air valve in place and glue.
Step 9: The Inner Air Chamber
Glue the dome in place.
Step 10: Air Release Button and Cap Screws
Since I didn’t trust my gluing, I decided not to use PVC glue in the external cap. What I did use was silicon but since I was sure it would not take the pressure, I secured it in place with 4 screws (just make sure that don’t go all the way into the water chamber.
I decided to use a bronze cap for my air release button (I thought it looked nicer) so I had to cut the plug down to size. If not, just drill a 1/2" hole in the middle of the plug.
Make sure that air can get from the external valve to the inner one before gluing.
If not, sand the bottom of the plug until it does.
Step 11: Air Release Button
Follow the pictures to assemble the air release button.
How does it work?
Well, a small screw is held in place by a rubber gasket. When you push the screw, it pushes he top of the inner valve, releasing the air under pressure into the water chamber.
I found that the rubber head of a number 10 syringe plunger was just the right part to seal the button of, but be flexible enough to allow me to push the screw underneath it.
Remember, if the inner valve fails, you can easily disassemble this button to get access to the valve and with the special screwdriver, change it
Step 12: Make Some Espresso!
Like all espresso machines, if you don’t want a lukewarm first shot, you have to preheat the machine.
Put some hot water into the water chamber and wait some 20 sec. for it to warm up.
Also, but some hot water in the basket and let it heat up.
Make the espresso
- Put your coffee in basket and tamper.
- With the main machine empty of the preheating water, use a bike-pump to pump air into the machine (I use 10 pumps)
- Fill the machine with 1oz of water for a single shot, 2 oz. for a largo.
- Screw the bottom of the machine in place
- Place over cup
- Press air release button
- Wait for the water to run out (about 20 sec)