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Hand held Espresso maker.

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Hi!!

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

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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:

  1. All water handling parts had to be either aluminum or stainless steel.
  2. All parts had to be easily and cheaply obtained.
  3. Only simple tools could be used.
  4. It must be safe (no exploding parts due to high pressure or hands burned by hot water)
  5. Must be easy to give maintenance (sometimes overlooked)

Step 2: Parts and tools

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This is going to be an odd part list, because the sized of some parts are going to be dependent on the size of the espresso portafilter basket you get. In the next step I’ll tell you how to correctly size the parts

Parts to be sized:
1 PVC union, sizes from 1 to 2 inches
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
 
Parts that don’t need to be sized.
1 espresso portafilter basket
2 tubeless tire air valves
1 1inch threaded PVC plug
1 1inch threaded PVC or bronze cap
 
When we get to the part of the air release button, I’ll show you the parts that I used, so that you can either use the same parts or look in you toolbox for some similar things that will do the trick.

Step 3: Part sizeing

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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

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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

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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.

Picture of 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.

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PVC and hot water don’t mix very well.

The thing is that the hot water will make the PVC soft and it will fail.
But not in this case, because:
  1. The hot water is only in there a short while.
  2. 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.
Since the rules say that only aluminum and stainless steel can touch the water, lets make the water chamber.

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

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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

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Glue the dome in place.

Step 10: Air release button and cap screws

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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.

Beware!
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

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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!

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Preheat.
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
  1. Put your coffee in basket and tamper.
  2. With the main machine empty of the preheating water, use a bike-pump to pump air into the machine (I use 10 pumps)
  3. Fill the machine with 1oz of water for a single shot, 2 oz. for a largo.
  4. Screw the bottom of the machine in place
  5. Place over cup
  6. Press air release button
  7. Wait for the water to run out (about 20 sec)
Enjoy you coffee!
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태영최2 months ago

PVC with hot water can harm your health. But this is a great idea!

urant (author)  태영최2 months ago

That's why the hot water never touches the PCV :D It's only the compressed air thats in contact with the plastic

Makedo3 years ago
the materials that are used in the wallmart tire valve maybe made in china. most like it has lead in the brass. and the plastic may also. there maybe other not so friendly chemicals involved also. be careful with any items from china.
urant (author)  Makedo3 years ago
The PVC is US made. As to the valves, the contact area es really small ant they are only in contact with hot water for a few seconds. But, to be safe...Is there any way to test the brass for lead content?
Makedo urant3 years ago
use a test stick you can buy. or find a lead inspector who might test it. it might cost you but you would know for sure.
urant (author)  Makedo3 years ago
Thanks, I'll do that

I just came across this and I think it is intriguing, although I'm not sure I understand how everything works.

In regards to the brass, it is probably free machining brass (C36000) which contains 2-4% Lead. If you live in California, they now has some restrictions on lead content (although it may not apply to bicycle valves, since they aren't designed for the food industry!).

Anyway, I was hoping you could upload a schematic. I was working on something similar, and I am hoping to steal ideas from your design and incorporate a pressure gauge, and if possible have an automatic pressure release (so you can't blow it up).

I just noticed the schematic. I guess I must have scrolled down before the image loaded. Sorry about that!

urant (author)  anirudhkalbag8 months ago

Hehe, no problems. Did you figure it out?

I think so. It looks like it is essentially 3 chambers. The bottom holds the coffee grounds in the filter, above which is the water pot which has an inlet valve (actuated by the bolt on the outer body) and the top most chamber is an air chamber that pressurizes the air (via the outermost inlet valve). Correct me if I am wrong.

urant (author)  anirudhkalbag8 months ago

You are right. You could simplify the design by eliminating the "explosive valve" from the outside. The idea was to release all the pressure at the same time, but in hindsight, the variations in pressure by directly coupling the bike pump to the machine will not be significante, especially if your using a "cream enhancing" portafilter. This way, you eliminate the valve that touches the hot water, and any risk of lead in the brass leaching out. Or you could change the valve for a espesso machine emergency and make the shot go off "automatically"

mastalyn10 months ago

hi,

what is the external valve ? ( on the right on ur first pics) what is its usefulness?

urant (author)  mastalyn10 months ago
It's the air inlet valve: It allows you to pump air into the espresso maker
mastalyn urant10 months ago
But there are two valves, one to release and another one to pump air into the espresso maker?
urant (author)  mastalyn10 months ago

That's right. You need the two valves in order to build up pressure. The Air inlet valve allows the pressure inside to build up, and the second one allows that pressure to be instantly released to the hot water.

Awesome work, already started collecting the parts! My filter fit perfectly in the the same size union you used :D A question I had, were both of the tire valves stripped down to the brass or is is the air filler valve stock with rubber? If it is stripped, how does it stay in the cap under pressure when silicon or PVC glue isn't adequate?
urant (author)  jonnyboy3231 year ago
Hi!
Yes, the valves are the normal stock rubber ones that i striped down. The way I got them to work was that the hole I drilled for them was just a tad small, so i had to pressure fit them in.
I can see how that works but seems a little dangerous for the outside valve. Why not leave the rubber bulb on and install it how it was designed by drilling a 1/2" hole and popping it into place? Is the bulb too big to fit in the air chamber between the two caps? Progress is being made, just wish I had access to a lathe to thin down these pvc parts...
urant (author)  jonnyboy3231 year ago
That's a GREAT idea!
since it's rubber you want to thin down, you could place the valve with the plastic top on into a drill and use it as a mini lathe.
Please tell me how your build goes
That is amazing. I am going to start looking for parts tonight.
It would be great if it had a pressure gauge on it so you knew when you pumped up to 16bar.
urant (author)  wakefield.chris2 years ago
Hi wakefield!

Look for a portable bike pump with integrated pressure gauge :D

If you can, share pics of you build!
I will look for one with a pressure gauge built in.
I know the air valve is spring loaded, but is there any added value in making the screw in the air release spring loaded?

Do you have any suggestions on places to get syringe plunger heads?
urant (author)  wakefield.chris2 years ago
Well, I don't think there's any added value, but I can be wrong.

As to the plunger heads, any Walgreans or Wallmart will sell syringes.
daresquid3 years ago
Somebody is likely to give you grief over the use of aluminum. And all stainless steels are not created equal. PVC is also likely not food grade.

Me? I don't care. The caffeine may be similarly unhealthy, especially at espresso doses. Perhaps you could call it the Coffee Crackpipe?
theres a pretty good rant on youtube about the merits of caffeine.. i lol'd and went and had a cup o joe.

http://www.youtube.com/watch?v=OTVE5iPMKLg
urant (author)  daresquid3 years ago
Well, all that grief made me come up with this design, so please, let it begin (mabe a 3 version will be on it's way)
tyty100 urant3 years ago
if you could market a design like this, you could be a millionaire in no time =)
urant (author)  tyty1003 years ago
My wife would love that :D
tyty100 urant3 years ago
i'd bet so
i would love to buy one too, maybe even 2 since i would use it so much it would probably wear out haha
Fantastic build.
Any updates after using it for a few months? Any thoughts on improvements?
urant (author)  senorescroft3 years ago
Hi Senorsecroft,

Well, actually I'm working on version 3 of my espresso maker. This will be (hopefully) a lever machine that put out some really high quality espresso.

On the other end of the espresso tool chain, I'm halfway done with a new kind of grinder.....let's see how that turns out
Sounds fantastic. Any sketches that you could post as a teaser? Are you thinking of a lever system similar to some of the water filters? I'm looking forward to seeing the result. Thanks.
urant (author)  senorescroft2 years ago
HI!

I´m actually trying to make a la pavoni type machine. The hard part is trying to "out design" the need for any type of metal manufacturing, so that anyone could built it. The PID boiler is also a real challenge, but I've come up with a new/old idea that will make it workable.
agate1233 years ago
Quick question, Could I use hot glue instead of pvc cement
urant (author)  agate1233 years ago
You know, I used Hot glue on my first attempt. It leaked air like crazy. It seams that hot glue and PVC don't bond strongly.
So, I had to use the PVC Cement.
I can't believe you would go and update your design while I was in the middle of building your pocket model. Now I have another project to add to the heap.
Just take comfort in it being well-designed!
gcc_mtl3 years ago
Great stuff! I just bought the pieces, but couldn't find the same diameters as you. Since I have to adapt my design, I have a few questions:

1) how do you pour water into the espresso maker, and then screw in the coffee cup, without spilling one, into the other?
2) what's the glue you are using? Isn't PVC glue toxic?
3) what's the pouring hole look like at the bottom?
4) can you make another video with more detail, maybe showing how one piece fits into another, and the entire process of making coffee (no skipping the water pouting step ;)

Again, an amazing instructable, thank you for posting
urant (author)  gcc_mtl3 years ago
Hi gcc_mtl!

I'll answer your questions in the same order.
1) Since I tamperd the coffee hard, I turn the basket + Union outer ring upside down without the coffee falling out :D

2)It is PVC glue, but since it never touches the water or the coffee it's not a problem.

3) I didn't understand this question, can you rephrase it?

4) Yes, I just have to wait till my wife gets back form a work trip, since I need an extra pair of hands.

When you done, tell me how good your espresso is :D
Quite ingenituitive I must say.... good job.
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