Heron's Engine (Steam Engine) Powered Coffee Maker

The Heron Engine-powered coffee maker incorporates the principles of the Heron Engine, developed by Hero of Alexandria in ancient Greece, into a coffee maker to make a unique, yet gorgeous piece of coffee equipment. Heron's engine is one of the earliest forms of the steam turbine and works by heating water in a chamber and pushing it through small tubes to generate a spinning motion. This mechanism is how I incorporated spinning into my project for the Make It Spin design competition.

As a Freshman Engineering student, I have a passion for design and coffee. This project blends the two worlds: showcasing my two loves in one machine.

Heron's Image source: Who invented the Steam Engine a.k.a. the Aeolipile? - HubPages

While much of the machinery I used here was using my university's makerspace, there are some elements that are homemade, so if you would like to recreate this project, don't be discouraged by the shear amount of equipment!

1. Pineapple Tin Can
2. 2 in stock aluminum round bar
3. 1/8" sheet aluminum
4. 2 in OD 1 in ID ball bearing
5. 1/4" diameter aluminum round bar
6. 3/8" ID copper refrigerator tubing
7. 1mm ID copper refrigerator tubing
8. Soda Can
9. JB Weld
10. Welding Equipment (I did TIG Aluminum)
11. Water Jet Machine
12. Manual Lathe
13. Sandpaper/file

Before any design work can be done, we must first understand the workings of the machine and basic coffee principles. First and foremost, to brew coffee, the water must be around boiling. Traditionally, when coffee is made, a kettle of water is heated until it reaches the correct temperature before it is then poured over pre-ground coffee. After the water reaches a boil, it can be poured over the coffee grounds by hand using a gooseneck kettle, or automatically (as seen in machines like the Keurig or coffee pot). This machine does the latter.

The machine works by it being placed on a stove which in turn brings the water to a boil. The steam generated from this rises to the top compartment, where the steam is forced through the 1mm copper tubing directed in a circular motion to create a spinning motion. This is the heron's engine. The spinning engine on top turns a shaft connected to an impeller inside the machine that forces water back out through the larger diameter copper tubing into the coffee grounds. This method ensures that water only reaches the coffee grounds once water has reached the boiling point. Figure 1 demonstrates the inner workings of this machine.

The very first step in designing the machine was choosing the main housing/casing. While I could have chosen to use more heavy-duty aluminum pipe, this can be quite pricey, and I wanted to keep this project as low-cost as possible. Therefore, I found a pineapple tin in my recycling and took the measurements of it. I found that it could hold around 20 Oz of liquid which was adequate for this project because a typical cup of coffee is 12 oz.

I started by sketching the circle, which was 3.25 in diameter of the aluminum can, followed by an extrusion of 4.5 in, representing the height of the can. Note that these do not have to be the values you use, you can adjust based on the unique size of your aluminum can or tubing. Finally, I used the shell command to hollow out the can with a measured wall thickness of 0.042 in.

Note: in order to measure the thickness of the aluminum can I used digital calipers to ensure maximum dimensional accuracy.

My next course of action was to design the base and legs on which the main housing would be sitting. I knew that everything here I would eventually cut using a water jet, so the thickness was a fixed 0.125 in. I chose for the diameter of the base to be 3.25 in, which is slightly bigger than the diameter of the outer casing. Additionally, you can see that I began to model one of the legs. I achieved this by ensuring the height of the base was approximately 2.2 inches off the ground, as this is exactly how high pans sit off the burner on my stovetop.

After designing the sketch of the leg, I extruded one of the legs to a thickness of 0.125 in. For this extrusion you must select the multi-directional extrusion and ensure that the "symmetrical " option is selected. This ensures that the original sketch is the center of the extrusion and will sit flush with the shape of the base.

Next, I made the impeller housing in a similar manner to how I made the original casing: circular sketch, extrude, then shelling out. The inner diameter of the impeller casing is 2.2 in, and the outer diameter is 2.4 in. The impeller blades are each going to be 0.5 in tall, I made the inner height of the casing 0.6 in to allow for some clearance as the blades spin.

I then centered this housing over the base, but inside the outer casing, and allowed for a 0.2 in clearance between the bottom of the impeller housing and the top of the base. This allows for water to be sucked in and into the impeller casing.

In order to hold the impeller housing the required 0.2 in above the base of the machine, I needed to create supports that attach to the side of the casing. I decided the best way to do this was to create tabs that attach to the legs so that in manufacturing, I can just cut one long piece rather than lots of little ones. In effect, I created an extension of the legs in order to support the impeller housing.

Pictured is the process of creating the slits in which the legs will insert into. They are 1/8" wide and I created a circular pattern around the outline sketch of the impeller housing so that they would be in the right position.

After finishing the cuts through the base and the impeller casing, this is what they look like together.

As we have already made the legs to support the base, I now need to extend the sketch of the base so that it reaches the top of the impeller casing. After extending the leg to the top of the impeller casing for support, I re-extruded the leg to the 1/8" thickness and selected "new body."

After this extrusion I used the circular pattern command, but instead of using it for sketches as with the previous circular command, I used it with a body and mirrored it around the impeller casing.

After finishing the structural components of the machine, I began working on the actual portion of the machine that spins: the shaft. I decided that I wanted my shaft to be 0.25" aluminum bar, therefore I created a 0.3" diameter hole in the center top of the impeller casing to give this shaft some wiggle room. I do not want this hole to be a perfect fit otherwise there will be too much friction generated. The shaft will be secured to the top of the heron's engine.

After making the hole for the shaft in the impeller casing, I created a 4.4in long rod that spans from the bottom of the impeller casing (again not touching the base of the machine) to the top of the Heron's Engine portion where it is fastened.

After creating the shaft, I needed to make a cutout for where the ball bearing would sit. A ball bearing is necessary to ensure that the steam turbine can turn as frictionlessly as possible. Without the ball bearing, the engine would not be able to turn at all, and if it could, then it would not be operating at peak efficiency. The engine will rest inside of this ball bearing. The engine itself will have a 1 in OD (outer diameter) so will slot perfectly into the 1 in ID of the ball bearing.

I created a 2 in cut straight through the top of the can for where the ball bearing will sit, then created an inner ring of 1 in ID which replicates the dimensions of the ball bearing.

Finally I created a cylinder with an outer diameter of 1 in at the base followed by a 1.5 in outer diameter on top, and stacking the two. The smaller diameter allows for the engine to be slotted into the ball bearing while the larger 1.5 in diameter allows for the accumulation of steam to build up pressure to turn the turbine.

Putting all of the pieces together, this is what the final CAD design looks like for the pieces that I need to manufacture.

For certain portions of the manufacturing process, I will be using a water jet to cut out pieces from a sheet of steel. Where I emphasized that the part needed to be 1/8" thick are the portions that I intend to cut out of the 1/8" steel plate. In order to get the 3D model into a 2D sketch that can be recognized by the water jet, I need to export as a DXF and then select the faces that I need to export. The blue rectangle is one of the four impeller blades. The dimensions are 0.5" tall by 0.75" wide. The pieces that I exported as DXF to be cut are as follows:

1. Leg X3
2. Impeller Blade X4
3. Circular Base X1
4. Top of Impeller Casing X1

In the above image, you can see the 2d sketch profile of each of the parts that I listed. The profiles that I designed are highlighted in green and the profiles in pink are called tabs. Tabs are a feature that are added in the OMAX Make software (the software used to operate a waterjet) that ensures that the profiles we designed don't fall into the water after they are cut. Think: if you were to just cut out a circlecle, it would no longer be attached to the sheet of metal from which it came and would fall. Tabs prevent this.

After uploading the 2D profiles, the software made a path for the waterjet to follow and cut. This machine is really simple, as after selecting the 1/8" aluminum to cut, we get our 2D profiles cut with no extra input from us!

Note: the additional circle featured in this cut but not in the previous image is for a different project

Taking the machined pieces off of the waterjet, you can see how they fit together where the legs slide up through the base and can be welded to the impeller housing.

To begin with the machining process for the heron engine one must understand the two basic operations of the lathe: turning and facing. Turning is the main operation I used and requires removing material from the outer diameter of the stock. I started with 2 in OD stock, and removed in small increments (20 1/1000ths of an inch) at a time until I reached the two outer diameters I needed: 1 in and 1.5in if you recall from the CAD design. As you can imagine, this is a rather lengthy process as you have to take off small amounts of material at a time to ensure that you don't break the turning tool.

I then used the operation known as facing (removing material from the ends) to adjust the total length of the bar. For the 1 in section, I ensured it was 0.7in (0.5 in for the bearing depth plus 0.2 in so that it could sit above the bearing). The 1.5 in diameter section had a total height of 1.5 in as well.

After the outer diameters were to spec, I needed to hollow out the inside. Again the same principle of facing and turning apply, but this time to the inside. I first started by center drilling the engine. This gives a guide hole for the drill bit so that it can go in straight. After this, I drilled all the way through the stock with a small drill bit and incrementally worked my way up to the largest drill bit that I had access to. At this point, a boring tool could fit inside the hole made by the drill and thus I could start turning the inside of the engine. I gave wall thickness of 0.2in for both the upper section and lower sections.

I was very proud with my machining of this casing as the outside surface finish is very shiny and aesthetically pleasing. It was within 0.003 inches of the dimensions I outlined in the CAD design. I repeated this process for the impeller casing, following the same process as I used for the Heron Engine.

The shaft was a little more difficult to work on the lathe than the previous two items and this was for two reasons: its longer and thinner. Ideally I would have liked to have had a 1/4" diameter rod, however I did not have access to this and had to turn it from the rod I had available, which I believe was 3/8". For something this thin, you have to take off even less material at a time otherwise the rod will snap. You should learn from my mistakes ( I snapped it many times).

In the above images you can see all of the parts before they were assembled completely.

In order to connect the pieces together, I decided that I wanted to use aluminum TIG welding. In hindsight I would have liked to have used JB Weld, which is not a food safe option, so would be only useful for prototypes. TIG welding joins the parts in a food-safe way that can handle the heat and pressure, which is why I chose this method.

To prep for welding, the aluminum has to be spotless, so I clamped the pieces down using a vice and buffed them with an angle grinder.

After prepping all of the materials, now time for welding! This is a difficult process, but I took it one step at a time, assembling the pieces according to how they are laid out in the CAD model. Although my welds are not the prettiest, they got the job done, and you can see an example of this on the impeller blades.

After welding, the next step was to cut a hole in the top of the pineapple can to make space for the ball bearing. To secure it I used JB Weld rather than actual welding because welding I would run the risk of ruining the ball bearing.

NOTE: JB Weld is NOT food safe. This is a proof of concept, and if you use this product, you should NOT consume the things it touches.

After attaching the ball bearing, I inserted the machined heron's engine into the bearing using JB Weld.

To finish the Heron's engine, I cut off the bottom of a soda can and removed just the dome portion. This fit snugly on top of the machined cylinder from the lathe. I used a file to smooth down the edges and then used JB weld to secure it to the cylinder. Cutting off 2 in of the smaller diameter pipe, I secured them so that the ends of the pipe pointed tangent to the edge where they were secured. This way they produce the most torque.

After finishing off the Heron's Engine, I connected the shaft and copper tube using more JB weld. The Copper tube must connect to the impeller housing.

This machine shows that age-old engineering principles can be spun (see what I did there) in new ways, and that your passions don't have to be exclusive; they can be mixed and intertwined with each other! I've learned so so much from this project and while I hit many (MANY) speed bumps along the way, I ultimately wish to use this as a learning opportunity for the future!