Creating Your Own Car Engine

Hello everyone! My name is Ishaan, and I currently attend Singapore American School. Ever since a little kid, I have been fascinated with cars - the sound, the speed, the models, everything! So, I decided, what better way than to combine my love for cars, which I’m sure every kid has loved at least once in their life, with my passion for engineering and designing, to 3D print my own car engine! I wondered if this was even feasible or not, but after some research, I realised that a V8 car engine replica was indeed a manageable task. I then spent lots of time trying to figure out what works and what doesn’t, and this instructable is a culmination of all the successes that did have. Now, without further ado, here is how to create your own car engine, from designing and modelling, to actually assembling the components and putting it together. Enjoy!

Note: the dimensions of your project, depending on what you decide, may vary from the ones below.

• 3d Printer and access to Fusion 360
• Ball bearings 2x
• Rubberbands
• Either (depending on how you want to hold your project together) :
• Pilot hole, screw bits, drill gun (mentioned accessories come with), and screws
• Feviquick glue (I recommend and used this)

Optional but helpful:

• F-clamps
• Jigsaw tool

Before we start the design process, it is critical to understand what exactly we are building. I won’t stress about explaining the whole thing (there are many good places online to do that), but I will touch base on the mechanics of our DIY car engine.

Pistons, or the cylinders that move up and down (the main part of the car engine), are connected to the crankshaft. Rotary motion induced by us (we crank the crankshaft, but you can also get a motor to make it faster) causes the piston to move up and down, however only if the connector (joining the piston to the crankshaft) is loose at the joints, which allows it to bend and move down.

It would be much recommended if you go online and check on YouTube a short video of how one actually works - this really helped me through my design process.

In my design, I used rulers, online tools, and sketching to choose the dimensions of my engine and the size of each component. Using fusion360, you can plan out your very own dimensions, or stick to the ones in this tutorial. Additionally, choose which type of engine you want - I created a V8 (V shaped with 8 pistons) but you can change the design to customise it.

Above shows the design process you will need to have, such as sketching the components out and their connections to make it easier to visualise, and organising all your parts to make it easier to keep track of what you need or what has arrived.

Once you understand how your engine will work and have all the parts written down, including the ones you need to 3d print (coming up), you can proceed to modelling.

The body refers to all but the crankshaft, which you will have to assemble. Above are the preview of each parts from fusion 360, and below are all STL files. First, design the stand, which the connecting rods will be attached to. The stand is the v shaped object that holds everything together, and has a hole for the ball bearing, in this case 22mm diameter, so the crankshaft can be inserted. To create this, keep your dimensions in mind, and use the conic curve feature to create the outline of the v. Then, use the offset feature to and push it in, with a width of your choice. Once you connect the offset and the original and have a blue highlighted sketch, you can extrude it and wala, you have your stand!

Continuing, let’s examine the piston holder, which will help hold the piston through its movement. You can start with a rectangle (this will be connected to the connector, so make sure the dimensions are accurate). Then, fillet one side (press the tool in sketch mode) until is becomes a distinguishable parabolic shape. One you extrude that, create a circle which is wider than the piston diameter by at least 3mm (learnt that the hard way). After, create a hole in the current body, and create a new cylinder that stretched down, 2mm wider than the hole, and again use the circle as a hole to obtain something shown in the design, connecting the top and the bottom of the piston holder.

Nextly, you have to create the piston itself. This does not require as much work as the others - simply create a cylinder, then a smaller cylinder to use as a hole. This will make the interior of the cylinder open apart from the walls. Then, similar to the process used to create the stand, make a conic curve, offset it, connect the two, extrude, and move it so it is connected to the piston, as the above photo shows. This will be essential to connect to the crankshaft in the following steps (beware, that’s the most tedious step!).

Let’s now examine the connecting rod, which is essentially just a cylinder connected to another cylinder, albeit on a different axis, with a hole in it, as the photo depicts. Remember, this connects the piston to the crankshaft, so the diameter should not be large, 4-5mm will do. The length should be in the range of 50 mm - 120mm (mine was 75mm). The cylinder with the hole does not need to be that big, as only a rubber band needs to be able to fit through (yes, a rubber band, more on that later). Use the automate feature to connect the two by selecting both faces.

Lastly, the connector itself, where the piston holder will be glued/screwed on. This is simply just a rectangle, with a width of around 10mm, and the length of whatever you choose, however make sure you come up with this with preparation in the blueprint phase.

Finally, you can slice the files in your app of choosing, however I recommend CURA, and then send it to the printer.

The crankshaft is essentially what causes the up and down motion of the piston. Since you can’t 3d print it all at once, we have to individually 3d print each part and fuse them together.

The crankshaft, however, is very rudimentary. Three of the parts are just cylinders.

Let’s consider Part A, which you only need two of. This connects the ball bearings to the crankshaft. It can be however long, but the diameter should be that of the ball bearing, or in this case 8mm.

Part C is where the connecting rod is attached, and is a 30mm long, smaller diameter cylinder. You need 4.

Part D is a 10mm long cylinder with an 8mm whole. You need 3.

Now, let’s consider part B. This connects the big cylinder to the small cylinder, and allows it to rotate properly. To create this, simply sketch a triangle in fusion360 and fillet the sides. Lastly, add two holes, as shown in the image above. They should be of the diameter of part A and part C respectively. You need 8.

Note that it is important to refer to your blueprint when creating this. My STL files are below.

Finally, the part you have all been waiting for - assembling the body, fusing all the work you have done. You want to first make sure that the ball bearing is properly inserted, as that will make inserting the crankshaft much easier. If you made the hole on the stand the same size as the bearing, you can just hammer it in. Also, don't mind the inserted crankshaft above - that was for prototype purposes (had to do a lot of those to see if this actually worked!).

Then, using the Feviquick glue (or screws), connect the four connecting rods, so that they are symmetric when the v stand is cut down the middle. Choose the height you like, as the “piston aesthetic” will only come if the height is correct. I recommend keeping the bottom connector at the lowest point of the connecting rod in its cycle.

Lastly, attach the piston holders so that they are equidistant, as shown in the photo. Apply little Feviquick, and then stick and hold into place, having 4 on each side. F clamps would make this process much easier, as the holding is not necessary.

Now comes time to take all the parts (A,B,C,D) and make them into one. This section will outline how is works.

Take Part A and connect it to the big hole of one part B. Then take the part c and connect it to the other side of that same part B. Then, take a part B, and connect the small hole to part C. After, take a Part D, and connect it to the other side. Continue this process until you finish on a Part A.

The photos above show how this may be done, including the final crankshaft and the steps along the way. Note that for each new ‘pair’ of parts, like the two part B’s and one part C shown above, rotate it slightly. This will keep your pistons at different levels, replicating the real world car engine. Additionally, if the parts aren’t going in the holes, you can use a lighter (please be safe and have supervision) to melt the PLA, or whatever material, and push it in. PLA, for one, melts instead of burning, but still be careful.

Now comes the somewhat tedious part. Before I explain, I would like to clarify that in the end, rubber bands for both connections were used, and while there were some other alternatives, arguably better, from a cost and aesthetic standpoint, rubber bands did the job.

To connect the connecting rod to each part c in the crankshaft, first pass the rubber band through the small hole, and tie a big knot around the part c. You can then tighten, double knot, and cut off the edges. Do this for all 8.

To connect the pistons to the connecting rod, first tie a knot and place it around the top of the part c. Tighten, glue it to part c, then use the ends of the rubber band to wrap around the piston and tie a knot, then double knot, then cut off the edges. Again, do this a for all 8.

The results for all connections are shown above.

Now, put the crankshaft inside the engine, as shown above. If it helps, remove the Part A from both sides, slide it into the ball bearing, and then connect the crankshaft from there.

Last but not least, hope you have strong knots, because you then have to bend the piston and slide it into each piston holder. Once this is done, turn the Part A that is protruding out the engine and wala! You have a working car engine replica. Amazing, right?