In this Instructable, we'll look at how to 3D print your own working V2 Pneumatic Engine. This type of engine relies on compressed air pushing down pistons connected to a crankshaft to produce rotational movement. The style of the engine is a 45 degree V2.
I've been working on creating a 3D printable engine for a few months now and this project combines the best of all my attempts.
The upper section contains a valve system which allows the piston to extend, only after being depressed (ie on the "upstroke"), letting the engine run both forwards and backwards and reducing the amount of tubing to a minimum.
I'm still waiting on my prints so no pictures of a working model yet, but I should have them in the near future. It is recommended you either print a flywheel or add a small, offset weight to the end of the crankshaft for smoother motion
This Instructable is entered in the "3D printing Contest", so if you like what you see and you enjoyed making your engine, be sure to vote for it in the contest.
So, what do you need to make this engine?
1) A 3D Printer - I use PLA but ABS should work too. Print profiles are up to you
2) 1/4 Inch or 6/7mm diameter rubber tubing
3) Lubricant - WD40, Vaseline etc to line the inside of the piston
4) All-Purpose Sealant*
6) Mixing Cups and Sticks*
7) Support Material Removal Tools
8) A Source of Compressed Air (eg Foot pump or Air Compressor)
9) Rubber Bands
*These will be used to make rubber seals for the valve section
Step 1: 3D Print the Parts
Using the following STL files, print off the required parts and remove any support material. Some files require being printed multiple times, so firstly work out how many parts you will need:
(The names here reference the .STL file names inside the zipped folder)
For 1 Cylinder With Valve:
1 x Piston
1 x Piston Case
1 x Valve Washer Upper
1 x Valve Washer Lower
1 x Valve Case
1 x Pin
1 x Piston Mould
1 x Seal Mould
For The Full V2 Engine:
2 x Cylinder With Valve (See Above)
2 x Crank Disc
2 x Crank Link Bar
1 x Crank Bar
2 x V45 Frame
Step 2: Create Rubber Seals
To create the rubber seals for the valve, we'll be mixing up Oogoo: a cheap rubber made from sealant and cornflour.
This method uses the rubber made from mikey77's Instructable (https://www.instructables.com/id/How-To-Make-Your-O...), and I'll cover the basics here.
First, we'll mix the sealant and cornflour in a 2:1 ratio within some mixing cups to create a sticky mixture. Once thoroughly mixed, this mixture is then pushed into the mould prints from the previous step (Piston Mould and Seal Mould). The seal mould will produce a thick O-ring and the actual piston piece is pushed into the piston mould, containing the rubber mix, to produce a "rubber cap" that will form an airtight seal once assembled.
These are left to cure for at least 3 hours, before being peeled out carefully ready for assembly.
An example of the piston curing inside it's mould is shown above in red.
Step 3: Assembly
Now we have all of our parts, we can now assemble them. Firstly, we'll tackle a single cylinder and then move on to the full engine. Following the cut away image above, assemble the parts glueing the top valve segment together and joining the valve to the piston's case with superglue. The lower valve spacer has two ends: one with an extruded circle and one with two "prongs" sticking out. Ensure these "prongs" face into the piston case when assembling
When glueing ensure the parts are held tightly together as the washers are designed to squish out the rubber to form a better seal.
When inserting the pin and piston, ensure they are properly lubricated first and slide easily.
A rubber band is then fed through the top loop of the pin before being hooked bellow the studs either side of the valve casing piece.
The piston should be able to push the pin up with light force, and be forced down slightly by the pin.
Step 4: Fitting the Crankshaft and Frame
Next, we can build the rest of the frame. After building two of the cylinders, assemble the crankshaft as shown above by gluing the crank discs, crank bar and crank link bars together. The two Cylinders are then slid on top of the middle of the crankshaft and the two V45 frames are slotted on to the end.
Ensure the 15mm short bars are at the ends as more components could be added at a later date
With any luck, when you spin the crankshaft, the two pistons should move together. It is recommended at this stage to print off your own flywheel or glue a small offset weight to the crank to provide momentum.
Step 5: Tube It Up and Give It a Test Run
Now we attach some rubber tubing to the inlet ports on the valve and apply pressurized air. If nothing happens try lightly spinning the crankshaft to trigger a valve and the engine should start running. Beware, if the pressure is too low, the pistons won't be able to trigger the valve on the return but if the pressure is too high, you risk blowing out the pistons from the case.
So there you have it: A 3D printed Pneumatic Engine. With any luck it will tick over nicely and if you have any questions please ask. Like I said I'm in the midst of printing mine so any pictures or videos of your own finished engines would be nice to see.
Thanks for reading and I hope you enjoyed the build.