As I told on part I (https://www.instructables.com/id/Home-Made-Model-Steam-Boat-Part-I/), this instructable introduce the steam engine part of the model boat. This part is the date back memory, not how to make it, but what I've made it. The video shown you how the engine move, the steam intake from above to push one piston down, as the time phase of both pistons is 180 degree, the second piston move upward to exhaust steam out, then the valve moved by the swash dish open the second piston and let steam in and push it down, the first piston then push steam out and cycle again.
Step 1: The Cylinder
The cylinder was made by brass tubing, just bought some length from hardware store, it look like round in shape, but actually not, this is the big problem. The base sheet was also made by brass tube, but need some larger one, then cut it in length and hammer it flat. The steam intake tube has two small valve piston arranged to open one intake hole and shut the other to the exhaust pipe.
Step 2: The Pistons
The pistons were made the fishing weight, firstly I used the cylinder as the mold and pour melted lead into, but the lead shrink after cool down and not good fit to the cylinder, so I found another mold slightly bigger than the cylinder to melt the lead, then file the piston to just fit, but unfortunately the cylinder tube not round in shape. The crank shaft arranged 180 degree phase, so one piston up the other down, however it will not auto start need to give it a push. The intake/exhaust valve was move by the swash dish turned by the crank shaft.
Step 3: The Assembly
This shown the explored parts of the engine, but no boiler, the boiler was rusted and leak water by heavy burning and flew away, only the engine left. With refer to the part I (https://www.instructables.com/id/Home-Made-Model-Steam-Boat-Part-I/) video, I just play once with this engine, but I felt enough, this instructable not shown how to made it, but ......... I can made it, so can you.