Third Entry: Final Preparations

Over the past few weeks Mike and I have worked diligently on our engine. We have spent every lunch period in the physics lab for the past week and a half finishing all the prep work for our engine and at last we are ready to assemble. This coming Monday we will begin assembling all the pieces of our engine so we can test it soon.

I have included some photos, as well as a short video clip of a basic test of our engine's pressure vessel construction.

Displacer:
We put a needle through the exact center of our displacer top and JB welded it in place. We then
JB welded the displacer top onto the displacer bottom. We attempted to weld it from the inside, but some of the epoxy was squeezed over the edge and ended up on the outside of our displacer. To eliminate this and thus minimize friction, we sanded
the edges of the bond until
the glue became flush with the surface of the can itself. We also checked for any tiny gaps, resealed them with JB Weld, and sanded again.




Pressure Vessel Top:

Our pressure vessel top will be what seals off the engine. We first put a whole in the center of our vessel top. We realized that more important than being the exact center, the pressure vessel top simply needs to be centered on the displacer to minimize friction. Thus, we used our displacer top to line up and punch the hole. Next, to make it air tight, we used a small washer and a small square of tin to create an air tight chamber around the whole in our pressure vessel top. Next we punched another whole through the tin part of the chamber. This creates a tighter seal that prevents air from escaping our engine. However, we also had to work the needle to slightly widen the hole so that there would be no friction when the displacer pin slid through the pressure vessel top. We attached all these parts using an RTV gasket sealant.


Crank shaft:

The crankshaft is what translates the lateral motion of the displacer into the angular motion of the flywheel. The width of it's bends are extremely important because they dictate the range of motion of the displacer. Therefore, it must be very precise if we want out engine to work. Note though: the angle of the individual bends is not extremely significant, what matters is that the widths of the bends are correct, and that the two bends are exactly 90 degrees out of phase.




Crank shaft supports:


These are simply attached to the pressure vessel to hold the crankshaft in place. Notice that instead of following the instructions and making two equal length supports, we cut one shorter so that we would not have to drill a whole and both attach our elbow joint to the support and the support to the pressure vessel. This decreases the odds of a leak.




Elbow Joint:

The PVC elbow joint with a balloon will inflate as hot air rises. The balloon is then attached to the crankshaft, causing it to rotate the flywheel.










A quick video of how it all works:

This video demonstrates simply the lateral motion of the displacer in our pressure vessel to test how well it will work. We saw that friction really is not much of an issue.