The PT-3 is the third paper turbine designed by SamuelFalvo?. Its purpose was to research the easy fabrication of TeslaTurbine?s. Fabrication parameters included:

This is the completed unit. You'll note that the rotor housing is constructed out of corrugated cardboard from a pizza box (Papa John's in particular. Good place to order pizza from; if you haven't tried them yet, you should).

Here, you see the engine with the top rotor housing "plate" taken off. You'll notice that the rotor consists of a stack of paper discs, called the RunnerAssembly?, mounted on a quarter inch (6mm) diameter soda straw used as the shaft. Each disc is also called a Runner. Note the exhaust vents in the RunnerAssembly?. Also note the location of the air inlet port, which is facing the front, near a rotor housing bracer.

Here is the rotor housing without the turbine installed. It consists of an octagonal housing, as that was the easiest approximation to a perfect circle I could get with the materials on-hand. Notice the location of the inlet port. It's close to the rotor housing so the air that is flowing in doesn't have to change directions more than once. This reduces losses due to eddy-currents induced from direction changes. As you might surmise from the picture, the turbine is intended to spin counter-clockwise in the orientation shown. You'll see the inlet port in greater detail below.

This image shows the RunnerAssembly? in greater detail. Each disc is separated approximately by 793um (1/32"). This distance happens to be equivalent to the distance consumed by three layers of the paper used to construct the disc. That paper, by the way, is the cardstock used to create Marie Callander frozen food boxes. Notice that spaces between the discs are largely empty; those things you see between the discs are there only to provide structural support and to ensure proper inter-disc spacing. They don't actually add anything to the operation of the disc (in fact, they remove from the turbine's efficiency. Experience shows that starting the turbine from dead-stop is much easier when flowing air into the turbine in an empty space than it is when a support is in the air-stream).

Here you see a projection view of one of the runners in the runner assembly. You can clearly see the supports. Also notice the exhaust vents. These exhaust vents consume one third the active surface area of the turbine's surface area. I emphasize active because it's important to realize that air flow never reaches the inner 25.4mm (1") region of the rotor. Thus, only the outer 77mm (3") is used by the air-stream. I could bring the exhaust closer to the shaft, but then structural integrity is sacrificed (it is paper after all). I could make the exhaust vents smaller, which would increase turbine efficiency, but at the cost of reduced torque. Thus, it selecting 1/3rd surface area for exhaust porting is a good compromise for my R&D needs.

Here, you see how the inlet port is used. Notice the soda straw is used to blow air tangentially across the RunnerAssembly?. It's important that the soda straw does not come into contact with the rotor assembly while in operation, as it adds unnecessary amounts of friction. In fact, I've damaged a fair number of straws this way, as the ends of the straws melted from friction-generated heat. It also throws the turbine off balance (and with a soda straw for a shaft, it needs all it can get).

What follows is a collection of images detailing the PT-3's final construction, showing the turbine in various stages of teardown.

Construction and Teardown


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