There is a special self-balancing aspect of the air suspension and spinning system. The spin chamber inner wall is closest to the bullet right where the body transitions to the nose. The spin chamber roughly follows the outside shape of the bullet but with shallow angle deviations that enlarge the annular spaces in the spin chamber upward and downward from this point. Air is delivered to the spin chamber by four small diameter jets that enter tangent to the spin chamber wall. These jets are located corresponding to a position on the bullet nose just forward of the bullet body.
The bullet can move downward in the spin chamber to close off these jets but air pressure raises the bullet. However, as soon as the bullet is raised by the pressure, air starts to flow upward, downward and around the bullet. Since the location of the jets corresponds to the narrowest annular space, this becomes the location of highest velocity and lowest pressure resulting in a force which pulls the bullet back down against the jets. A balance is achieved which holds the bullet in position just off the surface of the spin chamber. All this is occurring while the bullet is being spun by the tangential delivery of air.
The force holding the spinning bullet in its vertical position is so strong that the bullet will remain spinning in the chamber even if the system is turned upside down.
I used information from the design of high speed medical centrifuges as a starting point for selection of the shallow angles. It took several prototype chambers to get the dimensions right but bullets started spinning after a couple of days work.
The bullet can move downward in the spin chamber to close off these jets but air pressure raises the bullet. However, as soon as the bullet is raised by the pressure, air starts to flow upward, downward and around the bullet. Since the location of the jets corresponds to the narrowest annular space, this becomes the location of highest velocity and lowest pressure resulting in a force which pulls the bullet back down against the jets. A balance is achieved which holds the bullet in position just off the surface of the spin chamber. All this is occurring while the bullet is being spun by the tangential delivery of air.
The force holding the spinning bullet in its vertical position is so strong that the bullet will remain spinning in the chamber even if the system is turned upside down.
I used information from the design of high speed medical centrifuges as a starting point for selection of the shallow angles. It took several prototype chambers to get the dimensions right but bullets started spinning after a couple of days work.
