Since Svedberg developed high speed and ultracentrifugation in the early 20th century, the separation of solutes with weak buoyancy differences has been feasible due to the enormous centripetal acceleration generated by such instruments. In this work the transient motion of single walled carbon nanotubes (SWCNTs) in response to an applied centripetal acceleration field is used to achieve length separation. As rods of varying aspect ratio but a constant diameter, the velocity of each SWCNT scales approximately with the natural logarithm of its aspect ratio under optimized experimental conditions; this allows for sufficient separation in a properly designed experiment to allow for fractionation. However, non-ideal separation can occur under many experimental conditions, apparently due to additional surfactant condensing on the dispersed nanotubes at the high pressures generated in the separation. Parameters of the separation were probed to elucidate this effect, including the SWCNT concentration, added salt concentration, liquid density, rotor speed, surfactant concentration, and the processing temperature. A discussion on how the experimental parameters can result in ideal or non-ideal separations will be presented.