Roulette (curve) in this case, the point lies on the circle then the roulette is a cycloid. A related concept is a glissette, the curve described by a point attached to a given curve as it slides along two (or more) given curves. Formally speaking, the curves must be differentiable curves in the Euclidean plane. The "fixed curve" is kept invariant; the "rolling curve" is subjected to a continuous congruence transformation such that at all times the curves are tangent at a point of contact that moves with the same speed when taken along either curve (another way to express this constraint
Rolling stock of the South Manchuria Railway Mantetsu system. The numbering system is unclear for Period 1. Some locomotives – the 2-6-4 tank locomotives later designated Dabui-class, the 2-8-0 tender locomotives that became Sorii-class, and the 2-8-0 tender locomotives that became Sorini class – were numbered starting at 1, but there was no system of type classification. The first system of type classification for locomotives consisted of a letter of the Roman alphabet to indicate the wheel arrangement based on the American names used for the given arrangement. If a second class of locomotive of the same wheel arrangement was introduced, this was indicated by a class