Abstract
The authors point out in this paper that lateral oscillations, which either do not occur or are negligible at slow train speeds, are of vital importance at the high train speeds now demanded by the railroads in order for them to compete successfully with the swiftly moving automobile and the much swifter airplane. Aside from collisions and broken rails, practically all railroad accidents result from lateral derailments, since vertical derailments occur only on those rare occasions when a bridge or trestle collapses from flood or storm. Lateral derailments are caused by lateral pressure of wheel flanges against the rail. Therefore, the prevention of lateral derailments requires a knowledge of both the conditions which cause high lateral forces and of the conditions which must prevail in order to keep the lateral forces below some indicated safe value.
The literature on the subject of lateral oscillations of rail vehicles is rather meager. Nadal and Marie’ discuss the type of oscillations that are forced. Boedecker, as well as the authors previously mentioned, discusses the weaving motion of the wheel base due to the conicality of the wheel treads. The weaving action which Boedecker discusses must be started by an initial disturbance and, in the absence of further periodic disturbances, can neither build up to a higher amplitude than that produced by the initial conditions nor be sustained, but must quickly die away. Carter develops the stability condition for a rail vehicle as determined by the slippage at the treads.
The essential difference between the previous studies and the present one is that the previous ones discussed forced oscillations the life of which depended upon the application of some periodic force, such as that from cylinder action or rail joints, whereas the present discussion describes and explains a type of oscillation which, after an initial disturbance, even though a minor one, may build up to dangerous proportions and sustain itself indefinitely on absolutely perfect track. This type of oscillation is frequently encountered and is commonly known as “nosing”. It is only one phase of the whole problem, but it represents the most serious menace to the safe operation of rail vehicles at high speed.
