Wave Action in Gun Run-up Springs

Abstract

A number of articles and pamphlets have appeared on the waves and oscillations that occur in springs used for commercial purposes, notably the valve springs for internal combustion engines, and it has been shown that the forces experienced, and other results obtained, are very different from what would have been expected from calculations which assumed that the load is applied slowly through the amount of compression available. No such publications, so far as is known to the author, have appeared regarding springs for military use, such as those employed to run the gun up after firing. Textbooks have tacitly assumed that the load is so slowly applied that static considerations meet the case, so they have given the corresponding theory.

That a wave action does occur is observable by eye in some instances. In the 18-pounder Mark II field carriage, so well known during the war of 1914–18, the run-up springs were telescopically arranged so that the inner spring case was carried as a float between the outer and inner springs. That there was a wave action could readily be seen by carefully watching this inner spring case during the recoil of the gun on firing.

There also have been several instances in which a column of identical springs have been employed, and it has been found in use that the spring in one particular position is liable to take a permanent set or to fracture. This indicates that there is a wave action and that it is accentuated at the point concerned. It was a result of this sort that led the author to work out the theory of recuperator springs, taking the time factor into consideration. Their behaviour is shown to be quite different from that calculated on static considerations.