A Combined Vacuum Limiter and Guard's Brake Valve

摘要

At Frimley Lodge Miniature Railway, our locomotives are fitted with vacuum limiting valves, typically set to between 12 and 15 inches of mercury. Originally these were of the diaphragm type as described by Martin Evans and others. During the last 10 years, both commercial and home grown alternative types of limiter have been adopted which have turned out to be a much more reliable, robust, compact and easier to make limiter. These are, in effect, a negative pressure safety valve. The design I produced about six years ago is described here as embodied in the guard's brake valve, which is the subject of this article. We exclusively use automatic vacuum brakes on our passenger rolling stock at Frimley Lodge. A description of the type of brake cylinder we use was given in Model Engineer Volume 184, Issues 4116 and 4118 followed by a series of articles describing Guildford Club's adaptation of the system in Volume 188 issues 4167, 4169 and 4171.