A locomotive frame is the structure that forms the backbone of the railway locomotive, giving it strength and supporting the superstructure elements such as a cab, boiler or bodywork. The vast majority of locomotives have had a frame structure of some kind. The frame may in turn be supported by axles directly attached to it, or it may be mounted on bogies (known as trucks in American English), or a combination of the two. The bogies in turn will have frames of their own.
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In this Dossier
- ⭐ Core Definition: Locomotive frame
- Locomotive frame in the context of Cylinder (locomotive)
- Locomotive frame in the context of Hood unit
Locomotive frame in the context of Cylinder (locomotive)
The cylinder is the power-producing element of the steam engine powering a steam locomotive. The cylinder is made pressure-tight with end covers and a piston; a valve distributes the steam to the ends of the cylinder. Cylinders were initially cast iron, but later made of steel. The cylinder casting includes other features such as (in the case of Stephenson's Rocket) valve ports and mounting feet. The last big American locomotives incorporated the cylinders as part of huge one-piece steel castings that were the main frame of the locomotive. Renewable wearing surfaces were needed inside the cylinders and provided by cast-iron bushings.
The way the valve controlled the steam entering and leaving the cylinder was known as steam distribution and shown by the shape of the indicator diagram. What happened to the steam inside the cylinder was assessed separately from what happened in the boiler and how much friction the moving machinery had to cope with. This assessment was known as "engine performance" or "cylinder performance". The cylinder performance, together with the boiler and machinery performance, established the efficiency of the complete locomotive. The pressure of the steam in the cylinder was measured as the piston moved and the power moving the piston was calculated and known as cylinder power. The forces produced in the cylinder moved the train but were also damaging to the structure which held the cylinders in place. Bolted joints came loose, cylinder castings and frames cracked and reduced the availability of the locomotive.
View the full Wikipedia page for Cylinder (locomotive)Locomotive frame in the context of Hood unit
A hood unit, in North American railroad terminology, is a body style for diesel and electric locomotives where the body is less than full-width for most of its length and walkways are on the outside. In contrast, a cab unit has a full-width carbody for the length of the locomotive and walkways inside. A hood unit has sufficient visibility to be operated in both directions from a single cab. Also, the locomotive frame is the main load-bearing member, allowing the hood to be non-structural and easily opened or even removed for maintenance.
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