Antique Fish Plates in Railways

The history of rail transport is built on innovation, with each component evolving to meet the demands of heavier loads and faster speeds. Before the widespread use of continuous welded rail, track sections were connected using bolted joints. The key component in these assemblies, known as a fish plate or joint bar, was critical for maintaining structural integrity. For historians, collectors, and restoration specialists, understanding the specifications of antique fish plates is essential for accurately recreating or preserving historical railway lines. These components were the backbone of early rail networks, ensuring a safe and continuous path for trains.

This article provides a technical overview of antique fish plates, focusing on their specifications, materials, and function, with particular attention to how they were designed to fit historical rail sections, including those that correspond to later AREMA standards.

The Vital Role of Antique Fish Plates

A fish plate is a steel bar that bolts two sections of rail together at their ends. In a typical arrangement, two plates are used at each joint, one on either side of the rail web (the vertical section between the head and the foot). The plates are contoured to fit snugly against the web and the underside of the rail head, as well as the top of the rail foot. This precise fit is what gives the joint its strength.

The primary functions of antique fish plates were:

• Alignment: To hold the adjoining rails in perfect horizontal and vertical alignment, ensuring a smooth transition for the train wheels.
• Strength: To provide vertical and lateral stiffness, preventing the rail ends from bending or deflecting under the immense weight of a train.
• Expansion Control: To allow for a controlled gap between rail ends, permitting longitudinal expansion and contraction due to temperature changes without causing the track to buckle.

Without effective fish plates, the rail ends would sag, creating a weak spot that could lead to bumpy rides, excessive wear on both the track and rolling stock, and potentially catastrophic derailments. The term itself is believed to derive from the French word “ficher” (to fix or fasten) or from early shipbuilding, where “fish pieces” of wood were used to reinforce a ship’s mast.

Types of Historical and Antique Fish Plates

As railway technology advanced, so did the design of the joint bar. While modern systems have largely moved on, three primary types were common in the era of jointed track.

1. Standard Fish Plates: This is the most common type, designed to connect two rails of the same size and weight (e.g., two sections of 115 lb rail). They have a uniform cross-section along their entire length and are typically drilled with four or six holes for track bolts.
2. Compromise (or Offset) Fish Plates: These were specialized and ingeniously designed plates used to connect rails of two different sections or weights. For example, a compromise joint would be needed to connect a 115 lb rail to a 132 lb rail. Each half of the plate is forged to match the profile of the specific rail it is bolted to, creating a smooth transition despite the difference in rail height and head width.
3. Insulated Fish Plates: Used in signaled territory, these plates were designed to create an electrically isolated joint to define the boundaries of a track circuit. They were often made from a non-conductive material like dense composite or were standard steel plates used with insulating end posts and bushings around the bolts to prevent electrical continuity between the rails.

Specifications of Antique Fish Plates

The design of antique fish plates was not arbitrary; it was directly tied to the specifications of the rail they were meant to join. The American Railway Engineering and Maintenance-of-Way Association (AREMA) and its predecessors established standards for rail profiles, and fish plate manufacturers created products to match.

The key to a fish plate’s design is the “fishing surface” or “fishing chamber”—the space on the rail web between the head and the foot. The plate must make full, firm contact with these angled surfaces to properly transfer loads.

Materials and Mechanical Properties

Early fish plates were made from iron, but steel quickly became the material of choice due to its superior strength and durability. The steel used had to be strong enough to resist bending but ductile enough to avoid snapping under shock loads.

The chemical composition was carefully controlled to achieve these properties. A medium-carbon steel was typically used, providing a good balance of hardness and toughness.

Table 1: Representative Chemical Composition for Historical Steel Fish Plates

The mechanical properties were a direct result of this composition and the hot-rolling manufacturing process.

Table 2: Typical Mechanical Properties of Antique Fish Plates

Dimensions and Fit for AREMA Rail Sections

The most critical aspect of a fish plate’s specification is its physical dimensions, which must precisely match the rail profile. A plate designed for a 115 RE rail will not fit a 132 RE rail correctly. The table below outlines the key dimensions for standard fish plates designed for common historical AREMA rail sections. These plates were typically available in 4-hole and 6-hole configurations.

Table 3: Dimensional Specifications for Antique Fish Plates (Standard 4-Hole) for AREMA Rails

Note: 6-hole plates were longer (typically 36-38 inches) to provide additional stiffness for high-speed or heavy-tonnage mainlines.

The cross-sectional shape is just as important as the length and hole pattern. Key design features included:

• Height: The overall vertical dimension of the plate.
• Thickness: The thickness of the bar through its center.
• Contact Surfaces: The angles forged into the top and bottom edges of the plate had to perfectly match the fishing angles of the rail web. A poor fit would concentrate stress and lead to premature failure of the joint.

The Legacy of Antique Fish Plates in Modern Railroading

While continuous welded rail (CWR) has replaced most jointed track on mainlines, antique fish plates and the principles behind them are far from obsolete. Jointed rail is still widely used in:

• Yards and Sidings: Areas with lower speeds and traffic where the cost of CWR is not justified.
• Industrial and Shortline Railroads: Many smaller operations continue to use and maintain jointed track.
• Heritage Railways and Museums: Preserving historical accuracy often means using authentic jointed rail with fish plates.
• Temporary Repairs: Bolted joints are sometimes used as a temporary fix for a broken rail in CWR territory until a welding crew can make a permanent repair.

For those working with historical track, identifying the correct antique fish plates is a matter of matching them to the rail profile. Markings rolled into the rail web, indicating the manufacturer, year, and rail weight, are the primary clues. Once the rail section is identified, the corresponding fish plate can be sourced or fabricated.

the humble fish plate was a foundational piece of technology in the development of railways. These steel bars reliably held the network together, bearing enormous loads and enabling the expansion of railroads across continents. The specifications of antique fish plates reflect a deep understanding of mechanical engineering and material science, ensuring that each joint was a point of strength, not weakness. Their study offers a fascinating glimpse into the evolution of the track structure we rely on today.

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