Q: What are the key considerations for spike selection in a heavy-haul corridor?
A: For heavy-haul lines, spikes must withstand immense dynamic loads and vibrations. Key considerations include:
Higher Grade Steel: Possibly alloy steel for greater strength and fatigue resistance.
Robust Coating: Enhanced corrosion protection due to potential exposure to brake dust and other contaminants.
Possible Upsizing: Using a spike with a larger shank diameter for increased holding power.
More Frequent Inspection Intervals: Due to the higher stress on the fastening system.
Q: What is the "mechanical advantage" of a spike puller?
A: A spike puller (claw bar) is a classic example of a lever, a simple machine. The long handle provides a significant mechanical advantage. The effort applied at the end of the handle is multiplied, creating a much larger force at the claw that grips the spike head. This allows a worker to extract a tightly held spike that would be impossible to remove by pulling straight up.
Q: How are spikes counted and inventoried on a large project?
A: Spikes are typically counted by weight due to the impracticality of counting thousands of individual items. The project specifications will state a required number of spikes per sleeper and sleepers per kilometer. The supplier provides a known quantity per crate or bag (e.g., 100 spikes per 25kg bag). Inventory is managed by tracking the number of bags used versus track length completed.
Q: What is the significance of the head shape on a spike?
A: The head shape is functional. A flat, square head provides a large striking surface for the hammer or driving machine. The square shape also helps prevent the driving tool from slipping off. The head is designed to be driven flush with or slightly below the surface of the baseplate to avoid interference with train equipment and to provide a clean profile.
Q: What is " electrolytic corrosion" and can it affect spikes?
A: Electrolytic corrosion occurs when stray electrical currents (e.g., from DC traction systems or nearby cathodic protection) flow through the soil and use the spike as a conduit. The spike acts as an anode, causing metal to be lost from its surface at an accelerated rate. This is a concern in electrified territories and requires monitoring and specialized mitigation techniques.