Ultra-High-Speed Roller Coaster Wheel

Location: Six Flags Qiddiya, Saudi Arabia

Application: Ultra-High-Speed Roller Coaster Running Wheels

Material: Premium Vulkollan / NDI-based Polyurethane (CPU)

1. Project Overview

The Falcon’s Flight at Six Flags Qiddiya is the world’s fastest roller coaster, reaching speeds of 155 mph. For the wheel systems, this creates a mechanical environment similar to aircraft landing gear rather than traditional amusement rides. The wheels must survive extreme kinetic energy and the harsh thermal conditions of the Saudi Arabian desert.

2. Material Challenges

The choice of Polyurethane (PU) is critical because traditional rubber would disintegrate at these speeds. However, at 250 km/h, standard PU faces three main threats:

Hysteresis (Internal Heat Build-up): Rapid compression and decompression cause molecular friction within the PU, leading to temperatures that can melt the core of the wheel.

Dynamic Loading: High G-force maneuvers exert massive radial and axial loads on the wheel-to-steel-rail contact point.

Environmental Stress: Ambient temperatures exceeding 113°F plus abrasive desert sand.

3. Technical Specifications of the PU Wheels

4. Engineering Solutions

A. The NDI Advantage

To prevent the wheels from melting, the project utilizes NDI-based elastomers (Vulkollan®). NDI has a unique molecular structure that allows it to maintain its physical properties even when the internal temperature of the wheel rises during high-speed sections.

B. Heat Dissipation & Hub Design

The wheel hubs are typically forged from high-grade aluminum alloys or specialized steel. Aluminum hubs act as a heat sink, drawing thermal energy away from the polyurethane bonding layer to prevent thermal failure.

C. Optimized Geometry

The tread profile is precision-engineered to manage the contact patch with the steel track. A slightly crowned profile helps reduce friction during straightaways while providing maximum grip during high-speed banked turns.

5. Summary for Industrial Application

This case demonstrates that for extreme speed and load applications, the grade of Polyurethane—specifically the switch from MDI to NDI-based systems—is the deciding factor in operational safety and component lifespan.

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