Roof-mounted wire harnesses in trams are exposed to constant dynamic motion. At the articulation between carbody sections, harnesses must withstand yaw, roll, and shift without overstressing or exceeding bending limits.
Traditional CAD design (CATIA, NX, etc.) shows geometry but does not reveal how harnesses behave under movement. This is where IPS Cable Simulation provides unique value – offering real-time, physically correct validation of flexible parts.
Our customer provided us with the original design of roof harness routing in CATIA. The goal was to evaluate its performance under dynamic motion and propose improvements that would increase safety, durability, and compliance with industry standards.
Project Goals
- Validate current roof harness layout between tram sections
- Detect potential overstress and bending radius violations
- Explore design variants to reduce risks
- Provide recommendations for optimal routing and mounting
Simulation Setup
The tram articulation was modeled in IPS Cable Simulation with:
- Realistic harness material properties (bending radius, flexibility)
- Defined mounting points and brackets
- Dynamic motions in three axes:
- Yaw (OZ) – ±30° rotation
- Roll (OY) – ±4° tilt
- Shift (OX) – 80 mm displacement with 1.9° rotation
This allowed us to simulate real-world articulation and check harness behavior in critical conditions, including extreme positions and derailment scenarios.
Analyzed Variants
1. Baseline – Current Layout
- High stress detected during articulation
- Several critical bending radii exceeded
- Risk of premature wear and potential wire damage
2. Wire Length Extension
- Longer harness segments introduced
- Stress levels reduced in some positions
- Critical bending still present in extreme cases
3. Mounting Relocation
- Adjusted mounting blocks between tram sections
- Improved stress distribution and bending radius
- Some local overstress remained
4. Optimized Layout
- New mounting layout combined with adjusted routing sequence
- All bending radii within safe limits
- Stresses significantly reduced
- Harness motion fully reliable in dynamic operation
Results and Key Findings
- The baseline design was not sufficient for long-term safe operation.
- Simple length extension helped but did not eliminate risks.
- Mounting relocation improved results, but still required refinement.
- The optimized solution achieved safe bending and minimized stresses, ensuring durability and reliability of the harness system.
Conclusion
This project highlights the importance of dynamic validation for roof harnesses in railway vehicles.
While CAD tools define geometry, only IPS Cable Simulation can predict real-world harness behavior under motion. The optimized design ensures long-term safety, reliability, and compliance with railway standards — and sets a strong foundation for future harness projects.