Breaking the NVH Bottleneck in E-Bike Drivetrains: How Nylacast High-Performance Polymer Gears Won a New Market

Challenge: Surpassing Existing Suppliers in a Cost-Sensitive Market to Meet E-Bikes' Extreme Demands for Quietness, High Torque, and Reliability

A globally leading core e-bike drivetrain system supplier, renowned for its self-developed torque sensor technology, was seeking a superior transmission solution for its new generation of mid-drive motor systems. The customer already had an existing gear supplier and presented a stringent set of performance criteria. The gears must operate across a wide temperature range of -20°C to 85°C, deliver an maximum output torque of 100 Nm, achieve a gear ratio of 22, and have an outer diameter of less than 60mm. Crucially, the customer explicitly required the gears to possess excellent NVH (Noise, Vibration, and Harshness) performance to enhance ride quality.

The customer's deeper challenge was: how to find a gear that could meet all mechanical strength and durability requirements (including high/low-temperature torsional strength, salt spray testing, waterproof sealing, and long-term start-stop life tests) while significantly improving the noise and vibration performance of the drivetrain.

Solution: Providing a Comprehensive, Superior Gear Solution through Full-Process Engineering Services and Nylacast's Cast Polymer Core Technology

Upon receiving the customer's existing gear sample, the Nylacast Automotive team did not simply perform a basic comparison. We initiated our standard process as a Full-Service Supplier: from material science analysis, application engineering design, and precision manufacturing to final testing and validation.

1. Material and Process Advantages: We thoroughly explained to the customer the fundamental differences between Nylacast Casting Process and traditional injection molding (used by the customer's existing supplier). Our process produces ultra-high molecular weight polymers with an extremely narrow molecular weight distribution through in-situ monomer polymerization. This translates directly into two core advantages:

o   Higher Torsional Stiffness: Longer, more complete molecular chains result in less deformation under load, enabling more precise and efficient power transmission.

o   Superior NVH Performance: The material's inherent excellent damping characteristics effectively absorb and attenuate vibrations and noise generated during operation coupled with the accuracy of a hobbed gear, result in quieter and smoother running.

2. Customized Design and Engineering Analysis: Our application engineering team utilized advanced gear design platforms (such as KISSsoft) and Finite Element Analysis (FEA) technology to optimize the gear tooth profile and face width. (Beyond discrete gear optimization, we also provide optional integrated design concept --- a gear with an integrated shaft, which could further reduce component count, simplify assembly, and enhance concentricity and overall system rigidity.) The focus was on ensuring the gear could reliably withstand the 100Nm output torque and the demanding high/low-temperature static torque tests (>42 Nm at -20°C, >37 Nm at 120°C) without increasing its size (outer diameter <60mm), with targeted reinforcement for the helical gear application.

3. Rigorous Internal Validation: Before submitting samples, they were comprehensively validated the design using our in-house durability test rig (DTR) services and component-level testing capabilities (such as ultimate tooth torque testing and dual flank inspection) to ensure Nylacast’s market leading quality and guarantee reliable performance.

Test Validation and Performance Dominance: Winning Trust with Data

The customer conducted comprehensive testing over several weeks on the polymer gear samples provided by Nylacast, directly comparing them with the original supplier's MC gears. The results were clear and compelling:

·        Torque Testing: Nylacast gears significantly exceeded the drawing specifications for static torsional strength under all temperature conditions (room temperature, -20°C low temperature, 120°C high temperature), with no damage observed.

·        High/Low-Temperature Compression Testing: After undergoing cycles of 150°C high temperature, -25°C low temperature, and their alternation, our gears demonstrated higher toughness in crush tests, showing no damage, which highlighted the superior dimensional stability and material consistency across a broader temperature range with Nylacast products.

·        NVH Testing: This was the decisive factor. In complete motor assembly tests, the unit equipped with Nylacast gears performed significantly better in terms of noise and vibration levels compared to the version using the original MC gears, delivering a more comfortable and quieter experience for the rider.

·        Durability and Reliability: After undergoing 2000 hours of aging life tests and 50,000 start-stop cycle tests, our gears remained in perfect condition, fully meeting the customer's requirements for long-term product reliability.

Case Summary

Although the customer initially opted for IM?? material gears due to cost considerations, Nylacast Automotive successfully shifted the customer's decision by demonstrating the substantial performance improvements offered with Nylacast’s  polymer technology. Our gears achieved comprehensive superiority in torque capability, dimensional accuracy, environmental adaptability, and especially the critical NVH performance, proving they could deliver significant added value for e-bikes.

Ultimately, based on the comprehensive test data and the pursuit of enhanced ride quality, the end customer decided to establish a partnership with Nylacast Automotive and integrate our high-performance polymer gears into their mid-drive motor system.

Commentary by Nylacast Automotive CEO:
"The e-bike market's demands for drivetrain component performance, weight, and noise are rapidly aligning with automotive industry standards. This case successfully applies our accumulated expertise in polymer material science, gear design, precision gear manufacturing, and NVH optimization from the automotive safety-critical components sector to this emerging market. It once again proves that true value lies not in the lowest initial cost, but in the exceptional performance, reliability, and user experience delivered throughout the product's lifecycle. We are delighted to extend the safety and quietness of 'casting' to the broader realm of electric mobility."
— Simon Harvey, CEO of Nylacast Automotive