Why Electric Motorcycles Lack Multi-Speed Transmissions

Electric motorcycles typically do not use multi-speed transmissions for a variety of reasons. Understanding these reasons can provide valuable insights for enthusiasts, manufacturers, and those interested in the future of electric motorcycles.

Engine Characteristics

Electric motors have unique torque characteristics that differ from internal combustion engines. Unlike gas engines, which generate maximum torque at a specific RPM and lose efficiency as they operate outside this range, electric motors deliver maximum torque from a standstill. This means they can accelerate quickly without the need for multiple gears. Consequently, a single-speed transmission is effective in most riding scenarios, making the design simpler and more efficient.

Design and Weight

The absence of a multi-speed transmission simplifies the design and reduces overall weight. Fewer moving parts in the transmission lead to less maintenance, lower manufacturing costs, and a more straightforward riding experience. These factors are crucial in electric motorcycles where every gram of weight counts due to battery weight and the need for lightweight components to optimize performance and efficiency.

Efficiency and Complexity

Efficiency is another key consideration. Electric motors are generally more efficient at a wider range of speeds compared to traditional combustion engines. While a multi-speed transmission might seem beneficial for optimizing efficiency at different speeds, the efficiency loss from the additional complexity and weight of a multi-speed system often outweighs the potential benefits. The added gears introduce friction losses and require more sophisticated control systems, which can negate the gains in efficiency.

Rider Preference and Market Demand

The market for electric motorcycles prioritizes ease of use and a different riding experience compared to traditional motorcycles. This has led manufacturers to focus on designs that appeal to these preferences rather than incorporating complex transmission systems. Riders generally appreciate the smooth linear acceleration provided by electric motors and the simplicity of a single-speed transmission. This user-friendly approach enhances the overall riding experience and can contribute to customer satisfaction.

Historical Experiments and Market Impact

Instances of multi-speed transmissions in electric motorcycles have been explored, but not without challenges. Brammo, a manufacturer of electric motorcycles, experimented with a transmission in their Empulse model. However, the addition of a transmission led to the Empulse being at least a year late to market, and it did not significantly outcompete Zero Motorcycles, a rival in the electric motorcycle market. Despite Polaris promising to keep selling the Empulse, the model was eventually discontinued.

Electric vehicles, including motorcycles, benefit from a broader power band than gasoline vehicles. In a gasoline-powered vehicle, the transmission is necessary to keep the engine within its functional range, offering good power and allowing the vehicle to operate at different speed ranges. By contrast, electric motors are efficient across a much wider range of operating conditions. This makes the presence of a multi-speed transmission in electric motorcycles less essential. For example, the original Tesla Roadster was intended to have a two-speed transmission, but it proved unreliable and was eventually simplified to a single-speed without noticeable impact on performance.

Performance and Practicality

Electric motorcycles often excel in performance without the need for a transmission. Lightning Motorcycles, for instance, sells the LS-218, named for its top land speed of 218 miles per hour. This motorcycle has no transmission and can accelerate from a standstill straight to 218 miles per hour just by twisting the throttle. This illustrates the practicality and efficiency of electric motorcycles in certain performance scenarios.

When comparing Brammo and Zero motorcycles, both brands offer similar power and capabilities and compete well in races. The choice to include or exclude a transmission in a design decision has more to do with practicality and market demand than it does with performance alone. In the case of both Brammo and Zero, the inclusion or exclusion of a transmission reflects a broader design philosophy prioritizing simplicity and ease of use over unnecessary complexity.

Conclusion

The decision to forego multi-speed transmissions in electric motorcycles is based on a combination of engine characteristics, design simplicity, efficiency, and market demand. While a multi-speed transmission could potentially optimize efficiency, the inherent advantages of electric motors, reduced weight, and improved rider experience make single-speed transmissions the preferred choice for the majority of manufacturers and users.