Getting There Fast and Efficiently
After exploring existing motor options from first tier suppliers, we came to the conclusion that there were simply no motors available that met our requirements for price, size, quality and performance. We looked worldwide for the best motor development partner, and happily ended up in our own backyard with an experienced Dutch motor development company. Together we designed AppScooter’s motor, and ended up building one of the world’s most efficient drivetrains in the process.
The Optimal Transmission
Existing motors on the market were unanimously too expensive, inefficient and none were optimized for the transmission ratio required for the configuration we had in mind. Every percentage of efficiency won requires that exact percentage less in batteries; this directly translates to needing fewer batteries.
After simulating various scenarios, we found that a transmission ratio of 2.5 to 3 was the optimum you can get within the boundary conditions of design and required performance. Using just a singular belt transmission with a ratio of 1:2.7 kept part count to a minimum, and allowed us to set the performance requirements for the motor at an achievable level.
How do we know this is the best option?
Engineering the Etergo Way
We looked at all alternatives and made a comparison on price-quality and performance criteria. The two most used alternatives are an in-wheel hub motor or using an extra transmission. Here we will briefly elaborate why these are less
- Using an in-wheel hub motor. The size and shape of such a motor results in a large tradeoff in efficiency and max torque. Either limiting range or performance by 5-20%. Also these motors weigh 8kg more and are directly placed inside the rear wheel, which is not good for for your unsprung weight. If you value your comfort on bumpy roads (city street pavement for example), this is far from ideal.
- Using an extra transmission. This sounds like a doable option, however, -any- transmission inherently costs a degree of efficiency. It is simply causing more friction. Commonly, this causes 3% or more extra friction (eg. using a planetary gearbox for example or an extra belt drive) and thus requires additional batteries to achieve the same range, which is still pretty expensive. The biggest downside of the planetary gearbox is that it also requires more maintenance, which is something we are really trying to avoid. The additional belt drive is as close to maintenance free as you can get, but it is expensive, requires more than 3x as many parts (for the drive train) and introduces countless complexities that can fail and make maintenance more of an issue.
Therefore we concluded that the best solution was the simplest, using just a
singular belt transmission with a ratio of 1:2.7. This kept part count to a minimum and allowed us to set the performance requirements for the motor at an achievable level.
Better Performance Than Petrol, Cheaper Development, Unique Solutions
Existing petrol engines are produced by a small handful of manufacturers worldwide at the cost of millions for production, shipping and more. These costs are often passed down to the consumer, and for a product that performs far less efficiently than the electric alternative. Developing an electric motor is much simpler, expedient, and at the manufacturing cost of tens of thousands, substantially cheaper. And the performance upside is unmistakable. AppScooter accelerates from 0-45km/h in just 3.9 seconds. That’s three times faster than a 50cc class petrol Vespa.
Another benefit of creating our own proprietary electric motor was an ability to create design solutions that make AppScooter more efficient overall. It enabled us to use the swing arm as the casing for the motor, eliminating a need for extra housing. As the swing arm is made of aluminum, it also doubled as an extra heatsink, greatly reducing the need for active cooling.
Mounting the motor inside the front section of the swing arm also allowed us to balance the weight of the motor with the weight of the wheel, reducing unsprung weight and thus increasing comfort whilst driving over bumpy roads.
The Power of Going Green
AppScooter’s modular motor will be available in 2kw, 4kw and up to 7kw, offering up to 95km/h in speed with the most powerful option. Our motor provides world class response, powerful, smooth torque, and a lightweight design that requires little maintenance, purpose-built not to interfere with the visual aesthetic of your scooter. It’s not only a sustainable alternative to the internal combustion engine, but excels amongst its peers in quality of build and efficiency.
Would you like to pre-order your own AppScooter? It’s easy to do.
Simply follow this link to begin your AppScooter journey!