Yamaha hybrid prototype points to future big scooter
By Ben Purvis
Yamaha can be credited with essentially creating the concept of the maxi-scooter with the launch of its XP500 T-Max 25 years ago. Now the company is exploring how hybrid power could be adopted in future bikes aimed at the same category.
.jpg)
The HEV Proto is a rolling laboratory exploring the potential for hybrid powertrains, and Yamaha has released a video showing how its 'series-parallel' hybrid system works.
Normally hybrids, which are increasingly familiar on four wheels, are either 'series' or 'parallel' designs. A series hybrid is also often known as a range-extender, and mean an electric vehicle that has a combustion engine used purely to drive a generator, topping up the battery when needed.
A parallel hybrid, by contrast, has a petrol engine that drives the wheels as well as electric motors, with the electric power used as an extra boost to reduce emissions and improve fuel economy.
A series-parallel hybrid, as shown by Yamaha, offers a combination of both designs, allowing them to operate in all-electric mode while still including a petrol engine and transmission that can drive the wheels. Kawasaki's Ninja 7 Hybrid and Z7 Hybrid work like that - the only big hybrid bikes currently on the market - and Yamaha's design follows the same pattern.
In all-electric mode, the battery mounted between the rider's feet feeds an electric motor on the rear hub, allowing the bike to operate like any other electric machine as it pulls away. Once on the move, it initially enters series hybrid mode, with the combustion engine running but at low speeds all its power goes into a generator, recharging the battery, and it's not coupled to the rear wheel. At higher speeds, a clutch engages to couple the combustion engine to the rear wheel via a belt drive, and the electric power is disengaged to save the battery.
Like the Kawasaki hybrids, the Yamaha prototype also has a 'boost' mode where both the combustion engine and the electric motor are used to power the rear wheel simultaneously, maximising its performance and acceleration.
Yamaha says that in the future the system, while prototyped on a maxi-scooter style bike, could be used on all types of motorcycles, including roadsters and sports bikes.
