Small rear wheel hub motors are currently experiencing a renaissance. At first glance, the unobtrusive, lightweight and quiet-running mini units could also be mistaken for hub gears. Also, or precisely because they are much smoother at work than powerful mid-engine power plants, they are a perfect match for light and stylish urban bikes and gravel pedelecs. The drives consume less energy and therefore manage with smaller batteries. This also suits the designers of trendy style bikes, as the small energy sources disappear inconspicuously even in filigree frame tubes. Because the sensor technology of the motors has improved significantly, the hub motors are now also much more intuitive to ride than they were a few years ago.
Almost all drives in this class come from Asia or contain components from there. The motor of the Ampler Stellar is a joint Chinese-Estonian-German product. The electrical components are supplied by Chinese manufacturer Aikema, while some mechanical parts and the freewheel are developed in-house by Estonian bike manufacturer Ampler. The sensors are supplied by Alfred Thun GmbH from Ennepetal. In contrast, the Bafang motor in the rear wheel of the BZEN Brussels is a purely Chinese product. Both companies, Aikema and Bafang, have been producing electric drive components for the Asian market for many years, and their drives are also increasingly found in pedelecs from European manufacturers. For example, De Rosa, Qwic, Vanmoof and Prophete equip some models with Bafang motors, while Aikema supplies drive components for Ampler, Cowboy, Vanmoof and the motor manufacturer Mahle. The trend towards lightweight pedelec motors for urban, fitness, style and gravel bikes should significantly increase the presence of both manufacturers in Germany. There are currently not many sensible alternatives to Asian products in the low-assist segment. In Germany, the drives from Munich-based mid-motor manufacturer Fazua and the hub motors from Ansmann AG in Assamstadt are among the most popular.
DRIVE TEST
Not everything that a drive is capable of can be modelled and measured on a test bench. You can only find out how sensitively a motor reacts to pedal pressure and how strongly it accelerates during a test drive. This also applies to response and cut-off behaviour. The drive must be controllable and start up as quickly as possible when starting uphill. When you stop pedalling, the motor should switch off immediately and not push on.
TEST STAND TEST
We measured the maximum continuous power output of the motors on our roller test bench. This showed that the power output of the motors differs to a greater or lesser extent depending on the pedalling frequency (cadence). Measurements were taken at 20 km/h and with cadences of around 60, 70, 80 and 90 revolutions per minute. We simulated the rider's pedalling power with 100, 120, 140, 160 and 180 watts. The power curves on page 30 show not only the characteristic increase in power but also the maximum cadence and pedalling power at which the motor supports the rider. We measured the maximum motor power in each support level at 70 crank revolutions per minute.
You can download the complete comparison test of rear hub motors from MYBIKE 3/2021 including all individual evaluations as a PDF below the article. The test costs 1.99 euros.
