Our first experience with steel geared hub motors were the Heinzmann motor’s from the EV Global e-bikes circa early 2000’s. It was a brushed motor that screamed while operating at peak current. The Heinzmann geared hub motor was famed for it’s high torque output, however the loud operating decibels gave steel gears a bad reputation the industry just couldn’t shake.
We have now discovered a new take on hub motor steel gears. Helical cut steel planetary gears with chamfered edges.
Most traditional geared e-bike hub motors use nylon, straight-cut “spur” gears. While nylon is not as strong as steel, it does help reduce noise. Spur gears have a lot of disadvantages over helical cut gears like; the gear teeth experience a large amount of stress because of the larger/ deeper required contact patch and spur gears produce a lot of noise when operating at high speeds. Shown below is a chamfered helical cut steel gear (on top) and a traditional nylon spur gear (bottom.)
The angled teeth of helical cut gears engage more gradually than do spur gear teeth, causing them to run more smoothly and quietly. Helical gears are highly durable and are ideal for high load applications. At any given time their load is distributed over several teeth, resulting in less wear.
Most Big Power Motors (BPM’s) top out at about 48v-500 watts however, these new helical cut steel gears can produce a BPM with a nominal 48v-750 watts power. From our initial test when the hub motor was hooked up to DC power supply (operating at 350 watts) the hub motor ran quietly. This type of BPM would be ideal for e-cargo bikes and heavy torque design requirements.