Helical Cut Steel Planetary Gears for Hub Motors

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.

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11 Responses to “Helical Cut Steel Planetary Gears for Hub Motors”

  1. Ron/spinningmagnets June 10, 2015 at 1:07 am #

    I agree, this one change can open up a whole new world in the geared hub market. Right now, I only know about existing helical gears in a 250W EU-spec geared hub from MXUS that I saw at the Interbike show, Sept 2014. That would be weak by North American standards, but I am curious how they would perform in a 2WD…

  2. Ron/spinningmagnets June 10, 2015 at 1:15 am #

    I just wanted to add, the primary reduction in several well-known mid drives use helical gears. The BBS02, the Bosch, and the Panasonic (and I’m sure there are others), so…this works. Very high motor RPMs really help get the maximum possible torque out of a tiny motor when using reasonable voltages. I have wondered why helical gears haven’t been used in the much larger hub motors until now.

  3. Andytheswede July 9, 2015 at 5:10 pm #

    And where can we buy these gears?
    I have a MAC 8t

  4. topsecretev August 7, 2015 at 6:31 pm #

    I don’t think this would easily retrofit into a MAC motor.

  5. topsecretev August 7, 2015 at 6:37 pm #

    Ron, you are totally right…. We are working on some e-cargo type applications and metal gears really just make sense. There is a 48v*750watt nominal BPM metal-gear hub motor in the works, I am just not sure how loud it will be? Normally, would couple this motor with a 9-fet Sinewave controller which would help reduce some motor chatter.

  6. oliver higson June 20, 2017 at 1:13 pm #

    is there anyone out there manufacturing this idea, apart from Heinzmann ? We are looking for a high torque/low top speed bike motor that is lighter than a direct drive and more resilient and powerful than a MAC 12t – all thoughts welcome, ollie

  7. topsecretev June 20, 2017 at 5:38 pm #

    Hi Ollie, to be honest we have used the Heinzmann, while it’s reliable and high torque it’s also very loud operating at high current (just like the motor listed in our post.) A few years ago Panasonic displayed a metal-gear, moped hubmotor at Taipei Cycle Show but after visiting their booth at Shanghai Show this year they have switched back to nylon helical cut gears.

    So for now “Mac” is still the “high powered” geared hub motor king!

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  9. Chris March 3, 2019 at 1:57 pm #

    Surely straight cut gears made of any material should never be used in any high speed high torque system, they have not been used in autos for generations. Ok in clockwork watches!
    Helical cuts cost very little more than straight cut and life and noise will be much lower. I as an engineer am amazed that any one would consider straight cut gears, just goes to show how far e bike motors technology has to go, if they are still used.
    Straight cut gears Nasty Nasty things.
    They say using nylon straight cut gears over steel straight cut reduces the noise – where do they think all that noise is being transferred to? into the plastic material as stress and heat as the nylon teeth vibrate. Uggh = broken gear = short life.
    Helical edge cut gears much better preferably in steel.

  10. Eduardo October 23, 2019 at 1:03 am #

    Do you have a helical gear set for sale at this moment or can you get it? How about a larger size gear set for 5KW motors?

  11. topsecretev October 25, 2019 at 8:49 pm #

    Sorry we do not sell this gear set.

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