31
you are viewing a single comment's thread
view the rest of the comments
view the rest of the comments
this post was submitted on 06 Oct 2024
31 points (97.0% liked)
micromobility - Ebikes, scooters, longboards: Whatever floats your goat, this is micromobility
2403 readers
101 users here now
Ebikes, bicycles, scooters, skateboards, longboards, eboards, motorcycles, skates, unicycles: Whatever floats your goat, this is all things micromobility!
"Transportation using lightweight vehicles such as bicycles or scooters, especially electric ones that may be borrowed as part of a self-service rental program in which people rent vehicles for short-term use within a town or city.
micromobility is seen as a potential solution to moving people more efficiently around cities"
Feel free to also check out
It's a little sad that we need to actually say this, but:
Don't be an asshole or you will be permanently banned.
Respectful debate is totally OK, criticizing a product is fine, but being verbally abusive will not be tolerated.
Focus on discussing the idea, not attacking the person.
founded 2 years ago
MODERATORS
It's a pretty standard arrangement from what I can tell.
This might be more related to legal power limits and less that they can't figure out how to reduce a motor.
A design that stood out for me in this space was Dave's Tangent which developed something like 200Nm with 80:1 cycloidal reduction in 2.8kg.
I think you're spot on, since using a random power/torque/rpm calculator online, an 85 Nm mid-drive motor rotating at a reasonable crank cadence of 80 RPM yields a power output of 710 W. That's just shy of the max power regulation in the USA for ebikes, at 750 W. And motors can definitely go faster than 80 RPM.
Mid-drive motors could probably be built with even more torque, but because electric motors maintain near-constant torque through most of their RPM range, the motor controller would have to perform more current limiting at the higher RPMs to stay under the legal power limits. So there's less benefit, unless someone really badly wants more low-RPM torque.
At that point, though, other parts of the bicycle drivetrain might start disintegrating under such forces.
My Tangent snapped a Shimano XT chain in less than 1000km. I think that system could reach 200Nm peak torque. If I remember correctly it could peak over 2.5kW when unlimited. I had to switch to stronger chains and limit the torque to stop it from eating metal. That's easier these days since there are stronger ebike-specific drivetrain components from Shimano and others. ๐ But I don't ride that anymore.