Cogless dd scooter project

[Username1]

Hi I'm making this post to discuss and ask questions about an electric kick scooter project I would like to research and build. Ever since I first saw electric gopeds (chain transmission) and small electric hub motors, I imagined making an electric kick scooter that was almost indistinguishable in looks/function from normal small kick scooters.

Since then, many electric kick scooters have been released similar to my idea, but I would like to take it a step further. This means completely hidden wires, twist-grip for hidden throttle/electric braking, no brake levers, no display, and most importantly thinner wheels (200x25mm) each hiding a thin cogless dd motor. Not only would these things give the same size and look as a normal kick scooter, it would function the same aswell, with completely free coasting from the thin wheels/zero cogging (whether on or off).

Seeing as I'm a noob with electric motors, I'm researching to learn more about the topic, and any help or advice as I go would be appreciated as there's a lot to learn and think about. My first step is deciding what kind of motor to use.


Edit: Title and post originally focused on coreless halbach but were edited to simply focus on cogless instead after considering more kinds of motors. Also shortened to be more concise.

 

[Hummina Shadeeba]

why go coreless though? you'll get a lot more power and torque out of the motor if it has a core. it needs some iron otherwise i doubt you will get the power. the hallbach part will allow you to get rid of the iron in the flux ring behind the magnets but that's it and you'll still need a core inside the inductor coils.

if you have an axial flux halbach array motor in mind you've seen please post it. The only ones I've seen are very expensive and I dont know if I'd trust their ability to handle the extreme abuse that they'd get in a wheel. you can get your thin wheels with a typical out runner design.

this guy posts tons of great stuff on just what you're doing
http://www.etotheipiplusone.net/?page_id=133

 

[Username1]

My reason to go coreless, and one of the biggest differences to current scooters I've seen, is to have no cogging. It would roll freely like a normal kick scooter, meaning you could use it manually and have the ability to coast when using the motors instead of needing to constantly use the throttle.

I've heard conflicting things about power density of this kind of motor, but the power requirements are somewhat low here, and I would like to use 2 motors which should help.

An example of something similar I've seen (although not in a wheel) is below. It's also homemade and doesn't look especially difficult or expensive to build. Thanks for the link by the way.

Part 1 - http://build-its-inprogress.blogspot.ca/2015/02/coreless-axial-flux-motors.html?m=1
Part 2 - http://build-its-inprogress.blogspot.ca/2015/02/finishing-up-coreless-motor.html?m=1

 

[Hummina Shadeeba]

Great links. Maybe it does have the torque u need without a core. i think the hardest part will be the mechanical challenge. Look forward to seeing what u make.

 

[Username1]

Well maybe a coreless axial halbach motor would actually have heat problems after all, so I'm looking at other options too. I have been trying to find information on induction and switched reluctance hub motors, but haven't found much (except for a post about a larger induction motor being built, which actually seemed to suggest low power induction motors aren't so great).

Anyone have thoughts on which kind makes the most sense for this project? The main goals being cogless, direct drive motors inside 200x25mm wheels, capable of strong torque, operating between 0-850 rpm (0-32kph).

 

[Ianhill]

The syncrynous induction hub motor was lacking magnets so the gauss energy of the magnets had to come from the battery's making it power hungry, i guess this means the magnets are a good call for a battery machine, and iron makes good sence for cooling and guiding the flux lines we come to the basic conclusion that a dd outrunner hub is a very good design.

Each design is suitable for different applications reluctance motors are going to become a work horse in time due to being cheap to construct good overall efficiency and eliminates cogging so should be silky smooth.

For a DD hub motor on a scooter with a 6.5 inch wheel it will need to rotate around 1000rpm for 40mph that can be done with off the shelf parts around 72v, the wheel size and width is the limiting factor when fitting a powerful drive inside a small wheel bigger the wheel larger the power can be achieved, If small wheels are a must then consider a chain or belt system with an outrunner geared low or an inrunner geared high the wheel is no longer limiting power levels then, but the most power dense motors are outrunners they make use of their space very well and the magnetic area is on the outside of the can giving good leverage combined with a low kv they are the go to motor for torque.

 

[Hummina Shadeeba]

there's motor designs out there that use iron to get the torque but are still coggless. Slotless motors I think is one label. skewed stator teeth maybe. I can't remember the names but they're out there...with iron yet no cogging