CRF450R with LG washing machine stator wheel motor.

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Dec 13, 2017
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Hello, I want to try to take my old 2005 CRF450R and build a wheel motor for it. I've only ever rewound hobby RC type motors and I have a thread on RCGroups motor design forum. But you guys are obviously more experienced with dirt bike scale builds.

A bit of info on the stator. It's about 10" diameter, 1" thick, 36 tooth, 7 lbs.

Custom rotor with 16 pole pairs in a halbach array is planned.

Stator rewind is looking to be AaABbBCcCAaABbBCcCAaABbBCcCAaABbBCcC. I was contemplating a mid motor, but once I started looking at it and looked through some threads here, I think I want to do a direct wheel motor. On RCGroups some helpful folks estimated that for a desired 6.6 kv I would need to do about 10 turns per tooth. But at that time, I was planning chain drive (3:1 or so) and a max speed of about 30mph. But that will change now.

One thing that concerns me is what kind of rear swing arm "jacking" could happen with a wheel motor. There are probably geometries and linkages that could minimize that effect.

Another thing that concerns be is startup studder/cogging problems. I would think at the very least I should plan for a sensored ESC. I do have a VESC laying around somewhere that I could experiment with. It's only 80v 50 amp as I recall. But you guys also seem to be using some really advanced ESCs compared to the hobby world, so I'm hoping for some good advise there too.

The original bike is ridiculously powerful at 40kw, I was thinking 20kw would be a good goal to shoot for. Maybe 100 to 200 volts.

I have to admit, the new Koenigsegg motor got me thinking about doing a conversion.
https://www.roadandtrack.com/news/a38940998/koenigsegg-quark-electric-motor/

I'm even considering liquid cooling the stator. Inwheel motor, I get it, complicated. Big hollow axle needed.

I like the idea of getting a spoked rim more appropriate for onroad (and smaller diameter I would think) and would like to incorporate spoke holes in the rotor. They would obviously be short spokes.

Input desired!

Some pics. The pic with the partial wind was just a test to see how much wire I could fit.
 

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Some pics of the stator/bearing mount design.
 

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And here are some more detailed pics of the in wheel motor idea.

There are 32 magnets in the rotor and hopefully I can find a rim with 32 spokes and then I can add "spoke attachment points" at each of the 32 holes on the outside of the rotor that are holding the rotor together. I'm a bit concerned about the steeper outward angle the spokes will be at to connect to such a close hub. Is there a general maximum spoke angle for rims?

It seems a bit "beefy/heavy" at the moment, if I can get my FEM working I'll try to slim it down a bit.
 

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bjork, I'm pretty much leaning toward a supermoto style now and probably almost all street. But, I hear you, keeping sand and rocks out is a primary concern. Easiest solution, put some screens over the big yellow outer hub. That would still allow air cooling. But I'm also considering trying to get liquid cooling directly to the copper which would require the winds to be sealed off to prevent leakage. Then the big yellow outer rotor could be completely sealed off from dust and dirt. Although I would think some sort of clear Lexan or something would look cooler.

sherpa, very helpful site and there is even a section on large hub diameter spoke patterns.

https://www.sheldonbrown.com/special-spoking.html

kv is a big design concern, like I said I am considering high voltage 100-200. Even around a 6 kv that puts top speed pretty high almost nearing 100mph. I really would prefer to keep the top speed down around 60-70mph and have as much low/mid speed torque as I can.

Another fancy pic:
 

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That’s quite a lot of effort to do but fun project!

How do you know that the washing machine stator will give you a good motor? Seems like a bit of a gamble?What was the original rpm it was run at? What’s the lamination thickness?

As far as sensored/sensorless controllers go, i’ve used both on light builds and then they both work well. A small push to get going is needed with sensorless so it depends on how deep mud pits you foresee to get stuck in and total weight of your ride 😀
 
Sorry I got busy, but this is still on the table. Well the original motor ran on 120v AC and put out around 500-1000W? Obviously a 100 turn stator is not going to work. But I'm guessing 6-10 turn would. And then with Neo magnets it should have even more torque and slow it down to a reasonable RPM. That sound all very "seat of the pants" I know. But then after seeing folk build para gliders with washing machine motors, I thought, maybe there's something to this.

Of course the "ground" vehicle will need a good startup routine in the ESC, but overall, I think it's very doable. I did find a nice little machine shop that charges very reasonable prices for CNC work, and with my own homebuilt cnc, I think I can get it done. Just need time now, that old chestnut...
 
Yeah, that seems familiar!

my thinking is that consumer home products are highly cost driven and it's not until the last years where energy efficiency was in focus on the products. So there's got to be a driver for putting a motorbike capable motor or stator in this product? Next question would be if the use cases are somewhat similar but doesn't seem like that either.

The stator is large and heavy (more like one of those chinese paramotors than a hubmotor weight though) but still needs good laminations to be effective. So how thick lamination steel is it?
 
.5mm, I forget, I did a bunch of calcs and for a full size wheel (2' Diam) ESC frequency won't be very high, even with 32 magnets.

Motor will be heavy...for a motorcycle...maybe 15 lbs.

bjork, I have some updated designs with spokes, let me find them.
 
You could stack the two stator pieces together and wind around both of them. Double the width will allow double the torque.
 
And this was an attempt at a wheel motor for an 1/8 scale buggy. I only ever made one, it was too powerful and there were no good ESC controllers at the time. I drove it around the hobby store once, it was hilarious, it looked like an empty chassis. It's two 5-1/4" floppy stators stuck together.

1-8-wheelmotor.jpg
 
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