Wow. I started reading this thread thinking that it couldn’t possibly work well enough to be useful, but Corbin and Nathan’s comments amazed me.
That is a seriously nifty toy. Great work!
Next step: shiftable-on-the-fly gearing with handlebar controls and you’re in business! 
The machined bearing side where the cables show how even a non-electric techno hub could have (multiple) gears controlled by handlebar cable-shifters.
Sam
Justin-
That is a fantastic project. Great work and congratulations on what appears to be a complete success. Do you happen to have the full specs on the motor you used? I was interested in the complete wiring diagram and the mechanical drawings of the rotor and stator if they’re available someplace. I originally thought that you had wound the coils yourself when first looking through the thread (at which time I was stupendously impressed).
Did you design any part of the control circuit or modify an existing controller? Soft start features are usually just a simple time constant in the controller somewhere.
Again, that is a truly remarkable project. Thanks for sharing this with us.
Not exactly. I’ll be attending part of the U Games in Berkeley this July though, so if I still have this or newer prototypes then I’ll bring them down.
If anyone is coming through Vancouver and wants to give it a try then feel free to give me a heads up! I’ve been taking it down to our regular wed. evening unicycle meet ups at Science World too.
Exactly, I actually have a fair bit of experience designing brushless motor controllers and have one that’s mostly complete, just wasn’t done in time for Maker Faire.
The idea for this is that it will have bidirectional torque control, so you can dial in exactly how much torque you want the wheel to produce (forwards or reverse) and the controller will adjust it’s output to maintain this torque regardless of your speed. It should be more hands-off that way.
Regular ebike controllers are generally implemented with direct PWM control, so you have to keep adjusting the throttle up and down as your speed changes in order to maintain the right amount of power at the wheel. It takes a bit more concentration than is ideal.
It’s a very common style of hub motor with a 205mm rotor ID that came out a few years ago and is manufactured from dozens of companies in china. We get our directly from Nine Continent. The one I used in this project we’ve named the 2807, and there are more details here:
http://www.ebikes.ca/store/photos/M2807F26.jpg
http://www.ebikes.ca/store/diagrams/M2800F.pdf
and you can see the torque, power, and efficiency curves by selecting the NineCont 2807 motor option with the simulator page:
http://www.ebikes.ca/simulator/
Hey, well thanks for all the encouraging feedback so far! I wasn’t quite sure if people here would be excited or carry a lot of reservation about the idea. Certainly we’ve saw a lot of resistance initially from the traditional cycling community when it comes to embracing electric assist bikes, but mostly they’ve come around. 
Justin
Nice stator! did you hand wind it? Hey, I think the cranks on your giraffe version were recalled for breaking in '98… eyeball it for stress fractures on the crank arm itself. It was a shimano altus, or the model before it, can’t remember.
Energy Consumption Stats
So I had a chance to ride the electric unicycle on some round trips here in Vancouver on the weekend, and was surprised at how little net energy it draws from the pack when one rides at just a comfortable pace. That means using the motor on the uphills, and having the motor behave as a brake on the downhills, and riding unassisted and unhindered on the flats.
For the latest trip, which didn’t involve any super steep hills but wasn’t totally flat either, these are the details:
Trip Distance = 9.44 km
Max Speed = 23.1 kph
Avg Speed = 16.2 kph
Positive Amp Hours = 0.496 Ah
Regen Amp Hours = -0.238 Ah
Net Energy Usage = 1.1 Wh/km
By comparison, a regular electric bicycle typically uses 8-10 Wh/km of energy (but also goes at a faster speed). As well, the amount or energy returned to the battery from braking on the downhills was half again what was used on the uphills, while on an ebike this figure is usually around 5-10%.
It’s not too surprising since on a bike you only use the brakes when you are coming to a stop, while on the uni it was useful on any downhill grade more than about 2%.
At that rate at just 1.1 Wh/km, it means that even with this fairly tiny 5Ah battery pack I’d need to go over 160km before depleting it. Crazy.
-Justin
That is a great set of numbers Justin.What is the weight penalty and do you think a smaller motor would be possible.
john
Yeah, it’s been surprisingly consistent. This evening I rode it from our shop down to the Science World unicycle meetup and back.
The way there is pretty much all downhill, and so I only used the brake (no throttle) and put 0.239 amp-hours into the battery. On the way back, I didn’t touch the brake and only used the throttle, and consumed 0.458 amp-hours. Averaged 18 kph. Round trip was 7.4 km and the net statistics were again 1.1 Wh/km with the regen energy recovered on the downhill being about half what was used to go back up again.
Right now the motor portion of the wheel is about 4kg heavier than a regular unicycle hub, and the battery, battery mount, and electronics add about 2kg. So it roughly doubles the original unicycle weight. I can still hop with it, but it’s a bit clunky for that.
For sure it would be possible, but the efficiency wouldn’t be as good, especially in a big 29" wheel that is turning at comparatively low RPMs. That’s why I used one of these larger diameter motors for this project. In a 20" wheel then there are some smaller direct drive hubs that would have been well suited and lighter.
You could also use an internally geared motor concept and make something lighter still with the same torque, but usually there is a lot drag in that arrangement if the freewheel is locked (as you would need to do regen) and this would make it less fun to ride when you aren’t using the assist.
Justin
Any photos from U games or Muni weekend?
Hey, is there a chance that anyone here has either videos or pictures of the electric uni assist uni being ridden either at the U games or the vancouver muni weekend? If you do and are willing to share, please send me a PM or an email to justin - at - ebikes.ca
It turns out that a camera man from CNN was at the ElectraFest electric vehicle show here in Vancouver on Sunday and wanted to do a small piece on this, and asked if I had any other images or clips. But asides from the original build pictures I don’t have very much.
Thanks, Justin
From CNN:
Video at: http://ireport.cnn.com/docs/DOC-491972?hpt=C2
iReport — By now we’re all familiar with the various forms of electric vehicles, including some bicycles. Taking this to it’s logical endpoint, Justin Lemire-Elmore has developed and tested the worlds first electric unicycle. You’d be making a big mistake if you thought this was an attention getting novelty toy because Justin is about to smash several transportation records by being the first person to cross the United States from Canada to Mexico on a unicycle, while using a power source and motor that is not much bigger than your average home electric drill.
Improvements in the electric unicycle
Hey, just to clarify I didn’t make any claims about “smashing records” to the CNN guy, sometimes I guess they need to invent and sensationalize a bit. That said, I suppose this will smash the record of the longest ever electric-assist unicycle ride! (currently sitting at about 40km 
)
Anyways, I had a chance to make some significant improvement to the design in time for Interbike this year. The home-made handle bar was replaced with an adjustable KH touring bar, much stiffer and cleaner looking.
For the bar ends I installed two throttles, one on the left and one on the right, so you can easily engage the motor power regardless of which hand you have on the bar.
Similarly, the ebrake lever was mounted in the center and had an aluminum ‘spooner’ so that it can also be engaged with either hand.
The electronic controls were also finally updated a fair bit.
For those who test rode it, there is no longer that initial drag on the motor until the hub gets up to speed, it spins completely free forwards and backwards until a throttle or brake is pressed.
As well, the algorithm for the brake engagement has changed, so now when you just squeeze the brake it puts about 100 watts of regen force no matter what, and then if you need more braking you can add that with the throttle.
So, for those following things are still a comin’ along. -Justin
Hello Justin,
That CNN article was so sensationalized I did not take it serious, but the fact is that your unicycle is sensational.
+1, but I still thought it was good exposure for you.
Great project!
Looks good! I’ll have to come back up to Vancouver to give it a try again
corbin
It looks like you have things just about sorted now,it is a great project and I’m glad you are keeping us up to date.
john
So now the brake is either on or off? Wouldn’t that totally throw you when you engage it and then not be modular at all? I know that it would be very difficult to figure how to do it electrically with the regen on a lever instead of a throttle but that seems like the way to go.
It would be fun to try the uni with out the drag now.
It’ll be interesting to see how the battery lasts on your trip (with regen and all).
Nice video! You come across as one of those “mad scientist” types, exactly the kind of person who’d be behind such a project. It’s always good to see an endearing character and enthusiastic spokesman behind these projects.
Hopefully the positive TV coverage will get more people into the sport too!
