Electric Assist Unicycle at Maker Faire, this Sat. and Sunday

Hey, first post here but a long time fan of unicycling and other modes of personal wheeled transport in general.

Anyways, this weekend I am at the Maker Faire with a small table for “human mobility” and brought along a few one-wheeled projects that may be of interest here including this one:

The idea was not to do a self-balancing type of electric unicycle, but one that was fully pedalable and rideable, with the motor there either to provide steady assistance on the uphills or steady regenerative braking power on the downhills to help overcome the deficiencies of riding with a single gear ratio.

There is a full build thread here for those interested in the details:

In any case, I’m quite curious to see what commuter unicyclists think after trying this, so if there is anyone in the Bay area attending Maker Faire this weekend who wants to give it a shot, please come find us! We’ll be set up in the south end outdoors lot near Cyclecide and other bike related exhibits.


If you make it up to Portland, I’d love to try it out. Any chance on building one to a Nimbus Nightrider 36" frame :slight_smile:

Cool – I’ll be hanging out with Justin and AnSo. I’m also bringing my unicycle hacks:

Tandem: http://www.corbinstreehouse.com/blog/2010/05/tandem-unicycle-practice/
Recumbent: http://www.corbinstreehouse.com/blog/2010/03/recumbent-unicycle/


Wow, nice work on that Electric Assist Unicycle. It’s beautiful done.

What is is it like to ride? Is the assist easily ridable? Does the torque of the motor pushing the wheel, push back on the pedals so the rider has to pedal harder when the motor is driving? With the motor on, can the person pedal slowly, just enough to maintain balance? Can a person stop pedaling and let the motor drive? Could an expert rider possibly turn the motor off and coast?

Beautiful work Justin,a great idea and well thought out,nice machining work and thanks so much for allowing us to see the building process.I look forward to more reports and ride impressions.


Hey Corbin, super excited to try these creations out too! I’ve been dreaming for some time to have a go at a recumbent unicycle, and a front to back tandem is just crazy. Since you use the seat for left and right balancing so much, do you think it might be more rideable if the two seats could each swivel and with a bar linkage cause the wheel to steer?

Anyways, if others want to show up just with regular unicycles or big wheels or what not, I think it would all go over really well with the whole event.


Hey thanks, it’s actually my 3rd attempt, so I’ve had some time to think it over and refine the process a bit. First was giraffe style electric unicycle back in 2006, which had a freewheeling chain drive between the pedals and a hub:

This had self balancing type circuitry, and it worked OK when you used the pedals as foot rests, but as soon as you attempted to assist it with pedaling, it would get all wonky like you were continuously fighting the electronics.

Next attempt was over this recent christmas break, where I first tested the feasibility of modifying a hub motor to have the unicycle axle going right through it. This worked remarkably well, but some of the ball bearing fits were a little on the loose side and it had me a bit nervous about using it as the platform for developing and experimenting with the concept.

Good questions! Right now the electronics control is far from perfect since I’ve just got the standard ebike controller on it, and haven’t got a chance to finish my own drive circuitry yet. The throttle response is pretty twitchy for what you’d want on a uni, so if you aren’t really gentle in applying or removing the electric power then the sudden torque of the motor will quickly throw you off.

But once you have the assistance dialed in and are steady with the throttle, the effect is pretty much exactly like riding a uni with brakes, but in reverse. Or, like riding down a hill, but on the flats. And when you use the regen mode of the controller, it’s just like mechanical brakes in some sense but much smoother since there are no pulsations from varying rim width, grit etc.

I only got a chance to take it for one long ride before packing it up for the Faire, but I found it was very easy to get ‘acclimatized’ to the assist. The only times I fell off was when I suddenly released the throttle and had forgotten just how much it was contributing.

Kris was one of the first to try riding it on Wednesday when I just had a potentiometer on the handlebar rather than a throttle, so it wasn’t quite as ideal but he got the jist of it pretty quick!


Thank you for the info Justin, I’m not sure it is an assist at all. Seems to me that your arraignment is more of a unicycle with an electric automatic transmission, with the gear ratio set by the amount of ‘assist’. Your invention supports effectively gearing up (motor turning forward), gearing down (motor reversed) as well as evolving to offering a mode where the pedals are locked with a brake and a person passively rides. You have one dreamy cycle there.

Sorry Justion about my restating information you had alread posted, like I thought of it. I was just catching on to what you have rolling there. It is neat. (Maybe I should have said it’s a electric transmission, not automatic.)

I’m wrong, it’s not a electronic transmission since if you stop peddling, the motor would keep the wheel turning… I was thinking some of something along the lines, of having an encoder on the cranks which through the motor controller, would step the wheel some multiple of degrees of the pedals.

Hey all! justin came over and stayed at my house in the woods last night. we tried riding up one of my hills - one of which justin asked if i could actually ride up it on a coker (so it is steep!). I rode up it on my 36, panting and breathing hard, and then did it on the assist 29’er. It was effortless and smooth! I wasn’t breathing hard at all at the top. really cool!


At first I hated this,But the explanation has me really liking it!

This is most interesting, I now like the idea here. This is very cool, I might even get involved with stealing this idea for a version of my own, man it’s that good, After Saturday’s ride at Blackstar Canyon I know this would have been great both ways. Great Idea, good job.

Very cool! I wish I was there to try the electric assist, the tandem, and the recumbent. The part about this that is appealing is the braking, I hate going down steep mountains on the road on a unicycle, I really suck at using rim brakes and end up using my legs most of the way down, it hurts, and it just makes me wish I was on my bike. I love climbing with the unicycle though.

I hadn’t noticed that the motor stator was fixed to the frame (your drawing clearly shows.) So now I realize the motor truly assist the rider. It is fascinating.

Sorry, that I have been so slow to catch on to this, and so quick to add confusion to this thread.

Thanks corbin for the brief ride report but I would love to hear more about this creation.Justin,Corbin anyone please tell.


Justin, thanks so much for bringing the cycle over last night. Riding it up the hill on my street was the easiest climb of any hill anytime on any unicycle for me. It’s a great creation. And it was great to meet you too. See you at U Games this summer!


Hey, no worries and glad that you were able to make sense of it all in the end!


Ha ha, you’d think I’d given a mum order for people to keep buttoned up!

Anyways, the ride experience ended up being pretty much what I was hoping for, in that you could cruise along with the motor giving a huge assist behind the scenes, but not overtly affecting the pedaling and handling experience of the uni. What happens is that you get acclimatized to it, so you can zip along easily up a hill, then let go of the throttle thinking you don’t need it anymore and fall flat on your face because you didn’t realize just how much the motor was boosting until letting go.

The braking was really smooth, but unfortunately just a binary on/off lever rather than proportional control. So down a moderate hill it would peel off about 70-100 watts and put that into the battery and relieve your legs of braking duty, but on a steep hill it wasn’t nearly enough regen torque to do it all electronically. But this is something that can be changed easily with a different controller.

Also, the throttle control was a lot more touchy and sensitive than you would want on a unicycle, so you had to be careful to ease on the throttle gradually or else the sudden kick from the motor could throw you off. The plan was to play with a capacitive filter on the throttle line which will give a better soft-start to the system, but didn’t get a chance to do that yet.

Here are a few pictures from the fair. The flat parking lot busy with people wasn’t the ideal testing grounds, no hills and not enough room to get it up to full speed, but those who were already familiar with big wheels had no issues:




Very Nice!

Will you be traveling anywhere else to put on demonstrations?

You could build a motor control circuit that only allows gradual changes to smooth out the transitions. It sounds like that is what you have in mind. I know my Prius has similar controls to keep me from punching the gas and wasting fuel.


Justin,by all accounts your power assist uni concept is a success.The mechanical part is working perfectly by the sound of it and you just have to make the control more user friendly.The choices for control electronics is almost endless and I’m sure you probably have the final control circuits already built in your head.Great job,I look forward to more developments.