Self-balancing electric Unicycles, Skateboards and Twin-Wheelers

John Dingley

June 2015: Redesign of the MediCycle Urban Responder, now is the MediCycle-Mini:
Previous one had wheel(s) with too large a diameter and not wide enough to steer easily (see videos below). I searched all sorts of tyre suppliers for a wide, almost spherical tyre (think of the ball on a Dyson Ballbarrow) and in the end I was going to buy a lawn tractor tyre. However the tyre company suggested a kitesurfer tyre. Machine much more compact now. There is a steering system that moves the weight of the frame and rider to left or right of the wheel and a steering damper from a VW Beetle is used as the, well, steering damper! Lower frame reminds me of a Klingon spaceship.
September 2015: Slightly embarrassing. After riding it and reading accounts of how the Ryno machine is "intuitive to ride" I realised that mine is not intuitive to ride at all. This might be because my steering linkage is back to front! Turning handlebars right would shift body to right and so weight to right of wheel. This sounds correct but may be wrong. Need to think of it a different way: when turning handlebars to right you want tyre to lean over to the right, so now rolling on inner right edge, so machine curves to right. This actually means upper frame moves to left relative to wheel, but if you lean to right at same time, you do then get onto inner right edge of tyre as required. More testing to come.........
October 2015: Rides much better now steering linkage is the correct way around.
Oct 28th 2015: Wheel moved back to make it balance when frame + me are level not when leaning forward. Damper relocated slightly as a result. Pics to come.
Data displays all removed, now sent via wireless to wearable display in right eye, see further down page for further wearable "ViVi" display info. Slightly smaller 25 tooth wheel sprocket ordered from China (the only 420 chain 4-hole sprocket available in world it would appear) to increase speed slightly while retaining adequate torque.
Nov 2015: Future plans: Fly by wire steering system, yes really. Replace the VW Beetle damper with a linear actuator and get the thing to steer itself - in straight line only as the initial goal. Need to fit datalogger to IMU and potentiometer to steering column so I can work how I actually stay on this thing first before trying to program a computer to do it for me! Entering totally uncharted territory now, where the real excitement is of course, this is why I do this hobby.

Taking a rest in the bunker. The helmet and armoured jacket are essential when you fall off, which does happen.

YouTube Video

Video of me riding it outside the secret underground test bunker in Wales October 2015 with new steering.

YouTube Video

MediCycle-Mini and Jackal unicycles running together with on board cameras. Oct 26th 2015

October 2015: The machine now has no data readouts at all, just an LED. 
Data on Torque, Angle and Battery volts is sent via wireless to a wearable display in front of the right eye.
Here I am adjusting it. This has now morphed into a potential commercial product, the ViVi wearable data display click here for VIDEO.
Website:       ............looking for further investment capital.
Raleigh Chopper inspired unicycle (well, actually it is a di-wheel). 
Winter 2014.        This is finished now and I have an "Instructable" with build instructions for this here: Self-balancing Chopper

YouTube Video

Video of the ultra-dangerous full sized original Hackaday-competition MediCycle at Maker Faire 2015 Newcastle UK.

YouTube Video

 Video of the Chopper project in action.
                        MEDICYCLE URBAN RESPONDER Summer 2014 (The full sized ultra-dangerous MediCycle).

JUNE 2014: I entered the Hackaday Competition with Nick Thatcher and another friend. 
The entry was the Medicycle, twin-tyre unicycle design. Best project yet hopefully, here is the link:
OCTOBER 2014:  We reached the semi-finals from 800 entries which is not bad. The rules required the device to be "connected"
as part of its core functionality, and, to be honest, our medical data streaming to the web was a little contrived and clearly not absolutely 
essential to the working of a self-balancing unicycle! Thanks to everyone who supported us. We were also filmed by Discovery channel for 
their "Daily Planet" programme, due for broadcast October 2014 in North America and Canada.
 Click on link below to watch this, we are lead story of this episode.

Link to Daily Planet Programme (NOTE: this only will work in Canada), select 17th October (episode 155) from menu:

YouTube Video

Why build such things?  For the technical challenge and the fun of riding these machines. They are unlike anything else. Electronic self-balancing machines have existed since 1998 (a Japanese robot) but there is still a huge amount of room for further experimentation by amateurs. In addition the parts are gradually becoming cheaper to buy all the time.

Q: Can I buy a kit?  A: No although I did have a go at a kit where the balance sensors, Arduino and hand controller were all pre-wired together with software pre-loaded.
Here:     There are some Segway type kits out there (Elektor, Ewee etc) and several Chinese Segway clones.

What about the "Moto Pogo" on Kickstarter June 2015 which seems to have been suspended a few days later by Kickstarter?
May be because it looks very much like this one which is already for sale by "Ecoboomer", same guy in photograph by the look of it:

Uni-Mig at Newcastle Maker Faire UK April 2014. Video below along with Nick Thatcher and his Jackal one wheeled motorbike. The Uni-Mig was an experiment where I built something with a single wide tyre and low weight distribution, very much like a Vespa scooter, but with just one wheel of course. Worked pretty well and had good low speed steering control.

YouTube Video

Thanks, Rebel Legion UK. The stormtroopers all want one!

What else is new-ish on this site? 
Feb 2014:
a) Note new entry (8) on left describing how to hook up an Arduino to an OSMC motor power controller, including faster pwm.
b) The UNI-МИГ 01 (Uni-Mig 01)   Link (19) in left hand menu.  One wheeled unicycle scooter.
c) I have finally managed to get a self-balancer to work using a modern DIGITAL IMu from Sparkfun. Link: Click Here Also see the Chopper project at top of this page.

Heroes (we all need some heroes):
Trevor Blackwell who inspired almost everyone else doing this sort of thing:
Ben Smithers (Norwich, UK) who posted the first amazing video of a one wheeled skateboard:
Rodger Cleye, another early monowheel board builder:
Also have to mention Charles F Taylor, a farmer who built amazing mechanical gyro-stabilised one wheeled vehicles in the 1940's:
- almost lost in the mists of time but recently reverse engineered by two bikers:

New one June 2015, the "Eight-Ball" made by "Furbi". No idea which country it is from, does anyone know?

YouTube Video

Eight-ball looks really good on this video. Motors and battery within wheel, steering linkage.

"RoboWell Juno" unicycle from Russia. Bluetooth controlled from your phone. Hub motor. Proper steering system.
01/12/14 I have just been sent a link to this brilliant DIY one wheeler from Russia on YouTube built by Vyacheslav Kulakov. He has a 2 wheeler as well but the monowheel is really good. Has a brushless hub motor so I have asked him what motor controller he is using as this is the problem with DIY hub motor projects currently, enjoy.......

YouTube Video

Robowell Juno

Two slightly dodgy one wheelers with handlebars from China shown below. Yes these have started appearing now, no doubt inspired by the Ryno Motors one from the US that was all over the web a couple of years ago.


I suspect these will be quite tricky to learn to ride with the narrow tyre.

Not sure if handlebars move to shift the rider weight left or right, or whether they are just fixed. 

Suspect that Ferrari have not approved use of their logo in the one on the right.


My own classification of self-balancing one wheelers (so far):
1) Stand-on (skateboard style).
2) Stand-astride (Solowheel type design)
2) Unicycle (i.e. seat on top of wheel like a unicycle, e.g. the Enicycle or a one wheeled motorbike e.g. the Ryno)
3) Seat-forward ("Riot wheel" for example, seat in front of large wheel  )
4) Seat-behind (See Russian patent diagram at bottom of this page, where seat is behind a large wheel)
5) Prone-forward (See concept CAD image towards bottom of this page where rider is ahead of a large wheel lying prone).
6) Prone-unicycle (rider is more or less prone but above the main wheel.
7) Inside-wheel (Large hollow wheel with seat inside the rim of the wheel) as in older fully mechanical designs.

Note: There is also a Prone-behind category of drag motor bike where the bike drags itself along by a single front wheel with the rider hanging on behind. 
These do not self-balance though and are more like a powered sled:

One wheeled skateboard and Segway style machines.

2008 First machine that actually worked.                        The "Hot Wheel" variant.                                            The "Thing" V1. See link (4) on left.
See link (16) on left.

Two wheeled skateboard style machines
Twin wheeler, batteries in deck.  "Easy build" version.              With carbon fibre deck                    With ply deck.                           "Pneu-skate" with pneumatic tyres.
See link (1) on left.                    See link (3) on left.                                                                       See Link (6) on left.                    See link (2) on left.

Special ones:
Concept to put mechanism in a rucksack                  Best Skateboard so far. Compact, has Headway LiFePo4 cells and pneumatic tyres.
Extending handle also acts as handlebar and             I am unlikely to significantly improve on this skateboard type design. Wii-Nunchuck is for steering and trim.
is ridden like a small Segway.

Also see my "Instructables" DIY skateboard page for build instructions for a skateboard design with 2 wheels.

Solowheel type machines where you stand on the footpegs each side.
Abandoned for now as too dangerous. May work eventually but high chance of injury while ironing out the bugs!  See link (17) on left.

Monowheel projects

The "Thing" version 2 Derby Mini Maker Faire UK November 2013 with Nick Thatcher and his "Raptor" machine (far left and far right). This used all my 
old large monowheel skateboard parts to create a unicycle. Welded on unicycle seat and handlebars. It worked much better than expected.

The Tumblebug science fiction one wheeled motorbike.      The Uni-Mig 01 (UNI-МИГ 01), many parts now in the MediCycle (see top of page).

Assorted other curiosities...........
 Horseless 2 wheeled chariot seen in 1896 advert for first motor show ever in United Kingdom
 (Brown County Democrat, December 28, 1900.)   - The "Footomobile" of the future!

YouTube Video

Video of the "Easy-build" version I put up on the Instructables website in 2010. Had Arduino "brain" and lead-acid batteries.

YouTube Video

Video of the fully developed compact twin-wheel skateboard with LiFePO4 batteries and pneumatic tyres, May 2013. 
As you can see, the more you try, the better you get!

Has anyone else built one of these?
Oh yes! Ages currently range from 12yrs to 81yrs.
This Instructable is over a year old now, so yes indeed, people have. Here are a few I know of:
1)   Skateboard:
2)   Skateboard:
3)   The Velociryder:
4)   Great board video - Buffalo State College senior project:
5)   Another board based on this Instructable:
6)   A board based on old FIRST robotics parts + code from this instructable (FIRST robotics was started by Dean Kamen who also invented the Segway, to encourage youth to get interested in engineering):
7)   Carbon fiber racing car seat with 2 wheels also based on this instructable - the SciChair:
8)   Carey's self-balancing platform, good video:


Could this be ridden?                                                            Here is a similar one with a rear swivel caster for good measure.
Well this guy, Jackie Chabanais could probably ride it 
using good old fashioned circus-style skill:      Click Here




Would need a pretty big rocket to get 
that to the moon!

This look as if it was drawn (for a computer game) based on my original 1 wheeled "Thing" (link 4 on left) but who knows?

This is so cool. Was it ever built? Looks like a Soviet era patent. Does anyone have any information? Seat-behind design.

Inside-wheel designs.

Prone-Unicycle design
 "Sidecar Willy" pioneer of unimoto racing (Prone-behind design).
Dave Southalls' Red Max monowheel. 
He has his own website "Dave Southalls' Engineering Experiments from the shed"
and apparently will soon have his own TV show on the Discovery "Quest" channel.

I think I might have to build a full-scale one of these - that works.


Unusual Prone-forward design. Riot wheel.

So called "Redneck Segway."   Not sure how well it balances though.

Looks suspiciously like a rip off the Ryno motors unicycle general concept.                  The original German Einrad machine from about 2008


Weight distribution: Accepted wisdom is that a self-balancing robot is easier to build if tall with all weight at the top since motors have less work to do to move the (lightweight) lower region back and forth rapidly to maintain balance. This is why balancing a yard brush on your finger is slightly easier with the broom head uppermost.

This may be true for a small robot, however for a vehicle I have found by accident that having a lot of the weight low down, bearing in mind there is already plenty of weight up above (i.e. my body), smooths the overall ride. This maybe because for a very top heavy robot, if you hit a small obstruction, a pebble for example, the machine has to start to tip forwards, the computer recognises this and then applies more power to motors to overcome obstruction, so machine does a little “wobble” forwards, then carries on OK. If you have some mass low down however, good old fashioned forward momentum carries you over the pebble without the need for a “wobble.”

Spinning masses: If motor is heavy, and so rotating armature inside has a decent mass, the spinning momentum of this also helps you, as wheel hits obstruction and tries to slow the motor down, the motor resists simply because of this rotating mass acting back on the chain towards the wheel. Obviously if it were too heavy (e.g. a big flywheel) the motor would then not react fast enough to commanded changes in speed from the self-balance computer so there is probably an optimum band of sweetness for this effect…………………a small flywheel might potentially have some merit.


So, with my newer unicycle machines, by repositioning the very heavy motor more or less behind the wheel and battery as low as possible too, I find it is easier to ride than before especially at low speed. I suppose this is also true of petrol scooters like the Vespa – the main weight is low down all around the back wheel. The clever thing with the Ryno, which makes it relatively easy to ride, may be the hollow wheel. They have all their heavy components within the wheel, i.e. low down, probably even below the axle line. Another way to do this is to have the battery flat in the side struts going down to the axle (as in the Focus designs unicycle or the solowheel) and use a hub motor, but within the wheel is really neat. It does mean you probably need big lathe to machine your wheel rim though!

Having said that, there are many alloy car wheels now that are very wide with a huge offset, i.e. the spokes are all on one side and the wheel is more or less hollow. This makes me think you might be able to use a commercial alloy wheel to build a Ryno type machine. In particular in the US there is a craze for mega-diameter custom wheels so you can actually buy a 24inch diameter very wide rim with large offset off the shelf. 


Subpages (21): View All