Monowheels, by their very nature, are fairly simple machines; after all they only have one wheel! They work by driving a seated base around the inside of a circular track to push it forward — you might think of them as a perpetual roller coaster.
A complete monowheel is usually a custom build. Want to make your own? Here are the key elements:
1. Outer frame
Needs to be big and sturdy enough to sit in, and allow the drive to make it move. I used a 50mm diameter steel tube with a wall thickness of about 3.5mm, shaped into a 1.5m hoop. For tread, I cut up bicycle tires and pop-riveted them on the outside of the ring.
These allow the outer ring to revolve around the inner frame. I used custom-made 100mm nylon rollers with ball races to allow free movement. Mine has four, some designs use more. If cost is an issue, you can use skateboard wheels set at an angle.
3. Inner frame
Holds the rollers, power source, drive, and seat. Experiment with positions, but keep the center of mass as low as possible for stability.
4. Power source
This could be a petrol engine, an electric motor, pedals, or even steam power. It comes down to personal preference and engineering ability.
Usually a friction-type drive. I use the wheel from a MiniMoto, running against the inside of the outer ring.
Other things to consider in the design: The gearing needs to be calculated; I suggest a top speed of around 10mph if it’s your first attempt. Brakes are definitely an issue too — if your braking system effectively locks the inner frame to the outer ring when applied, you will roll completely around with the outer ring, known as gerbiling. Best to avoid if possible.
Every monowheel is a unique machine — these aren’t rules, just suggestions based on my builds and experience. For more details and ideas go to redmaxmonowheel.co.uk. Enjoy!