28/29″ unicycle with handlebars and a brake
Unicycles come in many sizes and shapes. The most common are the ones with 20-inch wheels. Great for learning and doing tricks but not very fast. Since you’re constrained to a 1:1 gear ratio (unless you’re willing to spend several thousand euros on a geared hub), the bigger the wheel, the faster you will be able to ride.
As unusual as it may sound, there are enthusiasts who ride unicycles for long distances or trekking. Ed Pratt even rode one around the world! These guys use special 36-inch wheels, which are quite hard to purchase and expensive.
I’m just a beginner who rides his unicycle for leisure from time to time. I simply wanted to move a little bit faster than my previous 24″ unicycle allowed. Not wanting to spend a large amount of money on something which is not my primary hobby, I decided to stick to a 29″ wheel, which is the largest size commonly used in bicycles. This way, I won’t have to use any unicycle-specific components.
So, I bought a cheap no-name 20″ unicycle and modified it to fit a 29″ wheel. To reduce pressure on my perineum, I added handlebars. Additionally, I installed a rim brake, which greatly helps when going downhill. This way, I created a machine that you can ride quite comfortably for several kilometers before your nether regions start to hurt.
A standard no-name 20″ unicycle
Cheap unicycles are usually made in China and sold under various no-name brands. They are all made of steel and have a cotterless hub with 90–150 mm crank arms. Higher-quality manufacturers, like Kris Holm, Qu-Ax, or Nimbus, usually use ISIS hubs. Since I lack the skill to do anything more than ride on flat surfaces, I don’t need anything sturdier than a cotterless hub. For this project, I bought a used unicycle on OLX for about 15 euros.
Welding the fork
To fit a 29″ wheel, I needed to extend the fork arms. I used a 29.8 mm steel post tube as the source of material. I cut the fork with an angle grinder and cut the seat post into two tubes, each 115 mm long. Then, I TIG-welded everything together. The process is shown in the pictures.
Building a 29″ wheel
I bought a 28”/29” (ETRTO 622, width: 21 mm) rim and a 2.1x29″ (52-622) tire, which is the widest tire I could reasonably fit into the fork, including the brakes. In fact, I bought two rims. The first one, with an orange tint, lacked the brake surface, so I bought another — the red one with yellow markings.
First, I disassembled the original 20″ wheel because I needed the hub anyway. The old spokes and rim were discarded. Additionally, I used that bare hub during the welding process, as shown in the pictures above.
Keep in mind that the rider’s entire weight rests on a single wheel, not two, as in a bicycle. That’s why the wheel needs to be especially sturdy. To achieve this, I laced the wheel in a standard 3-cross pattern with thicker-than-standard stainless spokes. After measuring the hub and calculating the required lengths, I bought 36 spokes: Sapim Leader 284 x 2.3 mm and 14 mm brass nipples: Polyax 13G. To calculate the spoke length, I used this very intuitive online tool.
The wheel was trued on an ordinary bicycle truing stand. However, I had a bit of trouble fitting the unicycle hub into the stand, but it turned out that just putting the hub on the calipers allowed the wheel to turn freely and gave enough precision to true it to a satisfactory level.
Adding handlebars and a brake
Brakes are rarely seen on standard unicycles because, normally, you can’t go fast enough for a separate brake to be necessary. However, they can be useful when going downhill. Their exact purpose is to spare you the need of applying pressure on the pedals in the opposite direction, such as when slowing down on a fixie bike. That’s why they are much more common on mountain unicycles (MUNI).
Nowadays, quality MUNIs have disc brakes; however, my cheap hub didn’t have the appropriate mounts for attaching the disc. I considered adding ordinary cable-pull V-brakes, but the cable might have gotten in the way of my legs while pedaling. After performing some research, I went for Magura HS33 hydraulic rim brakes. Their only moving parts are the brake pads themselves; furthermore, the outer shell has no sharp edges nor protrusions. For reference, the catalogue: Brakes of Magura, and spare parts.
This kind of brake is hard to spot nowadays, as most bicycles, except the cheapest ones, use disc brakes. However, they were popular in the 90s in trials and BMX. I looked for a while for them on OLX and finally found a nice box full of Magura parts, which I bought promptly.
To achieve compatibility with standard V-brake mounts, Magura is normally installed with a complicated system of two boosters (the U-shaped parts connecting the left and right sides of the brake). This is quite bad for unicycles, since the boosters are bulky and could get in the way of your legs when pedaling. Luckily, there exists a custom braze-on kit 0720425, which allows mounting the brake directly to the frame. This is a proprietary solution, though, used formerly in trial bikes. I bought the kit and welded the brackets to the fork. This made the brake look much cleaner, and the only overarching element is the hydraulic line.
Welding the Magura braze-on kit
To ensure the braze-on elements were positioned correctly with each other, I took a piece of PCB laminate and screwed the elements to it. I didn’t take the photos, though.
Welding the handlebars
The handlebars, in theory, should provide a comfortable resting place for both hands and, additionally, serve as the attachment point for the brake handle. By putting a bit of your own weight on your hands, you reduce the pressure on your perineum.
Since I took an old steel trekking/butterfly bike handlebar as the source of material for my handlebars, I was constrained by its dimensions. So, the overall length of the handlebars is 200 mm, and the distance between the arms is 135 mm. In hindsight, I should have made them longer, for example, by welding additional 15 cm tubes to the ends.
My AJATA Indivisual Slim Sattel seat had a designated spot for attaching the front handlebars. I cut a matching shape from a 1.5 mm steel sheet with an angle grinder.
Making a brake handle
On a unicycle, the relative position between the brake handle and your hand is rotated 90 degrees compared to a standard bicycle. Because of that, using a standard bicycle brake handle would be awkward. To overcome this, I simply customized a Magura handle with an ordinary tablespoon. The spoon was cut to match the handle and glued to it with two-component epoxy glue. To make the glue darker, I mixed it with finely ground coffee.
This spoon contraption stood out as something a bit dodgy, so I decided to clad it in leather. I soaked a piece of black leather in water and wrapped it around the spoon. The water made the leather soft and elastic, which eased the process. After some fiddling, I let it dry. Then, I cut off the excess pieces and glued the leather with epoxy again for good measure.
Assembling the brake
I assembled the hydraulic lines according to Magura’s manual. I didn’t bother buying the original Magura mineral oil (marketed as Royal Blood), but since I had some at hand, I simply used LHM oil, which is normally used for hydraulic suspensions in Citroën cars. I filled the lines with oil and bled the system with a syringe and a piece of plastic hose.
Adding protective bumpers
To minimize damage when falling off the unicycle, which still happens occasionally, I added rubber bumpers to the handlebars and the backside of the seat. The bumpers are random pieces of rubber I found in my workshop, probably door stoppers.
Final thoughts and things still to do
After some time of trying to ride this contraption in various conditions, I can say that the modifications were more or less successful. The most important addition turned out to be the handlebars, because putting a bit of your weight on your hands reduces the pressure on your perineum noticeably. If I were to start from scratch, which I might, I would definitely make the handlebars 15 cm longer. The brake turned out to be useful only on downhills, but it’s nice to have it anyway. I still have to paint the fork and the handlebars. I don’t consider the project finished.