[supermax]

Last year, when I was learning to ride my unicycle on light off-road trails, the left crank-arm started to wobble faintly. As I continued riding, the wobble got more and more pronounced and when I stopped, I saw that the crank-arm bolt had worked itself almost completely loose. Since I hadn't carried my extra large Allen key (M8), I couldn't fix it on the spot, so I had to stop mid ride and drive back home. Once home, I quickly tightened up the bolt, but when I took it out for a test ride, I found that the wobble quickly returned, no matter how much I torqued up the bolt. A local bike store diagnosed it as a busted crank arm, and since unicycle crank arms are not the same as bicycle crank arms, I needed to order from the unicycledotcom affiliate in Sweden. When I checked their website however, I saw that they had no stocks of the 125 mm cranks that I had on my unicycle, and when I called them, they said they had no idea when it would be back in stock either. I remembered then that I had a set of 150 mm cranks that I'd never used, and I thought I'd give them a shot.

Getting the crank arm off is no different from a bicycle; you need a crank-puller tool and before long, the 125 mm cranks were off. When I inspected them however, nothing seemed amiss, so I was a bit puzzled. When I tried to install the 150 mm cranks, I realized what was amiss; the screw seemed to be partially stripped, but the hole on the hub was in much worse shape, as the thread around the entrance was destroyed, probably when I rode a bit after the crank arm had loosened and started to wobble. Frustrating as this was, there was nothing I could do with a trashed thread till I got my hands onto a thread tapper, to fix the stripped thread.


A visit to the local tool store ('Biltema') the next day gave me what I needed, an M8 thread tapper, and before long, it worked its magic, and I could get the bolt into the hole again.


The M8 thread tapper.


The M8 thread tapper, up close.

When I installed the 150mm cranks, I discovered that the crank arms were way too long for my height, as my legs couldn't even reach and touch the pedals when the crank arms were in 12-o-clock and 6-o-clock positionn. The saddle was already all at the lowest possible position without the saddlepost hitting the tire, so if I needed to lower the height any more, I'd have to saw down the saddlepost. Since I didn't want to do this, I decided to order 114 mm cranks which were still available on the webstore. There were shorter than the 125 mm cranks I'd ridden the 24" unicycle with, but I was used to riding with 110 mm cranks on my other 29" unicycle, so it should be okay, I thought.



The red tool is the crank puller. The black crank arms are the 150 mm square taper cranks while the chrome ones are the 125 mm crank arms that were originally on the uni. On the uni in this picture are the new 114 mm cranks.

The new cranks arrived in record time and as expected, I was able to ride quite well with them, though the ride characteristics were quite different. In fact, I liked it better than with the 125 mm cranks, as the smaller tighter circle my feet made seemed a lot smoother than before. The bad news though, was that the wobble was back, even with the new cranks, letting me know that the problem had always been the hub; it was simply not capable of withstanding the torque I applied at the crank arm any longer. While the thread tapper had helped, it was still a no go, so as a final Hail Mary, I applied some superglue to the threads on the crank arm bolt and drove it in quickly and tightened it before the glue set. Left the uni to sit for a while and then tried it out gingerly, wishing I'd not hear the dreaded creak that signified that the bolt was unraveling, but the glue and the bolt held, at least for now. I rode for a while till I tired myself out, and called it a night. Here's hoping that the fix holds for at least a while longer, as this is a unicycle that I like to ride on the snow, and like the characters in the series 'The Game of Thrones' often pointed out, 'Winter is coming!'

[Jeroen]

Good to see a fellow unicycle rider!

I haven’t riden an unicycle for decades. But in my teens I was part of what is known as a Youth circus! I was involved in various acts, including riding and doing all sorts of tricks on a unicycle.

As practice I used to ride it everywhere. To school, to the shops to get things for my mum, to gym practices. Good fun!

It’s not as difficult as many people believe it to be. But it’s all down to practice, practice and practice!

Jeroen

[amol4184]

Interesting read. Can you not change the bottom bracket itself than using super glue. I wouldn't imagine it to hold up to so much torque but I have never super glued something like that so I don't know for a fact.

Since I have no idea about unicycles, curious to know if that's a regular 68mm English bottom bracket (Shimano UN300) that also does duties of a hub for the wheel or if its an entirely different, specific-to-unicycles part.

[supermax]

Originally Posted by Jeroen

Good to see a fellow unicycle rider!

I haven’t riden an unicycle for decades. But in my teens I was part of what is known as a Youth circus! I was involved in various acts, including riding and doing all sorts of tricks on a unicycle.

It’s not as difficult as many people believe it to be. But it’s all down to practice, practice and practice!

Jeroen

Wow, nice to hear that there's at least one other unicyclist here! I suspect there may be even more, but I'm no longer the only known one now Yes, it's a lot of fun, and I think it's a great way to stay in shape. I'm not the kind who enjoys workouts in a gym or on an indoor trainer. The uni brings me back into shape very quickly.

Originally Posted by amol4184

Interesting read. Can you not change the bottom bracket itself than using super glue. I wouldn't imagine it to hold up to so much torque but I have never super glued something like that so I don't know for a fact.

Since I have no idea about unicycles, curious to know if that's a regular 68mm English bottom bracket (Shimano UN300) that also does duties of a hub for the wheel or if its an entirely different, specific-to-unicycles part.

It's something entirely different! In a bicycle, the bottom bracket is connected to the chainring on the right side, to which the right crank-arm is also fixed. On a unicycle, there is no bottom bracket at all, but a hub that doubles as the bottom bracket, as it sits in the center of the wheel! A uni hub is a bicycle hub + bicycle bottom bracket.
My 24" unicycle has a hub like this one:
https://www.renegadejuggling.com/qua...quare-taper-36

If the hub goes, the entire wheel has to be rebuilt. I haven't built a wheel in a really long time, but its something I'm tempted to do again, for a uni, as building a custom uni wheel costs much less than the cost of a new unicycle!

[amol4184]

Good to know. I have heard wheel building to be a therapeutic, satisfying experience. Never done that but willing to do so in near future. I will keep an eye out if you decide to do so and write about it.

[14000rpm]

Originally Posted by supermax

Last year, when I was learning to ride my unicycle on light off-road trails,

Interesting. Didn't know you had this talent too. This is too cool.
Saw a teenager ride one in Munich recently and I was mighty impressed at her talent.

Clicked a pic to show it to my daughter but now I can show her your stuff too.