Hi,
We bought a cheap unicycle (B-Square 20") secondhand to learn on and were making good progress until yesterday, able to cycle along maybe 10 or twenty feet, when we encountered a technical problem…!!!
When we put pressure on either pedal, in order to “launch”, something seems to slip. The crank and pedal move but the uni doesn’t and we fall off. Can’t quite work out what’s wrong as all bolts seem tight etc. We were hoping to practice a bit more on this one and then maybe get a better one but the problem has come before we are ready to upgrade.
Any advice would be greatly appreciated.
Thank you 
I’m not familiar with your uni at all, so the advice is based on common issues that drop up on cheaper models.
When one crank slips is the other crank staying put or is it moving too? If both cranks are moving independent of the wheel your flanges could have broken free of the crank spindle.
If it is only one side that is moving you may have a missing cotter pin, or the wrong size. Of course you may not have cottered cranks in which case I don’t know what it could be.
In the first case you may be able to weld the flanges onto the spindle, but that is putting a bandaid on the problem. The real fix would be a new hub. I’d say that upgrade may be sooner than you thought.
In the second scenario you should just get two new pins and replace both sides. If you have cotter pins make sure that you set them with a press, or at least a hammer, and then use loctite on the threads of the retaining nuts.
Thanks jtops. 
I think it may be as you suggest, that the flanges may have broken free of the crank spindle.
Probably not worth the cost of fixing so we’ll start looking for a new one.
Would you suggest another 20" or a 24" this time?
A picture might help, but most of the problems which could cause this are probably not reasonably fixable.
A 20" is a little easier to learn on, and better if your goal is to perform or to do tricks. A 24" is better for riding around town or getting into MUni.
To piggy back on what tholub said the size is really about what you want to do with it. Personally I don’t have any use for a 20, but there are a lot of people who could say the same about a 26.
Smaller wheels are easier to learn on. Plenty of people have learned on a 24, so I don’t think it’s too big if you see any kind of distance riding in your future.
Dear Number One,
Are you, by any chance, the Queen?
If so, I suggest just buying a new, better quality uni.
How tall are you? I think taller people tend to do pretty well on 24"s, even as beginners. 20"s are good for beginners, and for learning new skills.
Good luck!
I take it that there are several of u using said uni? If there’s kids and adults I’d definatly say20". In addition to what’s said above u could do light trials on it. Which size really depends on your interests. If its being shared, I wouldn’t worry about it much since you’ll b getting a variety of unis 
esp if there’s several of u.
If 1+ of u are in the neighborhood of 200+# I’d say get something w/ a splined hub, like the Nimbus II.
Ha ha.
I wondered yesterday if the “we” would sound like the Queen, or maybe Nigel Mansell as he had a habit of using the royal we.
The we is actually my wife and myself who have taken up uni riding at the same time.
Thank you everyone, some great and helpful info, we are both fairly tall so may think about a 24".
We’ll mull it over, and make a decision soon.
So, what did you finally decide?
Get a pair of 24" Unis so you can ride together? (i love riding with my girlfriend while holding hands on our 24"s)
How’s your progress so far?
Please don’t just start this threads, keep us updated and share the joy of univolution.
Greetings
Byc