Chains keep failing

or possibly chain too tight / badly fitted chainring?

I did this on a langster, only afterwards realised that the chainring was offcentre. chain went slack then tight, then slack on one revolution. If you fit the chain too tight when the chainring is at a "slack" position, then rotate, it gets the chain overtight and will snap it pretty quickly.

It'd have to be pretty fucking tight. Did you not notice it binding and growling like a wounded dog every rotation??

it was a langster.