148/217's 2010 mechanism is a snail cam, not quite like this.
Winnovation (1625) 2010 used a choo-choo, but it was mostly popularized by the 2014 Build Blitz where Team JVN used it.
Here's a graphic I found on CD a few years ago (but couldn't find it with a google image search). Thankfully I saved it. Here it is:
In my spreadsheet, the blue link is the 'fling' arm and the red link is a cable which connects to the throwing arm. The length of the red link is not important as long as it pulls straight down on the throwing arm. Some designs use a hard link instead of a cable for the red link.