Hello. First time poster here 
Long story short: I've got tired of trying to figure out model relations in big rails projects with more than 20 models.
Before I've tried to use rails-erd, which turned out to be a PITA to conceive.
So I tried out a different approach where model relations are organized in a tree-like pattern like this (example from one of the projects):
Metric MetricConfiguration ActionInstance Action::EmailInstance Schedule Threshold MetricInstance
You can check out the tool here https://gist.github.com/4r2r/10317c83f964ee072066