Apache proxy to redmine server

I've been struggling with this for awhile. I have a virtual apache server, and turnkey linux container with redmine running and I want the main server to delegate requests to the /redmine/ folder to the redmine server.

I set up the proxy statements on the primary server, but all the followup requests for css, js, images whatever would be looking back in the main server's root again instead of on the redmine sever.

I had to add the following line to the end of /var/www/redmine/config/environment.rb

ActionController::Base.relative_url_root = "/redmine"

And that did the trick.... I have no idea how rails does whatever it does.