I have been trying to create my own mod using the wiki article "introduction to vehicle creation" (this one: http://wiki.beamng.com/Introduction_to_Vehicle_Creation) . I have made it up to the step where you test it in game for the first time (when you can test the jbeam structure for the first time), but I put it into my mods folder and the game doesn't even recognise it. I tried zipping it up, and putting the regular and zipped folders into the content/vehicles folder, and none...
Making jbeam structure visible in game
Making jbeam structure visible in game