I've just noticed I didn't do such a good job of chopping the models, there are a few stray faces near the gears that need cleaning up.
Script attached, it simply plays sound 0 for open and sound 1 for closing, the user will need to tweak the value of the openingSpeed variable to match the sound sample.
The script works at any angle btw so you can turn the bridges on its side and use it as a door for example.
The gears entity needs to be positioned by hand but that makes it more flexible as it can be placed anywhere that both gears mesh properly.
Main bridge entity should be always active, physics on and isimmobile=yes (I know it's counterintuitive but that's GG for you).
Geers entity needs to be always active, physics off ond issimobile=no.
Edited to add cleaned up bed model.
Been there, done that, got all the T-Shirts!
