Hello so I dismantled my blueray drive to replace the laser now the drive wont accept discs. I think its to do with the mechanism. Does one have any links to a video showing how the mech works? Thanks

I am sure the "bommerang" shape metalic thing, is the cause of your trouble. be sure it is in place, firm in the plastic, and the drive tray is lower downed, not like ejecting... also be sure you put the magent in proper place.

There's plenty of videos on youtube take a closer look if your gears are on same place.
I usually lift back part of ps3 to fix the top cover, the gravity puts the parts in place for mounting.