[Ianworld]

If you don't trust gravity you can always trust torsion springs. Attach a latch and have the torsion spring push your ramps down when you undo the latch. The trick isn't being able to pull them back up if they come down accidentally during the game, the trick is to make sure they only come down at the end of the game and stay down. If you're still worried about not being able to pull them back up, then try to make your design so that in the off chance they do come down early you'll still be able to drive your robot into the endzone(although you'll probably have to drive slowly and cautiously) to make sure you can still do your ramp/platform/lifter duties.