A sit down cable lift, and a Invert are completely different types and need their own types of technology. But I didnt know Everest was a Giga coaster? Maybe I missed that 300 ft drop somewhere?
*facepalm* That's not what I said, and you apparently don't know how these things work. "Hypercoaster" and "gigacoaster" were used simply to refer to Intamin's design. At no point did I say that EE was either of those. Plus, those are just Inatmin's buzz-words. A lifthill is a lifthill, regardless of what kind of coaster it is. It needs a means of propulsion, and a means of keeping the car from rolling backwards.
Guess I'm going to have to get more technical...
The physical means of pulling a coaster car up the hill, on both Intamin and Vekoma coasters (and pretty much any coaster for that matter, except perhaps pinch-wheel-motor lifts), are *separate* from the anti-rollback devices. They have nothing to do with each other. The cable or chain moves the train up the lift. That's all it does.
A traditional anti-rollback (the "clakety-clakety" kind) have what is essentially a short arm (called a "dog") hanging down under the cars. As it rolls up the hill, this arm drags along teeth in between the rails. It bounces along, making the distinctive noise. If the chain were to stop or break, the car would start to roll backwards, and this arm would then get jammed into the teeth, preventing further motion backwards.
Now, on silent lifthills, there is an added mechanism to the anti-rollback dogs (and it varies depending on application/manufacturer) that keeps the rollback dog lifted up out of the way while the car is in forward motion, at its designed lifthill speed. Most use some sort of magnetic flywheel to keep the dog up above the "teeth" in the track. But as soon as the train stops rolling forward, or starts rolling backward, that magnetic field goes away (because it was the motion of the train creating it in the first place) and the dog drops down, engaging the teeth.
The only time you get a clackety-clack is at the bottom and/or top of the lift where the speed of the train isn't constant. Between that and the slope changes of the track, the rollback dogs come in contact with the teeth.
Intamin used their silent lifthill technology on their CHAIN-DRIVEN, non-inverted lifthills dating back at least to 1999 with the opening of Superman at Darien Lake. In 2000 they opened Superman at Six Flags New England. There was one season early on in New England where the lifthill motor was running significantly slower than originally designed, and the rollback dogs weren't being held up high enough, making the loudest anti-rollback clacking noise you've ever heard. (Luckily it was fixed after a couple months)
A silent lifthill is not new, it's not groundbreaking. It's just that there aren't many of them out there.
-Rob