I was wondering if it's cheaper to use Hydraulics or Magnets.I'm assuming Hydraulics is cheaper but is less reliable.Also,is coaster that uses a lift hill generally cheaper or more expensive then a launch.Thanks.

Lift hills are cheaper than a launch by far, they operate at lower and more constant speeds, and so can offer years of trouble free use. I assuming that Hydraulics are cheaper since they have been adopted by the two biggest manufacturers: intamin and vekoma, they would also use less energy than the huge amounts needed to run rides like TOT, plus be kept cool. hydraulic is more reliable than magnetic IMO, im mean, they got Xcellerator to work ok and it was a prototype, but S:TE at SFMM took ages to get it working well, i think it opened a year late. Hydraulics are the wave of the future.

They probably are seeing as TTD and Kingda Ka use them.

Between pneumatics, hyrdraulics and LIM/LSM, it's generally considered to be pretty much the same in terms of power consumption. Benefits (or drawbacks) come from the fact that LIM/LSM draw a current at sudden and irregular times (i.e. when the train launches), whereas pneumatic and hydraulics are a constant (and smaller) draw. Naturally, a lift hill is hugely cheaper to operate than any launch.

On that subject, kinda, what is the maximum speed that conventional lift hills can operate at. Say, for the average roller-coaster with an average load which is brand new.

Are hydraulics / pneumatics used to launch some coasters?

I think we have established that.

I never knew that. I didn't think it would be possible to transfer enough energy. Obviously it is. I suppose they would need to be bigger than regular hydraulic actuators. Does anyone have a diagram, or can anyone explain how hydraulics are used to propel the trains? Is it just a hydraulic actuator that pushes under the train or more complex? Is a hydraulic launch as smooth as a magnetic launch? Thanks.

CoasterBuzz's RideMan (AKA Dave Althoff, Jr.) can help you out with that with this nice article. I'll leave all the explaining to him for now. Hydraulic launches are capable of accelerating much faster than LIM/LSM and pneumatic is again faster (or rather, capable of higher jerk/jolt). Of course, most coaster launches are pretty smooth (you wouldn't design a launch to be rough), they are more forceful, but good and fine so long as you keep your head back.

Thanks Richard, that was exactly what I was looking for.

And for idiots who decide not to on a ride as fast a Kingda Ka?

Lift hills are cheaper than a launch by far, they operate at lower and more constant speeds, and so can offer years of trouble free use. I assuming that Hydraulics are cheaper since they have been adopted by the two biggest manufacturers: intamin and vekoma, they would also use less energy than the huge amounts needed to run rides like TOT, plus be kept cool. hydraulic is more reliable than magnetic IMO, im mean, they got Xcellerator to work ok and it was a prototype, but S:TE at SFMM took ages to get it working well, i think it opened a year late. Hydraulics are the wave of the future.

About S:TE gaz, it did open a year late. It was meant to be the first ride of it's type, but due to probs pushed back it's opening date by far. Meaning TOT stole that crown. Good on ya Tower of Terror.

On that subject, kinda, what is the maximum speed that conventional lift hills can operate at. Say, for the average roller-coaster with an average load which is brand new.

*sigh*, can someone answer my question please?

I don't think there is something such as a maximum speed because there are so many variables involved.