Many guests complained about the high g-forces experienced in the first turn and there were rumors that the wheels on the trains had to be replaced at a very high rate due to the high stresses. As you may know, the ride initially opened with a top speed of 90 mph. I’d also like to take this time to talk about the modifications being made to Intimidator 305 at Kings Dominion.
To calculate the G’s felt for the ideal banked curve with no friction: G’s felt = 1/sin(theta) If the velocity of the car is changing through the curve then the banking angle of the track must also change to compensate. How do you produce a perfectly banked curve? The following equation is used: Tan(theta)=v^2/rg where theta is the angle where no outside forces other than gravity are required to keep the car from sliding to the inside or outside of the curve. This is done because an attempt to produce a perfect bank could accidentally result in an overbank due to a slower than expected train (possibly slower from high winds, half-empty train, etc.) Now, there are a few coasters which bank their track to the outside of the curve on purpose to create a thrilling effect and unique feeling ( see Steel Hawg). The passengers feel a slightly outward force around the curves which they expect and will naturally adjust too. Some curves on roller coasters are intentionally underbanked by a small amount. Friction is also needed to keep the car on the track. The rider feels a force pushing him away from the center of the curve. The guide and uptop wheels are holding the car onto the track.
The car could tip to the outside of the curve. Underbanking is just the opposite where there is not enough bank for the car’s velocity. Friction is needed to keep the car on the track. The rider feels a force pushing himself down into the inside of the curve. The guide wheels are holding the car on the track. In other words, the car could tip to the inside. Overbanking is where there is too much banking for the car’s velocity. This is the optimum scenario to keep the car on the track, where no friction is needed. The rider will feel a normal force pushing him into the seat of the car. At just the right bank for a coaster car’s velocity, the car will not need any type of undercarriage or guide wheels to stay on the track.
There are generally two scenarios a designer will want to avoid when designing a banked curve: overbanking and underbanking.
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