Roller Coasters used to come in 2 flavors, Wood and Steel. Both use gravity to pull the ride throughout the layout and for many years after they were introduced were all the same. Up the hill, slowly being pulled by a heavy, inefficient chain where it was released to travel the length of it layout. Top Thrill Dragster, at Cedar Point uses gravity, but only for the latter half of the ride. The first half of this 30 second ride uses kinetic energy to get the trains down 480 feet of track and up a ridiculous 420’ hill.
Top Thrill Dragster is unique. It was the first full circuit roller coaster to top 400 feet and travel at over 100 mph. 120 mph to be exact. That speed allows its trains to have just enough kinetic energy to scale the hill, and climb over the top at between 5 and 12 mph. From there, gravity takes over like a traditional roller coaster and the ride again accelerates to 120 mph and hits the magnetic brakes at the end of the ride. The ride was designed to blow your face off your face. I wonder what kind of Scotch gives a man the idea to design a ride to see how well skin holds onto the human body?
So how does the rocket bus accelerate from zero to 120 mph in only 4 seconds? With hydraulics. Monty Jasper, head of maintenance and construction at Cedar Point says the hydraulic launch system sends 10,000 hp via steel cable. This power is needed for only 2-3 seconds, which is a big reason why hydraulics was chosen over Linear Induction Motors — that’s a fancy name for magnets. Hydraulics has an inherent ability to store energy and release it rapidly with controlled acceleration and velocity. The Linear Induction Motors would have required much more space than this ride already takes up. Certain attractions would have to have been moved or taken out completely and that was clearly not on Cedar Point’s agenda.
The launch system uses two hydraulic systems paired together. Each results in 16 hydraulic motors that drive 2 internal ring gears. The pair of ring gears drives a planetary gearbox, which, turns a drum that pulls a cable to launch a coaster.
Fluid to the motors flows through a 2-inch hose, hose is also used for return flow to minimize pressure drop. Each motor is supplied by its own pump, so the launch system consists of 32 pumps and 32 motors. 32 motors is awfully different from the days when a small 2 cylinder motor pulled the train up a traditional hill.
Maximum go for the rocket bus is 10,000 hp and each pump-motor combination relies on a piston-type accumulator and gas bottles to supply the the flow for the 2-3 seconds needed for launch. Before each launch, all of the pumps force oil into the accumulators. The oil forces the piston which pushes nitrogen out the other side and into a gas bottle. The gas bottle when filled will wait patiently for the operator to push a button which tells the system to go.
When the operator pushes the button, a two way valve opens, the fluid then flows to one of the hydraulic motors. This combines with the pump to turn the drum and pull the cable. The cable is attached to a 2 ton sled which has a large magnet. That magnet pulls the train dog down from the bottom of the train before launch. Once the train reaches full speed, it accelerates faster than the sled as the drum starts to slow and disconnects. The Train is then free to scare the hell out of you.
And it does.
For a better perspective, here’s a video Mr. Jazdy shot of the roller coaster (and its neighbour) in action!
[A special thanks to Guest Contributor Prawo Jazdy and the Velocity Trumpets, still one of my favourite pseudonyms. Got a topic you're passionate about? Want to write for AtomicToasters? Send a sample submission to firstname.lastname@example.org!]