Coasters-101: How does a 4D coaster work?

In this edition of Coasters-101 we’ll answer the question: how does a 4D coaster work. A new 4th dimension roller coaster from S&S Worldwide, called Dinoconda, is opening this year at China Dinosaurs Park in Changzhou, Jiangsu, China. This is only the third 4d ride with controlled spinning built in the last ten years.

Why are these rides called “fourth dimension” coasters and how is the spinning controlled? For those not familiar with this ride style, the seats are cantilevered on each side of the vehicle (as opposed to above or below the track) which allows the carriages to rotate 360 degrees. This controlled spinning or rotation is in a direction independent of the track – hence, it’s like a fourth dimension. There are two sets of rails – one supports the weight of the vehicles while the other is what causes the seats to rotate. Actually, the vertical distance or displacement between the two sets of rails controls the rotation of the passengers by transforming linear motion into rotational motion, accomplished via a rack and pinion gear.

The Secret is in the Gears

The pinion, a typical circular gear, engages the teeth on a linear gear bar, also known as a rack. Thus, as the spacing between the rails changes, the wheels connected to the rack move vertically up or down, causing the pinion gear (or gears) to rotate, flipping the seats as much as 720 degrees. Pushing the rack up causes the seats to spin one direction while pulling the rack down causes the seats to flip in the opposite direction. The amount of rotation is proportional to the displacement between the two set of rails. No separate power supply is required – the forward motion of the vehicle due to gravity is enough.

The pinion gear may actually use a complete gear box in order to achieve the perfect ratio of linear to rotation motion. Of course it’s not as simple as it sounds because there has to be some flexibility built into the system due to vibrations and imperfections in the manufacture of the rails. Future versions may see the use of rotary hydraulic motors instead.

how does a 4d coaster work

A) Rotation of Seats
B) Seat on Axle
C) Rack Gear

Check out this excellent close-up video of  the seat rotation on Dinoconda testing below:

To learn more about how coasters are designed check out Coasters 101: An Engineer’s Guide to Roller Coaster Design.

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