Fairground rides and how they work

Carousel ride

Parts of a carousel ride

Geared motor: This is a DC motor (AC in the real world) that is geared, so it has a low RPM and high torque.

Wheel and axle: The carousel ride connects a wheel and axle to the motor. The wheel is connected to the carts.

Carts: These carts are held by support structures that can bend (mechanical piston in the real world) and keep the cart on the same orbit around the wheel, despite the bumps.

Bumps: A series of elevations in the path of the carts, to create changes in G forces for the riders.

Pole: A pole attached to the wheel that helps balance the ride, but mainly is there for visual appeal.

How does a carousel work?

A carousel ride is powered by a motor. In the model, the motor is directly connected to the wheel, however in the real model the motor can not produce that much power, so it is connected via a chain to the wheel to reduce RPM and increase torque. The real one also has mechanical support structures, with an actuator and a servo motor in each one to maintain the cart’s path. Each cart experiences equal centripetal and centrifugal forces, which keep it in the middle and it’s velocity at any constant is exactly perpendicular to the support arm. This allows it to rotate and maintain it’s path while constantly changing elevation. This continuous change of elevation changes the G forces. Climbing increases the G force, pushing the rider into the seat and descending reduces the G force, creating a slight feeling of weightlessness.

Pirate ship ride

Parts of a pirate ship ride

1- Geared motor: This is a DC motor (AC in the real world) that is geared, so it has a low RPM and high torque.

2- Ship: The ship is suspended by two beams on both ends and has rows of seats reducing in size from the centre to hold passengers. The centre of mass is exactly at the centre of the ship.

3- Wheel and axle: The motor is connected to an axle, which rotates when the motor does. This is a wheel and axle system.

4- Supporting beam: The ship is supported by two beams that are firmly attached to the axle, and will rotate around the axle when the motor is operated.

Forces that act on a pirate ship ride

Pirate ship rides are specifically designed to have different forces acting on them, to create different G forces for the rides to get the ‘thrill’ feeling. The centre of mass, or the centre of gravity is located in the middle of the ship, and as it rotates around an axle, a few forces affect it.

All objects that revolve around a centre of rotation have centrifugal and centripetal forces acting on them, with these pushing the object out and pulling it to the centre respectively. The two forces cancel each other out, and allow the object to rotate, but in the pirate ship ride, as with the ferris wheel, the two forces change, and create higher and lower G forces for the rider. When the ride is started, the ship’s velocity or path of inertia pulls it up, but gravity cancels that motion and so the motor is required at all times to keep it running.

5- Supporting structure: This structure supports the motor, axle and the ship.

Ferris wheel

Parts of a ferris wheel

Geared motor: This is a DC motor (AC in the real world) that is geared, so it has a low RPM and high torque.

Pulley system: The ferris wheel uses a belt drive pulley system that connects the axle of the ferris wheel to the motor, to transfer the rotaty motion of the motor to the wheel.

Wheel and axle: The ferris wheel is the wheel that is connected to an axle, so it can rotate freely when force is applied.

Carts: These carts are suspended on rods that connect the two faces of the ferris wheel. Due to gravity, the bottom of the cart is always parallel to the horizon.

Supporting structure: This structure supports the whole wheel and axle, allowing it to rotate freely and suspending it above the ground.

Forces that act on a ferris wheel

A ferris wheel relies on gravity for full rotation. The motor only drives it 180˚ up, and gravity covers the other 180 degrees. This is because the centre of mass is balanced on a single beam, and the wheel is designed to self centre, which allows gravity to operate half the rotation of the wheel. Due to the circular motion of the wheel, it faces centripetal acceleration horizontally and centrifugal acceleration vertically. Calculating the forces with the formulas !1 = $(& ( ) and !2 = $ & + ( shows that a rider will experience G forces between 0.5 and 1 at the top; 1-1.5 at the bottom; and exactly 1 at the sides. This means that riders will feel slightly weightless at the top and pushed down into their seats (heavy) at the bottom.

Drop tower

Parts of a drop tower

1- Geared motor: This is a DC motor (AC in the real world) that is geared, so it has a low RPM and high torque.

2- Tower: The tower is what holds the motor and pulley system up, and allows the cart to climb up, guiding it.

3- Cable: There are two cables connected to the pulley system that pull the cart up, and let it drop. The cable is strong, in order to support the weight of the car.

4- Pulley system: The cable is attached to a pulley system that allows the rotary motion of the motor to pull the cart up and let it go down.

Forces that act on a drop tower

The drop tower is also called the freefall; however, the cart is actually not dropped. The fall is controlled by the motor, as any other means of stopping the cart from smashing into the ground would be impractical. For example, magnets are incredibly tricky to work with, thanks to the whole ride being built from metal. The ride up is slower, because of the force required to lift the cart up. The drop is much faster, and gravity assists the drop, along with the motor power. The velocity at this stage is completely facing downwards. The drop tower is cleverly engineered to create a G force that is less than 1G, which creates a feeling of weightlessness for the rider.

5- Passenger cart: The circular cart holds passengers around it. It gets pulled up and down by the cable.

Cable car

Parts of a cable car

1- Gears: These two gears are used to force the cable to move. One is connected to the motor, and both are grooved (to increase friction and grip with the cable).

2- Geared motor: This is a DC motor (AC in the real world) that is geared, so it has a low RPM and high torque.

3- Cars: These are suspended by strings and attached to the cable. They are there to hold passengers and have windows.

4- Strutures: These supporting structures hold the motor and the gears. They are firmly attached to the base and are connected with a rod.

Forces that act on a ferris wheel

When constructing a cable car, designers have to pay close attention to the tension of the cable, and there is a very specific formula to calculate it. If the cable is too loose, gravity will overcome the cars, and they will be pinned to the bottom of the gear, creating friction and preventing movement.

If the cable is too tight, the friction force will be so high the cable will not move. The right balance will ensure that there is enough friction to maintain contact between the gear and the cable, but no so much that the cable can’t move. Each of the cars has gravity acting on it, which is cancelled by the cable tension, and the motor power moves it. They have aerodynamic drag (air resistance) affecting them, and so have a streamlined design. The force exerted by the cable needs to be stronger than the air resistance in order for the car to move. The car is freely suspended underneatch the cable and is designed to smoothly revolve around the gears when that part comes. The cable car gives a beautiful view to passengers in the theme park, but in mountains it is really useful for taking people up and down.

Disk o ride

Parts of a Disk’o ride

Geared motors: These are DC motors (AC in the real world) that are geared, so they have a low RPM and high torque.

Pulley system: The Disk’o ride uses two pulley systems to pull the passenger car both ways. It connects the two DC motors with two cables to the car. It converts the rotary motion of the motor to the linear motion of the car, with the use of a pulley and a cable.

Wheel and axle: The passenger car supports another motor, which rotates the passenger wheel. The wheel is connected to the motor through a wheel and axle system.

Car: The passenger car has four wheels, that are connected to two axles and can freely move, but needs the power of the cables.

Tracks: The track supports the car and is slighly rough to increase traction from the car.

Forces that act on a Disk’o ride

As the disco ride contains two moving parts, it has two sets of forces. The rotating passenger wheel contains seats. Each seat has a centripetal force (pulling it to the centre) acting perpendicular to it’s velocity (and path of inertia). Opposing the centripetal force is the centrifugal force, which is pulling away from the centre. These two forces oppose each other and keep the seats in place. The whole passenger car (in the direction it’s travelling) has the power of a motor pushing it. The other one just releases the cable. When the cart is going uphill, gravity acts against it, and vice versa. The velocity is pointed at the direction of travel. The uphill part of te ride creates a G force higher than 1G and when travelling downhill, a G force lower than 1 G. This creates a feeling of being pushed into your seat, and feeling slightly weightless respecitvely.

Mechanical advantage

Carousel ride- Wheel and axle

Pirate ship ride- Wheel and axle

Ferris Wheel- Pulley, wheel and axle

Note: As this pulley uses only one wheel, it’s MA by default is 1. If more than one wheel is used, the MA= Load/Effort.

Speed calculations

Drop Tower (uphill+downhill)

Cable Car (one revolution)

Disk’o ride (one way)

Drop tower Distance-time graph