OPERATING PRINCIPLE OF ROLLER COASTERS: CRAZY WORM

Updated 11.09.00

Click here to see how to assemble the Crazy Worm

Crazy Worm is only a short and low kiddie roller coaster but nevertheless it is still a proper roller coaster. Its technology is exactly the same as used in much bigger mobile coasters. Basically you could enlarge it simply by adding more track length and height. Once you understand how Crazy Worm and its components work you can also understand how the largest roller coasters work. As a matter of fact, the Crazy Worm is an excellent coaster to learn on. It's low, so you have easy access to all the components used for it.

Basic facts:

• Manufacturer: Sartori, Italy
• Length of the track: 138m (453ft)
• Height: 3.5m (11.5ft)
• Trains: 1
• Cars: 6 per train
• Passengers: 24 children or 12 adults
• Ride time: 1 min / circuit
• Moving power (lift hill): 8kW
• Lighting power: 3kW

Click images for larger picture

Step on board

The station slants slightly downwards. The train is sent along the track by releasing the brakes on the platform. There is a drop after the station that propels the train to the bottom of the lift hill.

Train on lift hill

Once it reaches the lift hill the initial energy of the train's drop from the station has been used up so it must be pulled up the hill by a motor.

Installing the chain

This image illustrates the operation of the lift hill. There is a chain revolving around the hill. It goes up above the track surface, and returns down under the track. The train engages into the chain from its belly and is hauled to the peak of the hill. The train moves clear of the chain at this point and is propelled by gravity to the end of the circuit.

Detail of the chain lift

In this picture the chain is almost installed. In the middle of the chain there are wheels that include ball bearings. These wheels make it possible for the chain to roll up the hill with a minimum of friction. There are pegs going through the wheels. The train engages to these pegs. Each peg can be installed and removed by a special tool like a bench vice, so there are no specific "ends" of the chain. You simply join the free ends and drive a peg through the holes. It's very easy to shorten / extend the chain if necessary.

Under the car

Some essential parts of the car are illustrated here. All these parts can be found in each car. The fork (A) is the "chain dog" which engages into the lift chain. Its arm is hinged, so the chain dog is able to jump over the first peg of the chain when the train reaches the lift but not move backwards. The advancing chain engages a peg into the fork and starts to push the train up. So, basically the chain lift is not hauling the train, it pushes it up the hill instead. When the train reaches the summit it requires no additional mechanism to release the chain.

Motor

This is the motor of the chain lift. The green part is an electric motor which operates using 3-phase mains power. It requires 8kW when operating. The blue part is a planetary transmission. It reduces the rotating speed of the motor to a speed suitable for the chain lift and increases the torque. There is a gear at the end of the shaft.

Gear

Detail of the same gear.

Chain, engine and tensioner

This is how the chain and the motor link together. The curved part above the chain is a tensioner which keeps the chain tight. Note the outgoing and returning chutes for the chain.

Gears on top of the lift hill

The chain rotates around these gears and returns towards the motor, which is mounted below the track.

Roll back arresters

The train is not allowed to roll back the lift hill if there is a malfunction. This is prevented by the anti-rollback device. The "ratcheted dog" is a claw-toothed bar permanently welded along the track, to the left of the chain. In the bottom of the car there is an arm (B in the image above) that is also hinged. It is able to jump over the arresters as the train moves forward. If the train starts to roll back, this arm catches on the ratcheted dogs and stops the train.

Train on circuit

After the lift hill the track falls away, propelling the train by gravity. Roller coasters are designed in a way that each downhill gives enough speed for the train to be able to climb the next incline. The train has no engine, nor has it any brakes...

Trim brakes

...but the track does. Trim brakes are used to control the speed of the train. The train goes faster if there are heavy passengers riding it, and vice versa. Weather conditions can also affect the speed of the train. The trim brakes are adjustable, so each train can be set to travel at the same speed. Crazy Worm has only one set of trim brakes, located in the middle of the "first drop". The adjustment is made by the ride operator. Larger roller coasters may have automatically controlled trim brakes.

Operating principle of the brakes

As with most other roller coasters, this one uses fin brakes. Like the brakes on a car, the train is slowed down by friction between the parts of the brakes. One part is on the track, the other is attached to the bottom of the train. This picture shows the brake segment of the track. There is a groove between the pads. The brake fins underneath the train run through this groove as the train passes over the brakes. The silver cylinder uses compressed air to open or close the gap, and so change the amount the train is slowed down by the amount the brakes grip the fin.

Brake fins

The picture is taken underneath the train. The brake fin (D) is affixed to the car and runs through the groove of the trim brakes.

Wheels

How does the train stay on the track? First, the wheels are hollow so they can withstand lateral forces on the bends without derailing. Second, there are upstop pads that ride under the track. They prevent the car from jumping off the track. Extreme hills on larger roller coasters might be able to throw the cars away from the tracks, so upstop wheels under the track are used instead of the pads so that the train is not slowed down.

Loading station

The brakes of the station (E) are similar to the trim brakes in the middle of the track. The bar (F) is used to release / lock the lap bars of the train. The bar is powered by pneumatics and it goes up or down accordingly.

Restraint locking device

The picture is taken at the station, underneath the train. The release bar (F) goes up and presses the release arms (C), thus unlocking the lap bars. When the bar goes down, all the lap bars are locked at the same time. Each lap bar has an individual release mechanism. If the train is stranded in the middle of the circuit, each lap bar must be manually released under the train.

Control panel

Welcome to roller coaster control. The buttons are:

• EMERGENCY, stops the lift hill motor and engages the brakes.
• START / STOP, controls the lift hill motor.
• COMPRESSOR ON / OFF, switches ON the compressor

For the pneumatics that drive the brakes and lap bar locking device.

• LIGHT ON / OFF, is a switch for the decorative lights.
• LAPBAR RELEASE, locks / releases the lap bars.
• PARKING BRAKE, switches ON the brakes in the station.

The potentiometers

• ADJUSTER, preset the station brakes or the
• DESCENT BRAKE, (trim brakes). The braking powers are indicated by meters.

Bottom of the control panel

This picture shows the pneumatic hoses from the control panel. There is an input from the compressor, and outputs for both brakes and for lap bars.

Train

It's time to board again, engage the lap bar and start another circuit.

The pictures were taken in Kerava, between 6-7.9.2000. Many thanks to Petri Sariola for the technical details of the ride, and also to the magnificent build up team Ossi, Jyri, Vesku and Luki, whose work I terrorized for two days with my camera. Special thanks to Mark Cook for helping me out with the translation.

Click here to see how to build up the Crazy Worm

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