Coaster101: What influences train speed?
Welcome to Coaster101! This is the start of a new series where we will be examining different aspects of roller coaster design in detail. Our first topic is train speed. There are several factors which affect the speed of a roller coaster train, the most prominent being the height of the largest drop or the power of the launching mechanism.
Why is speed important? If the train is going too slow it may not make it around the track. Too fast, and the forces on the riders may be too great. Several other factors that can influence the roller coaster train speed:
- Temperature – The lower the temperature the slower the train.
- Wind – The direction and speed of the wind affects the speed of the train (and sometimes forces parks to close the ride until conditions are safe to operate).
- Load – A loaded train (with weighted water dummies or people) will go faster than an unloaded train.
- Wheel Bearing Clearance – Correct assembly of the wheels reduces internal friction and heat.
- Wheel Bearing Lubrication – The amount and type of grease affects the speed of the train.
Track Lubrication – If the tack is lubricated the train will travel faster due to less frictional head losses. Track lubrication also prevents excessive wear to the rails and the wheels, especially those of wooden roller coasters.
These factors play larger or smaller roles depending on what ype of coaster you are looking at, wood or steel. For example, track lubrication is primarily a concern of wooden coasters whereas wheel material is a bigger factor for steel rides.
Some of these factors can be controlled by the park, such as the number of guests they allow on the train as well as when to use lubrication. Other factors cannot be controlled, such as temperature, wind (unless built entirely indoors), and the natural lubrication affect of rain.
Time of day is another factor of influence, especially on a wooden coaster. This is usually directly related to temperature. In the morning, the trains have been sitting cold all night and haven’t warmed up. Often times towards the end of the year, amusement parks will “deadweight” the coasters just to get them around the course. It’s due to the temperature of the wheels- if they’re cold the ride runs a vast amount slower than if the ride’s been running all day. It doesn’t make as much of a difference if the sun has been out for a while and the track is warm, because then the wheels will warm up faster. It’s because of this that enthusiasts like to ride at night; warm wheels mean faster rides.
Also, most coasters have set maximum and minimum values for the duration of the ride. Running too slow and lubrication is applied, too fast and trim brakes are engaged. There are also different types of greases to use depending on the time of year. Tune in next time for the next edition of Coaster101!
To learn more about coaster design read Coasters 101: An Engineer’s Guide to Roller Coaster Design.