Why Do Rollercoasters Run Faster On A Hot Day?

[robinschroder]

I was explaining to a friend of mine how Expedition GeForce and Balder always run better on hot days, especially towards the end of the day once they've had chance to warm up. He then asked why that was, arguing that if anything he'd expect a steel rollercoaster to run fractionally slower as a result of the fractional expansion in the steel track against the wheels due to the increase in heat! Ha ha - I wasn't really able to answer, except to say that they do definitely run better on a hot day and then I mumbled something about "Er... it's probably to do with the Polyurethane wheels"...

 

Now - why is it that rollercoasters generally run better on a hot day, or at the end of the day after having had the whole day to warm up? Is it down to the wheels? Or is something else at play? It doesn't really matter of course, as long as GeForce and Balder are running nice and fast to maximise our airtime opportunities - but I'm sure one of you will know... please enlighten me! Thanks!

[coasterlover420]

It doesn't necessarily have to do with the polyurethane on the wheels, but it is pretty much all about the wheels. It is basically the temperature of the bearings within the wheel and all the grease that is in there to keep them slick. When grease is heated it is a lot more fluid, whereas when it is colder, it is more like molasses. Not really to that consistency, but you get my point.

Of course, if you want to bring wind resistance into account, it would probably change the speed a very slight amount simply because cold air is more dense than hot air. That's not usually the biggest factor, though.

 

Another general theory is that wood coasters run faster after it rains. That's pretty much true because when flat metal track is wet, the wheels basically hydroplane (they are lifted off the track by water), whereas on steel coasters (well newer ones...) the wheels are firmly fixed to the track so there's no way they could be lifted up by water.

[palmerleeberry]

Why Do Rollercoasters Run Faster On A Hot Day?

 

I always thought rollercoasters run faster at night ( at least that's what my riding friend always say to me whenever we ride a rollercoaster at night. ), so I think it has to do with the track temperatures and the way that heat causes things to expand and cold causes thing to retrack. I don't have an answer, but we riders always love it when a coaster goes super fast. Maybe someone could do a study on this; I think it's worth an experiment or two.

 

"I would like to do an experiment: just lie your head upon me and fall asleep.

[ginzo]

As described above, there is less friction in the wheel bearings the hotter it gets. Also, magnetic trim brakes convert kinetic energy to thermal energy. When it's hot out, this happens to a lesser extent because of the excess of heat in the environment. So, the trims are weaker on coasters like EGF when it's hot.

[hyyyper]

Why Do Rollercoasters Run Faster On A Hot Day?

 

I always thought rollercoasters run faster at night ( at least that's what my riding friend always say to me whenever we ride a rollercoaster at night. ), so I think it has to do with the track temperatures and the way that heat causes things to expand and cold causes thing to retrack. I don't have an answer, but we riders always love it when a coaster goes super fast. Maybe someone could do a study on this; I think it's worth an experiment or two.

 

"I would like to do an experiment: just lie your head upon me and fall asleep.

 

Well, recently there was a 24hr marathon on Troy in Toverland. And during the night, the ride was indeed as fast as it had ever been. A lot of the energy created by the friction of the ride for half a day, makes the lubricant more 'slippery', like coasterlover said.

 

However, at a certain point in the night, the temperature drops which cools down the ride faster than it can warm up. Expansion/contractions doesn't seem likely, as you need a much higher temperature difference for that to become a factor. Also, you will notice that many tracks have little gaps between track segments to expand freely.

[robinschroder]

Interesting stuff - thanks for the replies!