You are right, temperature can affect the running of a roller coaster.
In no scientist but from what I remember from my GCSE science days, the cooler the temperature, the higher the friction between the wheels and track, thus making it slower and increasing the chance of a valley.
That's why a coaster gets faster as the day goes on, especially on a hot, dry day. As the train runs around the track, the wheels and track warm up creating less friction.
Of course the material of the coaster needs to be taken into account as different materials react to different weather conditions.
I think I'm right, but I do expect loefet to come along and condem my GSCE science to hell :lol:
^No, you've basically nailed it. There is also the effect of materials expansion under heat, which might affect the track and the trains, however I don't know how much this would really change the running of the coaster under 'normal' hot weather.
^I might have to disagree with Intamin & woodie, because El Toro won't run in subzero temperatures. The minimum temperature I've seen it run is 2 degrees (C) & they had to use blowtorches to heat the wheels before testing the trains for a full 90 minutes in order to be assured it wouldn't valley. We waited the full 2 hours to be the first to ride it that day & I've never seen the Wild Bull run so slow. It barely made it around the circuit.
You also have to consider what type of lubrication is being used in the road wheels. Early season operation requires a much thinner oil. I use 5w oil for the first few weekends our boomerang is open. You can also make adjustments to the locking nuts that hold the wheel to the spindle. The lighter weight oil and an adjustment to the locking nut makes a huge difference.
As the temperature warms you can readjust the nut and move to 30w oil.
Some parks use Kluber grease in their wheels instead of oil. Grease does not work as well when the temperatures are colder.