# Safe speeds in roller coasters

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1. Nov 15, 2015

### Lili123

From my research and understanding of roller coasters, their speed is mainly impacted by the force of gravity and it works on the basis of potential energy build up into kinetic energy. Therefore, my question surrounds the idea of safe speeds on coasters. Because a roller coaster car is only impacted by gravity, what is a safe speed and how might it be calculated? Is there an equation for this?
I have researched online and have yet to find any information regarding this topic.

2. Nov 15, 2015

### Orodruin

Staff Emeritus
It is unclear what you mean by "safe" speed. Roller coaster safety depends on many variables and a roller coaster will generally be constructed by competent engineers taking safety into account.

3. Nov 15, 2015

### sophiecentaur

The speeds of roller coasters are never very high. You must have done the sums. The danger is when you take a coaster and make it turn through tight curves, which increases the g forces (a = v2/r). The design needs to keep the forces directed down between the tracks - to avoid too much tilting. But there is a major issue with vibrations, structural strength and maintenance. Afaik, all accidents can be attributed to mechanical failure / maintenance and not the basic designs. (As long as people stay in their seats, of course)

4. Nov 15, 2015

### CWatters

People are more fragile than coasters.

5. Nov 15, 2015

### sophiecentaur

Oh yes, very much so. But the design g forces are pretty minute and even the speeds are pretty low. When there is no malfunction, they are surprisingly gentle with the passengers. I remember the fairground man walking around on the wavy platform of the "Waltzer" and casually taking our fares whilst we were quietly bricking it and holding on with white knuckles. He would spin the kidney shaped cars and make the girls scream with his ciggy in the corner of his mouth and a smooth grin on his lips, leaning in to the centre spindle. (He will be 80+ years old by now. lol.)

6. Nov 15, 2015

### CWatters

http://www.mirror.co.uk/news/uk-news/paralysed-teen-suing-gullivers-world-6804700

http://www.ncbi.nlm.nih.gov/pubmed/16271559

Last edited: Nov 15, 2015
7. Nov 15, 2015

### sophiecentaur

People make insurance claims for whiplash after the mildest road traffic shunts so looking for statistics of fairground injuries could give biased results.
But at least a car journey can usually be serving some purpose. Fairground rides are not compulsory and never serve any other purpose than to provide excitement. They look much more dangerous for most passengers than they really are (for most passengers). However, there will be people whose susceptibility to whiplash lies outside the normal range. A ride that's designed to keep everyone totally safe would have to be along the lines of a normal public transport ride. You can break a vertebra by doing loosening excercises.
People play rough sports and do rock climbing. They get injured. I question whether they are in any position to complain - assuming reasonable care has been taken. "Reasonable" care cannot exclude the possibility of injury.
It is easy to avoid fairground injuries - just stand (well back) and watch.

8. Nov 16, 2015

### CWatters

Agreed. My point is that a roller coaster could probably be made structurally safe at virtually any speed or g-loading, It's the passengers that would be the limiting factor.

I've ridden a few coaster and done aerobatics in small aircraft. On a coaster the g-forces due to bends and loops have always been modest but on one or two the short duration g-forces due to uneven track (?) were somewhat uncomfortable.

9. Nov 16, 2015

### sophiecentaur

SO we are singing from the same hymn sheet. That's always good.
Addressing the OP then. The fact is that you don't need excessive g forces if you want to provide an exciting ride but you do need to eliminate short duration g forces which can happen on transitions. These would be easy to neglect in an initial design. Rocking and fast tipping could do damage (like with bad driving).

10. Nov 16, 2015

### A.T.

This is a case where the rate of acceleration change (jerk) becomes relevant.

11. Nov 16, 2015

### sophiecentaur

Wing walking, too?
My biggest thrill was on my first parachute jump and it was from a De Haviland Rapide - a two engined biplane. You did the jump from a standing position on the lower wing (two suitable handles on the top wing). Only a few seconds to appreciate it and contemplate mortality then let go and a high g shock to the groin as the static like pulled you upwards by the harness to deploy the canopy. Then there was the high g landing. A really stupid thing to do, but young men in particular are attracted to that sort of thing.

12. Nov 16, 2015

### Staff: Mentor

Speak for yourself. I for one, avoid high G shocks to the groin.

13. Nov 16, 2015

### sophiecentaur

They played down that bit during the preparation training.