Cracked roller coaster in North Carolina

[BrettMRC]

https://www.bbc.co.uk/news/av/world-us-canada-6608...

The root cause investigation in this one will be interesting!

[Panamax]

Metal fatigue. A loaded coaster train has substantial mass to start with and under "G" will be pushing very hard against the track and its supports.

Any of,

• Faulty design (unlikely, the physics of these steel coasters should be well understood)
• Faulty steelwork
• Faulty construction (unlikely, it's difficult to see how it could have been built with too much stress already in it)

[57Ford]

Lessons learned: Suggest installation of weighbridge in load station.

[BrettMRC]

EmailAddress said:

Stress fracture, poor weld.

Next.

Possibly, but the RCA outcome may have implications for a lot of other installations.

[Panamax]

EmailAddress said:

Stress fracture, poor weld.

We're in the same territory. Do you think it went with a bang (fracture) or slowly crept across (fatigue)?

On balance I guess fracture is more likely since these coasters undergo rigorous inspection on a regular basis.

[pghstochaj]

EmailAddress said:

Stress fracture, poor weld.

Next.

Perhaps, but a stress fracture is not a root cause, it's the failure mechanism as a result of the root cause. Having been through a very similar situation with substantial losses (£100M+) as a result, I would point out that there are other possible causes:

- Fundamental design error
- Fabrication not following the design
- Fabricator causing some minor damage which has allowed a fracture to have a starting point (this can be as little as a very slight cut into the steel)
- Incorrect specification of weld (instead of poor quality of weld)
- Poor quality steelwork or filler (or incorrect storage of filler)
- Poor management of heat during welding
- Post weld heat treatment (if any) not done correctly

Of course some of those come under "poor weld" in general.

In my case, the failure was a fundamental design error coupled with the fabricator modifying the design slightly (exacerbating factor only) and use of poor(ish) quality steel (exacerbating factor only). If the design error had not been present, the secondary factors would not have been noticed as the in-built safety factors would have meant that there was no problem.

[andy43]

57Ford said:

Lessons learned: Suggest installation of weighbridge in load station.

I'm assuming the engineer that designed the load specs was aware it'd be used in America?