Tim Pearson

I've skimmed though this forum and read some good points, Joel on page 6 mentioned that the motor's modern PLC should be capable of fault logging, and Jamberoo Fan noticed the widened slat interval on the conveyor belt. This should be a child friendly theme park. That conveyor belt should be driven by a motor exerting the minimum force necessary to move 2 groups of adults up that slope, nothing more. You never see an electric window on a car slicing some kids arm off. This is because the motor lacks the power to do something like this and also that newer / modern cars have pressure sensors on power windows. It might break their bones in a worst case scenario. The basic protection system that is essential here starts with the motor contactor that controls the otherwise powerful 3 phase motor. There is also an adjustable overload breaker relay that is fine tuned to cut out when the motor is slightly overloaded. Any motor up to 900hp can be controlled with this. A Schneider Electric 3 Pole Contactor - 115 A TeSys F, 3NO, 55 kW would cost about $1402. There is no reason why such a low RPM device couldn't cut out immediately. It's not going to stop the motor if a person gets their arm trapped inside the conveyor belt, but it would cut out if the raft was being broken apart. The system would require a cut out switch available to the staff supervisor as well as an extra onboard remote control fitted to the raft. On the other hand, this onboard remote switch could be used to activate the conveyor belt instead of emergency dis activation, making the system safer and less reliant on staff supervision. Then there are the actual mechanics of the conveyor belt. The drive mechanism should be utilizing some kind of cam cut out clutch or friction disc torque limiting clutch. When they get used on tractors they cost only AU$300 and are rated up to 40 HP, I can't see it needing much more power than this. Then there are all the water level cutout switches that are discussed. The news articles were correct in stating that kind of thing would cost $3000 to get installed. This is the only way to make something dangerous safe again. But also this is a fun park, I have no concern about rubber tube rafts being used. But they are no different to Kid's inflatable rubber ring tubes, they are just toys. If you were to send your kid down that conveyor belt death trap, you would use something like this: NASA’s Orion Deep Space Capsule https://www.nasa.gov/feature/nasa-s-orion-deep-space-capsule-in-pictures-top-10-images-of-2019 The Orion Deep Space Capsule features an epoxy resin with carbon fiber hull with a phenolic impregnated carbon ablator heat shield. It can survive space. It could also technically survive the thunder river rapids ride, however forces in excess of 350kpa of compression stress would cause hairline fractures, without collapsing the entire capsule though. Fracture in Phenolic Impregnated Carbon Ablator https://www.researchgate.net/profile/Parul_Agrawal/publication/260671234_Fracture_in_Phenolic_Impregnated_Carbon_Ablator/links/555b86a008ae6aea0816c677.pdf Generally the issue here is the formidable conveyor belt and people often downplay the danger of this secondary environment. People say just place a water level sensor at the end of the ride and know where the emergency button is. But really the conveyor belt is only conditionally safe when there is an adequate water level. Kids fall from boats all the time. Infact it's compulsory for them to wear jackets on small boats in Australia. But it's not the drowning risk I'm concerned about here, it's the crush risk that exists between the wooden planks of this dodgy conveyor belt. It's only conditionally safe when there is an adequate water level and it's assumed that kids will never fall off this raft into the water. Because it's a theme park used by kids it should be completely safe to children. A continuous rubber conveyor belt before it even start's to resemble an environment that it safe this way. The last method of protection by the system is the friction disc torque limiting clutch. Beyond that point of protection, that's when human intervention is required and a manual cut out switch must be used. But inevitably for safety reasons, it's a system that requires 100% constant staff supervision and control at all times, unless you're doing something more innovative such as allowing the people on the raft to control their own conveyor belt, because by default it shouldn't be moving, it's because it's moving that it's dangerous.

There's some pretty unsafe equipment been used there. That's what reading up on the incident led me to believe. In most industries, a piece of machinery will have something like a rollbar, to prevent it injuring its occupants. And then you look at that conveyer belt and its not a conveyer belt at all, its some industrial chain with planks of wood bolted to it. Its a deathtrap. All conveyer belts I've seen are continuous multi ply rubber and they have exit platforms, like you see at airports. You don't engineer a conveyer belt that way just cos its cheaper and easier to implement. A ride running 1000s of times a day has this statistical probability that makes it super dangerous.