Posted Friday, October 14, 2005 12:58 AM | Contributed by PhantomTails
The collision of two trains on the California Screamin' roller coaster at Disney's California Adventure, which sent 17 riders to the hospital, was caused by air leaks in the braking system, according to a state report released Thursday.
Read more from KNBC/Los Angeles.
Tekno- What would neutering the ride have to do with the cause of the accident? No restraints failed. The brakes simply failed. What could they change in the ride experience? Its not a matter of heavier braking- Screamin' had no trims at all through the course to this point.
Hopefully the only change that happens is behind the scenes, with Disneyland really getting proactive with their maintainence procedures and practices.
Besides, there isn't much else they could do to tame that ride down anywho, unless they cut out the loop and the 2 bunny hills at the end (for me, the only redeeming qualities).
Many people were writing off the complaints of "disillusioned former cast members" but I wonder if they should have been taken more seriously.
I mean, shouldn't the air leaks have caused the brakes not to open?
I think most fin brakes on coasters are pneumatic, meaning they use air pressure to open and close the brakes. However I am not sure of the details of how these brakes work. Meaning I am aware that there is a fin below the car, and the brakes open and close and thus clamp the fin in response to the control system and air forcing the brakes to due such action.
So since the control system, was aware of the alarm, and eventually E-STop the ride, the brakes were trying to be put into closed postion. However due to a lack of pressure because of a leak, the brakes did nothave to chance to completely close or only some closed. This appears to be the cause ofthe colission. I also thought that the default position for brakes was closed, but wonder if they were open for allowing train to go from unload to station, or something along those lines. Like in braking sequnce, they go from open to close very rapidly and the control system is probably designed to make it a smooth entry from unload to load.
Also I am not familar with the ride, but quite a few rides have drive tires used in conjuction with brakes, to move train from one place to another. Also magnetic brakes are used on a few Intamin rides before actual fin brakes, to trim speed. Even the Beast at PKI uses magnetic brake before the actual brakes on the bridge to help trim speed and make for a smoother stop.
So I have a few questions for anyone more familar with this ride than me:
1. Where exactly did the colission occur and at what speed was the train going (I am assuming one was at rest)?
2. Does the ride have magnetic trims right before the pinch brakes on the brake run?
3. I don't understand how this can happen, maintenance always checked air pressuer on the Beast at PKI everyday, how can you do that and not notice something wrong. Also I wonder about the control system and ride operators. I just think if there is a low pressure alarm, you shut down the and call a mechanic/maintenance worker to look at the problem. If people were on the ride, you could either evacuate if necessary, or if there is sufficient pressuer, just cycle them off, and keep the ride closed till problem is corrected. So this is sort of a long question I guess, but isanyone really familar with the details of the control system or maintenace procedure that Disney uses for this ride?
*** This post was edited by Beast Fan 10/14/2005 2:57:32 PM ***
We DID think the same thing when it happened on RoS....while Disney certainly takes a hit or this one (and deservedly so I'd say), the DESIGN flaw is Intamin's....
As always, IMO, YMMV, etc.
What a crappy design. That's just asking to hurt people.
There is a report on the 'Net that describes the problem in great detail. I'm not going to get into a lot of detail here, but it was apparently an intermittent failure of an automatic dump valve attached to the brake actuator, a failure caused by a normal action of that valve. Disney is changing to a different type of valve.
Essentially, it's the valve that empties the actuating cylinder when the brake is released. That valve also allows some air to come out of the system in relief when the train smashes into the brake caliper at high speed. With some versions of the valve, the train entering the brake can cause the valve to stick open, dumping the supply pressure instead of maintaining pressure on the actuator cylinder. It's an intermittent failure that is impossible to detect during normal maintenance testing.
--Dave Althoff, Jr.
This is contrary to the norm for coasters and most industrial safety systems in which air is used to release safeties rather than to apply them.
Th only common safety system I know of that operates this way is the brakes on trains. However, train brakes are designed to apply the brakes from pressure in a resevoir if the air supply pressure drops thus a lack of supply pressure results in a safe condition. Also, trains have a separate brake system on each car and are therefore operating with many brakes, resevoirs and control valves on a given train resulting in the failure of a single brake system having little effect.
Oddly enough, the diagram in the report I read (it isn't a DOSH report, by the way...I'm not going to post the link, but it is presented as a manufacturer's bulletin, so you ought to be able to find it) seems to indicate that the brakes require pressure to move them to either position. In this case, it wasn't a loss of air pressure in the system that caused the failure, but rather a failure of the dump valve on the side of the system that applies the brakes. The valve is there in order to get quicker response from the system when moving the caliper. Also, it appears to serve as a 'pop-off' valve for the high-pressure spike when the train pushes the caliper open. If the valve were simply removed and replaced with a pipe fitting, the brakes would still function, but more slowly, and the aforementioned spike would be more likely to do damage to other components of the system.
--Dave Althoff, Jr.
My question becomes....shouldn't a set of brakes then have some sort of redundancy check...such as several 'pressure' sources in this case? I know I am not a ride-designer, but, it seems to me that if they were able to identify the potential problem, and develop a portion of the ride control program to identify and e-stop the ride in such a case, that they would have designed with that in mind.
I guess it does all come back to poor preventative maintenance. Correct me if I am wrong, but, the failure of one valve should not have caused this accident. There had to be several valve failures...or does one valve control a whole block of brakes?
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