kenwa said:
My guess for the problems is excessive vibration causing the break fins to fracture close to where they attach to the tower. I rode the thing awhile back and noticed many little circles on the fins drawn with a Sharpie. When I was closer I could see the cracks in the circles, made me think twice before riding.
That's interesting.
Magnetic break fins live a hard life. They experience high physical stresses due to the obvious force loading required to stop several tons of plummeting ride vehicle, and additionally (depending on design) they can face incredibly high temperatures due to all that kinetic energy being converted into heat. A lot of that heat dumps into the fins and their temperatures rise quickly. Even if high temperatures fall far short of warping/melting/burning a material, they still can change its properties, both during and after the high-temp stages of use. The material expands and contracts over and over, and at the microscopic level a lot goes on that can leave a component in a different physical state from the day it was made. An experienced designer gives careful thought to all of these things.
Vibration is a kind of interesting one. On a moving vehicle I'd expect a brake fin to experience far more vibration than a fin mounted to the side of Mach Tower. The operation of the ride surely will generate vibrations in the tower which will transmit to the fins, and the process of actively braking the vehicle may cause some complex and interesting vibrations despite there being no direct physical contact between vehicle mounted magnets and tower mounted fin. But the Mach Tower fins don't see the same dynamic vibrating loads you'd see in a fin that is attached to the
vehicle.
Anyway, these various stresses are applied cyclically, over and over, all day long when the ride is running. That can cause material fatigue, in which even comparatively lower mechanical and thermal stresses applied repeatedly can cause something to crack or otherwise fail in the long run. Bend a paper clip back and forth a bunch and you'll see it in action: the damage accumulates over time until it snaps. Bend it just a bit and it lives forever; bend it more aggressively and it eventually breaks; bend it back and forth like crazy and it breaks within just a handful of cycles. In fact there are a lot of variables that determine the safe lifetime of a component under cyclical loading. Fatigue analysis an entire sub-discipline of engineering design, and an important one.
Much of the mechanical design process deals with staying FAR FAR AWAY from these material limits, akin to keeping the paper clip cool and un-bendy. Engineers have a lot of rules and tools on hand to keep their products out of reach of failure events - not just barely, but by a lot, just in case. That assumes the engineering is done properly.
Looking at photos of the mag break fins on Mach Tower, it appears that they are replaceable bolted-on items. That doesn't mean the park would care to incur the time, expense, and headache of doing so regularly, but clearly it's possible. Those fins probably have a design life that is shorter than the design life of the ride, being intentionally replaced multiple times as years go by. I would assume that the intended replacement interval is supposed to expire
before significant quantities of cracks appear in the fins - hence the efforts to circle them for inspection and documentation. Somebody's talking to somebody.
But, you know, to be an ignorant-yet-fair armchair analyst pretending to know what's going on: Any cracks in the fins could be superficial surface cracks. They could be due to an anomalous event. They could be well understood and within the performance spec of the ride (though I'd be slightly surprised by that last bit). They could be a lot of things.
Or they could be indicative of another problem with a seemingly problematic ride system. Dunno.
