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| Once the
coaster cars are brought in the shop, they are disassembled. Certain parts, such as
the wheel housings, hitches and frames get tested on a regualr basis by using a method of
"Non-Destructive Testing" or NDT. Examples of
NDT are: Magnetic Particle tests, where industrial
electro-magnets are used to detect surface cracks in a steel object by the attraction of
metal powder to cracks. Cracks interrupt the flow of the magnetic force, thereby drawing
the powder right to the damaged area. Defective parts are
discarded or professionally repaired. A second form of NTD is Dye Penetrant. This uses two forms of ink in spray cans. A white and red spray are used one after the other, which highlights surface cracks by soaking the red color into the crack. For any of these tests, the surface of the part must be sandblasted and completely clean in order to test properly. The two forms of NDT mentioned are only useful when detecting cracks on the surface of a part. If you need to test a solid part, which could potentially have a crack or defect which is actually inside the object and not exposed on the surface, then other methods are used, such as an "Ultrasound" or even an X-ray. An ultrasound test is done usually on large shafts or unusually odd shaped parts that can not be completely disassembled or inspected. A wet flux material is applied to the part, kind of like when you get an ultrasound to see your unborn child, and then the probe is moved across the surface, which sends the electronic image back to the monitor, giving the trained professional an image of the inside of the part. This test is more challenging and time consuming, because the person doing the testing needs measurements and drawings of the object as he does the test, so he can understand what he is seeing. It does not show a 3 dimensional image like you are used to at the doctor. It basically takes instant measurements from the probe to the back surface of the part, and if there is a defect, it will give a shorter measurement than would be expected. |
|
Below, you can
see how the Dye Penetrant test is used on the high stress
areas of the lower frame of this coaster car. Notice the white "spray paint"
look on the black frame in the foreground of the photo. That is part of the dye
penetrant test. Cracks would typically form in corners or angled parts, which can be
hard to see if the cracks are small...hence the test. |
|
There are many things that need to get done when re-building a roller coaster. Obviously, the winter doesn't last forever and the mechanics also have other rides to rehab, so they need to budget their time wisely as they work. As one car is being tested, another car is being taken apart in the meantime. The wheels all come out of their housings, upholstry gets repaired, lap bars and restraints get taken apart....and so on.... |
