Posted by Rod Williams on October 4, 2007
What is holding those cars on the road ? That wobble is nothing short of frightening. Last time I saw a car doing that it had a fractured wheel and was about to come to grief. |
Posted by Joel Hinkhouse on January 28, 2008
The wobble on some of those cars (the 2nd car, in particular) is particularly disconcerting. How does that car stay on the tracks? |
Posted by truck hunting on July 17, 2008
The "wobbling" that you see in this video clip is a phenomenon called "truck hunting". It is quite common. The Transportation Test Center in Pueblo, Colorado has studied truck hunting and offered several observations and conclusions. First of all, truck hunting is the result of a combination of factors: worn truck components (i.e. bolsters, sideframes, wedges, snubbers, etc.), worn wheel profile, irregular track gauge, irregular track surface conditions, worn rail profile, etc. While it is quite possible that none of the component factors are outside of FRA safety standards, they can combine to create rather severe truck hunting.
Loaded freight cars do not experience truck hunting nearly as much as empty cars. Freight cars that are longer than 70 feet do not experience the harmonic effect of truck hunting as much as shorter cars. Radial trucks do not experience truck hunting as much as conventional box-frame trucks. The critical speed which causes the most severe truck hunting is about 57 MPH.
The solutions offered by the TTC have been very effective at preventing derailments. While the solutions do not eliminate truck hunting, they do allow safe operation. Limiting the speed of trains carrying empty cars to 50 MPH has been adopted by every major railroad in North America.
More agressive freight car truck maintenance would eliminate most of the "bad performers" of truck hunting, and the latest generation of lineside automatic defect detectors can identify these cars. Railroads nationwide have adopted more frequent rail-profile grinding to help reduce truck hunting. Rail-profile grinding also reduces rolling resistance (reducing fuel consumption) as well as lengthening rail life by controlling gauge corner cracking (which, if left unchecked, leads to rail failure).
Tom Dupee, locomotive engineer, CSXT |
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