Every train I inspect seems to have lots of them. Even right after departing a major terminal that has a car shop and lots of maintenance employees and equipment.
I've thought for some time that the thresholds on our WILDs are set too high.
As has been mentioned, the most common way for flat spots to form on cars is being moved while empty with the handbrake applied. Locomotives get flat spots too, but this is usually caused by heavy Independent brake applications while switching, 50 PSI in the brake cylinder is usually about where they lock up when the throttle is in idle. I try to avoid harsh Independent applications like that, but a lot of guys just don't care.
No matter how, once a flat spot is formed the wheelset will tend to stop on it, and the flat spot will get slightly worse with each successive stop.
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-an Articulate Malcontent
I've always used 5 cars. Most flat spots on cars happen because they are moved with the hand brake applied so hard the wheels don't turn. It doesn't take much to start the flattening.
(It was mentioned once at a rules class that one rule required releasing the hand brake before moving a car. Then another rule, when spotting a car on a stub ended track, to apply the hand brake to help control the movement when approaching the end of the track.)
I don't think there are any less flat spots now than in years past. A lot of times I've mentioned to my conductor about a passing trains having some cars with almost round wheels.
There have been cases where the flat spots were so bad that they've changed the wheel out right on the main track. I just heard about that happening a week or two back.
Jeff
Detection by WILD notwithstanding, there are parameters for judging flat spots.
From NORAC: Flat Spots If a flat spot on a wheel of a car or engine develops en route, a member of the crew must inspect it. Upon completion of inspection, the train will be governed as follows: a. Proceed at Normal Speed: The train may continue at Normal Speed if no other defects affecting movement are observed, AND if: 1. The flat spot is less than 2½ inches in length. or 2. If there are 2 adjoining spots, each is less than 2 inches in length. b. Proceed at 10 MPH: If a flat spot is found in excess of either of the above dimensions, but less than 4 inches, and no other defect is observed, two actions must be taken: 1. Speed must not exceed 10 MPH. 2. A report must be made promptly to the Dispatcher or Operator. c. Remain Stopped: If a flat spot of 4 inches or greater is found, the train must remain stopped until a report is made to the Dispatcher or Operator. When determined safe for movement, the Dispatcher (or Operator when authorized by the Dispatcher) will order the car or engine to be set out at the first available siding or terminal.
A rule of thumb that I've heard is that if you can hear the flat spot for seven cars or more in a passing train, it needs attention. You won't find that in a rulebook.
You'll often encounter flat spots on lighter empty cars - flats, centerbeams, etc, on which the weight of the car can't overwhelm the friction of the brakes.
Larry Resident Microferroequinologist (at least at my house) Everyone goes home; Safety begins with you My Opinion. Standard Disclaimers Apply. No Expiration Date Come ride the rails with me! There's one thing about humility - the moment you think you've got it, you've lost it...
Wheels being slid on top of the rail cause flat wheels. It may be a hand brake that wasn't released. It may be a car on which the air brakes didn't release.
In the past decade, the Class 1 carriers have installed a number of Wheel Impact Load Detectors - which measure the force with which wheels impact the rail passing over the detectors. On CSX they identified 4 levels of impact - Level 1 is a basic notification that a wheel has a minor flat spot and no further action is required. Level 2 indicates that the wheel is even flatter - CSX maintains a data base on each car and tracks the increasing levels or the repairs to the cars, no further action is required of Level 2 flat spots. Level 3 flat spots are more severe than level two. The Mecanical Dept. through the Train Dispatcher notify the crews of car(s) in their train that have attained Level 3 - those cars are restricted to 30 MPH from time of notification to destination and at destination they are to be repaired (wheel replacement) by the Car Dept. Level 4 are the most severe - th notification chain is the same as for Level 3, the restrictions applied to Level 4 are that the train must be stopped, the car inspected by the crew - if safe to proceed, the car is to be set off at the first opportunity and the train is not to exceed 10 MPH until the car(s) are set out. The cars will be rewheeled by the Car Dept. at the set off location.
In tracing car records, I have found empty cars registering Level 2 on their way to the mines, the same car registered as Level 4 under load on the return from the mines. The level of lading in a car affects the battering a flat wheel administers to the rail.
Never too old to have a happy childhood!
What causes flat spots on wheels? They don't appear as common today as years ago when most trains had at least one car that went thump thump thump down the track.. sometimes hard enough to shake the ground under one's feet.
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