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Re: Wheel Howl (not squeal)
Author: OldPoleBurner
Date: 01-02-2014 - 19:09
Since I was assigned to work on the property (BART) in the days when the first articles were delivered, all equipped with standard conical wheel treads which were very very quiet (scary quiet even) to anybody standing trackside; I have come to a theory about all that noise.
After the twelfth car was delivered, they started coming with non-standard cylindrical wheel treads, which were indeed a lot noisier, even then. This was supposedly because the ride (pitch & woo) was judged to be unpleasant. Rather than correct the dampening ratios, Bechtel came up with this solution. Of course, this means that no taper exists to help guide the wheels around curves. Flanges are all there is - much like a toy train!
Worse yet, the extreme rigidity of the trucks, and their inadequate dampening, was never fixed. Electronic studies of track circuit performance even revealed that wheels were routinely lifting off the rail by a few thousandths, breaking train detection, and probably accelerating corrugation effects. To my knowledge, nothing was ever done about any of this.
Moreover, even on tangent, both flange fillet radii must be in contact with gauge corners of the rail at the same time; in order to have any finesse control of the wheels. This leads to extreme wear on both wheel and rail; and indeed could be the cause of premature corrugation. Fact is, rail that should last nearly 100 million ton-miles (very light cars on heavy rail), continues to have a very short lifespan - much shorter than the average freight line. BART track is thus inordinately expensive to maintain; not to mention the systemic train control problems caused by wheels that can't keep the rails clean of rust. Rust beads were common on rail tops, for several years until the wheels were worn-in to a natural taper. (caused by the cant of the rail as seated in the tie plates).
Sometimes it just doesn't pay to re-invent the wheel! Especially, when it was already working just fine, and was not the problem. Not that anyone at Bechtel knew anything about that - or cared. They just ignored us young troglytes with any rail experience!
After the twelfth car was delivered, they started coming with non-standard cylindrical wheel treads, which were indeed a lot noisier, even then. This was supposedly because the ride (pitch & woo) was judged to be unpleasant. Rather than correct the dampening ratios, Bechtel came up with this solution. Of course, this means that no taper exists to help guide the wheels around curves. Flanges are all there is - much like a toy train!
Worse yet, the extreme rigidity of the trucks, and their inadequate dampening, was never fixed. Electronic studies of track circuit performance even revealed that wheels were routinely lifting off the rail by a few thousandths, breaking train detection, and probably accelerating corrugation effects. To my knowledge, nothing was ever done about any of this.
Moreover, even on tangent, both flange fillet radii must be in contact with gauge corners of the rail at the same time; in order to have any finesse control of the wheels. This leads to extreme wear on both wheel and rail; and indeed could be the cause of premature corrugation. Fact is, rail that should last nearly 100 million ton-miles (very light cars on heavy rail), continues to have a very short lifespan - much shorter than the average freight line. BART track is thus inordinately expensive to maintain; not to mention the systemic train control problems caused by wheels that can't keep the rails clean of rust. Rust beads were common on rail tops, for several years until the wheels were worn-in to a natural taper. (caused by the cant of the rail as seated in the tie plates).
Sometimes it just doesn't pay to re-invent the wheel! Especially, when it was already working just fine, and was not the problem. Not that anyone at Bechtel knew anything about that - or cared. They just ignored us young troglytes with any rail experience!
