Not-so-noisy trains?

ahendy's picture

Today I rode BART from Macarthur to Powell for the first time in probably about a month. Going through the transbay tube was usually pretty unbearable because of the noise. But today, it wasn't bad at all. In fact, I didn't hear any of the normal bart SCREECHING that is usually heard. Sure, it wasn't silent, but it sounded like a high speed train should, not horrible screeching like I used to hear. Maybe it was my train (didn't catch the car number), or maybe they've been working on the rails?

Anyone else notice? It seemed quieter on the way back to the east bay too, although it never seemed as bad that direction anyway.

Train Operator since 2003's picture

The rails in the tube were worked on the last couple of weeks while you were sleeping.

ahendy's picture

Excellent. So the whole rail-grinding thing has actually shown to improve the situation, eh? I know a lot of people were skeptical about it, quite a few people thought that rail imperfections weren't even the issue. Does this prove what the issue is, and that it can be resolved?

The collector shoe paddles don't normally hit the coverboard. If the coverboard support has failed to the point of the paddles hitting it, the paddles break off. This can be a show stopper that results in a dead train.

The paddles are notched so as to break off when hitting something. Otherwise the entire collector assembly would be broken from the car.

The paddles do bounce at the ramps in the third rail after a gap and also making a clacking sound that you can hear inside the car.

The part of the collector assembly that holds the paddle and provides tension is called a torsion unit and has an "upstop" that prevents the paddle from bouncing high enough to hit the coverboard.

New rail grinding equipment can be seen heading southbound out of Lake Merritt Station. They're parked on a siding at an Oakland BART shop facility.

Train Operator since 2003's picture

New rail being installed while the ties are replaced on the Concord line.

Will they be adjusting the rails so not to wear on the wheels as much?

I would want the wheels to wear less on the rails.. But that's because I would want the ride to be quieter, but thas not possible..

What happens when the wheels get worn? I just haven't heard what happens, besides maybe a derail. I have been on a train with a flat spot on it, but those seem rare..

Wasn't there a posting pointing out that the distance between the rails in the turn caused come uneven wear on the wheels.

What wears the wheels unevenly is passing through the same sharp curves that are in the same direction repeatedly.

As an example, if a car passes through the Oakland WYE every trip facing the same direction as it goes from Fremont to Daly City and back, the same wheels are always on the inside or outside of the sharp curve. The outside wheels have to travel farther through the curve than the inside wheels. Since the wheels are connected by a solid axle, the inside wheels are forced to "grind" on the rail over their shorter distance through the curve increasing the wear on those wheels. This mismatch also results in a force on the wheelset causing it to become cocked which presses the flanges against the rail causing the squealing noise.

Since there is no equally sharp curve in the opposite direction anywhere on that trip, the wheels wear unevenly.

The solution is to turn all the cars to face in the opposite direction periodically. To what extent this is actually done, I seem to recall it was an annual event. I remember hearing about it but was never actually involved in doing it.

The Oakland WYE actually conforms to the "wye" of railroad terminology which describes a triangular configuration of three tracks and three switches that can be used to turn a train in the opposite direction.

To turn a train from Fremont, it first goes to West Oakland. The operator changes ends and takes it to MacArthur. The operator changes ends again and heads back to Fremont and voila, all the cars in the train have been physically turned around.

The SFO WYE would be handy for turning trains that have their home yard at Daly City. The Oakland WYE is more convenient to Concord, Hayward and Richmond yards.

The yards have no wyes or loops
either of which takes a lot of real estate.

Some of the yards have a single car turntable but it is much easier to turn multiple cars with the wye method.

The yard turntables are used if the only available A2 or C car needed to make up a train happens to have the cab facing the wrong way.

Wheels are not allowed to wear to the point of causing a derailment as a wear indicator.

Wheels are inspected and measured frequently for diameter and flange thickness. Measurements are recorded during preventive maintenance.

Wheels worn to near the allowable diameter limit are replaced. Wheels with out of spec. flanges can be reprofiled on a wheel truing machine if enough usable diameter will remain afterward.

Wheels are a regular replacement item and don't last the life of the vehicle.

I saw a newspaper article about the derailment. The picture showed it to be at the switch in the tunnel just before 12th St. where the track from Lake Merritt merges with one of the tracks from the direction of West Oakland. The train coming from Lake Merritt was in the switch when it was hit by the train from West Oakland.

As far as the two tracks that are in parallel from the interlocking at the tunnel portal after West Oakland to 12th St. and beyond, I believe those are in separate bores but I don't know how far apart they are.