Anti-Lock Brakes for trains?

[CPSK]

Hi;
I just had this thought last night while trying to fall asleep and hearing a train rumble by on the nearby CSX River Line.
Why hasn't there ever been an attempt (or at least a test) to incorporate anti-lock braking systems to railroad locomotives and rolling stock.
In particular, I believe that such a system would be quite beneficial for passenger trains where frequent stops are necessary.

Wouldn't a train stop faster, and without wheel locking if an ABS system were employed?
This could essentially eliminate flat spots on the wheels, which causes excessive wear on rolling stock and rails.

I realize that for much longer freight trains, an ABS system would be much more difficult to implement, and require all locomotives to supply electric power to the train, and modification to all rolling stock to retrofit the ABS system, which would also include the addition of electric cables between cars.
Perhaps due to the length of the average freight train, such a system would prove ineffective and much too expensive.
I therefore limit my practical interest to passenger trains, but fantasize about having such systems on freight trains as well.

CPSK

[GOLDEN-ARM]

there is such a system, for pax equipment. they are called 'decelostats". they release the brakes momentarily, if a wheel is detected sliding. you can hear them "whooshing" off and on, when they are working. like an automobile, there's a ring around the wheel, and a pick-up, that watches the speed of the wheel, and measures it against the rest. if a wheel slows,or stops, in comparison to the rest, the brakes are released on that wheel, then reapplied. it reduces stopping distances, by allowing maximum braking effort. i remember an incident, at hokoken on njtroi, when the new arrow equipment first came into use. some testing had been done on the rails, on the southern most house track. a train coming into the shed attempted to stop, but due to some lubricant on the rail, the wheels started sliding. the decelostats worked as intended, and all of them started kicking off and on.the train was placed into emergency, but it plowed through the bumper on the end of the track. as i recall, initial blame was on the engineer, then the decelostats, and finally it was discovered, the rails had a layer of lubed on them, form the conductive testing, that had been done there, previously.

due to the intense maintainance they recieve, and the need for a power source at each axle, it's not feasible for use in freight trains. "dedicated" trains might benefit, but i would imagine economics ultimately prevent it from being used in freight. the cost of keeping it serviced, would be astronomical.....

[Jtgshu]

there is such a system, for pax equipment. they are called 'decelostats". they release the brakes momentarily, if a wheel is detected sliding. you can hear them "whooshing" off and on, when they are working. like an automobile, there's a ring around the wheel, and a pick-up, that watches the speed of the wheel, and measures it against the rest. if a wheel slows,or stops, in comparison to the rest, the brakes are released on that wheel, then reapplied. it reduces stopping distances, by allowing maximum braking effort. i remember an incident, at hokoken on njtroi, when the new arrow equipment first came into use. some testing had been done on the rails, on the southern most house track. a train coming into the shed attempted to stop, but due to some lubricant on the rail, the wheels started sliding. the decelostats worked as intended, and all of them started kicking off and on.the train was placed into emergency, but it plowed through the bumper on the end of the track. as i recall, initial blame was on the engineer, then the decelostats, and finally it was discovered, the rails had a layer of lubed on them, form the conductive testing, that had been done there, previously.

due to the intense maintainance they recieve, and the need for a power source at each axle, it's not feasible for use in freight trains. "dedicated" trains might benefit, but i would imagine economics ultimately prevent it from being used in freight. the cost of keeping it serviced, would be astronomical.....

the same kind of incident happened in NY Penn a few years ago to an NJT crew - they just got done graphiting the switches in the area, and the engineer could not get the train stopped in well over a train length when going just over 10mph. Went through the signal, but luckily the train ahead had cleared up and the switches thrown so nothing was hit or broken.

Decelostats are great in theory, but sometimes they are just a pain in that just a little wheel slide will let the train stop, but they just keep coming on and off, and keep going and going - kind of like early ABS systems in cars.

The ones in the new Multilevels work very well however, they aren't rediculously annoying and over-reactive and actually do a very good job getting the wheels rolling again with a lot of brake on still, as it seems that it doesn't release nearly as much brake cylinder pressure as the other car models tend to do, making for a smoother ride when they kick on, and better/shorter braking because the brakes are staying on, just not as powerful.

[ex Budd man]

ABS on passenger equipment has been around for many years. Westinghouse and Budd developed a system called Rolokron. This was an electro-mechanical system which compaired rotational speed of each axle. If one or more axle was not in sync with the others on that car the brake cylinder pressure would be vented momentairily, once the wheel speed mached the rest of the car, pressure is reapplied to the truck. Unlike modern ABS systems it does not react as fast and frequently. Today's cars have very sofisticated electronic controls.

[bengt]

The Anti-Lock devices of today are not quick enough. To overcome that problem there must be an fast electric device somwere in the brak-gear that can release the brake force within milliseconds. Otherwice a flat spot can devellop.
Still a problem is when the friction force is so low, rail - wheel, that a skidding wheel-set will contiue to skidd untill a spot with higher friction triggers the wheel-set to rotate again. A flat spot on a wheel can be made within milliseconds so there is a real problem for railways that there is no good Anti-Lock Brake systems on the market.

[CN Sparky]

Milliseconds? I think you're over-exaggerating a non-issue.

We've dragged locked axles around the yard... usually because of handbrakes... yet no detectable flat spots. Far more than milliseconds...

[typesix]

The problem is not the anti-lock system, but the compressed air braking system is too slow to react because air is compressible. That's why on many modern streetcars, hydraulic friction brakes are used, but is not likely to be used in railroading.

[Jtgshu]

The problem is not the anti-lock system, but the compressed air braking system is too slow to react because air is compressible. That's why on many modern streetcars, hydraulic friction brakes are used, but is not likely to be used in railroading.

True, but with Electro Pneumatic brakes, which are used on many passenger cars and now some freight cars, the brakes still use compressed air of course, but they are controlled electrically at the brake cylinder, which is very quick to respond. Not quite milliseconds, but pretty quick!

[clodderes]

So, with all its shortcomings, are these systems still implemented to the current modern trains? If it is, in what kind if trains, MU? locomotive? Light cars? so far it is no for freight, how about passenger coaches? are there any coaches supplied with these system?

And for locomotive is there such a system too being used in current models?

[gp9rm4108]

There is such a system on freight cars that are so equipped. It's called the load empty sensor. When the car is loaded the brakes apply harder than they would if it was to be empty. Greatly reduces the chances of a wheel lock up on empty cars during heavy brake applications.