Can a intense friction melt the brakes of the train... especialy air brakes?

Question

can friction melt the brakes and the wheel of a train untill the terain losses its brakes???

Answer 1

yes

Answer 2

Excellent question.  I've often wondered why questions usually concern power, tonnage, length or fuels, when the real story behind train movements is how to get the thing stopped where you want it to.

Indeed brake-shoes do melt, but they cannot melt a wheel.  Old brake-shoes were cast iron and are long gone.  New brake-shoes

are a composite of materials, including iron and phosphorous, and do melt.  When they do so, the molten material acts as a lubricant, making an already terrible situation even worse.

The last case where this happened on a large scale was several years ago in San Bernadino, Ca.  A unit train of taconite was mishandled due to an engineer who was making only his second trip, solo.  The train ran away on the grade into a 40 MPH curve at the bottom of the hill, derailing the entire train, except the helper units that were at the rear of the train.  The train's speed was estimated well over 100 MPH.  The train's conductor was killed, along with two or three "civilians."

Investigators determined that, even though brake failure did not cause the run away, the brake-shoes had in fact melted and behaved in the manner described above.

Wheels can and do melt, as well, but not from interaction with the brake-shoe.  If the wheel slides, due to a hand brake that was not released or an out of adjustment brake head or other component of the brake rigging, the tremenodus pressure and resultant friction where wheel meets rail melts right into the wheel and a derailment is just minutes away.

There is another problem with a sliding wheel, outside of melting or developing "flat spots."  When a wheel slides, even for a very short distance, the area where contact is made with the rail, not much bigger than a silver dollar, gets extremely hot, and can produce a "thermal" crack in the wheel, usually not visible to the naked eye, but another derailment waiting to happen.

Air brake and dynamic brake questions are important.  I hope they keep coming!  I've never heard of any computer controlled air brake systems, at least not in freight operations in the US.  Perhaps this is part of the high speed passenger service abroad.

Answer 3

No, in all practicality.  In earlier times the engineer had full control of the brakes, and it was human nature to put them full on if you saw a car on the tracks.  This merely locked up all the wheels and make flat spots which cost a bunch of money to replace.  So now it's computer controlled.  It will stop in the least amount of space without locking up the wheels.  Since each wheel also has a temperature sensor, it will back off a wheel if it begins to overheat.  The "hot boxes" you sometimes see on freights are bearings, not brakes.