40 foot boxcar rebuild

[Russ Bellinis]

You are right about friction of the wheels on the rail being the limiting factor for stopping. Regarding dynamic brakes, I don't think they are used for stopping except in an emergency situation where the engineer is trying anything to get it stopped. Primarily they are used to hold a train's speed down going down a grade. The problem with friction brakes is that if they get to hot, they will fade and stop working. Dynamic brakes don't have that problem, but I remember a wreck on Cajon Pass back before the mergers of the U.P. and S.P. or B.N. & S.F. The train was coming down grade toward San Bernardino when the resister bank of one locomotive blew up. The train ran away and crashed, I don't remember if it was a Santa Fe or S.P.

[sgtcarl1]

While I don't know much. I do know that I have seen quite a few freight cars with info about the brake shoes stenciled on the side.
I also recall when I was a wee lad, I aked my father what the "fringe" hanging down from a wire running across the tracks, just about 5 foot or so above the top of the boxcars was for. My father explained that they were there so that if a brakeman wasn't watching toward the front of the train, he wouldn't get knocked off the roofs of the cars by a low overpass. Thus also, the warning on the sides of buildings declaring "no room for man." Some railroads had brakemen hanging on the sides of cars, so that they could jump off and set the brakes. This was during the steam era, and yes, I remember that era very well!! (I also remember dinosaurs and stuff!!)

[Puddlejumper]

Dynamics brakes typically don't work below... say... 10 mph. Newer units, especially AC units, have dynamics that work to much lower speeds... i think around 3 mph. But Russ is absolutely right, they are for maintaining speed, not for stopping, although when an engineer is trying to stop ASAP without dynamiting the train then he will give a full service reduction on the automatic brake and full dynamic brakes. If the train gets dynamited (goes into emergency) then no dynamic would be used and the independent would get bailed off to prevent run in on the locos.

I don't think it's been mentioned but for those who are wondering, locomotives nowadays typically have 4 brakes on them, Dynamic (reverses the motors for braking), independent (air brakes for the loco only), automatic (air brakes for the loco and train), and the hand brake.

I believe the ropes hanging above the train before underpasses and tunnels were called tell tales and yes, they were there to warn brakemen on the roof top to GET DOWN NOW!