Emergency Brake application on a steam engine.

Interesting that overspeed has crept into the discussion.  A few months ago, I was on the eastbound Southwest Chief.  Soon after we descended the east slop of the Rockies, we started having problems, repeatedly stopping.  Crew announced that a loco overspeed limiter was cutting off the loco at 20 mph and they would try to reset the computer.  They did this a few times, and eventually left 1 of the 2 locos on a siding.  They didn't say which loco it was.

Based on what was said above, if the loco were the trailing unit, couldn't the overspeed could have been disconnected and if it were the lead unit, the 2 units switched?

RJR posted:

Interesting that overspeed has crept into the discussion.  A few months ago, I was on the eastbound Southwest Chief.  Soon after we descended the east slop of the Rockies, we started having problems, repeatedly stopping.  Crew announced that a loco overspeed limiter was cutting off the loco at 20 mph and they would try to reset the computer.  They did this a few times, and eventually left 1 of the 2 locos on a siding.  They didn't say which loco it was.

Based on what was said above, if the loco were the trailing unit, couldn't the overspeed could have been disconnected and if it were the lead unit, the 2 units switched?

The "overspeed" function is ONLY on the lead controlling unit, which obviously has its brake valve cut-in. If the unit's air brake equipment is computer controlled electronic air brake equipment, then things can get a lot more complicated. Sometimes it is necessary to take the lead unit off the train, and operate with the second unit, assuming it is facing forward.

Modern automobile speedometers are very accurate. We ran pacing for about 20 miles at 77-79 mph.

Where did that term, "traction motor unraveling" come from. Most traction motor armatures are not wound with one continuous long wire like most small motors we see in daily life. The armatures used in traction motors have long slots in them running parallel to the axle going thru it. Each slot is about 3/4" wide and 3/4" deep, running down the whole length of the armature, that insulated lengths of copper bars (about 1/8"x1/4") are grouped together then wrapped with fiberglass tape to create a 3/4" squares which are driven down into the slots with a leather headed hammer. Maybe it's possible for those squares to get pulled out of there slots from the centrifugal  forces increasing at higher speeds. Never saw it though in the motors I helped rebuild. There may be wire wrapped armatures in very small traction motors, like trolley cars used, that can unravel, but I never worked on them to know.   

Dave,

What usually comes apart first is the commutator, and/or the ends of the coils that are soldered/tig welded into each comm-bar. Such destruction is historically caused by serious overheat of the traction motors (stall burns also hurt the commutator). Once one piece comes loose, the the TM "bird nests" and that all she wrote! Generally the TM is then locked up, with sliding wheels. The pinion gear must then be cut in order to allow the wheels to turn again.

Thanks Hot Water. Always always wondered why we would get some in with the pinion cut off. At the time, late 1980's early 1990's we were charging the middle man an average of $20,000.00 per rebuild. So an engineer that don't drive by the rules can cost the company allot.

Dave Zucal posted:

Thanks Hot Water. Always always wondered why we would get some in with the pinion cut off. At the time, late 1980's early 1990's we were charging the middle man an average of $20,000.00 per rebuild. So an engineer that don't drive by the rules can cost the company allot.

It's not always, even rarely the engineer's fault. SH! There are no speed limits that high around here and axles would lock up from time to time for whatever reason and require the pinion to be cut off.

As for the "overspeed", this could be a problem with the cab signal circuits. We used to get that same problem at 20 mph and the shops had to come out and turn the cab signals off., this even though our line did not have cab signals.

Big Jim posted:

Dave Zucal posted:

Thanks Hot Water. Always always wondered why we would get some in with the pinion cut off. At the time, late 1980's early 1990's we were charging the middle man an average of $20,000.00 per rebuild. So an engineer that don't drive by the rules can cost the company allot.

It's not always, even rarely the engineer's fault. SH!

Stated like a true Hoghead! I must admit that I have never found anyone in the Mechanical Departments that would stall burn traction motor commutators, nor seriously exceed short time current ratings to the point that one could smell the insulation burning in the traction motors.

 

Don't worry about the mule, just load the wagon! 

Rob Leese posted:

Gregg posted:

Roughly 25 years ago... I' m not sure when CN-rail  started using dynamic braking. . 

It was early 1982 on the "unreconstructed Frisco" when the RFE's started riding with the pool engineers and firemen to demonstrate dynamic brake train handling. And it looked like they were actually learning the technique themselves as they taught.  

Haha, you said a mouthful, Rob.  The unwilling being led by the unable.

After having been merged into the BN for over 12 years, many Engineers and Road Foremen on the former Frisco lines were still acting like it was unreconstructed, in 1995, when the BN/Santa Fe merger occurred.  Engineers in all directions out of Springfield were stretch braking through every sag (and the Frisco was a roller coaster of a railroad).  They were good Engineers, but they were stretch braking everywhere, even on more or less level territory approaching Tulsa, and the Road Foremen were not interested in changing the practice.

Hot Water posted:

Dave,

What usually comes apart first is the commutator, and/or the ends of the coils that are soldered/tig welded into each comm-bar. Such destruction is historically caused by serious overheat of the traction motors (stall burns also hurt the commutator). Once one piece comes loose, the the TM "bird nests" and that all she wrote! Generally the TM is then locked up, with sliding wheels. The pinion gear must then be cut in order to allow the wheels to turn again.

Now what?    On the main line with no access with a road repair truck?   

If an axle seizes and it happens to be an inaccesible place then a hi-rail pickup or hi-rail carmen's truck will ride the rail right up to the front of your loco and then use their torch to cut the pinion. 

In photo a tooth broke off the pinion gear and jammed in the bull gear. The resulting forces and additional pieces broke out two big chunks of the the bull gear and completely stripped the pinion of all teeth.

And I suppose you could "skid" it to the nearest back track or siding. .   ?

Gregg posted:

And I suppose you could "skid" it to the nearest back track or siding. .   ?

Not really a good idea, what with over 65,000 pounds on each axle. Once stopped, it's best to just sit there until the Mechanical Dept. arrives with their big truck to either cut the pinion or axle "bull" gear off, or block the TM wheel set up off the rails, or simply pick that end of the unit up and change-out that TM.

Maybe not a good idea, but remember, RR's didn't always have the high-tech hi-rail trucks like they do today. Heck, if the wheel had actually locked up while moving, the wheel was a probably flatspotted so bad that the unit needed to be set out anyway. You'd just set the unit out, the shops would come out, cut the pinion off and try to weld up the flat spots.

Most of the time that I have seen anything similar to this happen, the problem was a slipped pinion. In this case, the wheel would usually turn enough to get the unit to where the shops could get to you and cut the pinion off.

I had one e-brake application while running steam with passengers,  but my experience was a little different. I was at the throttle of a H K Porter 2-4-0, built from an 0-4-0 saddle tanker.  3 coaches going downhill, coaches first.  I was only travelling about ten or 15 mph, with a light application on the coach brakes, basically drifting downhill.   We came across a contractor who had no idea how to read a track occupy warrant, and had a 6 to 8" tree across the rails.  He was using the rails as a prop to cut up the tree.  My conductor on the real platform had a emergency dump valve, but I didn't wait for him to try it.  As we came around a curve and the contractor came into view  (conductors' view, not mine).  The conductor voice started getting faster like a geiger counter heating up.  I dumped it and called out the e application on the radio.  

In my case, I did bail off the engine brake, because I was already bunched going downhill backwards and I did not went to stretch it out.  I  closed the throttle.  If I remember I think I closed the throttle and dumped the brakes at about the same time, one hand each.

I have to admit I never really thought about opening the throttle during an brake dump in case of a break in two.  The track I ran on was mostly 10 mph limit, it just wasn't something we discussed. 

Any way that was my experience. The contractor got the track cleared quickly, although one of them apparently dove for cover. the conductor 8n the back may not have been fast with the brake but he was very good with the horn!!

 3 coaches in emergency at 10 per would come to a an abrupt stop.   I'm not sure Rich would open the throttle during a back up movement in case of Emergency brake application... No way.

Actually it was quite smooth.  Since the brakes already had a light application the cars were already bunched up.  Also, even though I did dump the air I didn't jerk the handle all the way over.  I do remember turning it quickly, but not crazy fast.  Based on what I was hearing I was already increasing and then dumped it as the talk  over the radio got more excited.  The passengers knew that we had stopped but they didn't know it was an e stop

jhz563 posted:

Actually it was quite smooth.  Since the brakes already had a light application the cars were already bunched up.  Also, even though I did dump the air I didn't jerk the handle all the way over.  I do remember turning it quickly, but not crazy fast.  Based on what I was hearing I was already increasing and then dumped it as the talk  over the radio got more excited.  The passengers knew that we had stopped but they didn't know it was an e stop

Thanks for the story and it sounds like you guys are having fun. Good stuff. I enjoy reading these kind of stories.