Smoke, sparks, fire & scary noises.

[Anonymous]

Hey Mr. Stahl, thanks for taking the time to answer my questions. you have provided me with some great info. The picture is getting clearer.
Now lets see if I got it.
The main generator provides the field for all TMs
each grid handles 2 TMs (SDs) output
extended range cuts down the resistance of the grid (load)

This is one of those things where each answer brings up more questions. I hope you can put up with me[:D]

Say your going down hill in DB notch 8 gaining speed, about what speed do you hit the 700 limit, both in normal and extended range? my guess would be 25MPH normal & 12MPH extended.

If you have a grid failure on one set of TMs, do the other 2 sets kick out or will you continue to have 2/3 dynamics operating.

how are they paired up ? 112 233 , 123 123 ,

What do the actual resistors physicaly look like? Is the heat sync itself actually the resistance element, or is it resistors with seperate heat syncs.? If so what kind of resistors and how big are they.

Also is the cooling fan speed fixed, or does it vary with the amount of heat to disipate?

One more thing. How many "grids" are there? so far it seems at least 6 seperate ones are needed.

Thanks

[Randy Stahl]

Good questions!!!
First , the circuit is pretty simple ALL six traction motor fields are connected in series with the main gen. the traction motor armatures are connected in pairs.. 2 armatures 2 grids.. 3 sets, all their own little circuits ( on an SD ) Extended range dynamic brakes are very simple, all that is done is shorting out sections of each brake grid. Use ohms law to figure the values. under 10 mph you will not approach the 700 amp grid limit, you can though if you short out a part of that grid.
It is more correct to say that the rate control cap discharges faster , the higher the grid amps go. Very good questions!!!
Randy

[Anonymous]

Yes it does, thank you.
Am I correct in assuming that the discharge rate starts to increase faster and faster as speed increases ? If so is it linear or exponential increase.
Also Iv'e seen DB force graphs that indicate that some transition ocours in dynamics, but have not seen any mention of this. Is this something that happens on extended range dynamics? Is it about different methods from different manufacturers?
Also are dynamics series or parallel?
thanks.

[Randy Stahl]

One other thing worth mentioning is the fact that not all locomotives have ground relay protection in dynamics. The conventional ground relay circuit is only in the gen power circuit with no connection to the grids, remember that electricity ALWAYS returns to it's source, in the case of dynamic brakes the current source is the traction motor armatures. The only ground protection is on the tractionmotor fields and with only 975 amps and around 50 volts on the fields chances are slim of tripping the GR. there is a way to protect the grids and newer locomotives are protected.
Randy

[Randy Stahl]

Dynamic brake grids are rated at 700 amps, you are absolutly correct. The resistance of each grid is .86 ohms. All of the regulation is done by main gen exitation, maximum traction motor field current is 975 amps, of course traction motor armature current is also 700 amps. A you increase traction motor field amps there is a proportional increase of traction motor armature current You understand that at hi speeds it does not take long before the 700 amp grid current is reached, perhaps at 50 mph it only requires 150 traction motor FIELD amps, you will not get maximum braking effort until you can achieve the 975 field amps. simply put you must cut stronger lines of flux inside of each traction motor. The dynamic brake regulator senses the grid current and when 700 grid amps is approached the DBR discharges the rate control capacitor lowering the amount of main gen exitation.
I hope this effectively answers your questions. Keep them coming.
Randy

[Anonymous]

Mr. Stahl,
You have a knack for explaining tech issues, perhaps you could explain something for me.
I understand that the dynamic brake is limited to 700 amps (is it 700 at the grid or each traction motor? not shure) and that as speed picks up braking power increases untill that 700 limit is hit and from that point on the braking is less effective as speed increases. I would like to know how this is acomplished. I mean the regulating the current. Is it done by varying the excitation in the generator(traction motor) or is it modulated with some sort of time division. Please explain.

[Anonymous]

I can't call the GP40 story, But I find your thread very interesting.

[Randy Stahl]

Thanks JCHNHTFD, I didn't think too many people were reading my little thread. Any guesses on the GP-40 story??
Randy

[jchnhtfd]

Only one wheel not on the track? How very odd...

Seriously -- all I do is fly a desk these days, and it's so durned great to read these tales and get reminded that there is a real world out there with real people and real things in it! Keep it up!

[Randy Stahl]

The ho
ttest train on the RR was for many years the pig train 218 that ran from Green Bay to Chicago. One night the round house got a call from a very concerned dispatcher .
It seems the lead GP-40 had caught fire, the fire was under the locomotive and was put out in good order but soon caught fire again. The night foreman was going to send a couple of mechanics to look at this engine assuming they would only have to cut a pinion. I overheard this conversation and reminded the foreman that pinions don't usually catch fire, so I wormed my way into a gravy road trip , on overtime even!
When we arrived at the locomotive the fire dept. was just wrapping up and we were able to inspect the locomotive , the one thing I thought was strange was that ONE wheel on the locomotive was not on the track .
Let me know what YOU think is wrong with this GP-40
Randy

[Randy Stahl]

One of the nicest things we didi on the Wisconsin Central was modernizing our fleet of SD-45's to microprocesser traction control. The first few engines we did woked great. We needed to see just how these locomotives improved perfomance so we arranged to take three rebuilt engines on a heavy train up Byron hill. A bunch of us from the shops rode along to monitor TM temp, motor current, axle speeds etc. Leaving Fond du lac we were impressed, the train was accelerating smartly as the hogger made a run for t he hill. The engines were on their knees as the 1.5 % grade started in earnest but these SD-45's made an impressive show as they dug in and pulled at 7 mph. Over the hill we started picking up a little speed when at 22 MPH the engines made transition, ALL of the engines made transition at exactly the same time, We were impressed by the accuracy of the micro but the train went into emergency as the train parted our enthusiasm evaporated. A software change was in order to make transition speeds more or less random.
Randy

[Anonymous]

QUOTE: Originally posted by Randy Stahl

I don't know if anyone else has this problem? I have a hard time staying awake on freight trains. Often times I ride trains to diagnose a mysterious problem, I'll take my trusty laptop, my tool pouch,food etc.sometimes I ride a train right after my usual shift. One time I got into trouble. On a train to Chicago I fell asleep, I was sleeping very soundly because I failed to notice the crew change. The WC crew delivered the train to the CSX, the CSX crew took over and I was happily sound asleep. When I woke up the train was just like I remembered it exept I didn't recognize the countryside. I was riding the 3rd unit in the consist. I waited for the train to stop for a meet and walked up to the cab. I must have scared the hell out of the crew, they weren't expecting someone coming in the back door. I didn't recognize the crew and I started getting that old sinking feeling. Turns out I was somewhere in eastern Indiana, I was in a panic. It was decided that I should get on the next westbound train and get back to Chicago. I arrived back at the BRC and had to wait several hours for the next WC train so I climbed into the cab of the WCs and took a nap...

I think everyone has this problem to a greater or lesser extent. Of course, I have never fallen asleep in a cab...

I have found that since becoming an engineer and having to keep running the train at all times it is much easier to stay awake and focussed than it was as a trainman.

LC

[Randy Stahl]

SD-24 smoke: I think we had the last SD-24s in regular service. These were very challenging locomotives to troubleshoot . they had many , many , steps of transition. I believe they started in series, four steps of field shunting , to series parellel, four steps of field shunting, to full parellel, four steps of field shunting. I think I remember this engine having 30 high voltage contactors. The timing of the entire transition was controlled by relays and resistors, recalibrating itself after each step of transition. Toss in about 100 control rectifiers to prevent feedbacks and you have alot of stuff that can go wrong. The arrangement of the electrical cabinets was almost whimsical, I used to joke that the locomotive must have been designed at the tavern on tavern napkins, this was not an easy locomotive to get at the switch gear, especially in the rear electrical cabinet.
I was often assigned to work on these engines and developed a healthy fear of them. We used a motor gen set to set the transition and many times I got knocked on my rear by 600 volts. With so much stuff in the transition circuits it seemed like everything you would touch was live
Randy

[Randy Stahl]

I don't know if anyone else has this problem? I have a hard time staying awake on freight trains. Often times I ride trains to diagnose a mysterious problem, I'll take my trusty laptop, my tool pouch,food etc.sometimes I ride a train right after my usual shift. One time I got into trouble. On a train to Chicago I fell asleep, I was sleeping very soundly because I failed to notice the crew change. The WC crew delivered the train to the CSX, the CSX crew took over and I was happily sound asleep. When I woke up the train was just like I remembered it exept I didn't recognize the countryside. I was riding the 3rd unit in the consist. I waited for the train to stop for a meet and walked up to the cab. I must have scared the hell out of the crew, they weren't expecting someone coming in the back door. I didn't recognize the crew and I started getting that old sinking feeling. Turns out I was somewhere in eastern Indiana, I was in a panic. It was decided that I should get on the next westbound train and get back to Chicago. I arrived back at the BRC and had to wait several hours for the next WC train so I climbed into the cab of the WCs and took a nap...

[Anonymous]

QUOTE: Originally posted by Randy Stahl

I work with some very rough and tumble guys. alot of the machinists are over 250 lbs 6'1" you know the type, beer drinking loud and tough. I found out just HOW tough one night. I was selected to repair a dynamic brake hatch on an SD-45, the cabling was badly burnt and we were out of the correct cable. the best we could do was try to strip some cabling out of a scrap engine ( I think the 8993) I asked for and receive a helper in the form of Donny A, a big tough RR man from the GBW. We crawled up into the hood of this locomotive hulk and proceeded to unbolt cableing. I was briefly startled by a group of pigeons sitting directly on the cables I was taking. Since it was pitch black out the birds didn't want to fly away so I figure I'd just move them to a different perch. I grabbed one and said "here Donny, put this stupid bird over on your side , I jumped a foot when Donny let out a blood curdling screech, I thought he was hurt. Igot out from inside of this hulk and pressed Donny to find out what the problem was, he said he didn't like pigeons and he proved it , squeeling like a little girl . Of course he wanted to make sure that we kept this to the two of us.
Randy

[:D]

He's probably seen that Alfred Hichcock movie one too many times.[:0]

[Randy Stahl]

I work with some very rough and tumble guys. alot of the machinists are over 250 lbs 6'1" you know the type, beer drinking loud and tough. I found out just HOW tough one night. I was selected to repair a dynamic brake hatch on an SD-45, the cabling was badly burnt and we were out of the correct cable. the best we could do was try to strip some cabling out of a scrap engine ( I think the 8993) I asked for and receive a helper in the form of Donny A, a big tough RR man from the GBW. We crawled up into the hood of this locomotive hulk and proceeded to unbolt cableing. I was briefly startled by a group of pigeons sitting directly on the cables I was taking. Since it was pitch black out the birds didn't want to fly away so I figure I'd just move them to a different perch. I grabbed one and said "here Donny, put this stupid bird over on your side , I jumped a foot when Donny let out a blood curdling screech, I thought he was hurt. Igot out from inside of this hulk and pressed Donny to find out what the problem was, he said he didn't like pigeons and he proved it , squeeling like a little girl . Of course he wanted to make sure that we kept this to the two of us.
Randy

[Anonymous]

Great Stories, very amusing! [:D]

[Randy Stahl]

Part of my job is to test locomotives after major work is performed, such as turbo changes etc. We usually loadbox engines that come out of the shop to make sure everything is working, cooling fans etc. It's also important to make sure the engine is making the correct horsepower. On one such evening I was sent out to loadbox an SD-45 that just had it's turbo changed. I started the engine and went into the cab to allow the locomotive to warm up. I sat down in the firemans seat and glanced out the rear window and noticed smoke coming from the area near the turbo, thinking that there was an exhaust leak I went ahead and walked around to see what was going on. The aux gen drive was glowing red and smoking, I ran aroung the other side, and pulled the layshaft back to shut the thing down. No sooner did the engine stop rotating that a loud bank followed by a dandy orange fireball lit up the night . A coworker walking past the engine took off running as the top covers blew open. After I stopped shaking I realized that the locomotive had a limited crankcase explosion. We let the locomotive sit for the required 2 hours following the explosion and upon investigation found that the installer failed to provide lateral play in the aux gen causing over heated bearings and an oil fire inside the prime mover.
Randy

[Anonymous]

this is cool hee hee, once i saw cn 304 at washago with a red fuel tank, i thought thats not normal, then when he went through the greasers at the end of a home switch, the tank fell off and sent fir everywhere. that was so hot that day. hee hee

[M636C]

I had a scare while checking a newly built English Electric locomotive in the Rocklea plant near Brisbane. Thermometers were located at crucial points in the cooling circuit and I had been tasked to walk around and note the readings at ten minute intervals. The locomotive was connected to a load box, a big (variable) resistor capable of taking more than the 2025 HP from the 12CSVT engine which was running for the first time since installation. I opened the hood door nearest the radiator, read the thermometer, and closed the door. There was a loud bang followed by a hissing noise and it got very hot very quickly. The radiator header tank just behind the engine had a drain plug on my side, or to be more correct had no drain plug. When the tank was painted, the threaded hole had been taped over to keep paint off the threads. It had been taped very well, enough to hold a full tank of water, at least until the steam pressure built up as the temperature increased. The correct plug was put in, the tank refilled and the test continued but I read all the temperatures with my head well clear of the hood for the rest of the test.

Peter

[mvlandsw]

I had the blue fire effect from the dynamics on B&O GP30 6900 one night. I had stuffed the train orders in the space between the radio and the top of the control stand. Some of them slipped partially out and unfolded down over the brake warning light blocking it from view. This was before the brake current was automatically limited to a safe level and I apparently exceeded it.. I was coming south down hill on the BR&P slowing down approaching the Echo train order station when the night lit up brighter than day. There were power lines along the tracks and I thought we had derailed and knocked them down. When I looked back along the unit blue fire and sparks were coming out of every opening and crack in the hood. Later when I looked at the brake grids only a small part had melted but it sure made an impressive sight.

[Randy Stahl]

6582 is an SD-45 . A few years ago it was having problems with ground relays . I was assigned to look at this engine so at 5:00am I made my way out to the service tracks. I was having a little trouble getting going at that early hour, I decided on a little shortcut, I placed the locomotive into self load and started notching out, I was expecting the ground relay to trip but I did not expect what happened next. The sky and the surrounding area were lighted by a blinding flash, followed by a report like a cannon. in the chaos the ground tripped and the engine returned to idle, I knew what happened and that old sinking feeling came over me. I dreaded looking out the rear window for fear of what I would see. Sure enough the top of the locomotive was on fire, and what a fire, it looked more like a blast furnace, the flames were at least 25' high. I grabbed the fire extinguisher and jumped onto the roof. After emptying several I began to dawn on me that I was wasting my time. My coworkers started feeling sorry for me and came with a couple more fire extinguishers
and the comedy began. I was firing my extinguisher down from the top and a couple of other guys were shooting up from the bottom. I could'nt figure out why I was getting the powder back in my face. The foreman called the fire dept. and they were afraid of electrocution I had to assure them that it would be fine to put water on it , the only way to get the fire out is to cool off the grid hatch.
I was very disappointed with myself , the reason the grids blew out was because the DB fans were not running and I failed to check this before I loaded heavy, all I would have done was take a piece of paper , hold it up to the grids and see that the paper is sucked into the grids. The 6582 was badly damaged, the hot molten metal from the grids melted holes in the carbody in many places, the dynamic brake cabling was destroyed , all six grids were gone and the freshly painted locomotive needed repainting.
Of course there was an investigation and it was found that a wire fell off a #4 traction motor cut out coil, this wire was the neg for the rear load test contactor.
By the way that trick for getting fireworks in dynamics is a gimmic I use for chasing unwanted people out of the cab, you don't have to move the isolation switch though, all you have to do is slam the dyn selector to off, the "B" contactor will open with a loud bang and a bright flash, thats normal... after all it's only 975 amps and about 50 volts
Randy

[adrianspeeder]

Sweet, I love electrical stories, don't get to hear many. Going into electrical engineering is what i always wanted to do. It started when i was plugging an alarm clock into an extension cord and somehow it zapped and threw me across the room. I wanted to know exactly what happened and that took me to where i am now.

Adrianspeeder

[Anonymous]

You are joking, right?

[Anonymous]

Hey LC, take an old EMD -2 , put it in dynamic #8, open up the electrical cab door, then take the start / Isolate - run switch and turn it to start and watch the fire fly. Don't worry thats how you check the dynamics.[(-D][:-^]

[Anonymous]

I can't say from an electricians standpoint but only from my own as an Engineer. One night I was running an older GE and a couple other 6-axles off the hill. We only had about 40 cars and I had about 10 pound of air holding the train well as we rolled onto the flat. I wanted to cool things down so I released the air and set the throttle to idle and began counting down to switch to dynamics for a short speed restriction ahead. As I set the dynamics and brought them up to the fifth position (I can never bring myself to call them notches, that is a throttle only to me), a bright BLUE flash lit the night and my conductor (who had assumed the backseat, feet up attitude) almost jumped out of his seat. I asked him if it was close dry lightning as it was a humid late summer day . He looked and me and was about to speak when I set the dynamic up a bit. ZAP! There was that flash again. He was pointing out the back window at the resistor grid and said in a shaky voice, "It's lighning alright, came right out of the dynamics! Five forks of it too!". Needless to say we didn't use the dynamics for the balance of the trip And they were on my report to the Mechanical folks. My Conductor, loves to tell that story to this day, how "forked lighning" was coming out of the unit as we blazed down the hill. That's my only really good electrical story...

LC

[Anonymous]

Interesting stories. Please share more.Being a electronics technician myself I find your stories particularly interesting.

[locomutt]

QUOTE: Originally posted by Randy Stahl

With all the sophisticated test equipment available these days it's easy to forget that the best trouble shooting tools are still the eyes,ears and nose.
On one particular evening I was asked to look at a GP-35 that was having some loading problems, I could smell something was wrong as soon as I stepped into the cab, burnt semi-conductors..I stuck my nose into the electrical cabinet to smell my way to the problem. I found a little red rectifier hanging by it's wires , it seemed that the smell was indeed coming from this device. It was a hot night and I was sweating alot so when I moved closer to sniff the rectifier a bead of sweat rooled down my nose and made contact with the positive side of the rectifier, since I was holding on to the negative with my hand I completed a current path through my nose. Got two black eyes!
Randy

OUCH!
And you have to love those rectifiers. Slightly off topic,but I have a couple of scars on two fingers where I touched a power supply I was working on here at the house,and got bit.[:p]

[Randy Stahl]

With all the sophisticated test equipment available these days it's easy to forget that the best trouble shooting tools are still the eyes,ears and nose.
On one particular evening I was asked to look at a GP-35 that was having some loading problems, I could smell something was wrong as soon as I stepped into the cab, burnt semi-conductors..I stuck my nose into the electrical cabinet to smell my way to the problem. I found a little red rectifier hanging by it's wires , it seemed that the smell was indeed coming from this device. It was a hot night and I was sweating alot so when I moved closer to sniff the rectifier a bead of sweat rooled down my nose and made contact with the positive side of the rectifier, since I was holding on to the negative with my hand I completed a current path through my nose. Got two black eyes!
Randy

[Anonymous]

awesome stories...more more more!