Smoke, sparks, fire & scary noises.

[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]

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]

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]

All good questions: The grids are actually in pairs with a pair of traction motors usually motors; 2&5, 1&4, 3&6. the traction motors cutouts also work with this combination. Or it would also be accurate to say that there is one grid per traction motor, on the scematic it shows the pairing, an example in a gp 40 only has 4 grids, 4 motors. I think your right about the max dynamics at around 25- 30 mph the extended range has another peak at around 10-15 mph.
The cooling fans are 2 wires connected across a portion of two of the grids 2 fans on an sd , 1 grid on a gp. they operate off of voltage drop across a grid so the higher the grid voltage is , the faster the fan will run. The grids on an older emd look like BIG electric heaters, there is no heatsink because the grids are air cooled, on newer emd's the grids are arranged in a circle beneath the big cooling fan but the wireing is the same. the grids on an sd40 weigh 200 lbs each the sd60 is 900 lbs for the whole assy.
I was an instructor in this area for a while, I enjoy teaching my trade to others. Not at all like the journeymen that I worked for , I havn't been called a worthless little maggot for many years, I vowed that I would never be like they were. Keep the questions coming guys!!!
randy

[Anonymous]

Mr. Stahl,
Thanks for your explainations !!! I have ben a train enthusiast all my life, and an electronics technician (communications) most of that too. I have never come across someone that can explain things to me like you. I have more questions for you, but right now I don't have the time to post them. It's great that you have the attitude that you do about teaching others. I have thew same attitude about sharing what I know, But in todays world most people try to monopolize information to be the "smarter" one. Thats a sign af a weak mind to me.
Anyway thanks again and when I get a chance I'll try to pick your mind again. [;)]

[UPTRAIN]

Good stories, keep it up!!! [:D]

[Anonymous]

I used to work at company that made custom generator packages and sometimes when starting a unit for the first time, a feedback loop between the generator and the governor would cause violent surging in the engine's rpm, is this a problem in locomotives? When working on older Detroit Diesels and starting them for the first time after an overhaul before any adjustments have been made to the governor, they will "run away" and must be carefully kept from overspeeding, is this also a problem?

[Randy Stahl]

If you are familier with Detroit engines you have a leg up because EMD engines are very similar. Good thing the idle speed on EMDs is only about 300 rmp other wise overspeeding the engine might be a problem. Woodward governers are set before they are installed, we have very few problems with them. As far as a feed back loop causing rpm problems: at idle there is no power to the governer in fact the locomotive will idle fine with the gov unplugged, this is normal idle. EMD engines have an overspeed trip device that trips at about 1000 rpm.
The biggest problem starting a freshly overhauled EMD is getting it up and running for the first time, With the poorly seated rings and valves the prime mover needs a little help making fire. This gets a little scary, most guys use 2 cans of ether, one in each airbox, if the ether ignites in the airbox and the covers are on tight the fire will blow back into the air filters, I've seen doors blow open, covers fly off,enought to send the whole shop running.
If a locomotive prime mover is hunting: there are a variety of reasons, if it hunts in idle there may be air trapped in the gov. a bleeder screw is provided to burp the gov. there is also a compensating needle valve to extract air and even out rpm.
The most common form of hunting is throttle 7-8 hunting, this is most commonly a problem with the exitation system causing an overload of the prime mover, which is trying to compensate by moving the load regulator, the load regulator moves kinda slowly so instead of immediate load correction the load reg and the exitation sys just don't get it together
I hope this answers your question!!
Randy

[Anonymous]

I guess stationary generators are set up a little different because they don't have operator input. I am under the impression that the engineer's throtle does not directly affect engine RPM, but loads the alternator, then the governor acts acordingly.

Is there a single RPM that the governor will hold when operating under load, and vary fuel setting to maintain that RPM?

One other question, I noticed a 567 has scroll type blowers for intake air. It is a common misconception on Detroit Diesels that they are super-charged because they have a blower. The blower on a Detroit typically turns a little bit less than twice crankshaft speed to produce a few inches of water pressure for exhaust scavenging. A Detroit Diesel is not considered supercharged until it has a turbo. Is the same true for the 567?

[adrianspeeder]

I love the sound of a two stroke diesel, nothing like it. There is an old guy down the road with a big genset that is powered by an old Detroit Diesel. I am grinnin like a foamer when that thing roars.

Question: What are the differences in electrics for AC vs. DC dynamic brakes?

Adrianspeeder

[Randy Stahl]

First I'll try to answer the questions about locomotive governers, you are right on the money to say that there is a single rpm the governer maintains for each throttle setting.
There is a hard wire connection between the locomotive controller and the governer, in fact there are 5 wires running almost directly to the gov. Inside the gov are 5 speed solinoids, A valve , B valve, C valve , D valve the corresponding wires are 15T ,12T, 7T, 3T. All wires with a "T" are trainlined, that is they also go to the M>U> heads. The RPMs are controlled by combinations of these valves being energized. In parelell with the circuits to the gov is the throttle response panel or TH module, this module gives the exitation system it's notch reference and sets KW/ trottle notch. The last valve inside the gov is the over riding solinoid , this solinoid over rides the gov pilot valve, the gov uses the pilot valve to control the load regulator, if the engine looses rpm because of too heavy of an electrical load the gov will reduce exitation ... just to maintain the set rpm.
A 567 or a 645 roots blown engine is what you are referring to , they are not super charged or turbo charged, simply blown
Adrian speeder, We don't have AC engines on our RR. I have a BASIC understanding of these engines but do not consider myself qualified to explain these complex machines,,,sorry
Randy

[Granny74]

Bob has enjoyed hearing this thread and appreciates both the questions and the good answers you give. As Bob is legally blind, I read the forum postings to him. Now I don't understand all of this, but he does! Thanks for the info.
Bob and Nance from AZ

[Mookie]

Nance - bet you are like me, you are learning - even if by osmosis!

Mookie

[Randy Stahl]

A while back I began telling about a GP-40 ,I'll continue the tale: I was sure this was going to be a gravy run, when I saw the ONE wheel off the track I knew that it was goint to be a long day. The thing that made sense to me was the somehow the gauge of the wheelset had changed, shrunk. I confirmed this by crawling under the engine and as soon as I seen the traction motor support caps I knew what I would find ,,A broken axle.
Seems the lubricating wick had fallen out and so much heat built up, enough in fact to shatter the axle in side of the support cap.
The crew was gone, dead on hours, The only people around were the two of us from the roundhouse, 2 carmen to put things back on the track, and one train master. of course the whole RR was tied up and many trains were going to die on time . Needless to say the pressure was on. first thing we had to do was get rid of the freight train that was attached to us, A following train cut away from their train and pulled our train south. The GP -40 we discovered would not stay on the track going north so of course we had to limp it south 15 miles. had we been able to go north it would have been only about 3 miles. The only thing to do with this locomotive was to get it to a spot accessable to a crane and change the truck out, so since my engineer card was still good I was selected to run these engines south to a quarry at the brake neck speed of 4 mph. A few hours later we spotted the locomotive ,set a hand brake and set off for home.
As we were driving home it occured to me that this could have been a major disaster, driving through the small towns our RR ran through knowing that if circumstances had been different , the sleeping people would have been awakened by the sound of a derailing freight train.
Randy

[Anonymous]

I should have been more courageous. I figured something along those lines but because I couldn't give an exact answer, I refrained from answering. I have asked you so many questions, I don't want you to think that I was ignoring yours.

I am guessing that the axel broke on the side opposite the pinion, or there would be damage to the motor? Or would it make a diference?

[Anonymous]

QUOTE: Originally posted by adrianspeeder

I love the sound of a two stroke diesel, nothing like it. There is an old guy down the road with a big genset that is powered by an old Detroit Diesel. I am grinnin like a foamer when that thing roars.

Question: What are the differences in electrics for AC vs. DC dynamic brakes?

Adrianspeeder

Detroit Diesels, at least the older ones, have a bad reputation for being smoky, oily, overly complicated, and unreliable; but can be trouble free if well maintained. Personally, I like them, and when they're fully loaded they scream like a banshee!!

I once sat in the bilge between two 8V71's freshly overhauled out on a shakedown, one clockwise, the other counterclockwise. Each one was rated at 600 hp (marine engines can do it because of the cooling), with twin turbos, and double intercooling, they flat out screamed!!!

[Randy Stahl]

I would have enjoyed those detroits, I can't resist listening to a 20 cyl emd in an sd45.They still impress me to no end!!!!!

[tree68]

Part of the sound of a fire truck going by (along with the wind-up siren and the airhorns) is that Detroit...

[Anonymous]

Detroits are almost universally in fire truck engines.

since the mid eighties, Detroit has gone four stroke. I think they still make the two-stroke but I'm not sure.

It seems all of the engine manufacturers are coming to the same conclusions; four stroke, crossflow heads, electronic unit injectors, single overhead cam, smaller turbos...

[Anonymous]

QUOTE: Originally posted by jruppert

Detroits are almost universally in fire truck engines.

since the mid eighties, Detroit has gone four stroke. I think they still make the two-stroke but I'm not sure.

It seems all of the engine manufacturers are coming to the same conclusions; four stroke, crossflow heads, electronic unit injectors, single overhead cam, smaller turbos...

EPA emissions regs...

LC

[UPTRAIN]

Randy, tell us some more!!!

[Anonymous]

Mr. Stahl,
Could you please explain to me what the ground relay is all about?

[UPTRAIN]

Yes Randy, please do so [:D].

[Randy Stahl]

First let me say that the questions so far have been very good, I would hire any of you in a heartbeat as my apprentice.
First lets establi***he sources of the electric currents in a locomotive , remembering that electricity always returns to it's source
1. Batterys, provide power to start the locomotive about 64 volts d.c.
2.Auxillary gen/exiter. A self exiting direct current generator that provides 72 volt d.c. for battery charging, exiting the D-14, all control power, lighting and cab equipment
3. D14 alternator. exited by the aux gen, makes power proportional to engine rpm. at idle approx 65 v.a.c. throttle 8 approx 270 v.a.c. provides power for cooling fans, inertial blower, traction motor blowers{if equipped} and AR10 traction alternator exitation.
4. AR10 traction alternator, exited by the D14 via SCR, provides high potential for traction motors.
With all these different electric potentials it is important to keep them isolated from each other therefor all locomotive wireing is 2 wire, nothing is grounded like in the automotive industry.
Lets look at the AR10. AR10 is actually 2 alternators in one, a left side and a right side. They connect at a common bus on the positive and neg bus. so the 2 sides of the AR10 are connected in parellel.
Each side has a neutral connected at the center of the Y windings, this connection is the basis of the ground relay detection circuit.
A traction motor will run until the insulation in the motor breaks down, at that time any leakage of current will find a path back to that connection we talked about,this can be very destructive, so what the clever engineers did is look a very sensitive relay, connected one side of this relay directly to ground and the other side to the AR10 neutrals, so that when voltage/current get too high this relay operates and stops the locomotive from loading. One other thing, remember I said that the AR10 is really 2 machines connected in parelell, if one side of the machine is making more power it will trip the ground relay. Because the diodes and fuses that rectify the traction power some times blow an imbalence can occur so the clever engineers placed a bridge rectifier BETWEEN the 2 neutrals with that ground relay coil sitting right in the middle.
I hope this is a good answer guys
Randy

[Anonymous]

Yes it is.
thanks

[Anonymous]

I recently spent the weekend reading the manual for an FP-40, and while it was an awfull lot of information to soak up in one sitting, I do remember the bridge rectifier, because of the "baseball diamond" in the scematic, which rings the bell in my head, "ding - bridge circut!". If the the potentials are equal on either side, there is no current through the circut; current flows to the side with the higher potential when a difference exists.

I also remember that the D-14 mates directly to the AR-10, and the auxilliary generator has an external reference voltage generator that controls aux. gen. exitation by changing duty cycle of a constant voltage signal.

[Randy Stahl]

Yea, a voltage regulator { easier to say} lol, and you are correct about the D14 and the AR10
Randy

[Anonymous]

I should also add that the design of the AR-10 having two sides with the bridge in between IS very efficient, because it deals equally with any type of fault - a ground, an open, or a short.

You were saying not all locomotives have ground fault protection in the dynamic braking, I think that's what promted the questions.

[Anonymous]

Oh, Randy, I actually have close to enough money for the S-1, and a good place to work on it with a pit and a drop table!

The only problem is these funds were previously allotted for a mortgage downpayment at some future date. I checked with the comptroller (wife) if we could make a budgetary revision and her answer was beyond the decorum of this page. Sorry!

[Anonymous]

Mr. Stahl,
The next question I have (on a list of many) is what are the pin assignments on the M.U. cable (not nessasarly the numbers, but what do they do) I.E. contact closure, voltage controll, ect.,,,