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Dynamic vs Air Brakes....When do you use which?

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Posted by UPRR engineer on Wednesday, April 30, 2008 3:56 PM

Yep....Now that i've read part of my own post again, the part thats in bold, i ment, with a real train.... one with some tonnage. All thats all true tho buddy.

Working with younger, cut back engineers, had more then one freak out on a big double stack with me as i passed a flasher at 70 (or more), looking to hit some 40mph cross overs up ahead. Passing that first mile seems like she's not gonna sit down. Last time my heater didnt work, i couldnt even see out my window... "air is what slows this thing down."

 

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Posted by BigJim on Wednesday, April 30, 2008 3:36 PM

Dynamic brakes dont work as well at speeds above about 35 or 40-ish with any kind of train, its even worse on a grade.

I would like to clear one thing up.
While it is true that the dynamic brake gets less effect the higher the speed goes over 30, its effectiveness is related just as much to the trailing tonnage and the decending gradient. The three, speed, tonnage and grade are all related very much like OHM's Law. Just like the units will only pull so much so fast up a certain grade, they also will only hold back so much at a certain speed on a certain grade. So don't read the above quote and get to thinking that the dynamic brake won't hold above 40mph. It just depends on the grade and tonnage how well it will hold.

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Posted by UPRR engineer on Wednesday, April 30, 2008 12:00 PM

 transitrapid wrote:
No its when a Stack Train is about to pull out of the yard,,,Each couple has a cushion spring and it seems that the train is using the combined pushing power of 200 of those springs to push the train forward kinda of like those toy cars that you pull and push forward

What your thinking is wrong, there not using the drawbars to "spring" forward. If they have enough horse power (a mainline train not a switch engine) to move the train which ever way its left for them, bunched or streched, they shouldnt be getting slack to yank the train out. What ever there doing (or did) they shouldnt be moving like that.

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Posted by UPRR engineer on Wednesday, April 30, 2008 12:00 PM

 transitrapid wrote:
No its when a Stack Train is about to pull out of the yard,,,Each couple has a cushion spring and it seems that the train is using the combined pushing power of 200 of those springs to push the train forward kinda of like those toy cars that you pull and push forward

What your thinking is wrong, there not using the drawbars to "spring" forward. If they have enough horse power (a mainline train not a switch engine) to move the train which ever way its left for them, bunched or streched, they shouldnt be getting slack to yank the train out. What ever there doing (or did) they shouldnt be moving like that.

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Posted by zapp on Wednesday, April 30, 2008 11:51 AM

 daveklepper wrote:
Were the DP's approximately 50 cars back or about 33 cars back?

they were the rear two! All the way on the rear of a 100 car train!

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Posted by UPRR engineer on Wednesday, April 30, 2008 10:24 AM
 zapp wrote:

I got the weirdest train yesterday morning,................

 We'll see if the experiment continues.

Don't get too excited, the reason for the "no break train" is to run the trains ran from space.

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Posted by Anonymous on Wednesday, April 30, 2008 8:40 AM
No its when a Stack Train is about to pull out of the yard,,,Each couple has a cushion spring and it seems that the train is using the combined pushing power of 200 of those springs to push the train forward kinda of like those toy cars that you pull and push forward
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Posted by daveklepper on Wednesday, April 30, 2008 2:26 AM
Were the DP's approximately 50 cars back or about 33 cars back?
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Posted by zapp on Wednesday, April 30, 2008 2:11 AM

I got the weirdest train yesterday morning, a loaded grain train with a single unit on the head end and two DP's! It had 100 cars, 14,000 tons. It took a little getting used too, but my MOP said UP is trying to stop break in two's. This goes against everything they have been preaching about "no air" because with this configuration you have no real dynamics on the headend, so you have to use air to slow the thing really down, but it sure is fun starting up a steep grade in notch 2 on the head end and notch 5-6 on the rear!

We'll see if the experiment continues.

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Posted by UPRR engineer on Tuesday, April 29, 2008 11:18 AM
Are you talking about a switch engine doing that move? The idea isnt to spring the train forward, there getting some slack. Its easier to move the cars that way, hard on equipment, but sometimes a switch engine cant move them other wise. Its physics, im sure you can see in your head why it would be an easier way to get them rolling.
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Posted by Anonymous on Tuesday, April 29, 2008 9:06 AM

So whats going on when I see a train back up to move forward out of a Intermodal yard?

Is the train using the springs of the couplers to back up and "spring the train forward?

 

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Posted by BaltACD on Friday, April 25, 2008 9:12 PM
 zardoz wrote:
 transitrapid wrote:

http://ge.ecomagination.com/site/showcase/erie.html  

Now the rules have changed?

Interesting that the track that the new locomotive is shown running on has catenary overhead.

I believe the GE Test track at Erie, has catenary to test the Electirc locomotives they build.

Never too old to have a happy childhood!

              

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Posted by RailfanRailroader on Friday, April 25, 2008 8:11 PM
Thank you. I have been told to pull tight many time so much for the 400 ft rule. The BRC is famous for it.   As for a bridge to sell, yes but it has a 5 mph slow order on it and it's not all that high.
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Posted by UPRR engineer on Friday, April 25, 2008 1:30 PM
More on getting her close to the lights, where i work they need us to get as tight as we can so they can squeeze another one behind us. I've put her as close as 20 feet from the block.
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Posted by UPRR engineer on Friday, April 25, 2008 1:25 PM
Take it easy on him. I've had my MOP ask me if i was gonna get her stopped, no one else in the cab thought i was show boating. My thoughts are the same, if ya cant show your boss ya know how to run.... ????
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Posted by BigJim on Thursday, April 24, 2008 1:59 PM
 RailfanRailroader wrote:
  It's even better when the manager is behind you sweating about the red signal and you smile as you lay it down one car length from the insulated joints. 


zardoz wrote:
And you have a bridge to sell us as well?


Hmmmm...Do you need a high place to jump from?

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Posted by zardoz on Thursday, April 24, 2008 11:48 AM
 transitrapid wrote:

http://ge.ecomagination.com/site/showcase/erie.html  

Now the rules have changed?

Interesting that the track that the new locomotive is shown running on has catenary overhead.

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Posted by zardoz on Thursday, April 24, 2008 11:46 AM

 RailfanRailroader wrote:
  It's even better when the manager is behind you sweating about the red signal and you smile as you lay it down one car length from the insulated joints. 

And you have a bridge to sell us as well?

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Posted by Anonymous on Thursday, April 24, 2008 9:35 AM

http://ge.ecomagination.com/site/showcase/erie.html  

Now the rules have changed?

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Posted by RailfanRailroader on Wednesday, April 23, 2008 11:02 PM
My personal choice depends on the territory I run on.  I like to get in and out of slow orders quickly so I use air mostly.  Dynamics are nice on the long downgrade or if your airbrakes don't do what you like.  Having a locomotive fleet with both equipped and non-equipped forces you to make the choice.  Knowing how much dynamic braking effort you have compared to the weight of the train is mandatory.  Too many young engineers and I'm only 27, come to rely on the dynamics.  Then winter comes and you have to make a emergency stop and then they can't.  I learned a lot from a IC veteran about air.  Some of the things I do may scare the hell out of someone from another railroad.  I listen to what the old timers say and not what the college graduate manager that never ran a train says.  When you got 15,000 tons and stop exactly where you want is a great feeling.  It's even better when the manager is behind you sweating about the red signal and you smile as you lay it down one car length from the insulated joints.  Running with someone that doesn't understand the air really makes me nervous.  And having your dynamics cut out on you can get bad quickly.  Reaction time is the number one thing when running a train.  As my friend said you'll feel what the train is doing through your ***.  The vibrations up the seat into your body.
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Posted by csxengineer98 on Wednesday, April 23, 2008 5:11 PM
 BigJim wrote:

you know as well as i do that the carriers want you to learn how to strech break too..

Do I?
Well I would hope that there is someone, somewhere in the system that knows what they are doing, however, it doesn't seem to trickle down in a heavy enough stream. It's amazing how brainwashed some of these low level officials turn out to be.  

yes i do.... and i was tought how to strech brake as well as dynamic brake.. and im sure you where at some point and if you dont teach your hogger trainees when you have them how to do it..your a fool and have no right to talk about anyones else lack of teaching it... myself..i do use and like to use DB more then air when i run.. mostly becouse in cold weather it donst run the risk of getting a stuck brake... and it takes all the quess work out of if the train has a kicker.. and you should know that with kickers they are unpredictable as in they might kick once for every 10 times you use the air or might kick every time..or kick once and never kick agin.. yes there are ways around that by useing the feed valve (if you have a unit in the lead with one..the new engins have that thourgh the comptuer screens and cant change the EQ res settings while moving) but they frown on that too... the bottom line is they want you to run a train the way that the "powers to be" think it should be run.. and thats is all well and good..they are the ones signing your pay check.. but it dont hurt to know what your doing and learn how to do it from an old head or if you have a short train to do alittle experimenting on your own from time to time to get the hang of it...

csx engineer 

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Posted by SSW9389 on Wednesday, April 23, 2008 3:22 PM

From Chapter 8 "Pa Choo Choo 1954-1967" of Cotton Belt Engineer: The Life and Times of C. W. "Red" Standefer 1898-1981. Red worked for Cotton Belt from 1917-1967 in engine service. In this quote Red is talking about dynamic braking.

It was a time when the old hoghead had to learn new tricks. He said about the diesel, "Well, there's a lot of difference. The braking was similar with the exception of the dynamic brake, which you might say is an electrical brake, that (they) would use in letting a heavy train down into, for instance a place like Greenville. Coming from Ft. Worth or Dallas, you come down into Greenville. It's a steep hill, and I always . . . . Now, a lot of the fellows didn't like the dynamic brake. I did. It's just put the traction motors kind of in reverse. All the slack would come right in against the engine, and you could control your speed down a hill comin' into Greenville like. But you didn't dare touch the air brake when you were doing that because you'd slide the wheels. When you slide the wheels on a locomotive, you're getting in their pocketbook because it costs several hundred dollars on account of those . . ."

"Explain that," said interviewer Joe Fred Cox an  East Texas State University History Professor.

"Well it burns flat spots on the wheels, and every time those spots come over and hit a rail, it's an awful pounding. They have been so large and would hit with such force, they'd break a rail. When the company has to renew those wheels on account of flat spots, they don't like . . . They don't get along with the engineer very well."

 

 

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Posted by SSW9389 on Wednesday, April 23, 2008 3:16 PM

EMC's original FT was built without dynamic brakes. Look at a photo from its demonstration days in 1939-1940. I am also quite sure that dynamic braking originated with electric locomotives and not on diesels.

 

 BaltACD wrote:
 Sunnyland wrote:

 

Dynamic Braking has been around since the orignal EMD FT demonstrator locomotives of 1939.  In it's simplest form it is nothing more than electrically changing the Traction motors into generators.  The train momentum supplys the 'power' to turn the traction motor/generator....the more current the engineer demands from the traction motor/generator the more retardation is generated on the train.  As generators the traction motors generate current that is disapated into heat on the dynamic brake grids and thus create braking power on the train.
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Posted by wsherrick on Wednesday, April 23, 2008 2:44 PM

I also hear it referred to as, "power braking."  The general rule is you either want to run with the slack bunched or stretched out.  Either way is fine as long as the engineer is consistent with his braking.  The trouble comes when part of the train is bunched and the other part is not.  When the automatic brakes are applied the braking starts at the front of the train and works back to the end.  The longer the train the more time this takes.  You can apply brakes and release them too quickly causing an accordion effect in the train which may pull a coupler knuckle or worse derail the train.  This is especially bad when you are pushing a consist over switches and around curves.  Too much slack action can cause wheels to climb over the rail in certain situations.  On steam locomotives you have to bail off the independent brake (engine brake) when making a reduction because it is easy to over heat the tires, causing them to expand and come off of the driving wheels.  Bailing off releases the brakes on the locomotive while the brakes are applied to the train. It has always been normal braking practice on the four railroads I have worked for to bail off when you make your first minimal reduction (6 pounds) and for each application after that.  In an emergency situation with a long train you may not want to bail off because the hard application stretches out the slack on the train very quickly and if you bail off the engine will still maintain a forward motion which could snap a coupler. I guess it depends on the situation. Even though my current operations manager wants you to bail off in the event of an emergency application.

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Posted by zapp on Wednesday, April 23, 2008 2:33 PM
We also call it "power braking". On the UP we get "gigged" on it if we do it and they download the engine. I hate to run DB on auto racks without some air under it first, just so I don't get an airhose on a crossing. But I guess they have been getting better about hanging those hoses higher cause I haven't got one in a long time. 
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Posted by BigJim on Wednesday, April 23, 2008 12:27 PM

but what is "stretch braking"?

That is using the automatic (train brake) against the throttle to control the speed of the train. In other words the units are pulling against the brakes on the train and keeping the train stretched out.

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Posted by TopekaRR on Wednesday, April 23, 2008 11:49 AM

Excuse my newbie ignorance here, but what is "stretch braking"?

Thanks,

PaulH 

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Posted by UPRR engineer on Wednesday, April 23, 2008 11:06 AM

Heres a couple more before i lay down (worked lastnight), or maybe just one.

When i was still a pigglet (hoghead in training) had a good engineer show me how to bomb off the hill west of town with a heavy train. He didnt like taking the ride vs. being the one in the seat running it. But anyways he did a good job showing me, now i call it "running it in for a beer" when i have a crew that doesnt like it. When i did get onto another job with a hoghead whos skills werent the best, after a few days of seeing me come into town, he said he wanted to take the train down the hill. The way i was taught, and he watched me during the past days was to get her up to speed as quick as you could after you crested the hill then set min at the top see how that does, every trains different, more of this.. less of that, just depends. He starts down the hill, gets it up to speed then starts using heavy dynamic brakes. Speed down that hill is 50, so there screaming at 45.... cars still pushing us faster, round the curve at about 50 looking at a flasher about a mile up the road.... still no air set.... with 100 loads of soda ash and three big motors doing 50, they will almost hold it at 50 but they wont slow you down. Dynamic brakes dont work as well at speeds above about 35 or 40-ish with any kind of train, its even worse on a grade. So anyways we're howling by the flasher, the times ive done that (and i dont like doing it), and the times ive saw guys that run better then me do it, once they hit that flasher they grab 10 pounds right away. So we go another mile or so and were still doing 50 (suppost to try to get it down to 40 when ya pass a flasher), we might be looking at a yellow around the next curve and possiblily have to stop at the light after that. ANYWAYS were past the 10 pound, were out of control, i speak up and say "better see what full service does or else...." We round the next curve, sure enough just a yellow, eveything is grabbing now, knock down the signal and come to a stop about 1/2 mile past the block. He asks "guess i better kick them off and pump on her a bit".... "i would dude". This is when it gets bad, even before the cars start to push on us once again, he decides it time to go down there and stop at the A block. I bet we didnt move maybe 10 cars he grabs initial. Thats what pissing your air away is. I start ripping on him.... "you know what you just did?"...."ya i know"... "NO... NO you dont....you just stopped the motors from charging the cars back up... the only real brakes were gonna get now is if we plug it." He had no idea that grabbing the air so quick didnt do anything. We ended up getting better lights sometime during the education of how the air works so there wasnt a need to dump the train.

Hopefully someone on here can answer questions about the in's and out's and why while i sleep.

 

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Posted by tery84_trainee on Wednesday, April 23, 2008 8:21 AM
its funny how you talk about back stabbing, over hear in aus its the same altho were not called engineers just loco drivers. with the braking over hear you have to know how to use the air, the railway i work for have alot of loco's withourt dynos and of the locos we use that have dyno's some dont work realy well. but we are encouriged where posible to use dyno's pver air as it is alot cheeper using a little diesel than burning up brake blocks

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