Dynamic brake useage.

[Murphy Siding]

     Are dynamic brakes used for braking on reletively flat tracks, or  garden variety hills, or just on the *big* hills?

[Ted Marshall]

     Are dynamic brakes used for braking on reletively flat tracks, or  garden variety hills, or just on the *big* hills?

 Here in "flat" Florida, dynamics are used regularly to slow trains. The use of dynamics vs. friction brakes results in reduced brake wear/maintenance which save the railroad money which is the bottom line.  In hilly or mountainous terrain, dynamics compliment friction brakes by preventing them from overheating on downgrades as well as helping the engineer control slack.

[CShaveRR]

Besides the reduction in maintenance, the use of dynamic brakes saves the time and energy required to release the brakes when you wish to move or increase speed again.

[Saxman]

Yes dynamic braking is used on "flat Land".  It is an effective braking system especially the extended range high capacity braking of the new locomotives. I prefer it over the air especially during cold weather and with long trains.

[mackb4]

 All mentioned.

 The NS-1 states that the use of the dynamic brake is first priority in slowing down a train.

 I'm sure most railroads ask that of their Engineer's.

 

[ndbprr]

A little known fact is that with dynamic braking you can have too much braking.  IC limits dynamic braking to 16 axles on a train for that reason.

[Murphy Siding]

A little known fact is that with dynamic braking you can have too much braking.  IC limits dynamic braking to 16 axles on a train for that reason.

What happens if you have too much braking?  Skid marks?   Also, is are the dynamics an all-or-nothing type affair?  For example, if a train is being pulled by 3 locomotives, do the dynamic brakes of all 3 work in unison?

[Modelcar]

....That was my question too....Can Dynamic braking be varied from locomotive to locomotive and or not used on one of the {3}, that might be at the head end of the train....?

[csxengineer98]

A little known fact is that with dynamic braking you can have too much braking.  IC limits dynamic braking to 16 axles on a train for that reason.

What happens if you have too much braking?  Skid marks?   Also, is are the dynamics an all-or-nothing type affair?  For example, if a train is being pulled by 3 locomotives, do the dynamic brakes of all 3 work in unison?

you can slow the head end down to fast and buckle the train and derail... and if the DB is cut in on all the units and the units are all equpiped with DB..then yes..they all work in unison just like the throttle dose...

css engineer 

[zardoz]

....That was my question too....Can Dynamic braking be varied from locomotive to locomotive and or not used on one of the {3}, that might be at the head end of the train....?

Dynamics cannot be varied between locomotives that are connected via the 27-point jumper--they will all work at whatever level they would work at if they were single units responding to similar throttle positions..

DP units can be operated independently of the lead units (one can even work power on the DP unit while at the same time working dynamics on the lead units-a great way to keep the train bunched).

[daveklepper]

The disadvantage of dynamic braking is that only the locomotive is exerting the braking force.   Thus, if all the locomotive power is at the front of the train, and the  train is long, the rear of the train wishes to keep moving and with too much brake effort a buckle will occur, with cars in the middle derailing.   So, limiting the amount of dynamic braking in design only solves the problem if only one unit is used, or possibly two.  Of course, some of this problem still exists with air brakes, since it takes time for the drop in air pressure in the train line to pass to the rear of the train, activating the brakes there.   Being a locomotive engineer is a profession of skill, not for amatures, that is for sure!    On mountain railroads, there are varous measures to mitigate the problems, including distributed power.

[ndbprr]

Yes it can be limited but not proportionately.  I believe there is an electrical switch in the cab that lets the engineer turn off the DB in a particular engine.  That is how IC limits the axles with DB and I assume all railroads do. 

[jeffhergert]

Yes it can be limited but not proportionately.  I believe there is an electrical switch in the cab that lets the engineer turn off the DB in a particular engine.  That is how IC limits the axles with DB and I assume all railroads do. 

Correct.  Most of our newer DB equipped units have a switch that has a cut in, cut out for DB Axle restrictions, or cut out defective options.  

We also have restrictions in how much DB force to use going through turnouts and curves to reduce in-train forces.

Jeff    

[Murphy Siding]

     Thinking of this as like a truck, downshifting to save the brakes.....does using dynamic brakes a lot, cause undue wear on the locomotive?  Perhaps wearing out the electrical equipment faster in a mountainous area, verses a flat area?

[Gambi80]

Can the dynamic brake 'power' be regulated? For example, an engine brake in a semi has typically 3 settings...1-low, 2-med, 3-high.

Also...say...if a non-DB equipped engine was leading 3 other DB equipped units does the non-equipped unit have a provision for DB control...?

[METRO]

I've always wondered how much dynamic breaks used to cost? I've not seen any newer engines without it, but I know several roads (CNW, CRI&P, NKP ECT) didn't equip certain road engines with it. However if a line saves on maintainance, couldn't that offset the initial cost of dynamics?

[Modelcar]

.....Comparing braking force in a truck to a locomotive using DB and what it might effect to wear faster.

Many years ago when we were doing {automotive testing}, in the Pennsylvania mountains with trucks and automatic transmissions, which included a hydraulic retarder.  Of course using the retarder on all downgrades, loaded the pinion and ring gear sets in the trucks differental as opposed some of the time using the air brakes, etc....

Over in the locomotive...{and I'm not the expert on that}, but I would think using DB exclusively would put more wear thru the gearing between the traction motor and the axle.  Each side of the gears too, because all engines are run in both directions.

[BaltACD]

Can the dynamic brake 'power' be regulated? For example, an engine brake in a semi has typically 3 settings...1-low, 2-med, 3-high.

Also...say...if a non-DB equipped engine was leading 3 other DB equipped units does the non-equipped unit have a provision for DB control...?

Dynamic Braking has 8 settings....the 8 notches of the throttle.  On the controlling locomotive the selector switch gets set to power or braking, you cannot have both at the same time.  Once the switch is set to braking, the engineer notches out to the level of dynamic braking he requires.  1st notch is a limited level of dynamic braking, the 8th notch is the maximum level of dynamic braking.  The position can be varied as needed by the terrain and the actions of the train.  When power is required, the throttle is notched back to idle and the selector switch set back to power and then the locomotives can be used to pull again.

If the lead engine is not DB equipped, there will be no DB on that engine consist, even if all trailing unit are equipped. 

[CShaveRR]

Balt, the throttle and d/b have used separate levers for quite a few years now.  They still can't be used simultaneously, though.

However, I think I read somewhere (an owner's manual, perhaps?) that when the same lever was used, the lever operated "smoothly" for dynamic braking.  So there weren't just eight positions--it was an infinite number (in theory, anyway).

[clash]

Dynamic brake regulation on more modern locomotives comes from an analog signal that can vary from 0-about 72 volts. The signal comes from a potentiometer in the control stand linked to the dynamic brake handle. It is a smooth arc and not divided into notches like the throttle handle.We still have a few of the old style control stands that use one handle for both functions but they are getting pretty long in the tooth and probably wont be around much longer.

[DPI]

Besides the reduction in maintenance, the use of dynamic brakes saves the time and energy required to release the brakes when you wish to move or increase speed again.

 

Not always true,, We have a spot where the speed drops from 60 to 50. Its much easier to squeeze off 10lbs, let the speed drop about 5mph, kick off the brakes and keep right on plugging away. All this in about mile. Now to do it by the book (which I always do*) You have to stair-step your throttle down to idle, wait 10 seconds, move the dynamic brake lever to set-up, pause and now move it into braking. But not too much. Only about 200-300 amps first, gather up the slack then full dynamic. After you get the train down to the desired speed, shut off the dynamic brake, go back to power, stretch out the slack then start pulling on them again. The newer locos have excellent dynamic brakes but horrible response when you go back into power. They seem to take forever to start to load up. And when they final do, your another mile down the track and your speed has dropped another 5mph. 

*just in case anyone with any authority is reading. Hello Roadforeman!        

[BigJim]

BaltACD wrote;
Dynamic Braking has 8 settings

Clash replied;
 The signal comes from a potentiometer in the control stand linked to the dynamic brake handle. It is a smooth arc and not divided into notches like the throttle handle.

Thanks Clash for clearing that myth up before it got out of hand.

[zardoz]

Besides the reduction in maintenance, the use of dynamic brakes saves the time and energy required to release the brakes when you wish to move or increase speed again.

Not always true,, We have a spot where the speed drops from 60 to 50. Its much easier to squeeze off 10lbs, let the speed drop about 5mph, kick off the brakes and keep right on plugging away. All this in about mile. Now to do it by the book (which I always do*) You have to stair-step your throttle down to idle, wait 10 seconds, move the dynamic brake lever to set-up, pause and now move it into braking. But not too much. Only about 200-300 amps first, gather up the slack then full dynamic. After you get the train down to the desired speed, shut off the dynamic brake, go back to power, stretch out the slack then start pulling on them again. The newer locos have excellent dynamic brakes but horrible response when you go back into power. They seem to take forever to start to load up. And when they final do, your another mile down the track and your speed has dropped another 5mph. 

*just in case anyone with any authority is reading. Hello Roadforeman!        

I don't think even a road foreman would be dumb enough to expect one to do a dynamic speed reduction in the situation you describe; at least I would hope not, unless the train is less than maybe 50 cars long.

Of course, if you're just drifting along in the 3rd or 4th notch, power braking might not be the best idea. And one must also consider the load/empty distribution, as well as the grade, and the speed requirements 5-10 miles further down the line, etc.

[CSXDixieLine]

     Are dynamic brakes used for braking on reletively flat tracks, or  garden variety hills, or just on the *big* hills?

There are some spots where I railfan around Atlanta that look flat to the naked eye, although when you zoom in on sections of this track you can clearly see the very slight grades. And when the trains are coming "down", you can clearly hear the whine of the dynamics. In fact, its sometimes eery to me for some reason to hear that sound when I expect to hear the "regular" roar of diesels instead.

[mvlandsw]

BaltACD wrote;
Dynamic Braking has 8 settings

Clash replied;
 The signal comes from a potentiometer in the control stand linked to the dynamic brake handle. It is a smooth arc and not divided into notches like the throttle handle.

Thanks Clash for clearing that myth up before it got out of hand.

The Western Maryland had some non dynamic units with a control stand equipped to control dynamics on trailing units.     Mark

[tree68]

The runaway at Watertown, NY involved an elevation drop of around 200' over better than six miles.  If my math is correct, that's around .6% aggregrate grade.  About a quarter of that 200' is in the first mile or so.

The two cars managed to acheive speeds as high as 60 mph.  I know CSX sometimes uses dynamics for at least a part of that route.

[ValleyX]

Besides the reduction in maintenance, the use of dynamic brakes saves the time and energy required to release the brakes when you wish to move or increase speed again.

    

I don't think even a road foreman would be dumb enough to expect one to do a dynamic speed reduction in the situation you describe; at least I would hope not, unless the train is less than maybe 50 cars long.

 

I knew you'd been away from the industry for awhile.

[wabash1]

dynamic brakes have changed  and most on here are talking old school. Engines have 2 differant kinds of dynamic brakes, flat and tapered. let me start with tapered this starts as when moving dynamic brakes into set up wait for a few seconds for the relays to set up then move nto dynamic brake get about 300-400 amps and let the train come against the engine once the train is up against the engine then increase the amprage to controll your speed. now this is tapered so you really haft to apply to get the amps up. in some ( older engines sd-40s) they go to 700-750 amps total. as your speed comes down the amps come down.  now lets talk about flat. these engine will load all the dynamic avalible by notch 4. they are cheaper to build and maintain that is why the carrier goes this route. it still has 8 notches  but you have all by notch 4. now i hear you say why have 8 notches if you have all of it by notch 4? because you just might have units behind you that are tapered and not flat so you still need 8. the nest questions is do you feel a differance in braking or reaction. the units that comes on quicker ( flat) does all the work you wont feel the differance until you get all 8 notches making the other units work. there is also extended range and high adhishion unit. most carrier wont mix power they want power to be the same for better train handling, back in the day we ran trains with what they gave us and some were nightmares of power lashups.  what wears out fastest dynamic seams to keep going and going, mostly the grids need replacing when they blow thats real pretty blue /white flash of light followed by a loud boom. ( sorta like lightning) then silence. the dynamic is not like in trucking  we can very the braking forces easy over a broad area .

[Gambi80]

the dynamic is not like in trucking  we can very the braking forces easy over a broad area .

Just a broad analogy...both essentially use the drive wheels and/or power unit to provide the braking effect.  But how each work are very different.

[GP40]

I've always wondered how much dynamic breaks used to cost? I've not seen any newer engines without it, but I know several roads (CNW, CRI&P, NKP ECT) didn't equip certain road engines with it. However if a line saves on maintainance, couldn't that offset the initial cost of dynamics?

1. One reason why the RR's you mentioned did purchased dynamic brakes was they were first marketed by the builders as mountain RR equipment and the dynamics quit at 20 MPH.

2. Their engineers were mostly still steam era and they were used to using the automatic train brake as their primary. 

3. As the dynamics improved in performance with extended range and RR's got into serious operational cost cutting and also when certain modern cars seemed to have problematic train brake(TTX cars had a reputation of going into emergency when given a low to moderate brakepipe reduction). Not to mention the modern practice of run through power .Then Dynamics became the rigeur for all road locomotive purchases.

There were of course the serious holdouts. The MoPac purchased a few DB equipped SD40-2's only because they had interline those uints on unit coal trains.