Thanks to Chris / CopCarSS for my avatar.
The locomotive is no longer in such service as would require dynamics, say, yard service or local service on a billiards table.
I recall reading that C&O bought differently configured Geeps for it's northern section (Michigan - the former Pere Marquette lines). They did not have dynamics, while the southern (mountain) locomotives did.
Larry Resident Microferroequinologist (at least at my house) Everyone goes home; Safety begins with you My Opinion. Standard Disclaimers Apply. No Expiration Date Come ride the rails with me! There's one thing about humility - the moment you think you've got it, you've lost it...
Back in the days when C&O was ordering its GP7s (and much later, truth be told), dynamic brakes were an expensive option and a maintenance item. C&O's GP7s with dynamic brakes were a rarity, and all were initially assigned to lines with steep grades. By the time the GP9s came around, C&O had seen the wisdom of using dynamic brakes, and ordered all of their units with them.
CNW didn't catch on until they ordered their first SD40-2s in 1974. They removed dynamic brakes from the ex-CGW units that had them, because they were an unnecessary expense, in their way of thinking. It was interesting to see the bulletins encouraging their use, once they had them!
MP ordered road units either with or without dynamic brakes, depending on whether they would be used in pools with UP units. Same with MILW and RI, I think--and that may have been the impetus for CNW finally getting them, too.
But even nowadays, dynamic brakes are being removed from road units downgraded to yard service. We're using a former UP SD40-2 that was rebuilt to an SD38-2 for hump service. Still has three radiator fans like a 40, but no evidence that it ever had a dynamic brake.
Carl
Railroader Emeritus (practiced railroading for 46 years--and in 2010 I finally got it right!)
CAACSCOCOM--I don't want to behave improperly, so I just won't behave at all. (SM)
Dan
No, exhaust is not the item that is used to apply braking force in dynamic braking system.
The electric traction motors are electrically modified to act as generators on a down hill grade and that generated current is fed to a massive "resistance grid" which creates a "load" on the motors..{gernerators}. This creates a massive amount of heat in the grids and requires copious amounts of fan driven air over them to dissipate the heat. This process puts a "load" on the traction motors and provides braking force.
Quentin
Illinois Central was another road that did not have dynamic brakes on its locomotives. Their profile was pretty close to water level over most of the system so dynamic braking would have been an expensive and relatively unnecessary option. I believe that they removed the d/b on the SD40-2's they acquired from BN (6100 series on IC).
The C&NW SD45's without dynamic brakes presented a most interesting appearance.
Murphy Siding wrote: If a road bought someone else's locomotives, that had dynamic brakes they didn't want, wouldn't it be easier just to disconnect them?
The Florida East Coast also did not have units with dynamic brakes.
What really puzzles me is why the CN has units without dynamics. Even on some of their high-HP units! I once caught a CN piggyback train out of Butler (it was a detour due to Native Americans blocking the tracks in Canada). This train was huge (12,000' and 10,000 tons). It had 4 SD40-type units on it, with NONE of them equipped with dynamics. What a pain-in-the-keester that train was to run. To make it worse, it was about zero degrees out.
Why would a railroad of Canada not have dynamics on their locomotives?
Wasn't that runaway a few weeks ago on the CN that killed the crew on a non-dynamic equipped loco? And now there is another runaway due to (allegedly) no dynamic brakes?
I wonder how many times this must happen before railroad (mis)management gets the hint?
CN made it through the Rockies without a grade over 1%. Only 30 of their 241 SD40's, and 80 of their 123 SD40-2(W) had them. I believe all of their units since the SD50's and SD60's in 1985 have had dynamics.
They have a flat railroad culture, and so does Mr Harrison, from IC, and the 2.2% grades on the former BC Rail are foreign to them. They are the only class 1 railroad without AC locomotives.
I wonder if DME will buy AC's if they make it into the PRB ?
....Dale, tell us a bit more about the CN route through the rockies with a grade not greater than 1%....That is wild...! Is there any other transportation through the same "pass"....Highway or railroad....?
I doubt if any railroad in the USA makes it across the Rockies with such a min. grade....I never heard of such a low "pass" mentioned anywhere before...{I don't doubt your word, just so surprised}.
Is the route full of tunnels and cuts and fills, etc...or is there just a location of open passes that allows such a route. The surveying engineers putting that route through back "when" must have jumped for joy in "finding" such a route.
Rock Island never bought (or leased) a brand new locomotive equipped with dynamic brakes. Even when they picked up some secondhand E8s and E9s from the UP, they removed the d.b.
Seeing how MILW had locomotives with and without dynamic brakes, what sort of operating challenges were involved taking a train say with three d.b. equipped locomotives and two locomotives without d.b. down a mountain grade? Or did the Milwaukee try to minimize such situations out on the Pacific Coast Extension?
Another railroad that never had dynamics was Grand Trunk. Didn't have any grades to suffice them.
Cris_261 wrote: Seeing how MILW had locomotives with and without dynamic brakes, what sort of operating challenges were involved taking a train say with three d.b. equipped locomotives and two locomotives without d.b. down a mountain grade? Or did the Milwaukee try to minimize such situations out on the Pacific Coast Extension?
Modelcar wrote: No, exhaust is not the item that is used to apply braking force in dynamic braking system. The electric traction motors are electrically modified to act as generators on a down hill grade and that generated current is fed to a massive "resistance grid" which creates a "load" on the motors..{gernerators}. This creates a massive amount of heat in the grids and requires copious amounts of fan driven air over them to dissipate the heat. This process puts a "load" on the traction motors and provides braking force.
While the traction motors are not drawing amperage, but are still being forced to turn due to the train's momentum down grades, they become generators because they are essentially the same as dynamos that are forced to turn in hydro generation plants. They do not want to turn, but must, and this resistance robs the train of kinetic energy over time. The dynamic brakes, therefore, turn kinetic energy into resistance energy, and ulitimatley a lot of heat, since nothing on the train is using the energy produced by the braking. So, as stated above, the dissipation system comprises radiators and fans to blow out the heat build-up.
This is my rudimentary understanding.
Murphy Siding wrote: Are dynamic brakes of any use in breaking on a level track, or do they only work decending a hill?
Brakes are breaks, They work weather the train is going uphill or level or downhill. Though the way dynamics work the force varies. As the speed increases from zero there is a linear increase in breaking effort till the max amperage of the resistance grid is reached, 700 amps. Then from that point on the current is modulated (time division) so that 700 amps is not exceded. From this point the faster you are going the less effect the dynamics will have. For normal (non extended range) dynamics in run 8 that point is around 25 mph. For extended range that speed would be 12 mph (extended range DBs work at lower then normal speeds. Al Krug has a chart, I'll see if I can link it here.
OK here it is.
I think that's what he meant Quinten.
BTW- a portion of the energy is consumed running the fans to as they are powered by the grid current too.
Modelcar wrote:.....To remove the heat from the resistance grids a massive fan or fans directly removes heat from these grids...{not aware of radiators to do this job}, unless you cite the grids to act as radiators.
Hi. Yeah, even though they may be described as a grid, they still qualify as a radiative structure since the fans must do what they do in order to improve heat transfer to the medium...air. If the air temps were allowed to reach equilibrium with no convection or displacement, there would eventually be no heat escaping from the grid, and you would get overheating. The fans keep cooler air running over the grid (which thus becomes a sort of radiator) so that physics takes care of heat exchange with the delta of temps between grid and surrounding air. I believe it is the Stephan-Boltzman equation that specificies heat transfering between mediums based on the fourth power of the heat differential, so the more and cooler air you get around the grid, the faster the heat transfer.
I hasten to add that I have no schooling or expertise in this, just my basic physics coming back from the distant past....as in, waaaay distant past.
...Dale that's interesting....Getting across the conteninental divide at that altitude {3717}, at less than 1% grade surely hasn't been accomplished at other locations.
Over in the east where the ex. Pennsylvania and ex. B&O crosses the high point {Allegheny Mt.}, they make it at roughly 2200'. And to get the tracks up and over and through, required roughly 1.8% grade....with just a few places a bit steeper....That woud be the "Horseshoe Curve" and "Sandpatch route".
...Murphy, I believe a poster back further did indicate they can be an expensive item to maintain....Guess if their territory didn't have the grades to really "need" them they consider it an expense they can do without.
I would guess anything that is working in such a harsh environment would be a costly maintenance item...i. e. excessive heat cycles. and additonal heavy duty electrical controls, etc....
Murphy Siding wrote: Which leads back to the first question, I guess. Why do some roads remove them? It sounds like they would still be useful to a flatlander railroad? Are they a maintenance problem, if left on the locomotive? Or, perhaps the resale value of the parts is enough incentive? I'm confused.
beaulieu wrote: Murphy Siding wrote: Which leads back to the first question, I guess. Why do some roads remove them? It sounds like they would still be useful to a flatlander railroad? Are they a maintenance problem, if left on the locomotive? Or, perhaps the resale value of the parts is enough incentive? I'm confused.Simple answer, if they are there the FRA says they must work or the locomotive must be taken out of service for repairs. Of course if they fail enroute, then the locomotive can continue to a reasonable maintenance point. So if say the IC doesn't want to spend the money they remove the d/b. No money needs to be spent maintaining the d/b.
Aha! Now I see. Thanks
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