From time to time, I’ve read where a railroad has removed the dynamic brakes from some locomotives. Why would they do this?
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.
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.
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?
Aren’t dynamic brakes similar in function to the “Jake Brake” on a tractor-trailor in that they use the engine’s exhaust as a source of compression to slow the prime mover down?
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.
Ahh! Concise explanation! Thanks!
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.
Sure, but you want to get rid of the extra contactors in the electrical cabinet and the motorized switch that transfers the locomotive from traction to dynamic (the tow-motor switch) so you don’t have to maintain them. Also, you can sell the grids, fan, contactors, etc., as spare parts, and realize a not small amount of cash.
If a road is generally flat, then the dynamics wouldn’t really be needed. That would be a reason to remove them, though I also would think they would be just disconnected. Remember that the New York Central avoided dynamics as their relatively flat route didn’t call for 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.
Hi Quentin. That is Yellowhead Pass, on the British Columbia-Alberta border, just west of Jasper. Canadian National’s route over Yellowhead Pass was built by two Railways, the Canadian Northern and the Grand Trunk Pacific. The CNoR completed their line to Vancouver on Jan 23, 1915 and the GTP completed their line to Prince Rupert on April 7, 1914. The two lines through the Pass were consolidated into one line during a WW 1 scrap drive. Both of the railways were merged into CN after WW1. Grades are less than 1% due to the elevation of only 3717’. Via Rail’s Canadian and the Prince Rupert train use it as well. There was a lot of debate during the building of the CPR if they should use that route or the direct, shorter route they chose. The Yellowhead highway travels through there as well. They did not have to build a lot of tunnels, or cuts and fills, the CPR had those issues to deal with.
Google Map
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.
As of July 20, 1972, dynamic brake equipped SD-40-2s were assigned to Tacoma to power hotshots #261 and #262. Little Joes were added to those trains between Avery and Harlowton.
Trains #263 and #264 were assigned locotrol and dynamic brake units SD-40-2 (replacing SD-40 and GP-40 equipped units), SD-45, and non-dynamic brake FP-45’s all operating out of Harlowton.
However, whenever I actually saw an FP-45 in service in the mountains during that period, there always seemed to be electric power on the head end – I vaguely recall someone mentioning it was more for braking than power, but it’s been too long to recall specifics on that. In any event, the FP-45’s didn’t last very long out West and were quickly replaced by newly arriving SD-40-2s and sent back east. Other trains were assigned dynamic braking units or electric power.
Trains #265 and 266 were assigned SD-40s from the Coast Division power pool, and EF-4s were added when they operated on the Rocky Mountain Division.
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.
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.