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Dynamic Braking and EMD 'E' Units.

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  • Member since
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  • From: Louisiana
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Posted by Paul of Covington on Monday, February 21, 2022 9:12 PM

   Thank you, Dude.

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  "A stranger's just a friend you ain't met yet." --- Dave Gardner

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Posted by BigJim on Tuesday, February 22, 2022 9:10 AM

Paul of Covington
It also concerns me that there would be less pressure available in the emergency reservoirs if you do have to use the emergency application.


The "Emergency" Reservoir has a third more volume than the "Auxiliary" side. Pressure is a relative figure. Reading through this from Al Krug might be helpful to you: http://www.railway-technical.com/trains/rolling-stock-index-l/train-equipment/brakes/north-american-freight.html

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Posted by Paul of Covington on Tuesday, February 22, 2022 10:35 PM

   Thanks, BigJim.   I had read Al Krug's account many years ago, but was glad to brush the cobwebs out of my old brain and re-read it.

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  "A stranger's just a friend you ain't met yet." --- Dave Gardner

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Posted by RailfanGXY on Friday, February 24, 2023 4:09 AM

BEAUSABRE

One thing to note - many mountainous lines preferred F units after trying E units in the hills (GN, NP, ATSF come to mind) because they liked the idea of all locomotive weight being on the driving wheels. So the E unit became a flat land railroad's unit (CB&Q jointty owned by GN & NP continued to buy E's. SP&S, the other GN/NP serf was almost all Alco, not sure about whether the grades down the Columbia River Gorge would have led to E's or F's). As mentioned, as long as D/B was an extra-cost option, these lines figured they didn't need it and could save some money by not ordering it. Of the two biggest E8  owners, PRR stayed out of the D/B club because they figured whether they had E's or F's leading, they'd still need helpers over Horse Shoe and didn;t need it east of Altoona or west of Pittsburgh (I don't think the Buffalo Line (Keating Summit) ever saw E's on a regular basis). NYC? They were the Water Level Route, man...The same logic as the PRR might have applied to the B&O over Sand Patch, but why C&O didn't apply it to its 31 E8's, I must admit is beyond me

 

I'm tempted to say tonnage might've been a reason why. The C&O probably didn't have passenger trains heavy enough to consider installing DB on their E8's. Either that or they figured it would be easier to keep replacing any worn-out brake shoes since passenger traffic made up a much smaller portion of their revenue compared to the two other WDC-CHI routes. I'm not too well versed in the mechanics of locomotives or all of their benefits and handling in operation (I'm slightly unsure on what Power Braking is and how that differs from Dynamic), but C&O probably wouldn't want the extra equipment for a market they knew firsthand was quickly out.

BDA
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Posted by BDA on Friday, February 24, 2023 5:10 PM

Something I'd like to add about air flow and stretched vs bunched freighters .

People used to say that long trains would always take longer to charge or recharge in cold climates because cold air was "thinner" and the train leaked more .

I remember thinking no , cold air would be denser than warm air so how can this be . Eventually the maintainers said that there are bolted flange joints in train pipes under wagons . Apparently these sometimes don't seal as well when they are cold . This made more sense that the original theory .

A previous employers ore trains I ran were around 9017 feet long and keeping the train pipe charged with head end power only was interesting in winter . These trains used NYAB EP60 equipment and it will only allow the EOT BP pressure to drop so much before it pulls you up .

Interestingly I worked one of these trains out of a mine one winter morning and the EOT BP pressure varied depending on which way the line curvature went left or right . As the sun came up and the temperature increased the problem went away .    

 

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Posted by Overmod on Friday, February 24, 2023 6:42 PM

BDA
People used to say that long trains would always take longer to charge or recharge in cold climates because cold air was "thinner" and the train leaked more.

Not only is the cold air denser, it probably contains less moisture.

And it certainly got hotter than ambient when it was pumped up, some of which heat would be carried preferentially to any 'leaks', at least forward in the train, during pumping up.

I was taught the usual problem was shrinkage and some hardening in the seals between the gladhands in cold weather.  There was an article in Trains many years ago about a solid consist loaded with beets that had this issue in vicious cold weather: they pumped for two hours and got not a whit of trainline pressure.  Still makes me shiver a bit thinking about it.

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