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eaglestar

"Power braking" SMEEs

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I got to thinking about the relationship between the master controller and brake valve on an SMEE. Let's say a T/O has the master controller in paralell (which is the highest position of power, if I'm not mistaken.) They then take air on the brake valve. I'd imagine that the power automatically gets cut until the air is released. If so, would the master controller need to be brought back to “off” before the car will take power again (as it is on our [Amtrak's] electrics?) Or will the car automatically take power as soon as the brakes are released? Also, would there be any reason for not knocking off the power before grabbing air/ do some T/Os make a habit of it? Obviously wouldn't be possible on an NTT.

 

Thanks in advance, it's fascinating to learn these nuances.

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It is possible to take power while holding a brake. A standing brake test involves dropping your straight air to 30lbs and taking 2 points of power. If the train doesn’t move, your brakes are good. Sometimes when you need to make exact movements when spotting a train, you hold a brake so that when you knock off power, the train will stop on a dime.

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Years ago I had an NJT motorman explain to me that his trick to smoothly braking the Arrow consists was to apply the brakes while power was on. I doubt the maintenance department was a huge fan of his work, but he did operate remarkably smoothly. 

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22 hours ago, INDman said:

It is possible to take power while holding a brake. A standing brake test involves dropping your straight air to 30lbs and taking 2 points of power. If the train doesn’t move, your brakes are good. Sometimes when you need to make exact movements when spotting a train, you hold a brake so that when you knock off power, the train will stop on a dime.

wow where have you been? 

22 hours ago, MHV9218 said:

Years ago I had an NJT motorman explain to me that his trick to smoothly braking the Arrow consists was to apply the brakes while power was on. I doubt the maintenance department was a huge fan of his work, but he did operate remarkably smoothly. 

Browsing railroad forums, many of the retired engineers shared their "stretch-braking" stories. Seems to be a popular technique many of them used to keep the slack from running in. Not sure how popular this method is nowadays since the railroads or big on fuel consumption. Maybe @INDman can enlighten us on that.

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23 hours ago, INDman said:

It is possible to take power while holding a brake. A standing brake test involves dropping your straight air to 30lbs and taking 2 points of power. If the train doesn’t move, your brakes are good. Sometimes when you need to make exact movements when spotting a train, you hold a brake so that when you knock off power, the train will stop on a dime.

AKA " flashing your motors ". Loved to do this in a yard next to an apartment building or complex. Nothing like setting off sparks in the nighttime when the kids were supposedly asleep.😊

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Thanks, guys. 

When running the diesels (P42s), we tend to stretch 'em to avoid slack (also, the GEs don't load up so fast- idle to notch 8, and we're talking a good 30-45 seconds to get full horsepower, so keeping the power on cuts down on the delay.) The electrics (ACS-64s) don't allow such a luxury, as they automatically cut the power as soon as the brakes are applied (although the "loading" is instant, so the primary concern is slack, which can be abated by keeping the engine brakes "bailed off" [another alleged no-no, but one they often look the other way on.]) 

 

Blended braking (shutting the throttle off and allowing the brakes + dynamics to apply) is the "preferred" method, but one that, depending on your territory and how you do it, may not be enforced. 

 

Thanks again for your insight- it makes the rides that much more interesting.

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So you guys are allowed to go straight to full throttle from a standing still on any locomotive hauling passenger cars?  I always assumed you had to ease your way up to prevent in-train forces (like freights). 

Also are you guys allowed to use dynamic braking in passenger service?

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I wouldn't say "allowed" (although most road foreman probably wouldn't say anything.) If the slack is stretched, it wouldn't be as much of a problem.

The electrics (especially the venerable old HHPs) tend to slip, especially if rail conditions aren't anything but ideal. So it's a good idea to ease into it (but again, not everyone does.)

The diesels are something of an enigma. Coming from idle to notch 1 or 2 while stopper will result in an instant 300 or 600 amps, respectively. "Racking" it to notch 8 causes a delay of amps for about 5 to 10 seconds and then an almighty surge, usually followed by slippage, followed by the train slamming into the back of the engine, so we usually let the amps stabilize at the lower end and THEN notch out to 8. The diesels also react differently from notch to notch. For example, going from notch 1 to 4 brings your amps up quicker than from 2 to 5, etc. Of course, these are 25 year old GE computers doing the magic, so....

And yes, we sure can dynamics. In fact, they're encouraged as a "fuel conservation" technique. I try to use dynamics as much as I can, but when one factors in the 10 second delay from power to dynamics, or vice versa.... Lots of times, its just better to stretch. The dynamics also drop out insanely early, about 25 MPH they start to fade and are virtually useless below 10. 

And don't even get me started on the blend...

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9 hours ago, eaglestar said:

I wouldn't say "allowed" (although most road foreman probably wouldn't say anything.) If the slack is stretched, it wouldn't be as much of a problem.

The electrics (especially the venerable old HHPs) tend to slip, especially if rail conditions aren't anything but ideal. So it's a good idea to ease into it (but again, not everyone does.)

The diesels are something of an enigma. Coming from idle to notch 1 or 2 while stopper will result in an instant 300 or 600 amps, respectively. "Racking" it to notch 8 causes a delay of amps for about 5 to 10 seconds and then an almighty surge, usually followed by slippage, followed by the train slamming into the back of the engine, so we usually let the amps stabilize at the lower end and THEN notch out to 8. The diesels also react differently from notch to notch. For example, going from notch 1 to 4 brings your amps up quicker than from 2 to 5, etc. Of course, these are 25 year old GE computers doing the magic, so....

And yes, we sure can dynamics. In fact, they're encouraged as a "fuel conservation" technique. I try to use dynamics as much as I can, but when one factors in the 10 second delay from power to dynamics, or vice versa.... Lots of times, its just better to stretch. The dynamics also drop out insanely early, about 25 MPH they start to fade and are virtually useless below 10. 

And don't even get me started on the blend...

Do you by any chance run dual modes into Penn?

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8 hours ago, Jsunflyguy said:

Do you by any chance run dual modes into Penn?

Nah, I work out of D.C. I've heard that the Dual Modes have their own list of quirks. I'm curious as to how they'd pull, given that they have a lower HP rating (but only by 400, given that the '42s can only put out 3650 in HEP mode), but AC traction. I'd imagine their dynamic is stronger than the DCs, too. 

As I understand it, dual modes have no dynamic when operating in third rail mode, not sure if that's the case. I've also heard that the MNRR dual modes have no bail off feature, thus necessitating the use of blend for everything, can anyone confirm?

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6 hours ago, eaglestar said:

Nah, I work out of D.C. I've heard that the Dual Modes have their own list of quirks. I'm curious as to how they'd pull, given that they have a lower HP rating (but only by 400, given that the '42s can only put out 3650 in HEP mode), but AC traction. I'd imagine their dynamic is stronger than the DCs, too. 

As I understand it, dual modes have no dynamic when operating in third rail mode, not sure if that's the case. I've also heard that the MNRR dual modes have no bail off feature, thus necessitating the use of blend for everything, can anyone confirm?

Our DE/DMs have the bailoff pinned, so I wouldn't be surprise at MNRR being the same. I was curious how they operated into NYK since MN goes to GCT with 1 engine, and so does Amtrak. Although they have a substantial number of advantages in terms of Grade vs loading.

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2 hours ago, Jsunflyguy said:

Our DE/DMs have the bailoff pinned, so I wouldn't be surprise at MNRR being the same. I was curious how they operated into NYK since MN goes to GCT with 1 engine, and so does Amtrak. Although they have a substantial number of advantages in terms of Grade vs loading.

Hmmm, interesting... So do your dual modes drop the load when you set the automatic? 

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8 hours ago, RTOMan said:

Good Post here i learned a few things!

Same here.

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The P32 dual mode indeed to not have dynamic in third rail mode. Part of the electrical circuit used for dynamic braking is re-tasked for 3rd rail ops.

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can't wait to see what will happen if they put in the order for the dual mode Chargers Siemens mentioned a few years back. 

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