CSX AC44CW Dynamic Braking issues during distributed power mode

[Hyperion]

While running the "Building America [Part 2]", train had 3 AC44CWs, two at the lead group, one at the trail. As I have read from other posts, the trail one was not properly set up, so I ran back there and set it up as stated in the manual.

Then after reaching a descent, when applied dynamic brake, the speed started jumping around, as if the whole train is braking and releasing, which does not happen for SD40 and GP38 locomotives. Even B2.B3 was about to bring the train to a halt, which is very strange.

The settings that I changed on the trail locomotive were turning ON all three switches, changed Headlight settings, Radio, Cutout and Valve were already correctly set.
Anyone else found the issue? DId I do something wrong?

[Jackthedragonkiller [Chirch]]

At Dynamic Brake settings 2 and 3 were enough to bring the train to a stop? It seems as if there's to much braking force because the Dynamic shouldn't be enough to stop a fully loaded coal train.

Have you tried the scenario without touching the trailing locomotive? I haven't played the downhill portion of it yet but I've been able to get going and up the grade with ease and never once touched the rear loco.

[Hyperion]

Originally posted by Jackthedragonkiller:

At Dynamic Brake settings 2 and 3 were enough to bring the train to a stop? It seems as if there's to much braking force because the Dynamic shouldn't be enough to stop a fully loaded coal train.

Have you tried the scenario without touching the trailing locomotive? I haven't played the downhill portion of it yet but I've been able to get going and up the grade with ease and never once touched the rear loco.

Well, I didn't actually let it stop the train, (and probably it wouldn't anyway). This is how it went,
Going down at 30 mph, set B3, then speed starts to decline in this weird pattern, as if its one step forward two steps back...
like 30 -> 32 -> 28 -> 25 -> 28 -> 25 -> 23 etc, and then if I even bring it down to B1, it still keeps doing this, as long as I do not take it off (or at setup).
So I was forced to keep it steady with Independent brake, which isn't probably an intended use of the brake.
I tried to run it without changing anything on the rear loco, it was very hard to get going, cause the rear one was probably applying brake force..... Not sure though.

[Hyperion]

On the other two locomotives, I am usually able to maintain a steady speed, using a combination of dynamic and independent brake, very close to (almost at) track speed, regardless of whatever. This seem to be a problem for AC44CW only. Currently trying again without the pusher at the end, will see how it goes.

[Hyperion]

Ok, just tested without the trailing loco, I think the Dynamic Brake system on AC44CW is just broken or bugged. It keeps pulsating the brakes, and once the pulsating starts, you have to to take it down to B0 to make it stop. Its like constantly pulling the lever back and forth.

How annoying.

[Jackthedragonkiller [Chirch]]

It may just be the locomotive bugging out then. Which is a little sad since last time they touched how the locos work on Sand Patch was like 1-2 years ago.
If you want you can just use the independent and train brakes going downhill. Heck I did that with every loco before I actually realized that the dynamic is easy to use and works efficiently.

[LeadCatcher]

Since dynamic brakes only effect the prime movers, on long steep downhills, apply the train brakes to help slow the consist and use the dynamics to adjust the speed.

In the past trains would stop at the top of the hill and crews would set brakes on cars through out the consist to control the descent. Once off the slope, the train would stop and the car brakes released.

There are plenty of videos where consists are surrounded by clouds of brake dust during the descent. Most roads would rather replace brakes shoes rather than clean up derailments.

[Hyperion]

Originally posted by Iron Knights:

You don't want to burn the brake pads downhill, that's why engine brake is better, I use it automatically, but when it doesn't effect the speed I put on initial reduction for the start & release it immediately after it starts slowing down.

Well, as I mentioned, I do that too, and it works well with GP38-2 and SD40-2 locomotives, I am having trouble doing that in AC44CW.

The train feels like it was throwing out some rippling brake... when I start to apply higher dynamic brake levels.

Finished the CSX journeys, and not touching the ACs anytime soon.

[rgx107]

I think the bug is in the engine physics itself. Normal behavior for dynamic brakes is that the brake force increases with increasing speed. On the implementation of AC4400 it's the opposite, you see the brake force going up as the locomotive slows down, and vice versa. It's as if the dev team got a minus sign wrong in the calculation.That makes it really hard to drive, and also causes the oscillations.

[Hyperion]

Originally posted by Iron Knights:

I found it's best to leave the Radio On and Control On as well as the other switches in the trailing AC4400CWs, in order for them to run full power and not dead weight. Got up to 75mph going uphill at 1.5% aka 5.4deg. climb. I got no idea who or why invented the % and what use is it to anyone.

Well, according to the manual, that's how we are supposed to set up the lead of trailing set. And I did that. Besides, I don't think there is any part of the road where you can go 75 mph without violating the speed limit. The sole purpose of this post was that I wanted proper braking so that I do not have to go over the limit, and at the same time finish the run in shortest possible time.

[Metallos]

Originally posted by Iron Knights:

Got up to 75mph going uphill at 1.5% aka 5.4deg. climb. I got no idea who or why invented the % and what use is it to anyone.

That % is the climb ratio / grade, for example 1.5 % is climbing (or the opposite...) 1.5 m on 100 m (horizontally) distance.
Much easier to handle than degrees and it's the standard on road and rail traffic.

[Hyperion]

Originally posted by Iron Knights:

As for braking, if the dynamic doesn't do it, just run with Initial Reduction.

I tried that too, but the problem with long freight trains is that, once the initial reduction catches up, the entire train start braking and speed drops suddenly. That works well for other maps though, like GWR or the German lines, but for CSX, it is a nono.

[Hyperion]

Originally posted by Iron Knights:

I It is not a set it and forget it type of brake. Unlike the SD & GP, the pressure valve for the brakes is set in the computer, make sure it is not set too high for the locomotives set to cut-in.

I'm pretty sure I set it to 90 psi as per the manual, but did not experiment with it.

Again, guys, I know the workarounds, I completed all chapters of the Journeys months ago. Just needed to know if the dynamic brake mechanism is faulty or not, or if I had set something wrongly.