Train Brake vs. Dynamic Brake

[Tomisnic]

I was wondering if someone could school me on when to use one vs the other. I use mostly the train brake now regardless of the situation...slowing down or stopping but I have no good reason for doing so...I've just started playing TS and know next to nothing about how actual trains operate. Thanks.

[skinnyraf]

I used dynamic brakes mostly when on a long downhill stretch, usually on US passes. When engaged, dynamic brakes allow much smoother adjustment than air brakes. I think there is a risk of derailment if a gradient is to steep though.
Most modern locos use combined air/dynamic brakes anyway: at higher speeds and lower breaking effort use only dynamic brakes. When stronger braking is needed, air brakes supplement dynamic brakes. Below some speed (30 mph?) is pure air brakes.

[mvsmith]

As said above, Dynamic braking is used for speed control on downgrades, never for stopping. Dynaamic brakes have the advantage of not depending uppon friction with brake shoes, which wears out shoes and wheels. Also, speed control via train brakes involves many apply/release cycles that can deplete the air supply and leave you with no brakes.
On the other hand, Dynamic brakes are like the locomotive brake, in that they cause the slack to run in and can cause derailment if applied too strongly.
Train (air) brakes apply braking to all wagons, so there is less slack run-in; however, brakes at the head-end do set first because it takes time for the pressure drop to propagate down the train line. Some trains have an End-of-Train device that dumps air in emergencies at the rear end of the train pipe to get better slack control.

[Tomisnic]

Got it. Thank you both.

[p.metzger59]

Thank you skinnyraf and mvsmith. I'm a novice driver. The tutorials for the ACS64 I believe recommend applying minimum air brakes periodically during the mild downgrade into Penn Station, but based on what you've written, sounds like pulling the throttle lever below 0% (this is dynamic braking for this loco, right?) would be the way to go.

[Ax Kramer]

The foregoing are correct and I would add that the effectiveness of dynamic brakes depends directly (approximately) on speed and the practical minimum for use of dynamic brakes is about 15 miles per hour. The dynamic brakes are using the traction motors to generate electricity instead of using it to turn the motors. On electrified lines traditinally that electricity so generated was "pumped" back into the overhead wire; for Diesel locomotives, the electricity is passed through resistance grids and converted to waste heat energy. Fans are used to cool the grids.

Set the dynamic brakes to hold the train speed approximately constant at the desired value and then use the air brakes to control the train from there. On many locomotives, the dynamic brakes have a lag of a minute or two after initial application before they actually activate.

[p.metzger59]

Thanks.

[skinnyraf]

@axkramer:

I was actually doing it in reverse, of course depending on incline. Yes, enabling dynamic brakes takes a long time, but when they are active, adjustments are much smoother than for air brakes and there is no risk of depleting the reservoir.
So I would engage air brakes only on slopes so steep that dynamic brakes are insufficient or pose a risk of derailment (tight curves). Then I would give a baseline with air brakes, engage dynamic brakes and use it for fine adjustments.

Disclaimer: I am not a rail engineer, so this experience is purely limited to Train Simulator.

[p.metzger59]

Thanks. I'll try applying the dynamic brake early in the gentle descent into Penn Station and see if I need to use airbrakes at all.

[Kyrah Abattoir]

In the real world dynamic braking cannot stop you as it's efficiency drop with your speed.
Because loco/dynamic brakes are only on the locomotive, you want to "compress" the train first by putting a light amount of air brake, this will compress all the train's linkage, you can then engage the dynamic brake and release the air brake.

Slapping the train in reverse is not dynamic braking tho.

[skinnyraf]

Wow, Kyrah, that's what we were missing. TS simulates train slack/compression (another question is if properly), so I wonder if this should be the approach in the game as well?