The ABTH (Air Brake & Train Handling Rules) tell engineers when and how to use dynamic brakes. I would like to know how to set this up on my Super Chief system. Which CV’s do you use on the decoder and which function key would you use to simulate the use of dynamic brakes.
It really has nothing to do with the system you’re using for DCC, it’s the decoder in the engine. Some just create the sound of the dynamic brakes but don’t change the engine’s handling, some make the dynamic brake sound and reduce the diesel engine rumble to ‘idle’ sound. Some will reduce the engine’s speed a set amount when the dynamic brake sound is engaged. You’d have to look at the manual for the decoder in the engine to see what is available and how to adjust the CVs to get what you want it to do.
Many decoders have settings for grade compensation. The manual will describe the CVs and suggest how to manipulate them for a given effect in motion. But as was already stated above by wjstix, this isn’t a function of the operating system, only a characteristic/configuration of the decoder installed.
Yes, indicated the system not the decoders. Am I correct that CV’s 55,56 and 57 are the ones that I need to configure?
Digitrax Turning on Back EMF describes the use of CVs 55, 56 & 57. they don’t seem related to dynamic braking
Which CV’s would you set to simulate dynamic braking? I would like to press a function key for example F7, and have the correct CV’s act like dynamic brakes and slow the train.
That depends on what decoder you have installed and it’s functionality.
Peter
I prefer the TCS plug and play 4 function decoders over the digitrax decoders because I do not have the problem of the decoder not making contect with the chassis due to it being too thin. The only function that I use is F0 for lights.
what would the difference be between dynamic, independent and air/auto brakes?
wouldn’t they all just result in a reduction in speed?
The difference is air brakes use the air in the trainline to apply the brakes, the independent brakes are the locomotive brakes and the dynamic brakes are the braking action created by turning the movement of the alternator to the brake grids to slow the train by creating resistance. All three slow the train. The ABTH (Air Brake & Train Handling Rules) state when the engineer is to use one or more of these to slow the train under particular circanstances. I would like to simulate dynamic braking. Looking at the TCS Comprehensive Programing Guide, it looks like CV’s 125, 126 and 127 would allow me to set them for decending values and I can then program them to a function key and simulate dynamic braking. Air and independent braking can be accomplished using the throttle to simulate the amount of air and/or independent braking is being applied.
Digitrax decoders have a setting for momentum; that is to say, accelertion (CV-03) and deceleration (CV-04). I only know about the motion control, not sound. But there is a noticeable change in the rates of accel and decel when you adjust the values for those variables.
Once you get the visuals of train motion to approximately something you like, you might have to piddle with the sound settings on your decoders to complete the illusion.
Hope this helps.
Robert
For model engines, the pressing the function button for dynamic brakes causes the sound decoder to make the continous whirring / moaning sound of the regenerative dynamic brakes being on. Some decoders also slow the speed of the engine during the time the dynamic brake noise is being heard, but for some it’s just a sound with no affect on the speed.
If the decoder has a train brake, pressing that usually stops the engine and makes a brief ‘brake squeal’ sound just before the engine stops. TCS Wow-Sound decoders (which might be what the OP is using?) come with CV4 deceleration momentum set very high (like 90-something) so pressing the train brake slows the train down around 1/3. You have to press it several times to stop the engine, unless you reduce CV4 to around 30 or less.
I think what the OP wants to do is set the decoder up so when he activates the function button for the dynamic brake sound, the engine also slows down - and perhaps so the ‘diesel rumble’ sound goes down to the idle/neutral sound? Without knowing exactly what decoder model he’s working with, it’s not possible to give a definitive answer.
For a model, there really is no difference in operation. Unless, like someone has observed, you want to change the sound to simulate the dynamic’s “whine” when in operation.
For models, dynamic and independent brake operations are the only two that act like the prototype. They both only apply to the locomotives and not the cars themselves. Both will cause the slack in the train to push or run into the locomotive. On the prototype improper use of both can, and has, caused derailments.
For the automatic brake on a model, it of course slows the train but not in the way the real thing does. On the prototype, the automatic acts on the cars. When applying the automatic brake, engineers are supposed to actuate or “bail off” the independent to keep it from applying.
Current practice is to use the dynamics as much as possible to control speed for fuel conservation. If dynamics aren’t enough, then use of air in conjunction with dynos is favored. Power or stretch braking, where the locomotives are still pulling the train while the automatic is applied is allowed up to a point because there are times and locations where it’s better for train handling.
I just have plain old DC, and don’t use the momentum and brake option on one of my MRC throttles. For those that want to simulate the difference in brake systems by using the throttles that look like a protot
not sure why choice of brake affect fuel consumption
my understanding is the maximum brake force is 10% the weight of the car/loco.
this means air brakes affecting every car and the loco applies a braking force of 10% the weight of the train. independent or dynamic brakes which only affect the locos is only going to apply a brake force of 10% the weight of the locos
of course, air brakes will slow/stop a train (a loco with cars) much more quickly than just the brakes on the loco
my understanding is independent brakes which can be partially released (like car brakes) are needed to position a loco precisely such as under a water tower or coal bin, or when switching cars. not so sure about positioning passenger train at a station
my understanding is air brakes affect the braking in the loco. i can see how that would apply dynamic braking and any sound (fans)
not sure about the effectiveness of dynamic vs independent brakes when comign to a stop
In dynamic braking the diesel engine is operating about equal to notch one in power. Stretch or power braking is done with the throttle in power, and either not reducing or only slightly reducing the throttle. It burns more fuel that way.
The independent can be fully released and normally is when making a automatic brake application, except when stopping. This is to keep the locomotive, which will brake harder than the train, from ramming into the cars following it.
On modern AC engines, dynamics can be used all the way to a complete stop. (Depending on train and grade conditions.) On the older engines, dynamics would fade out below a certain speed.
The independent is also used when starting a train to control speed so the head end doesn’t roll out and brake a knSpeed.
Jeff
thanks for trying, but don’t know what this trying to say?
my understanding of motor braking is that the motor is connected to a load that sinks current instead of a generator that sources current. it make sense that the load can be controlled with the notch with the generator idle.
can’t imagine how both a load and generator can be connected to motor at the same time (unless generator power is reversed)
applying brakes while under power certainly would burn more fuel. why apply power while braking except to “drag” the train to a specific stopping point (e.g. passenger train)
706
Power braking or stretch braking is having the engine still pulling while applying the train brakes, to keep the slack stretched in the train.
It provides a very smooth stop with little or no slack, at the cost of fuel consumption. It was the default method of braking before dynamic brakes and is used for passenger trains, because it provides such a smooth stop.
Dynamic braking is used when the engine and train are going downhill. The wheels of the engine are turning because the engine is being pulled downhill by gravity. In dynamic braking the turning wheels turn the electric motors in the trucks, changing them from using electricity to generating electricity. This causes the wheels to not turn as freely as it would if it were just coasting, and this slows the locomotive down. It uses little fuel during dynamic braking, since the diesel motor only needs enough fuel to keep turning at idle or a very low level until it’s needed again to pull the train on flat or uphill track.
On electric locomotives, it’s called regenerative braking, because an engine going downhill can feed the electricity it’s creating back into the overhead wire, which can then be used by other engines.
Hello All,
While I understand what the OP is asking for I don’t believe it is available as a single function in DCC–for diesels.
Under dynamic braking in The Digitrax Big Book Of DCC; pg. 143, it only compares the Back EMF of a decoder to the prototypical practice of dynamic braking.
It talks about how Back EMF relates to motor speed stabilization and not as a braking control function.
At one point it says that Back EMF is like cruise control on an automobile and that its function is to manage the speed of the locomotive motor to provide a consistent speed relative to the throttle setting.
Which seems to be the opposite of what the OP is asking.
Steam sound decoders have chuff synchronization and load compensation sound effects.
I don’t know if these could be “translated” to dynamic braking in diesel sound decoders.
My best suggestion would be to map the dynamic braking sound to a single function button and then manually manipulate the throttle to slow the engine(s) as they descend.
Hope this helps.
During the application of dynamic brakes the engine speeds up to provide power to the traction motor blowers and the fan which provides air flow for cooling.
The throttle can also be used to modulate the amount of braking by changing the amount of power delivered to the traction motors for that purpose. More power, more braking.