How do 2 Loco's together work

Hi Everyone, I have been thinking about this for awhile. I seen it on model trains and all the time on full size trains. Some trains have 2 or 3 or even more loco's. How do you make this happen on a model train set. How can you have the loco behind the lead train be turned backwards and is it alive train or just a shell? I assume you can use to loco's facing the same way and have them both be working. Just curious about this.

Thanks Robert

 

If you're using DCC, you would program the units you want to run together as a consist. Here's how it works with NCE's Powercab. Let's say you've got two units, #800 and #802, and you want #800 as the lead unit and #802 trailing and facing backward. You'd hit the 'setup consist' button and assign a number to the consist (it starts as 127 and works downward). Then it asks what units you want to assign, first as the lead unit, then the trailing unit, and then any additional units in between. So you enter 800. It then asks what direction the unit will face, so you'd enter F. Next you'd enter 802 and R, since it will run in reverse. Now the two units are programmed to run in tandem. If you want to break up the consist later on, you would clear consist #127, which would reset the decoders in each unit.

 

Robert, Chriss pretty much told you how to set up a consist. Not difficult at all with any DCC set.

As a different way of looking at it is in analog,or DC, the direction of the loco is determined by the polarity on the tracks. To change direction you stop the loco change the direction switch on the power pack and start up again. For DCC, keep in mind that the control system, Digitrax, Lens or whomever, puts one constant polarity and voltage on the rails over the entire layout. The voltage may vary from one Manufacturer to another but I think it is safe to say that for N scale the typical voltage would be in the 13 - 17 volts range. Now the DCC decoder installed in the locomotive determines the direction of travel, speed, lights on/off, things of that nature.
When you stop and change direction on your throttle the decoder picks up those instructions and reverses the motor, thus the direction.

I think my explanation is pretty much right on but very simplistic. All of what I just said is what makes DCC so enjoyable. You control your train and not the rails.

Hope this helps you and thanks for reading.

Carl

 

The other thing that DCC makes possible for MU and distributed-power (e.g., mid-train or end-of-train helpers) is speed matching. With a bit of effort, you can adjust the speed of individual locomotives to match each other almost perfectly. DC locos from even the same manufacturer often vary significantly in how fast they run at a given throttle setting. This may not matter too much for MU (two or three locos at the front of the train), but if you try to cut in mid-train or end-of-train helpers in this kind of situation, you'll have a disaster. DCC makes it possible to do.

I know there are a lot of folks that don't want anything to do with DCC, and are quite happy with analog DC. My own view, FWIW, is that DCC makes some things (not all) simpler, but the real advantage is that DCC makes operating a model railroad like the prototype possible in circumstances where you just couldn't do it on an analog DC system.

John C.

 

Thanks guys for that info, I am running DC now but will be switching over in the near future. DCC does make it seam easier and nicer if you want to run more than one loco inline. I have no need to right now but hopefully will in the future.

Thanks Robert

 

Well put John!

I love to do the long trains with mid-train and end-of-train helpers! And yes that has only been successful with good DCC programming. What I need to add here is that the mid-train helpers need to be speed matched, but they also need the momentum to be different. When the train starts, the mid-train helper needs to be have slightly more momentum so that it starts rolling just a little after the front-end locomotives start rolling. Essentially when the slack comes out of the couplers of the cars in front of the mid-train helper. Similarly, the end-of-train helpers need to start rolling a little after the mid-train helper.

But when slowing down the reverse is the case. The front-end locomotives need to have a larger momentum setting than the the mid-train, and the mid-train needs a slightly larger momentum than the end-of train locomotives. The will have the lowest decceleration momentum value. This keeps the tail of the train from over driving through the cars and having a mess to deal with.

Unfortunately, even with DCC, this can still be tricky. It will depend on the number of cars in the sections of the train to dial it in correctly. One way you can dial them in using a small oval is the judge how much time it would take to pull out the slack of the train in front of the helpers.

As an Example:

75 ACF 3 Bay Hoppers with MT couplers between the head end locomotives and the mid-train helpers.

75 ACF 3 Bay Hopper with MT couplers between the mid-train locomotives and the tail end locomotives.

Lets say it takes about 4 seconds per set of cars to "take the slack" out. Then all you need to do is set the momentum of the mid-train helpers to start rolling 4 seconds after the throttle starts the train. Next the momentum of the tail end locomotives needs to be set to start rolling 8 seconds after the throttle starts the train. So the tail end locomotives have the largest momentum setting.

For slowing down the momentum differences are much smaller, but the highest momentum setting for decelleration is on the head end locomotives and the lowest would be on the tail end locomotives.

It is this ability in DCC that makes long trains with helpers possible.

 

Don't do What I Do
I fully agree with all of the previous points save only that I have never used / dealt with DCC. Given that you plan to move to DCC this post is moot except to be aware that it can be done in DC with great effort.
I have successfully balenced trains to run with one to two lead locos and one mid train loco. It requires trial and error and lots of extrapolation.
I discourage anyone from doing this except for the fun of it.

 

How about the accuracy of tachometer-speed-control in HO for consisting. I already have an HO steam locomotive test bed with this feature. I am working to have open-source HO Bluetooth control boards available toward the end of this year. This will provide another option for those of us that do not like complex CV adjustments and/or also be ablity to run on any type of powered HO track.
Bob

 

DCC makes pretty much everything easier. For a while I held off on switching, but now you couldn't pay me enough to go back to DC. Just getting rid of the block wiring rigmarole makes it worth it.