A DCC Update

It’s been a while since I ruminated on my technological transitions on the model railroad. This should be quick.

For those who don’t obsess about some complete stranger’s model railroad, here’s the refresher. My HO scale version of the Moffat Subdivision was built using standard DC block-control wiring, which uses a simple current-based method for controlling trains. Increase the power to the rails, and the train moves faster. With the implementation of Digital Command Control (DCC), things are different– in some ways much simpler too. Because, when using block control, one flips a switch to kill the power to a block of track, and all action in that section comes to a stop. DCC, you simply leave all the blocks on, all the time, and let the command system control which trains move.

In my case, I simply installed a master bypass to go between power sources. To run DCC, I set all the block switches in one direction, flip the big one from DC to DCC, and bingo– we’re running on command control.

So, why not simply remove all the spaghetti and just make one great big power block to the track? I’m glad you asked.

Even though I’ve been adding decoders to locomotives at a steady pace, I still only have about 25% of the motive power converted over to the modern method. As long as I still have standard DC locomotives, it’ll be necessary to retain the ability to use DC block control to run them. So for that reason, I’m quite happy that I originally built the railroad as DC. That means, I can literally operate anything HO on it. That’s the first reason.

A couple of other less-obvious reasons have come to light, though. Now that I’ve been using DCC for 18 months, I have discovered that using consists is a great way to use remote locomotives (DPU, in the real-world parlance). But what happens when you have a single remote unit tacked on 24 cars behind the leaders, and the train goes into the reversing-loop section that only holds 14 cars (plus power)? There’s no way to run them in together without going into a short circuit situation when the leaders exit the reverse loop. Well, it turns out there is. Here’s the process. I drive the train into the reverse loop, stop it, uncouple the remote unit, turn off the power block where it sits, flip the polarity in the reverse loop, pull the train out of the loop and onto the lead track, turn THAT off, turn on the other block where the remote unit sits, reverse the polarity in the loop AGAIN, move that unit (using the consist’s train ID) into the loop, reverse the polarity to match the leaders, couple it on to the rear, and turn on the block where the leaders sit. And now the train is intact, with the consist all linked up as before! It sounds worse than it really is.

A second reason is: if there are units that I don’t plan to utilize for a while, I kill the power to their blocks so as to divert some amps to the remainder of the fleet. Sometimes, power gets scarce, especially if taking a heavy train up the grade.

And the final reason is: safety! In the Union Station scene there are tracks that have no bumpers on them. I’d hate for a train to accidentally get sent a command to move, and drive off the end and onto the concrete floor! (Don’t laugh. Once I thought I had shut down a consist, but it turned out their throttle was still set to 1. Two hours later I found these units clear up the mountain, apparently not moving at all but in reality just creeping very slowly!)

Yes. Having a versatile, hybrid railroad has turned out to be serendipitously cool.

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