I think I understand how reverse loops work, but do I need a automatic reversing unit? I have the NCE Power Cab. You guys have been very patient and helpful, any advice you can give is appreciated. Thanks in advance.
BTW, I have chosen to model the Wexford County RR (in HO) featured in February's 2011 issue of Model Railroader and is here in the Track Plan Database. I have mirrored it on my 4 X 8. I Just started it and all I have is the plywood base down and some lines drawn on it. waiting for some materials to arrive so I can start working on it. I have decided to raise the track 2" with Woodland Scenics sub terrain Lightweight Layout System with advice from you guys here. Thanks. I will try and keep you posted on how its going, and I will certainly have a s**tload of questions, so be forewarned. Thanks, Trev
T
Just when you thought your layout was done, it's time to expand!
No, you don't have to have an automatic reversing unit -- you can use a toggle switch to reverse the loop's phase as you go around, but you'd have to stop the train before throwing the switch in order to keep your locomotive from briefly stopping and restarting. An automatic reverse module keeps this from happening.
If you're going to have a reversing section then get a reverser. You're just asking for trouble otherwise.
Good Luck
Springfield PA
cacole No, you don't have to have an automatic reversing unit -- you can use a toggle switch to reverse the loop's phase as you go around, but you'd have to stop the train before throwing the switch in order to keep your locomotive from briefly stopping and restarting. An automatic reverse module keeps this from happening.
Is that true about having to stop the train before throwing the toggle switch?
I recently set up a reversing section using a DPDT switch while waiting for an auto reverse unit that I had ordered to arrive. I did not need to stop the train.
Rich
Alton Junction
Not with DCC, you don;t have to stop the train when you flip the toggle switch. Since there will be a brief interruption of power, if the loco has sound it might trigger the sounds to restart depending on the decoder, for a motor-only decoder you will probably see just a slight flicker of the headlight.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
What if I wire the loop separately and keep it isolated from the rest of the track?
G1techguy What if I wire the loop separately and keep it isolated from the rest of the track?
Since you are operating in DCC with the NCE Powercab, if you don't want to invest in an auto-reverse unit, then set up a reversing section of track in isolation from the main layout.
String a pair of feeder wires from your main bus wires to a pair of end contacts on a DPDT switch. Then, wire a pair of feeders from the center contacts of the DPDT switch to the sub bus wires for the reversing section. The sub bus wires should be separate and isolated from the main bus wires.
String feeder wires from the sub bus wires to the track in the reversing section.
Lastly, cross wire the four end contacts on the DPDT switch to form an 'X" so that the flip of the switch will reverse polarity. Make sure that the DPDT switch is not a center off switch. You want a simple flip of the switch to immediately reverse the polarity.
Hey tech guy.
I Feed my reverse loop with a dpdt switch.I have a "Y" turn out to the reverse loop. The dpdt switch is feed to the center contacts and then out to the loop from the end contacts from the opposite side. the loop has insulators on both ends and both rails so that the loop is completely isolated. when I enter the turn out I make sure that the DPDT is in the same position as the turn out lever. Go right, both to the right. Go left, both to the left.Works for me.
Lee
That's what you HAVE to do. The problem occurs when crossing the rail gaps either entering or leaving the loop section - one way or the other, the polarity will not match (since DCC is a square wave signal, technically it's 'phase' and not polarity).
Wiring a toggle as above will do the polarity switch for you - you cna flip this right under a runnign train and it will continue running, the polarity of the track power has nothign to do with the direction of the train with DCC. However, you will ned to remember to set the toggle so polarity matches on the entrance of the loop for the next train - say you just ran a train around and exited the loop. If you leave the turnout as is, and bring the next train into the loop where the first one exited, all will be fine, the polarity will match and the train will enter the loop, at which point you can flip the toggle and line the turnout. But if you flip the turnout after the first train leaves the loop, you will also need to flip the loop power toggle as well, or the train will short as soon as it crosses the gaps.
Which opens up the mostly automatic option - if your turnout is controlled with a machne that has contacts on it, you can use these contact (or connect a relay to them) with the relay contacts wired in the X patter just like a DPDT toggle - so that when you aling the turnout, the track polarity will automatically switch.
Just remember that any of these electro-mechanical methods with toggles or relays can cause a long enough interruption in the signal that some brands of sound decoders will 'restart' and play an entire startup sequence. A quick flip of the toggle should keep this to a minimum. This type of control is in some ways better engineering-wise that the automatic reversers. Using the toggle, you are PREVENTING a short. The automatic reversers all work by first witing for a short to occur and then quickly reversing the polarity to make it go away.
Trev:
Just to add a bit to the suggestions about using a DPDT switch to control your reverse loop, I have seen examples where the modeller has used a slide switch (as opposed to toggle) mounted next to the turnout with a hole drilled through the switch handle to allow a wire link to be connected to the throw bar. That way you will be throwing the switch and the turnout in the same move. You may have to experiment with the link. If the DPDT switch and the throw bar move the same distance then the setup would be easy. Otherwise you might have to put a 'Z' bend in the wire link to give it some flexibility. With a little creativity you could make the DPDT switch resemble a remote control switch machine. The body of the DPDT switch can be buried in the layout with only the handle showing.
Dave
I'm just a dude with a bad back having a lot of fun with model trains, and finally building a layout!
Thank You very much for all your helpful hints and ideas. You guys are great!