I’m a self-taught novice model rr’er (3 years off and on, more off than on, but now a medical condition is giving me a lot of free time in need of filling, so…). My question is so simple, I’m almost embarrassed to ask, but I have no choice.
I’m building a simple HO DC layout with a double loop, a siding and a spur, with six remotely controlled (I hope) turnouts. The track is all laid and tacked down, and wired for track power (switches aren’t wired yet).
My question? Why will my brand new locos run in only one direction, right to left?
I knew the electronics would be my downfall. I can’t solder for beans, so I don’t do anything requiring it. I’m using a standard Atlas power pack as primary, and an Athearn as back-up – the problem happens with both. I have both a terminal joiner for power (didn’t work very well), and terminal track. I’d like to post pictures of how it’s wired, but doing so here is a challenge to say the least. I have 20 gauge red wire from the common rail, or in the case of the terminal joiner, the common-rail wire, to the red attachment of the power pack. It’s a bit dicier with the Athearn since the polarity at the screws is not labeled. The locos, both of which are Walther’s HO models, both “DCC compatible.” (again, no interest in DCC at this time).
I have checked the track a dozen times to make sure everything is properly connected and cleaned, and there are no short circuits. I’m using the Atlas wiring book as my guide.
Bottom line: My brand new locos will run only one direction on my HO DC layout. The problem is almost certainly in the wiring. Any ideas?
Mel is correct. To me it sounds like the reversing switch in your power pack is faulty. That is rare, fortunately.
Try reversing the wires that come out of the pack to the track (reverse them anywhere - at the pack or at the track). The engines should now go in the “other forward.”
If the reversing switch is faulty (and assuming we are not talking a brand new DC power pack that can be returned) it is possible to save the pack and use an Atlas reversing switch; somewhat more cumbersome but frugal. I think the Atlas 220 controller would work, although it is intended for a reversing loop situation.
There may be cheaper reversing switches out there - any double pole/double throw toggle switch would work - but they may call for going to other than a hobby shop.
The DC motors turn one direction only…at a time. In the same length of powered track, both locomotives will move one way…only…including only one direction around a loop. If you take one locomotive and turn it around, they’ll do the same thing…both moving the same direction around the loop. This is because, while you have reversed the direction one of them faces, you have also reversed the power orientation below the engine…you have reversed the polarity of the rails. When you reversed the power below the locomotive whose motor now has been rotated 180 degrees, you make that motor spin the other way. Logically, it still moves the same way as the other locomotive.
Let me try to clarify and give a little more detail. I only had time to try one thing, and gather some details. For clarity’s sake, let me start with my terminology definitions.
“Forward” and “Reverse” are vague, relative terms. “Forward” to me means the front of the train moving clockwise (to the left), “Reverse” when it’s moving counter-clockwise (to the right) .
I am only referencing one power pack, a Railpower 1370 which I know works fine.
I’m also only talking about a terminal rail – I didn’t have time to test the terminal joiners as a power access point. To me, when looking down at the power pack the “fwd/rev” switch is: left = fwd, right = rev.
The loco I used (and for continuity’s sake the one I will continue to use to carry out any other tests) is a Bachmann #62812 GP9 DIESEL (DCC EQUIPPED) - Bangor & Aroostock #80. I did not bother using the other – I won’t be running it, it’s just a hair too long for my layout – so I wouldn’t muddy up the waters any further.
Power is supplied through a terminal track connection, #20 Red to the common rail screw, thence to the left DC screw on the pack; #20 Black from the negative (non-common) screw on the track to the right connecting screw on the pack.
I hope I make sense.
Now, with the switch on the power pack to the left (“forward”), and the rear of the loco facing clockwise (left), the loco travels clockwise. When I flip it around so the front of the train is facing clockwise (left), nothing happens. When I move the switch to the right, and the front is still facing c
To confirm your track wiring from the power pack try a non DCC locomotive. If a non DCC locomotive works correctly from the Forward/Reverse switch on the power pack the problem is in the DCC locomotive, most likely not programmed to operate in DC mode or the decoder is corrupt.
Mel
Modeling the early to mid 1950s SP in HO scale since 1951
Ah I think I see, although your description is a bit murky to me. In DC forward and reverse are not related to the locomotive’s front and rear, but to any thing on the track. Instead of thinking forward and reverse think of “this way” versus “that way.”
So if the “front” of a locomotive goes right, and you pick up the locomotive and turn it around and put it back on the track without touching the reversing switch on the power pack, it should still go right.
And vice versa
The electrons don’t know where the cab or front of the locomotive is and don’t care.
DCC is different but not relevant to this discussion.
This is why you can have, say, F units back to back and they’ll run in the same direction (assuming they are wired to NMRA standards) and not pull or push against each other.
The OP is saying when he turns the loco 180 degrees it doesn’t go at all. The forward and reverse switch on the power pack does nothing. With his loco at the 6 o’clock position on a roundish layout, the nose facing 5 and the tail facing 7, the loco moves in the direction the tail is pointed.
It is DCC equiped, with a dual mode decoder. If you bought this from a dealer, out of the box, it should be set for DC.
If you bought this from a previous owner, like from Ebay, it may have been switched over to DCC. Not that this might have anything to do with the loco running in one direction only. Just thinking this through outloud.
What do the lights do? With the directional switch on the power pack, does the light on the loco change? from the front to the back?
Mike.
EDIT: OK, the link doesn’t work. When you go to Bachmann’s site, and look at HO scale diesel locomotives, scroll down, click on GP9’s, you’ll see what I’m seeing. For whatever reason, it doesn’t link.
If I am understanding your post correctly, your loco only runs one direction, and only when facing that direction?
As in it only will run by the power pack when facin left, moving right to left?
And when you flip the switch to reverse, to run left to right, it doesnt run at all?
If the loco faces right, it won’t move at all either direction?
Curious, if this is correct, what is your second loco? Is it also DCC Equiped?
And, my silly question time, when you are placing the loco on the track facing right, it’s on the rails fully, and the power is turned back on, right? (Sometimes the silly reason is it, but something tells me it is not this…)
Dave – I just want you to know there is nothing about your post I find remotely insulting or offensive.
[quote user=“dknelson”]
The electrons don’t know where the cab or front of the locomotive is and don’t care.
That’s the kind of metaphor my brain likes.
Ajhall
Now, with the switch on the power pack to the left (“forward”), and the rear of the loco facing clockwise (left), the loco travels clockwise. When I flip it around so the front of the train is facing clockwise (left), nothing happens. When I move the switch to the right, and the front is still facing clockwise, nothing happens. When I flip the loco again (rear facing left), it moves to the left (clockwise).
I hope the above helps, and doesn’t make thing murkier.
Ah I think I see, although your description is a bit murky to me. In DC forward and reverse are not related to the locomotive’s front and rear, but to any thing on the track. Instead of thinking forward and reverse think of “this way” versus “that way.”
So if the “front” of a locomotive goes right, and you pick up the locomotive and turn it around and put it back on the track without touching the reversing switch on the power pack, it should still go right.
I have a lot of testing to do when I go down to the layout later this afternoon. I may try to do a short video with my phone, and upload it to YouTube or create an Instagram account and post the link. If I can’t make that work, I’ll take notes on what I’m seeing as I try all the suggestions.
I want to thank everybody for taking time from your day to answer my questions. It’s appreciated.
I just had a thought. Would it help if I tried getting a DC power reading with a multi-meter. I’ve never tested for DC power, just AC circuits, but it can’t be that hard to figure out.
I’d suggest setting up an isolated test track. I’m assuming you’re using Atlas track since you mention using one of their booklets on track and wiring. Get one of the 9" terminal tracks and hook it up to one power pack’s DC output. Maybe add a couple of straights on each side (either their sectional straights, or add a piece of flex track to either side).
Try the engines on the test track one at a time. Don’t pick up the engine once it’s on the track, just use the reverse switch on the power pack. If an engine works OK in both directions facing one way, then turn it 180 degrees and try it again. If they both work on the test track, then the error is in your wiring on the layout.
If the goal is to check the reversing switch on the power pack, disconnect the two track feeders at the power pack terminals. Set your meter for DC voltage, at a setting more than 12 to 14 volts DC. Connect one lead to one of the power pack DC terminals, and the other lead to the other terminal. Move the power pack control handle/lever to the increasing speed position.
You should see a voltage value on the meter. It will either read a plus or minus value. Throw the reverse switch. The meter should now read the opposite voltage value (assuming you did not change the lever position). If it does, this means that the reversing switch is okay.
With an Iphone this is easy to do. I’m sure other smart phones are up to the task.
It never hurts to measure voltage when locos don’t run. That said, I think the reversing switch is a red herring and the problem is the decoder needs a reset. Why?
You put the loco on the track and it runs in one direction.
That proves you have adequate voltage in the track
That proves you have adequate electrical pick up in the loco
Turn the loco 180 degrees and it doesn’t go.
The track voltage hasn’t changed
The electrical pick up hasn’t changed
You haven’t told us you are pushing any other buttons or switches that we don’t know about.
DCC decoders that need a reset can do weird stuff on DCC, why can’t they do weird stuff on DC? Does the other loco actually do the same thing?
The Bachmann loco he is using for the test has the brass wipers. What are the chances that both feeder wires from the wipers came off, on one side. [:^)]
Although, it has happened to me, once, from an Ebay deal. Bought the loco as parts, ad said it didn’t run, and that was the cause.
I dunno, one of those things that you wish you could be there, and see whats happening. [(-D]
If both pickups fell off the loco on one side, it wouldn’t run at all. That does not seem to be the issue at all. It’s as if the motor simply can not turn one way - if it runs with one combination fo facing a certain way AND the direction switch set one way, if the loco is physcially tuend around AND the direction switch flipped, then the motor would be turning the same way it was in the running configuration. Since that fails, I can only guess the direction switch is broken and no power gets to the rails. However, with the loco physically turned around but the direction switch untouched - the loco should move in the same physical direction as the working mode, except that it will be running ‘backwards’ relative to the cab position. Since that also does not work, it seems to rule out the direction switch. This is definitely a mystery, it makes no sense electrically. Unless there are actually two problme shere, one being a failed direction switch int he pwoer pack, the other being something wrong internally in the loco. Easily verified with a cheap digital meter set to DC volts. I just don’t knwo what could make a loco alone behave like that - only spin the motor in one direction, sure, lots of ways to mess up the internal wiring to make that happen. But turning the loco end for end on the rails AND flipping the direction switch does not change the direction the motor is trying to rotate.
