Reverse rolling -- repost

cabdriver

cabdriver

Member
Jan 23, 2005
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Sorry if I am messing this up -- I posted this in the general Tech forum and it was suggested there that I post this in the DCC section. I have copied my question over here. The thought in the general reply was that it might have something to do with startup voltage.

Hi all --

I've been trying to get logged in to the the-gauge for a couple days now -- had some technical problems that got resolved with the tremendous help of the admin folks here at the-gauge. Wooohoooo! Thanks guys!! I can now post!
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I've been reading many posts over the last week or two trying to get up to speed on a few things. I'm like many of you -- picked the hobby back up after many years, and am now building out a layout with one of my sons. We're having a BLAST!

Now that I can post, I'd like to get some help on a puzzling situation I just noticed. I have a P2K GP38 that I am running on our brand new track layout setup with DCC. The track is all on one level -- no changes in grade. I noticed yesterday that when the loco is stopped and the direction button is indicating forward, with no throttle the locomotive stays put. When I simply change the direction button to reverse, with no throttle, the train starts to move slowly backwards.
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Any ideas?
 
Have you got the make and model number of the decoder?

It could be that the voltage that causes the loco to go forward is higher than what causes the loco to go backwards. A speed table adjustment might be in order. It is also possible that the motor isn't running as well in the forward direction and operates better in reverse. Mechanical bearings etc. being as they are. An other possibility is that something is a bit off in the control unit, the throttle may actually get a little kick from pressing the direction botton.
 
Dave, how would you suggest I try to debug this? You mentioned some possibilities, but I am not sure how I would zero in on the root cause. I'm also not sure that this is something I really need to be too worried about at this stage of the game -- wanted to make sure though that it wasn't symptomatic of some bigger problem that might bite me big time later on.
 
I wouldn't worry too much about it. After the engine is run more you may notice that if you have it stopped that any change of direction will cause the engine to move .... forward if the engine was formally in reverse and reverse if formally in forward. This would indicate that movement on the control system is causing the throttle to move. If this becomes the case then an adjustment to the starting voltage (get out your decoder manual) would be in order or a different trottle was in order. When you get to the point of consisting you will discover that various settings sometimes need changing.

The control signals may be digital but everything else isn't.
 
Dave, thanks for setting me at ease on this. As I'm sure you can certainly appreciate, any deviation from what you expect, especially early on in a project, makes you wonder if you have done something wrong. When it comes to wiring, DCC, or locomotive behaviour, I'm certainly no expert.

This loco is brand new, so as you suggest, it may just be some start-up stuff. Since I'm new to the hobby I'm not always sure what is normal, to be expected, abnormal, or really a problem. That's why I appreciate the experience from you guys.
Thanks.
 
I hear you on the deviations. I always try to run my engines for a bit before doing any work on them. I was worried that one of my old timers wouldn't want to run again. A good cleaning, a light lube job, a bit of running back and forth and the little darling works great. But the first few back and forths were a bit rough. I'm still working on my newest loco, spent about an hour moving cars around the puzzle this afternoon. Plenty of back and forth doing that. But considering that is basicly all I can do right now I'm happy.

I just got back into the hobby and going to DCC on the restart. I've got a couple of locos I'm going to be putting decoders in. Right now I'm in the design phase and will be for a bit longer.

Goal is to somewhat model the interconnections of the B&M, MEC, B&A, GT, CP, and CN. I would really like to do the facility at Northern Maine Junction however boilers are in the way so I'm going to compress Northern Maine Junction (boy am I) . I like to run trains so structures and such take a back seat to track, rolling stock, locos, and signals.
 
When I got back into the hobby, I decided right away to go DCC. Thought it would give me more possibilities and I believe that is true. I got the P2K GP38 loco and put in a decoder (with a little help from the LHS). Runs great. I've got another DCC loco on the way, so I'll really be able to see the fun of running multiple locos on the track.:)

I'm modeling what my son and I call the "Alamo Southern line" -- late 1960s in South Texas (obviously my era, but boy does my son love the period cars -- 1967 mustangs, etc). What did I just say -- my era, period cars??? :eek: I can't be that old already! :D

Your track sounds ambitious. I have a long way to go with scenery, buildings, etc. What fun, though!
 
I graduated high school in '68 and lived about 1/4 mile if that from train yard.

Oh well I've got to pack it in, I was up early and spent all day on this one eyed monster except to move cars for an hour and fix and eat meals. This working at home is for the birds at times. Oh well my semimonthly bill was remitted via email this evening so a paycheck will arrive by Friday. Semi retired isn't bad. All the work one could want and all the freedom to play. Enjoy the hobby.
 
Cabdriver
Look for something like forward and reverse trim in your decoder manual. If it has such an option you can tune the forward and reverse running characteristics.
 
Yes, one always should read the decoder manual. There are dozens of knobs you can adjust and all decoders aren't the same. But first run the engine a bit, they really need to be run before making adjustments. Before changing a decoders settings make certain you can reset them.
 
Thanks guys for the suggestions. Any reason to run the engine is good, and I'll see what the manual says.
 
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