Bachmann DCC Onboard Stuttering GPs

[Flashwave]

Posted this before, but I didn't get help, so I'll try again  with video this time.


A little video: Please note that the light flicker in the engines are the engines shorting out. These are stock Bachmann locomotives from the DCC line, and not one car on the train is derailed, nor is the engine I pick up off the track and put back on. The train is on a hill, the single GP is not strong enough to lift the train out of the bowlbut you can see its headlight is solid through the controller's cable, and as soon as I put the other engine back on, they run fine together. They were consisted on a 400 and then dumped so I could run them on my UT4. It doesn't matter which engine I pull off, and sometimes putting one of them back odoesn't fix it. They onyl do it in that section of the layout, so I'm inclined to think there's something they don't like about the way its blocked, but those two are the only engines that short like that through there. Different engines, different consists, different trains don't give anyone the same problem. It's just those two.

[Jhanecker2]

Flashwave from the viewing angle of your video ,  your track elevation appears to be excessive  and your radius appears to be too tight .  You could be overloading the engine , check your track width with a NMRA gauge to make sure your not binding the wheels .  Just an opinion .  Do  you  have a Voltmeter and an Ammeter that can read   DCC Voltage & ampereage ? An ordinary  VOM  will not do , your trying to read Pulsed Square Wave in
DCC signals.  J2.

[railtwister]

Flashwave,

Is there an operating light on the second unit as well as the first? If so, turn it on and see if it stays on when the lead unit's headlight goes out. If so, then it's not a short, it's an open circuit in the lead unit, causing it to lose power. If both lights go out, then it's a short, and could be in either unit or both, or between the two if you have metal couplers in metal frames (a long shot, I know). It looks like there is a bit of a dip in the track where the problem occurs, so if this were to cause one of the lead unit's trucks to pitch up or down slightly, just enough for it to break contact and lose power, it could cause the train to stall. Have you tried switching the locos (put the second one in front), or pick up both and turn them around as a pair, or add a third loco to the consist, to see if anything changes? Also, does it only happen with these particular locos, and does it happen without the cars attached to the train, or only with the weight of the train?

Bill in FL

[jonathan]

Having watched your video several times, I am inclined to believe there is a trackwork problem, not a locomotive problem.

I understand other locomotives are making it through this area without issue.  However, it could be the other locos are just forgiving enough to pass through this area.

You have a curve and sharp incline happening at the same time.  Can't study the problem in person, but I would be checking for good current flow through the rails in that area.  Also, I would push one of the locos through very slowly, without power, to see what's going on physically with the loco, as it moves through the curve and comes out of the 'bowl'.  There could be any number of track issues that could cause a momentary lapse in power.

Just an opinion.

Regards,

Jonathan

[bapguy]

Since you mentioned a UT4 throttle,I assume you're using a Digitrax system. With Digitrax, a short will cause the system to beep several times and shut off the power to the tracks until the short is removed. If you hear no beeps when the loco stalls, it's not a short bbut probably a track issue. If the problem only happens with one loco and not runnig both together, the second loco might have all wheels contacting the track and pushing the lead loco. Once past the spot the lead loco will then pull the second one over the bad spot. Just a thought.  Joe.

[Flashwave]

The radius there is I believe 30" but there is a known and documented bowl there nonetheless. It might only be 28.  There's a few spots it'll do it in, that's just where I caught it in. One's in the middle of a yard, the other's through the main with only a passing track and a short spur. I inherited Dad's voltmeter, not sure what type it is but I'll check it next time I'm down at the club.

The Headlight: No, the second loco does flicker with the first engine, both of them short until I take one of them off the track. You can't see it because some dummy stuck the throttle in the way, and if it weren't coupled to the train, then I could take the rear loco off and get the same result.

I don;t think the train makes a difference, but as I think about it, I'm not entirely sure about that, so I'll look at that as well, and try hand-pushing them through that bowl. As far as I know, it's only those engines, they're the only ones of mine that act up, and I haven't had any problems with the four Bachmann RF16s I've put through there, but its been a while since I've run them.

Thanks guys! I'll take the list with me and check these.

[rogertra]

Hard to tell what the issue is without being there and without taking the lead locomotive apart.

What we do see are: -

The grade in the curve seems excessive.  Are these metal cars and are their bodies touching?

Can't really comment on the curve radius as from the viewing angle it's hard to tell.  If it's a sharp curve, less than say 28 inches, are the bodies touching?

There is a noticeable dip in the track where the lead engine stalls.  Wonder of this causes the locomotive to ground out, the fuel tank perhap?

Are you using all metallic couplers between the two locomotives?  That could cause a short.

What happens if the trailing unit becomes the lead unit, does the lead unit still stall?

[Flashwave]

Hard to tell what the issue is without being there and without taking the lead locomotive apart.

What we do see are: -

The grade in the curve seems excessive.  Are these metal cars and are their bodies touching?

Can't really comment on the curve radius as from the viewing angle it's hard to tell.  If it's a sharp curve, less than say 28 inches, are the bodies touching?

There is a noticeable dip in the track where the lead engine stalls.  Wonder of this causes the locomotive to ground out, the fuel tank perhap?

Are you using all metallic couplers between the two locomotives?  That could cause a short.

What happens if the trailing unit becomes the lead unit, does the lead unit still stall?

1) Noted, and no. Those are Walthers coaches. Plastic bodies. Kadee Couplers, so if they are somehow communicating a current into the coupler screws and then into the lighting systems, but that's a fairly large if.
     1a) It's not the lighting systems in the coaches ut I have already ruled that out

2)Nope.

3)Hmm. Will add that to the list of things to check on

4)I don't believe I've changed the couplers out, I think those are the stock plastic ones. Will check when I get to club.

5)Both engines are stalling at the same time. Will check directional toggle again just to be sure, but I don't believe it matters.

Oh, and to keep in mind, the negines ARE pulling for that brief moment their lights come on. It's not actually a stall like I'm used to thinking of them, hence my calling it a stutter. They do also stall out other engines in the DCC block too when they act up

[rogertra]

You don't have a stall. you have a dead short.

A stall is even though power is applied, the units are working, they cannot pull the load up the grade.  That's a stall.

It seems what what you have is a dead short as both engines stop working.

Basic trouble shooting is required. 

- Do both motors stop turning?

- Do all headlights go out?

- Does any other motive power in the power district also stop?

If the answer is "yes" to any of the above that = Dead short.

Run each locomotive round the curve, up the grade and through the dip on its own.

If one or both short as they run though on their own, then you know the trouble is either inside the body shell or both locomotives are shorting due to the poorly laid track that creates the dip.

If neither shorts when running alone, then you know the problem is only caused when they are coupled together.

Try running just the locomotives, coupled together through the dip.

Which one shorts?  Just the lead or just the trailing unit?  Swap them around so that they take turns leading and see if it's always the same one that shorts?

You have to try all these combinations to find the fault.

[Flashwave]

You don't have a stall. you have a dead short.

A stall is even though power is applied, the units are working, they cannot pull the load up the grade.  That's a stall.

It seems what what you have is a dead short as both engines stop working.

Basic trouble shooting is required. 

- Do both motors stop turning?

- Do all headlights go out?

- Does any other motive power in the power district also stop?

If the answer is "yes" to any of the above that = Dead short.

Run each locomotive round the curve, up the grade and through the dip on its own.

If one or both short as they run though on their own, then you know the trouble is either inside the body shell or both locomotives are shorting due to the poorly laid track that creates the dip.

If neither shorts when running alone, then you know the problem is only caused when they are coupled together.

Try running just the locomotives, coupled together through the dip.

Which one shorts?  Just the lead or just the trailing unit?  Swap them around so that they take turns leading and see if it's always the same one that shorts?

You have to try all these combinations to find the fault.

-Yes, both motors stop turning. And then they start again. And then they stop. Then they start. Then they Stop. Then they start. Then they Stop. (I start saying colorful words and yank them off the layout) ecetra, ecetra, ecetra. As fast as your reading that is aabout how fast it happens. Its almost like dirty wheels more than it is what I think of as a dead short. Hence why I'm here. Amd tey are moving a miniscule distance.

-Yes. See above.

-yes. When they do this stuttering short, it fubars other engines in the block. I'll gety back to you tomorrow as to whether or not they stutter as well or if their dead dead.

They won't act out if the other one is not on the layout, even if they're still consisted. So yes, it has something to do with them being together, but those are plastic couplers, so its not shorting through the coupler and they aren't touching bodies. Also, they'll run just fine for long parts of the layout, so the problem seems to be

bachmann GP7 5607+Bachmann GP7 5608+a few key spots in that particular block like the one I videoed=Stuttering/Pulsing/Rolling Dead Short.

So its either something about the track, or the wiring, that is disagreeing with the engines. (Ooh, trip pins maybe?) But since it seems to only be these engines, I came here. 

[rogertra]

My first thought is the poorly laid track that seems not only to dip but also seems to have a twist as the lead engine seems to be leaning to its left.  Unfortunately, at the key moments, the telegraph pole is right in the way as is your throttle and we can't see anything

As you don't seem to have answered by question about running them singly, do the following test: -

1)  Run 5707 and run it slowly through the dip, on its own with no cars attached.  Did it short?

2)  Run 5708 and run it slowly through the dip, on its own with no cars attached.  Did it short?

If neither locomotive shorts in the above tests then do the following: -

3)  Couple the two engine together and run them slowly through the dip, on their own with no cars attached.  Did they short?

If, in either test 1, 2 or 3 you get a short circuit, turn off your throttle, to protect your electronics, and really look hard to see if any part of the locomotive(s) other than the wheels is touching the rail.

[bapguy]

Several thing I would check: take off the body on both units. Chech the wires to the decoder to make sure they are all attached and no strands are touching another wire next to it, take the weight out and check the wires from the trucks to be sure they are attached. Also is this part of a reverse loop or y track? If yes it could be the auto reverser acting up.  Joe

[jward]

i don't think the problem is due to grade or radius, at least as far as the locomotives are concerned. i am running gp7s and similar sized first generation locomotives on 18r and 4% grades with no shorting whatsoever. think about it for a minute. would you even want to buy a 4 axle locomotive that wouldn't negotiate an 18r curve? 

if your locomotives are stiff in curves, on most bachmann diesels there is a screw on top of the gear towers that can be adjusted similar to a bolster screw on a freight car. that will help locomotives track better but doesn't seem to be applicable in your case.

the rapid cycling of the track power off and on would seem to indicate a short. your dcc will try to reset the circuit breakers, then pop them again because the short is still there. when i first got dcc, i ran into this problem when locomotives and cars were running through switches. if the points are different polarity from the stock rails, a short occurs whel the wheel backs touch the adjacent point. if you are going fast enough, the train keeps moving. if you are going slosly, the short can stop the train. the solution here is to gap the frog and hard wire the points to the adjacent stock rail.

not sure if this post helps, but i'm sure others will find this info useful.

[railtwister]

It does sound like a short, especially if it's affecting other trains in the block. It was mentioned earlier but I didn't see an answer, is the Digitrax booster/command station doing any beeping during all this? Also, do either or both locos have back emf, and are you using any kind of additional electronic circuit breaker (other than the Digitrax onboard one) between the track and the booster? If you have a separate breaker, what amperage is it set to trip at?

Bill in FtL