What Causes That Loss of Power in Loco After Direction Change?

[John]

Back in the day when we had mechanical tuners & volume pots, there was a spray-on product called “tuner cleaner” by a number of manufacturers that would take all the audible “scratch” sounds out of your stereo gear.

Has anyone tried using something like that to clean the electrical contacts. I wouldn’t get it on any painted surface... just in case.

carbon tetrachloride .. bad ju ju

[tehachapifan]

I can't argue that either way. I apologize if I offended you....

No offense taken! That's not what I meant....I was taking exception to the idea that Joe average modeler was cleaning axle cups with some regularity.

[Steveruger45]

carbon tetrachloride .. bad ju ju

Yep, I was going to say that too.  Good old “carbontet” (said he ironically) was even used in fire extinguishers.  It is really bad stuff, carcinogenic, and has been banned a long time now.
I still remember an old guy, when I was young, used to wash his hand in carbontet after working with transformer Oil of the PCB (poly chloro byphenols) Kind.  Also really bad ju ju.
He died later, but of a car accident.

[peteski]

No offense taken! That's not what I meant....I was taking exception to the idea that Joe average modeler was cleaning axle cups with some regularity.

You do have a point.  Average modeler probably just cleans the wheels, but they are probably also more forgiving of an occasional stall that you are analyzing.

I hope you can humor me bu answering few more diagnostic type questions.

How many actively used locos do you have?

How many of those experience the problem?

Do they all use the same design, or locos using different mechanism design have the problem?

How often does the problem occur, and is it easily repeatable (or just happens once in a blue moon)?

If the problem is easily repeatable on a particular model, that will make it  easier to pinpoint the problem areas.

[CRL]

carbon tetrachloride .. bad ju ju

I know that stuff’s been banned, but even WD-40 has a specialist electronic tuner cleaner spray. Has anyone tried any of the “legal” formulations?

My dad used carbon tetra chloride during WW2 to clean brake fluid off of Army Air Corp fighters & bomber brake pads. He died too, but from pneumonia, not cancer.

[MK]

Back in the day when we had mechanical tuners & volume pots, there was a spray-on product called “tuner cleaner” by a number of manufacturers that would take all the audible “scratch” sounds out of your stereo gear.

Has anyone tried using something like that to clean the electrical contacts. I wouldn’t get it on any painted surface... just in case.

Now a days, DeOxit serves this purpose.  One of many contact/tuner cleaner formulations out there.

[tehachapifan]

You do have a point.  Average modeler probably just cleans the wheels, but they are probably also more forgiving of an occasional stall that you are analyzing.

True! Plus, I run a lot of sound-equipped locos now and a complete power dropout is a much more significant event.

I hope you can humor me by answering few more diagnostic type questions.

How many actively used locos do you have?

Probably far too many!

How many of those experience the problem?

I would say the issue is too infrequent overall to really be able to pinpoint locos that experience it the most often. That said, chanced increase if doing some slow switching with a single loco. Even still, I can't say I've identified certain locos that are especially problematic (except for those Kato/Conco switcher drives discussed earlier).

Do they all use the same design, or locos using different mechanism design have the problem?

Aside from those Kato/Concor switcher drives discussed earlier, the rest employ the standard contact strip design.

How often does the problem occur, and is it easily repeatable (or just happens once in a blue moon)?

Somewhere between relatively infrequent and blue moon territory for the most part. That said, if a loco is getting to the point were it's about time to clean wheels, etc., it could probably be repeated with that loco fairly consistently.

If the problem is easily repeatable on a particular model, that will make it  easier to pinpoint the problem areas.

Agreed, but I suspect my (admittedly-vague) answers aren't going to be that much help. TBH, I sort of expected this to be a relatively common occurrence, where others chimed in with the "I've noticed this too" type responses where we could then compare notes, share findings and brainstorm for the common good. Wasn't really expecting to be alone on this. As such, perhaps it's not worth much problem solving if it's not really a common issue and the answer, as you've indicated, is that I simply need to do more frequent disassembly and cleaning.

...you'll be happy to know that tonight I did disassemble and clean a loco that just recently started acting up a bit (an Atlas 8-40B that I purchased second-hand a little while back and installed a sound decoder in). Yeah, the axle cups were really bad as were the contact strips. I often do a post (second-hand) purchase cleaning, if it looks like it might need it anyway, but didn't on this one before now.

[peteski]

Tehachapifan,
Thanks for providing those answers.  I suspect that you realize that what you are seeing is how a loco behaves when it needs cleaning.  Wheels, pickup strips, and possibly axle cups are all contributing to the problem.

Especially telling was this answer from you:
Somewhere between relatively infrequent and blue moon territory for the most part. That said, if a loco is getting to the point were it's about time to clean wheels, etc., it could probably be repeated with that loco fairly consistently.

To me the dirty wheels are the proverbial last nail in the coffin. Then, as you also noted, you didn't get numerous "I have the same problem" responses. It doesn't seem to be a common problem.   But even for you, the problem is worth solving, and the solution is . . . clean  the damn contact points and wheels.    To me this is as clear as day. I don't see anything else that can be brainstormed, unless maybe coming up with some way to keep all the contact points clean for a longer time.  I presented my method (polishing the contact points).

I'm glad to hear that you did do a thorough cleaning on one of your locos.  May it run long and smoothly. 

[Maletrain]

I have not chimed-in on this thread because all of my experience with this lose-power-upon-reversing phenomenon has been with steam engines.  But, to keep Tehachapifan from feeling too lonely, here's my 1-1/2 cents worth of experience:

On light steam locomotives with short wheel bases, mainly 4-4-0s, I have had them lose all power promptly after going into reverse, but not from reverse to forward.  This was particularly an issue with an N scale Atlas 4-4-0 and an HO scale Bachmann 4-4-0, both DCC.  What I could see was that the reverse force on the tender made it rise slightly in the front and drop down slightly in the back.  Because the tender wheels are not powered, but do provide pickup, I don't think this is the same problem as what happens in a diesel loco with all wheels powered and also providing contact. 

Cleaning wheels has not solved this problem for me.  Pushing down on the Atlas tender does fix it when it happens.  Adding weight to the tender for the N scale Atlas loco has solved that problem for at least one other poster here on TRW, but I have not tried that yet.  (He made a metal oil tank casting to go over the coal bin, but I need to make an N scale wood load out of lead for my fix, so not yet attempted.  Anybody know of quarter-round material made out or lead, with a curved side radius of about 0.06" or 1/16"?)

On the HO scale 4-4-0, I could fix stalls with a slight nudge.  I ended up taking that loco apart to see if I could put a keep-alive in it, but ended up not doing that because (A) the hookup is not simple and there is little room for a substantial capacitor, and (B) when I put the thing back together, the problem has not repeated.  All I really did for that locomotive was clean everything that has electrical contact (except the motor brushes).  However, I suspect that the pin connector between the loco and tender was not as tight as it should have been before I reassembled it.  Taking up the slack in the drawbar might have put enough torque on the wires to slightly move the connector just enough to open an iffy connection on a pin.  That one is a 6-pin connector, so track power to the decoder could have been interrupted at that point.

I am not seeing how any of this could be directly applicable to diesels stalling, but I'm throwing it in so that it might jog somebody else with more experience in diesels.

[tehachapifan]

Thanks, guys!

Maletrain, thanks for chiming-in and giving some company! I suspect that, while the exact cause of your stalls may be different, there's still may be a mechanical component to this with at least some diesels that causes a rare and intermittent physical separation of electrical contact, which is exacerbated when things start to get dirty.

...one last comment so that we don't close this out with the impression that this was all because I have filthy loco wheels that I rarely clean. I would say that I keep loco wheels pretty darn pristine overall. Before I switched to DCC, I could not stand to see any headlight flickering whatsoever and would clean wheels and track accordingly. It was probably bordering on an unhealthy obsession. After switching to DCC it all became about staving-off sound dropouts as decoders, for the most part, seemed to eliminated light flickering as a gauge for cleanliness.  I don't currently add caps to my sound installs and very rarely experience a sound dropout due to my keeping wheels and track clean. Perhaps decoders, even sound decoders without added caps, mask symptoms a little longer that the non-DCC light flickering did and, as such, I unknowingly became a little more laxed? At any rate, despite my penchant for clean wheels, cleaning axle cups (and then adding a small amount of lube as discussed in other threads) was not a regular occurrence...but it will be from now on.

         

[woodone]

Going to the post by Maletrain~ Steam loco’s are a whole different Animal than a diesel.
The steamer has a ridged wheel base-lift one driver off the rail and more than likely you will lift all same side drivers off the rail.
The diesel has two driving trucks that have pivot movement up and down that tends to keep wheels in contact with the rails.
But it is still the same problem— no power getting to the motor.
WOW,  Carbon. Tetrachloride- have not see that name in a while- I recall it being use has a fire extinguisher fluid you could shoot at a fire! Removes Oxogen real quick!
 Has our loco’s get used we introduce them to many small problems that can not be seen- A little oxide on the rail & or wheels- a bit more on some mechanical connections, a little more friction on all bearing surfaces. Motor has carbon build up on the comunactor —
Pretty soon we have a failure. So singling out one thing becomes almost impossible to pin point.


 

[John]

My motive power sits on the layout for months at a time without moving .. I've noticed that once I finally hook one up to the DCC throttle, it takes a while to get it rolling -- in either direction . it's almost like arthritis has set into the gears .. I only have about 50 engines .. about half are on the layout at any given time .. and maybe 4 or 5 run regularly .. I try to clean them at least yearly, and run them around the test loop for a while in each direction .. In my case, its probably a case of tarnish, built up dust and gears not moving for long periods of time.  I use labelle light oil when I do maintenance ..

[peteski]

...one last comment so that we don't close this out with the impression that this was all because I have filthy loco wheels that I rarely clean. I would say that I keep loco wheels pretty darn pristine overall.

It was never my intention to imply that this is the case.  As I see it (and mentioned that repeatedly) is that the problem is caused by a combination of (slightly) dirty or oxidized contact points.  Again, there are the 3 contributors:  Pickup strip contact area loses contact with the truck nubs, axle with the axle cup, and the wheel tread with the track.  If all those 3 areas (on both trucks) lose contact in a perfect storm fashion, the loco will stall with a "no power" symptom, which can be easily remedied by giving the loco a manual nudge. That nudge will cause at least 2 of those failed contact points (one for each track) to reconnect and start conducting electricity. 

If the wheels alone were very filthy, the loco would not run well in any direction, at slow speeds, or even at faster speeds. And lots of headlight flicker.  But since the wheels of your models are not too dirty, the problem you described is very intermittent, and by your own admission, gets worse the dirtier the wheels get.

[tehachapifan]

It was never my intention to imply that this is the case....

I know it wasn't but I could see how someone might draw that conclusion reading thru the thread. All good!

[mmagliaro]

I have had this problem.  Usually with steam, but not always.

First, a suggestion.  As a general rule, when I have an engine that is plaguing me like this, I use an extremely fine, flexible bit of wire in an alligator clip to one rail and then the other, just lightly grazing it across a pickup wheel on one side and then the other, to see if electrical pickup is definitely the culprit and which side it's on.  Nudging it can also move the wheels and gears and doesn't isolate mechanical from electrical problems.   Sometimes, I find that the loss of pickup is ALWAYS on one side and that's a really helpful clue.

In the case at hand, since the power goes truly dead when reversing direction, as evidenced by no headlight and no sound. I completely rule out mechanical binds, climbing gears, an armature that loses contact with it brushes, or any of that stuff.  If you had contact, you'd get sound and/or headlight no matter how jammed up the mechanism is.  My strong vote is that it's in the truck pickups.  I think I'm in alignment with Peteski on this.
That's what shifts the most when you change directions.    All those axles and pickup cones have pressure on them in one direction.  When you stop, the pressure stops and they can all "relax", which can cause them to stop touching each other unless they are clean and all the contact pressures are in good shape.

And yes, when an engine becomes troublesome like this, I clean the wheels AND the axle point cones.