Possible K4 issue and fix

[Dave V]

Over the last few weeks I started seeing some stall issues with one of my two Bachmann K4s (#1361).  I've been double heading them so usually it's just a momental stutter as the other loco (#5448) drags or pushes it a bit and it wakes up again.  This was happening in three spots on my layout, so at first I suspected the track.  Of course as a precautionary measure I cleaned the wheels on the #1361 thoroughly.  When that didn't fix the problem, the track was thoroughly cleaned, joints re-soldered, and everything checked.  The track was fine.  And #5448 was happy.  What could it be?

I took special care to clean the tender wheels and ensure the sideframe cups were making contact and clean.  When that wasn't enough I finally popped open the tender to check the DCC harness.  What I noticed was that the four pickup wipers were bent upward, away from the sideframe pickup posts.  I gave them a gentle bend downward, and now #1361 has no pickup problems or stalls.

Just FYSA in case you run into a similar problem.  #5448 has been very well-behaved so I haven't had reason to open her tender and see what the pickup wipers look like.

gfh edit - added scale icon.... 

[glakedylan]

good to know
have not run mine much
just a test track at this point
but this information may very well come in handy down the road
thanks
Gary

[mmagliaro]

Good catch, Dave. 

And now... the "rest" of the story...

An awful lot of Bachmann tenders I have come across have at least 1 of the 4 strips inside the tender  pointing enough away from the trucks to avoid contact.  It's so common that I routinely pull the shell off the tender to check for this as a standard repair check.

There is an inherent flaw with using short strips attached to a circuit board (like the K4, the Berkshire, and quite a few other locos
like the ConCor 2-10-2).  They should be long, floor-length strips affixed only at the center.  The problem is that the
length of the shorter bronze strips is too short. 

Phosphor bronze is a great pickup wiper material because unlike brass, it is very springy.  It can bend to and fro and spring back to its original position, unlike brass, which tends to just bend and stay bent.  But even the phosphor bronze has its limits.

Those tenders with the short PC board-attached strips are very vulnerable to the strips getting bent up and out of position like that, because they are so short that the bronze can't withstand that much deflection and still spring back to its original position reliably.
This would not happen if they were floor-length.

That K4 ran fine when you got it.  This leads me to believe that the strips weren't bent when you got them and they gradually bent
up over time.   So keep an eye on it.  If this problem returns, the strips in that tender will need to be redesigned to really fix the problem.
You may have just pressed on the tender inadvertently a few times without even realizing it and bent those strips up.
(But again, that still would not have happened if they used floor-length strips)

[Dave V]

I'll definitely keep an eye on both now...  Thanks for the heads' up Max.  Didn't realize that was a systematic flaw.

In the meantime put some more loops around the Juniata Division on the 1361 and she's fine for now.

Hard to believe that I'm running double-headed K4s and a pair of M1bs--all running flawlessly--with sound...  If I didn't have so much post-1950 rolling stock I'd be tempted to move my calendar to the late 40s!  Suffice it to say I've not run a diesel or a GG1 in many weeks.

[nkalanaga]

If the problem continues, rather than redesigning the strips, it might be easier to solder some very fine wire between the truck pickup tabs and the existing strips.  Use wire with black insulation and it shouldn't be any more visible than the tabs and strips.  Depending on the available space in the tender, you could use a fairly long piece of wire, and stuff the excess up into the tender, making it easy to remove and work on the trucks without unsoldering the wires.

If the wires didn't work, redesigning the strips would still be possible, as you wouldn't have done any permanent damage to the trucks or PC board.

[Mike C]

If the problem continues, rather than redesigning the strips, it might be easier to solder some very fine wire between the truck pickup tabs and the existing strips.  Use wire with black insulation and it shouldn't be any more visible than the tabs and strips.  Depending on the available space in the tender, you could use a fairly long piece of wire, and stuff the excess up into the tender, making it easy to remove and work on the trucks without unsoldering the wires.

If the wires didn't work, redesigning the strips would still be possible, as you wouldn't have done any permanent damage to the trucks or PC board.

But if you're going to go through the trouble to do that , a decoder swap to a better sound decoder isn't all that much more work .

[Dave V]

But if you're going to go through the trouble to do that , a decoder swap to a better sound decoder isn't all that much more work .

 

I'm worried about locomotive pickup from the rails into the tender...  I'm not necessarily looking to change decoders.  Sure running them alongside the M1bs does tend to bring the shortcomings of the K4 sound a little more to light, but with the pile of "silent" locomotives I have that are waiting for a sound upgrade, I'm not going to change the board on an already sound-equipped locomotive unless the decoder dies outright.

[Mike C]

I haven't heard ANY locos that sound as good as those M1's . ( for the most part , I think the chuff is a little funny )  There just isn't enough room in most tenders for a great speaker with that much low end .

[chicken45]

There was some HO scale guy on the PRR N scale Facebook group telling us how "bad" the M1 sounded compared to the K4. I was like...huh?

[Dave V]

There was some HO scale guy on the PRR N scale Facebook group telling us how "bad" the M1 sounded compared to the K4. I was like...huh?

Yeah, and he wouldn't let it go, either.

[eric220]

There was some HO scale guy on the PRR N scale Facebook group telling us how "bad" the M1 sounded compared to the K4. I was like...huh?