I just bought a new MTH Railking K4 steam engine (30-1743-1), and discovered that it derails on my nearly-new Ross 042 switches - even at very slow speeds (3-5 mph).  It runs great everywhere else.  What happens is the pilot truck makes it past the switch frog ok, but the lead driver climbs over the frog.  I have run 3 other engines over these switches with no issues.  The new K4 is rated for 031 curves, so I don't think the radius shouldn't be the problem.  Any ideas what might be causing this and how to fix it?

Thanks in advance for the help.

Original Post


Let's do some detective work.. You state that this K-4 derails on your Ross 042 switch- all switches? or just one?  Looking at the locomotive by pulling up the product number it seems like the second set of wheels on the pilot truck is very close to the drive wheels.  Check the spacing here with other steamers.  Is it about the same space? or less?  Next hold the engine in one hand, upside down and rotate the pilot truck.  Do the wheels or frame of the pilot truck interfere with the locomotive frame or drive wheels?  Next you could remove the pilot truck from the engine and run it through the switches.

What we are trying to do is find out if it is a problem with the switches or this particular locomotive.   What do you find?


After I wrote this post, I did some more detective work too and found this out:

1. Of the 4 Ross 042 switches I have, it mainly has a problem with two of the switches, and I only have a derailing problem on the curved leg of the switch (where it enters the base of the switch and is directed by the points to take the curved leg).

2. I tried running the engine in both directions and that's when I found out it had a problem with the second switch.  The switches are configured as a crossover, to go from one adjacent loop to another (I know, I probably should have used Ross turnouts instead of the 042 switches).  So one crossover (2 switches) gives me issues in either direction, but the other crossover arrangement seems to be ok.   Visibly, I cannot see any difference between any of the 4 switches.

3. The engine will sometimes go through the switches fine if it is not pulling any cars, or maybe just one car.  But when I start adding cars (heavier passenger cars, especially), that's when it will derail all the time.

4. There is no interference with the pilot truck and the first set of drivers, or the frame.

A few thoughts:

1) The spring under the pilot truck may be too stiff, thereby reducing contact force on the front driver enough to cause it to climb over the turnout rail. Easiest way to check this might be to remove the pilot truck and test. If it improves, reduce spring tension on the pilot truck by slightly compressing or shortening the spring.

2) Add weight inside front of locomotive and test.

3) Interchange the switch with another on your layout and see what happens on both switches. I know that's a lot of work but...

4) Incorrect driving wheel or pilot wheel lateral spacing?



Thanks to all for the suggestions.  I removed the pilot and it did not make a difference.  It seems to me that the driver spacing (gauge) is ok.  The roller pickup doesn't seem to be causing any issue.  All of the rails through the switchesd are level and even.  I also checked the guardrail opposite the frog (particularly the spacing between it and the outside rail) and it seems to be fine.  The problem continues to be that the flange on the lead driver will sometimes hit the frog and climb over it, especially when the engine is pulling cars.  I haven't pulled the switches up because yes, that is a LOT of work, and I am not sure how moving them somewhere would help fix the problem.

1) Add weight in the nose or over the drivers if possible. First test it with some weights taped on externally if possible.

2) How are the traction tires? Try new ones?

3) If you exchange the switches and the problem moves with the switches, you know the problem is with that particular switch. If the problem remains in the same location, the adjacent tracks are the problem. That still might not rule out the locomotive.

How about some closeup pictures of the underside of the locomotive, the tender drawbar/tether, and the switches?


Have you ruled out the pickup roller as a problem?  If that catches, it would cause the driver wheels to raise up and derail.

I bring this up because that is the problem I had with my scaletrax switches.  The pickup roller would catch in the gap between the center rail and the diverging outer rail.  

To fix this I wedged in a piece of blue foam to fill the gap.  Now the pickup roller can't catch and the trains stay on the track. 

I have not finished this area of my layout yet.  Look how much the running trains colored the blue foam to black for me. ; )

Have Fun!



"I'd rather be lucky than good"


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