Lionel Powered Truck Axle Centering Spring

I might have answered my own question (see below).  I could use some confirmation on that though.  Lionel shows out of stock on this item so if this is the correct part I could use some help tracking it down.  Looks like Bill at S&W does not stock this.

How does it cause a derail? Backing up, it "jack knifes" too much?

I've had/got a few broken springs and pulling was never an issue, backing seldom an issue unless there was an S.

Coupling IS near impossible though

Not trying to deny it's happening or something;  just trying to understand it to confirm for myself it's the issue.

The lead axle has vertical play built into to it.  Now that I lost horizontal centering one flange is no longer forced against a rail.  When turning out in a Switch this allows that axle to climb up and out of the turn.  

Note: this is not a coupling centering spring.   This is the lead axle centering spring.  

Might try a womens long hair pin, or buy some spring steel rod, , try mcmasters-carr catalog

@DougB posted:

Might try a womens long hair pin, or buy some spring steel rod, , try mcmasters-carr catalog

That's what I was thinking. Even if it is temporary.

The metal is maybe 1/2 the diameter of small paperclip.  I do have some very thin brass rod that may work.   I prefer to pursue the Lionel part if somebody has it or potentially get a used one from a bad truck that somebody has laying around.   

You need spring steel. brass rod will not do it as it will take a set and have no spring action.

As long as you don’t yield the material (steel, brass, spring steel, etc.) it will return to original shape/size.   The stresses involved with centering this light axle with 2 wheels are very light.