SD40's 2033471

So I finally got around to testing out this issue, myself.  As mentioned above, all my curves are O-60, except for a single half circle on an inner loop, which is O-48.  I so I put the SD40 on the route to the O-48's.  As I expected, running by itself, the trucks on this loco have more than enough pivot to negotiate the curve.  The problem is the couplers, which on this model, is a separate assembly from the trucks, and are not influenced by the trucks' pivot on a curve.   I put one, single, 15 inch hopper car on the SD40, and tried the curve. What happens is that both knuckles move to the outside of the outermost rail on the curve.  Basically, hanging on to each other for dear life, like somebody extending a hand to another person already over the cliff....  So it is pretty clear any size consist, the coupling is going to pull apart, or even cause a derailment.  So when they say O-54 min. curve, it is not a suggestion.  So ok, I can stick to running this pair of SD40's on the outer loop, only.    But I will not likely buy any additional locos in the future, which cannot handle up to O-42, or even O-48 (if that exists).  Thanks/Alex

Lionel calls these things a "kinematic pilot."  I too have found that they are quite good a dragging rolling stock over the rails.  As long as the rolling stock is somewhat heavy and has a swinging coupler, it does pretty well.  If it is has a fixed coupler (rigidly mounted to the truck) it's almost guaranteed to derail, even on O60.  I've also resorted to putting a second engine without a kinematic pilot behind it as well, and then it is pretty bulletproof.

As a point of continuing education, there are no dashes in EMD diesel  model numbers. The engine under discussion here is an SD40, not a SD-40. I edited and corrected the previous posts in this thread.

Here endeth the lesson….