Newbie problem with Lionel 0-72 turnouts

[Anonymous]

I am new to the hobby, and in the process of converting the dining room into a large O guage layout. I have built the outer loop, including some 0-72 turnouts that will enable crossovers to an inner loop that goes in next. I tried running some trains over the outer loop, but I am having problems with train cars "derailing" on the switches. What is happening is that then last set of wheels, the rear wheel trucks, of the last car in any group of cars that ruin through the switch are jumping up onto "the points that swivel" of the switch. Let me try to explain that a little better: The switch is set for the train to continue straight through the switch and not to go onto the turnout. Yes, I made sure all the connections with the track are tight, and yes the "swivelling points" part is set fully in the position to let the cars go straight through. The first few cars do fine, but the the flange of the wheels on the last car ride up onto the metal point, and then slip over to align the wheels onto the turnout track. Happens every time with different manufacturers of cars, engines, etc. If I run an engine through with a tender, it happens to the rear wheels of the tender. If I add a car or a caboose to the train, the tender goes through just fine, but the rear wheels of the final car get fouled.

Very frustrating!!

Also, I noticed that this did not happen at first, but then (after about 30 minutes of "operating") it was consistent with every switch (turnout) that I had installed. Could the switch metal have "heated up" and expanded?

Any advice appreciated.

Trevor in Lancaster, PA