I can run my trains in about 10-20 cars with no problems but when I do a 40 car train I get a couple of cars that derails one at turnout and another on a turn, usually closer to the front of the train because as I move them to the rear they go around my layout no problem. I think they might be derailing due to a wheel out of gauge and all the weight behind them makes them hop the turn out. Am I on the right track of thinking or might be something else?? And I am fairly sure it is not the track as I have had no problems even with a 6 axled Athearn dash-9 on the same spots.
It could be the wheels, but I’m inclined to believe it’s the weight of the car, or how that weight is distributed. The drag behind the car will pull it inward on a curve. If the car is too light, or if it is top-heavy, it will tilt inwards and take weight off the outside wheels. Then, it’s easy for the wheels to roll up over the rails.
For any given curve radius and set of rolling stock, there’s a limit to how long a train can be before even the best of cars will start doing this.
Before anything touches the layout, gauge the wheels and ensure that the trucks are free-swiveling.
While you are at it, make sure all your rolling stock is weighted to NMRA specs (most are light out of the box) and make sure that every turnout is within gauge (none are out of the box).
David B
David,Actually adding weight to RP20.1 has nothing to do with it…I run 30-35 car train up and down grade all day long during the county fair with zero derailments and all of my cars are stock weight.
Here’s the facts…As you know wheels that are properly gauge and coupler trip pins at the correct height will stay on the track where poorly gauge wheels and low trip pins will cause problems.
Accept nothing less then 100% derailment free operation.
Another thing you can look at is the wheels, particularly if they are plastic. As dirt and grime build up on the tread and flanges it gives them a roughened surface, giving them grip to climb the rails. It would be more prevalent with more cars behind it as the forces would pull it into the sides of the rails. The easiest thing to do to check this is simply change out the wheelsets.
Another cause of what sounds very much like a close cousin of string-lining is too sharp a curve radius on the turn, and perhpas through the turnout. Running long trains demands closer adherence to the 3X radius rule (radius greater than or equal to 3 times the length of the longest car) than short trains, due to the increased divergence of pull angle to the inside of the curve by the remaining train drag on sharper curves. As has been mentioned in other threads, sharper curves demand closer to perfection in almost every aspect - trackwork, truck free-rolling, wheel gauge and alignment, equal weighting of cars (and in proportion to their free-rolling capability).
Fred W
Before going too far simply put the heaviest cars towards the front and lightest towards the back. If you get the lighter ones in the front they’ll pull right off on turnouts or S curves.
I also noticed this too, on my new layout, the longer the train, the more I discovered not so perfect trackwork.
Re-check your trackwork, in my case, I had some spots were the soldered joints were, there was excess solder which caused a very slight bump on the inside of the rails. As more tension from the long trains pulled the cars and hit the bump and caused derails.
Once I fixed all the solder joints, no more derailments. I feel like inspector gadget now! LOL
Thanks for all the insight, the one thing I did not know was the 3x rule but that would make sense as it is a 18 inch curve and one of the culprits is a top heavy long grain hopper car and I can see it as when the car starts to turn and the back end gets loaded up enough to force the wheel over the rail. I think the force and direction would make a highschool physics teacher giddy.