With that layout I have a few tight turns. I wonder why some long locos go thru fine and a couple of them the same lenght will come off every time.So this means I have some locos with sound to sale. Two Union Pacifics SD mac 70’s wi9th sound and a steam locomotive too with sound.
As for you slow loco. I would do a reset of the DCC decoder, it may have a speed table in it different that what you like to run. I know have I had installed new Digitrax decoders in my trains, some run fine out the door, one that was a creeper and one that went from dead stop to full blast at the first click of the throttle. A CV8 reset fixed that problem. As for your locos derailing, 99.999% of the time is a track issue, slight dip or rise in the track that the train does not like. My layout was fine with no issues even on 6 axled locos and I bought a new SD70 and it found a couple bad spots that it did not like and a little shimming of the track fixed that problem. Some locos have a little more “suspension” in them than others. Watch where the loco derails and I suspect it will be at the same spot and a little shimming will fix your problem
I compared the one that comes off to 3 other ones that have 6 axles and are the same lenght and they have no problems what so ever Tomorrow I’ll keep running them till I hopefully figure out the problem, Thanks to everyone.
When you say tight turns what radius are you talking? Also what manufacturer and model of loco?
The reason that 6 axle loco’s typically have more trouble than 4 axle is because of the distance between the front and rear wheel of each truck. on a 6 axle loco the distance is much farther making the truck ride against the flanges on tight turns. Any imperfection can potentially grab the flange and derail the truck.
Do you have an NMRA gauge? Check the wheel gauge. Out of gauge wheels especially on six axle engines will hang up and lift the truck on tight radii. The center axle on a three axle truck sometimes needs to be just a little tighter than the other two to keep from binding on sharp turns. Be careful though, because just a little too tight and it will pick points on switches. My SD80’s and 90’s will negotiate a 12 inch radius but they need the included extended couplers installed for any radius under 18 inches. My SD70’s perform about the same.
As for the slow Atlas engines. Try a reset of the decoder. Check the decoder manual for the proper reset value. While a value of 08 to CV8 will reset newer model decoders, older decoders require a value of 33 written to CV8 to reset. if you want to see painfully slow, pick up an Intermountain FT or a Lifelike C Liner.
A reset may not make a difference. Atlas engines are significantly slower than KATO engines. Atlas switched to "scale speed " motors in their N scale engines several years ago. KATO N scale engines will run run like slot cars.