I would start with the loco wheels. 100% of the time I've ever had an issue with a car or loco over Atlas turnouts, at least the Custom Line ones, it was the wheels being out of gauge per the NMRA gauge.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
I agree with Jim, start by testing the equipment against standards, including the wheels on the locomotive. I would also check if the turnout is levelled and that it functions properly. One cannot exclude a turnout problem because other locos can go through it successfully.
It might help if you give us more information about the turnout. Would you know the number or type? Also, does the loco derail when creating the short? Does it short when changing track or when going straight through? This loco has four drivers, which means that it may not take a sharp turnout without causing problems.
Simon
I would turn off the lights and then look for a spark just prior to the breaker opening at track level. Be sure to verify the trucks are not shorting to the body also.
If you cannot see the far side of the loco, a inspection or similar mirror can help.
Might not be a bad ideal to check the spacing of the switch with a NMRA gauge. If its a snap switch, look where the rails form a V as a wheel may be bridging the gap.
Jim
I recently purchased a new Lionel HO Scale Polar Express Engine and tender. When the Engine crosses one of my Atlas turnouts my NCE PowerCab DCC command station trips the circuit breaker and shuts down the track. It tries repeatedly to repower the track and shuts down each time. Other locomotives have no problem with the same switch. Please make suggestions on how I can diagnose and correct this issue.