Got 0-6-0 chassis working nicely except after going straight following wide curve. Give it lots of power and would often slow down but still manage to get passed straight and into next curve. Appeared to just lose power, slightest touch and away it went. runs without whirr so no binding. looked and looked and looked..... Finally tried connecting rail to motor with seperate wire in case all pickups not in contact. Sometimes appeared to leap away again, but not always. Of course only did this on side with pickups cos cant be problem on other side - of course not. Well checked other side. oh dear, it always leapt away. Got meter out to check wheels. Yes one is an insulated wheel. Had replaced it a while back cos ..(thats a different story).
cheers, Simon