Should clarify the rocking I reported. The problem is with my track. Using a strait edge the wheels are completely flat with no rocking at all. Also no vertical movement of the centre wheel set. Almost all if not all my other loco's have a bit to a lot of vertical float in the centre wheel set, thus they can accommodate a degree of miss-alignment in the track. Rob, I think you have a very good point about why the L1 is such a good puller when you say that all 6 wheels are in contact with the track. This is good, but it does introduce a new dimension to track laying. I consider my self to be better than average (false modesty in a situation like this does not help solve a problem) and one has to wonder how many people would end up being totally frustrated by this situation. One has to wonder if, with the introduction of near museum quality models, it my soon be necessary to put floating (hornblock) axles on "commercial" locomotives. I know it will add to the price but based on the length of this thread and others there clearly is a problem although one can argue about just how big it is.