Working on a recent part built purchase, I fiited the con rods (Derby 4f 0-6-0) and the wheels will not rotate the full three sixty degrees. I have double checked the distances between hole centres on the con rods and they are o.k. I did not turn the wheels or fix the drive pins. In Don Youngs build notes he describes "easing" the "bearings" on the con rods, just wondering how much of this is allowed? Obviously not much. Or should there be no need to apply this