hi gill,

careful miking of all the parts is a start. i would suggest you make the crosshead to be attached to the piston rod – carefully getting the piston rod parallel with the crosshead slides. then fix the slidebars temporarily in position. any mis-allignment will be obviously apparent. then its a case of carefully filing or machining the rear end covers or adding shim to the underneath of the slidebars till all fits snuggly and is parallel. if the piston is a jolly good fit in the cylinders and the rear cover perfectly concentric then any friction with no slop in the hole in the end cover for the piston rod then any mis-allignment will show up with the slidebars and will be readily apparent. one of these jobs easier to do than describe! just takes a bit of time and patience and as with all things loco wise 'fitting' is the key to success and long trouble free running.

cheers,

julian