I'm using bushes because the holes in the coupling rods are of the size to demand it.  I've used screwed De-Luxe crankpins on the front and rear wheels, and an old-style plain piun  on the driven axle.  This allows me to solder the return cranks in place without gumming up any threads.  In the absence of non-threaded bushes, I drilled the screw thread out of the de-luxe versions.   Anyway, its all together and working!  It runs very nicely in a straight line, and even goes round c