Modifying Part Designs To Obtain Proper Fit

    By modifying the 3D design model the axle and drivers fit together much better.  A modest amount of filing and grinding were done to optimize the fit.  The wheels slide snugly unto the axle.  The picture at left shows one pair and axle completed and the second pair awaiting printout of one driver as this blog entry was written.
    The wheel gauge is off a bit, somewhat too wide for the design goal of 1/2" to the foot of american standard gauge of 4' 8 1/2".  The axle length will be adjusted to bring the gauge closer to scale dimension.
    The approach being taken is to now build sample PLA parts on ABS raft and support structure, check fit and key dimensions, adjust the design to correct any significant errors and build new parts.  This seems to be working.  It will take longer and use more material, however, the machine repeats build sizes fairly well and it appears that this method can achieve the desired scaling.
    The drivers built for the above picture are used for the front and back pair of the Mikado locomotive.  Two other sets are needed, the intermediate pair and the main pair.  Before assembly of the driver and axle sets, the bearings need to be fabricated and slipped on the axles.