Locomotive Springs

    The previous blog post showed results of fabrication efforts of the locomotive spring leaves.  Leaves have been built on the side edge and on the flat of the spring.  Above is shown spring assemblies of those methods.  The closer spring assembly was fabricated on side edge while the further one was fabricated down flat.  The leaves built on edge have varying thickness and must be at least 0.03" thick which results in fewer leaves and a noticeably stiffer spring assembly.  The ones built flat are 0.020" thick which results in a lower stiffness judged to be more realistic for this model.  The side built leaves have poorer hole and slot definition.  The flat built ones required sanding to remove the green ABS residue.  It is easy, but tedious to remove, but doable.

    An attempt to build springs vertical was also done, examples are shown above.  These exhibited very poor definition of holes and slots.  The BFB-3000 printer cannot easily fabricate the narrow strips of material close together as needed around the holes and slots.  This leads to badly distorted unusable parts.

    A second run of leaves printed flat was attempted using the small amount of green ABS left which resulted in a very poor raft structure, probably due to the difficulty the printer had drawing the small amount of remaining ABS on the spool.  This was attributed to the high spring force of the ABS.  The machine was re-loaded with clear PLA to make rafts and support structures.  The first run with clear PLA and flat spring leaves is shown above.

    The leaves were readily removed using care, mostly by flexing the raft by hand.  The smaller spring leaves popped off while the larger ones needed a bit of coaxing using a model knife to pry loose small portions that wanted to stick.  The leaves had good definition and only a very thin layer of clear PLA residue remained on the leaves.  They may be usable without the need to sand off the residue.

    The spring leaves are to be mounted on the spring riser and clamp parts with the holes in the spring leaves fitting over the post on the middle of the riser.  When checking for fit it was discovered that this set of spring leaves have overly small holes and will not readily fit over the post.  Rather that run the risk of breaking the post, the design was modified to increase the hole dimensions for better fit.  It takes near 3hr to fabricated a set of spring leaves.