Test Assembly of MIDS with Wheel Sets and Bearings

    After cleaning up the MIDS frame a test assembly was made using two of the wheel-axle sets with bearings that were used to check glue procedures.  One set was black PLA while the other had green ABS drivers with the balance being black PLA.  The green driver set are actually Front (or Back) drivers instead of intermediate drivers as should be in that location.  The rear slot should be occupied with a main driver set, not the Front (or Back) set used here.

    The principle concern was whether the bearings would fit well between the frame internal surfaces and slide freely up and down and whether the wheel tire would line up properly with the brake hanger slot.  The bearing outside surface in contact with the frame was a bit too wide causing binding in the slot.  It would fit but required too much pressure to permit freedom to slide.  This is being corrected by building additional bearings that will fit Front, Intermediate or Back driver axles.  Later a set of main bearings will similarly be modified with a similar thinning of the outside flange on the bearing.

    The above photo shows a top view of the assembly with the bearings in the slots.  The portion of the bearing showing is the inside flange.  The spacing between the flanges is a bit too tight also, so the new bearings being made feature a wider slot between the bearing flanges to loosen up the fit with in the frame slot.

 

    The front view shows the frame spreaders located behind the bearings of the intermediate and main drivers.  The clearance between the spreaders and bearings is adequate with no contact.  The parts used here are fairly close to prototype configuration with minor adjustments of size for the 3D printer tolerances.  The parts look to be scale and generally have quite good agreement with scale dimensions.
    The next step will be fabricate both intermediate and main drivers, axles and bearings, assembly those and install in the MIDS frame assembly.  They will be built in ABS except the axles which come out much better in PLA.
    The size of the above assembly is approximately 5 1/2" long by 3" wide by 2 1/4" high.  One part that was omitted is the rear link brace which also provides a boiler attachment.   That part would have greatly complicated the support structure, so was deemed better to be built separately and attached to the frame.  I attaches directly centered between the two brake hangers with an "L" shaped bracket that is ideal for gluing. A test version of that part also needs to be made to validate dimensions, adjusting if necessary to get a good fit.